Research ArticleApplication of Electrochemical Techniques onStudy of Effect of Nano-ZnO in Conductive PolyanilineContaining Zinc-Rich Primer
Ximing Li 1 and Homero Castaneda2
1Chemical and Biomolecular Engineering The University of Akron Akron OH 44325 USA2Materials Science and Engineering Texas AampM University College Station TX 77843 USA
Correspondence should be addressed to Ximing Li xmli2012gmailcom
Received 31 August 2017 Revised 20 December 2017 Accepted 10 January 2018 Published 28 February 2018
Academic Editor Stefan Schmatz
Copyright copy 2018 Ximing Li and Homero Castaneda This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited
Effect of zinc oxide nanoparticles on anticorrosion performance has been studied in conductive polyaniline containing zinc-richprimer in 35 wt NaCl solution using Electrochemical Impedance Spectroscopy (EIS) and localized electrochemical ScanningVibrating Electrode Technique (SVET)The results showed that the addition of nano-zinc oxide particles in conductive polyanilinecontaining zinc-rich primer made the reaction of zinc more stable and slower further increasing the effective cathodic protectionperiod EIS and SVET results confirmed that three performance evolution stageswere obtained for zinc-rich primer being immersedin 35 wt sodium chloride solution
1 Introduction
Zinc-rich epoxy primer (ZRP) has been used as anticorrosionprimers since the 1930s [1 2] highly recommended foroffshore environments refineries power plants bridges andso forth ZRPs are expected to provide sacrificial cathodicprotection (CP) at an early stage and the formation of zincoxide products would provide further barrier protection atlater stage [3] Intrinsically conductive pigment has beenadded in ZRP to improve CP efficiency of which polyani-line (PAni) was studied due to its excellent environmentalstability controllable electrical conductivity and interestingredox properties [4ndash7] In our previous work [8] differentPAni states including nonconductive emeraldine base (EB)and conductive emeraldine salt (ES) were added to ZRPto study the effects of different oxidation states on anticor-rosive performance EB is electrically neutral while doped(protonated) and the resulting ES form is highly electricallyconductive The addition of a small amount of conductivePAni to ZRP slowed the activation process of zinc particlesand further improved the cathodic protection effect while
the nonconductive PAni EB accelerated the activation of zincparticles The formed zinc oxide products were compact andprovided better barrier performance than the commercialZRP
Coatings combined with metal oxide nanoparticles suchas ZnO [9] TiO2 [10] and Fe2O3 [11] would providebetter corrosion resistance and improved protection whencombined with PAni This is because the combination ofnano-metal oxide powders and coating matrix tends toproduce crack-free uniform coating interface and also helpsto form uniform passive layers on the surface of metallicsubstrate Mostafaei and Nasirpouri [9] synthesized a seriesof conducting PAni-ZnO nanocomposites materials and thestudy results showed that the addition of ZnO nanorodsand PAni significantly improved the barrier and corrosionprotection performance of the epoxy coating The increasedinhibition of PAni in the presence of metal cations likeZn2+ ions would likely be attributed to the formation ofcompact clusters and enhanced by more amounts of electronrich benzenoid groups that facilitates the greater adsorptionon the iron surface and hereby prevents further corrosion
HindawiInternational Journal of SpectroscopyVolume 2018 Article ID 7160381 15 pageshttpsdoiorg10115520187160381
2 International Journal of Spectroscopy
[12] Furthermore ZnO nanostructured materials may act asbarrier in the paint film and may reduce passing routes usedby electrolyte and corrosive ions The studies of protectionperformance of combination of PAni with ZRP are stilllimited [13] More studies are needed on the application ofPAni on ZRP to obtain a more protective coating that willcombine both PAni and ZRP properties
To investigate the anticorrosion performances of metalrich coatings Electrochemical Impedance Spectroscopy(EIS) has been considered as a common technique to char-acterize and quantify the performance of typical coatingsexposed to a corrosive environment [14ndash17] EIS providesqualitative and quantitative magnitudes that characterize theperformance of the coating under exposed conditions [18ndash21] Different processing methods and fitting models weredesigned to investigate the corrosion protective mechanisms[22ndash26] Although EIS is a valuable technique for studyingdielectric properties it fails to provide enough spatial reso-lution and only an average behavior can be achieved on thestudied surface The idea of a localized measurement is toexamine areas within a sample that differ in their activityindividually which has promoted many studies Recentlythe development of microelectrode techniques and scanningelectrode techniques has made it possible to measure electro-chemical processes on a local scale which has attracted lots ofstudied on the local electrochemical processes on corrodingsurfaces and investigations of localized corrosion [27] Scan-ning Vibrating Electrode Technique (SVET) is a powerfultool to permit a better understanding of the mechanisms andprocesses of corrosion at defects and underneath coatings[28] This technique can provide valuable information ofthe electrochemical interactions between a coating and itssubstrate at a defect The analysis of the current distributionwould be useful considering the anticorrosion mechanismincluding the generation and development of defects and theinfluence of pigmentsinhibitors on corrosion of substrate ata defect
This work is to investigate the performance of PAni-nano-ZnO containing ZRPs in a 35 wt NaCl environmentand characterize the associated mechanisms Different elec-trochemical microscopy techniques were used in this workincluding electrochemical and localized scanning vibratingelectrode spectroscopy technique
2 Experimental Design
21 Materials and Preparation The 1008 steel samples wereused in this work All the samples were mechanically grindedwith different grit sizes of SiC papers to 1200 used assubstrate coatedwith the developed paint Before applicationthey were degreased with acetone and ethanol solution inan ultrasonic bath to remove the impurities and rinsedthoroughly with double distilled water and dried in the air
PAni emeraldine base (PAni EB) molecular weight ca65000 was supplied by the Aldrich Chemical Company Allthe other chemicals were obtained from Aldrich in analyticalgrade purity Conductive PAni emeraldine salt (PAni ES) wasprepared by dispersing 10 g PAni EB in 250ml of 1molsdotdmminus3ethanolic solution of phenylphosphonic acid and stirring
overnight Then the PAni ES product was filtered washedwith distilled water air-dried and subsequently groundunder liquid nitrogen to give powders oflt20120583mparticle size
Zinc-rich primer used in this work (Amercoat 68HS)is a commercial polyamide cured epoxy resin pigmentedwith zinc dust pigment purchased from PPG industries Itis composed of epoxy base hardener and zinc dust whichcontains approximately 80 zinc in dry film with 70 plusmn 3volume solids Zinc oxide nanoparticles (lt130 nm) 40wtdispersed in ethanol was purchased from Aldrich ChemicalCompany whose density is 125 gml plusmn 005 gml at 25∘CTwo paints are designed PAni-ZRP and PAni-ZnO-ZRPFor PAni-ZRP paint conductive PAni powder synthesizedabove was added in the premixed ZRP coating componentby 02 wt under agitation until fully mixed For PAni-ZnO-ZRP paint 01 wt PAni powder and 03 wt nano-zincoxide powders were added accordingly to the premixed ZRPsystem under agitation until fully mixed Coatings were thenpainted by high pressure spraying on prepared panels Theaverage dry coating thickness was detected in the range of170ndash180 um
22 Testing Environments and Methods
221 Coating Characterization and Weight Loss Test Afterthe prepared samples were completely dry contact angletest was applied to check the tendency of water uptake onthe coating surface according to ASTM D7334 [29] Four-pin conductivity tester was applied to check the percolationcondition of various coating systems Weight loss test wasdesigned to check the cathodic reaction of zinc particles andformation of zinc oxide products in coating interface Thecoated samples (in duplicate) were taped at the back side andedges leaving the tested area of 1 cm times 1 cm and then wereimmersed in 35 wt NaCl solution over a period of 120 daysat room temperature Before and after being immersed all thesamples were weighted to check the weight loss conditionsThe surface morphology of the specimens was observed byField Emission Scanning Electron Microscope (SEM) at abeam energy of 5 keV accompanied by energy-dispersive X-ray spectroscopy (EDS) In addition pH of the electrolyte wasmonitored from time to time
222 Electrochemical Spectroscopy Technique MeasurementsThe EIS tests were conducted using Gamry Reference 600Potentiostat instrument Three-electrode system was appliedfor electrochemical tests steel samples serving as workingelectrode saturated calomel electrode (SCE) as the referenceelectrode and platinum mesh as counterelectrode In EISan alternating current signal with a frequency range from100 kHz to 10mHz and amplitude of 10mV was applied tothe working electrode at the corrosion potential Besidesopen circuit potential (OCP) was also recorded in each studysystem to check the electrochemical status All the tests areset at room temperature over a period of 120 days in 35 wtNaCl to simulate chloride neutral corrosive environmentDuplicate samples are considered for each test to verify therepeatability
International Journal of Spectroscopy 3
Computer
35wt NaCl
Test cell
SCEreferenceelectrode
Counterelectrode
Workingelectrode
Potentiostat
Sample
(a)
Carbon steel with a thin coating
Pt-Ir microelectrode
Calibration wire Sample
To electrometer andlock-in amplifier
Vertical vibrationamplitude 30 m
Ionic current flow fromsite of electrochemicalactivity
(b)
Figure 1 Illustration diagram of EIS test system (a) and SVET Scanning System (b)
SVET was tested by VersaScan Electrochemical Scan-ning System The SVET microelectrode applied was a PtndashIrmicroelectrode (Microprobe Inc) with a 10 120583m diametertip The vibrating separation of the microprobe was around100 120583m above the samples with the amplitude 20120583m alongthe 119883 and 119884 directions A platinum wire circle was usedas the reference and counterelectrodes when performingthe calibration process The ZRP samples (1 times 1 cm2) wereprotected by a polyester tape to make the exposed area of3 times 3mm2 to be the scanning area An artificial scratchwas introduced to half of the scanning area to simulatethe galvanic couple of ZRPs and steel substrate The probewould move across with a 31 times 31 scan generating a 961-point mesh across the surface Scans were initiated 10 safter immersion and repeated every half an hour All of theSVET measurements were performed in duplicate at OCP in001 wtNaCl solutionThe experimental setup for these twoelectrochemical tests are shown in Figure 1
3 Results and Discussion
31 Coating Characterization and Weight Loss Test Thetest result of coating surface hydrophobicity is shown inFigure 2 PAni-ZRP and PAni-ZnO-ZRP exhibited a muchlarger contact angle value than the commercial ZRP whichindicates both two coatings are more hydrophobic thanzinc-rich primer coating This property would postpone the
activation time of zinc particles after being immersed insodium chloride solution in agreement with the previousstudy [8] Comparing these two coatings the addition ofzinc oxide nanoparticles does not change the coating surfacehydrophobic property so much just a little bit of ignorableincrease Itmakes sense that the surface property of zinc oxideparticle is similar to zinc particle (spontaneous oxides on thesurface) The main factor would be conductive polyanilinemaking the surface more hydrophobic The resistivity 120588holds an opposite relationship with conductivity which canindicate the Zn-to-Zn connection condition of ZRPs Thesmall amount of conductive PAni improved the Zm-to-Zncondition of the ZRP which has been discussed in previousstudy [8] while the addition of nano-ZnO particles inPAni-ZRP increased the dry coating resistivity with largederivation probably because of the addition of ZnO and thecombination of ZnO and PAni which counteract the effect ofconductive polyaniline in ZRP
The results of solution pH and sample weight loss wereplotted in Figure 3 for PAni-ZRP with and without ZnOnanoparticles The pH for 35 wt NaCl solution is 639 ThepHevolution of these two systems is similar over time a quickincrease during the first 5 d followed by a slow increase till120 dThe increase of pH is due to the cathodic reaction listedin the following
12O2 +H2O + 2119890
minus 997888rarr 2OHminus (1)
4 International Journal of Spectroscopy
50
60
70
80
90
PAni-ZnO-ZRPPAni-ZRPZRP
Con
tact
angl
e (de
gree
)
(a)
100
200
300
400
500
600
700
PAni-ZnO-ZRPPAni-ZRPZRP
Coa
ting
resis
tivity
(o
hm cm
)
(b)
Figure 2 Contact angle (a) and coating resistivity 120588 (b) of PAni-ZRP and PAni-ZnO-ZRP
0 20 40 60 80 100 12060
65
70
75
80
85
90
pH
Time (day)PAni-ZRPPAni-ZnO-ZRP
(a)
0 10 20 30 40 50 60minus07
minus06
minus05
minus04
minus03
minus02
minus01
00
01W
eigh
t los
s (w
t)
Time (day)PAni-ZRPPAni-ZnO-ZRP
(b)
Figure 3 Solution pH and weight loss of sample PAni-ZRP and PAni-ZRP-ZnO over time
Later due to alkaline environment the corrosion of Zn maybe related to the following equations This makes the secondperiod exhibit a slowly increasing pH
The weight loss was negative meaning the formed zinc oxideproducts were compact and adhesive in the coating matrixpH value of coating PAni-ZRP is larger than PAni-ZnO-ZRPindicating the more reaction of zinc particles In additionthis agrees with the weight loss data PAni-ZRP gains more
weight than PAni-ZnO-ZRP Hence the addition of nano-ZnO in PAni-ZRP presents a slower zinc cathodic activa-tion
The surface morphologies of PAni-ZRP and PAni-ZnO-ZRP before test and after 60 d of immersion are shown inFigures 4 and 5 respectively The surface morphology ofcoating PAni-ZnO-ZRP is more uniform and has less poresthan PAni-ZRP (Figure 4) And after 60 d of immersionthe coating surface was covered by zinc oxide products theoxide products of PAni-ZnO-ZRP are more compact Thecross-sectional SEM images after 60 d and 120 d are shown inFigure 6 Zinc particles at the inner coating matrix were also
International Journal of Spectroscopy 5
20 m
(a)
20 m
(b)
Figure 4 Surface morphologies of PAni-ZRP (a) and PAni-nano-ZnO-ZRP (b) before test
40 m
(a)
0
20
40
60
80
100
SiC ClOZn
0203
193
467
335
PointAtomic percent (norm)
(b)
40 m
(c)
0
20
40
60
80
100
SiC ClOZn
0405
186
501
303
PointAtomic percent (norm)
(d)
Figure 5 Surface morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 d
reacted for PAni-ZRP after 60 d of immersion (Figure 6(a))The zinc oxide layer formed on PAni-ZnO-ZRP coating ismore compact than PAni-ZRP comparing Figure 5(a) and5(c) And the EDS mapping was conducted at the coatingmatrix by scanning an area of 40 120583m times 40 120583m (above thesteel substrate) Notably even before test the oxygen contentwas approximately 10 wt at the zinc particle surface becauseof the presence of native zinc oxide The EDS mappingsof element of Zn O Cl and Fe were detected to trackthe waterions transportation and cathodic reaction of zinc
particles in coatingsteel interface (Figure 7) Before 20 dthe mass percent of element O and Cl in coating PAni-ZRP is higher than PAni-ZnO-ZRP indicating that water andions transported to the coating PAni-ZRP interface quickerthan PAni-ZnO-ZRP This shows that the addition of nano-zinc oxide may reduce the passing routes of waterions andimproves the coating barrier performance in agreement withpublished literature [30] In addition a small amount of ironwas detected for PAni-ZRP at 120 d showing an localizedattack of substrate corrosion
6 International Journal of Spectroscopy
100 m
(a)
100 m
(b)
100 m
(c)
100 m
(d)
Figure 6 Cross-sectional morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 days (a amp c) and 120 days (b amp d)
0
40
50
60
70
80
90
100
120202
Mas
s per
cent
()
05
ZnOCl
Fe
Time (day)
(a)
0
40
50
60
70
80
90
100
Mas
s per
cent
()
12020205Time (day)
ZnOCl
(b)
Figure 7 EDS mapping of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at different immersion time
International Journal of Spectroscopy 7
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07O
CP (V
ver
sus S
CE)
Time (day)
(a)
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07
OCP
(V v
ersu
s SCE
)
Time (day)
(b)
Figure 8 OCP changes over time for PAni-ZRP (a) and PAni-ZnO-ZRP (b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
(a)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
QＩＲＣ
RＩＲＣ
(b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
W＞Ｃ
(c)
Figure 9 Electric equivalent circuits (EECs) models applied for EIS data fitting
32 OCP and EIS Results and Discussion OCP can be cor-related to the anticorrosion performance stages of ZRP [2]Three main periods were differentiated in the ZRPrsquos lifetimeafter immersion in 3 NaCl solution (a) the ldquoactivationrdquoperiod corrosion potential shifts to cathodic values (b) in asecond period the electrode potential shifts to more anodicvalue and then reached the limit of CP (c) at the thirdperiod the corrosion potential is out of the CP range andthe coating provided barrier protection depending on theformed zinc oxide products and coating morphology Thechanges of OCP of PAni-ZRP and PAni-ZnO-ZRP coatingswere detected after being immersed in 35 wtNaCl solutionfrom time to time The OCP for steel 1018 was tested beingminus860mV versus SCE which will be the limit potential ofeffective CP range That is when OCP is more anodic thanminus860mV the cathodic protection provided by zinc particlesdisappears [31] As shown in Figure 8 OCP increased slightlyover time after 5 d immersion for the two coating systems Butthe potential is still inOCP range lower thanminus860mV versusSCE which is the corrosion potential of bare steel used in thiswork
Interestingly the OCP presents a decreasing period intwo different slopes at initial 5 d immersion except the sharpincrease for PAni-ZRP a faster slope and a slower slope inagreement with the published work [2] The higher slope isrelated to the activation of zinc particle and increasing arearation of ZnFe and the slower decreasing slope was dueto the increasing contact resistance between zinc particlesLater the formation of zinc oxide productsmade the potentialshift towards anodic value Comparing these two coatingsystems PAni-ZnO-ZRP coating system has more stable
OCP than PAni-ZRP during the initial period The sharpincrease in OCP value for PAni-ZRP is because of the quickand accumulated formation of zinc oxide in coating interface
The EIS results were fitted using equivalent electricalcircuits (EECs) models to get valuable parameters related tocoating evolution as shown in Figure 9 These EEC modelshave been used in many published studies related to ZRPs[32ndash34] 119877119904 represents the electrolyte resistance 119876119888 and 119877119888represent the constant phase element (CPE) and the resis-tance of the coating respectively 119876oxi and 119877oxi represent theCPE and the resistance of the zinc oxide products while 119876dland 119877ct represent the CPE of the double layer and the chargetransfer resistance respectively119882dif represents the Warburgimpedance CPE elements are typically applied in the EISfitting procedure to characterize the surface roughness atthe interface [35] or to describe the frequency dependenceof nonideal capacitive behavior [36] The impedance of theWarburg diffusion element 119885119908 follows
119885119908 = 120590 (1 minus 119895) 120596minus12 (4)
where 120590 is the Warburg coefficient in units of Ωsdotcm2sdotsminus12The CPE impedance is calculated using the following [35]
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
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Submit your manuscripts atwwwhindawicom
2 International Journal of Spectroscopy
[12] Furthermore ZnO nanostructured materials may act asbarrier in the paint film and may reduce passing routes usedby electrolyte and corrosive ions The studies of protectionperformance of combination of PAni with ZRP are stilllimited [13] More studies are needed on the application ofPAni on ZRP to obtain a more protective coating that willcombine both PAni and ZRP properties
To investigate the anticorrosion performances of metalrich coatings Electrochemical Impedance Spectroscopy(EIS) has been considered as a common technique to char-acterize and quantify the performance of typical coatingsexposed to a corrosive environment [14ndash17] EIS providesqualitative and quantitative magnitudes that characterize theperformance of the coating under exposed conditions [18ndash21] Different processing methods and fitting models weredesigned to investigate the corrosion protective mechanisms[22ndash26] Although EIS is a valuable technique for studyingdielectric properties it fails to provide enough spatial reso-lution and only an average behavior can be achieved on thestudied surface The idea of a localized measurement is toexamine areas within a sample that differ in their activityindividually which has promoted many studies Recentlythe development of microelectrode techniques and scanningelectrode techniques has made it possible to measure electro-chemical processes on a local scale which has attracted lots ofstudied on the local electrochemical processes on corrodingsurfaces and investigations of localized corrosion [27] Scan-ning Vibrating Electrode Technique (SVET) is a powerfultool to permit a better understanding of the mechanisms andprocesses of corrosion at defects and underneath coatings[28] This technique can provide valuable information ofthe electrochemical interactions between a coating and itssubstrate at a defect The analysis of the current distributionwould be useful considering the anticorrosion mechanismincluding the generation and development of defects and theinfluence of pigmentsinhibitors on corrosion of substrate ata defect
This work is to investigate the performance of PAni-nano-ZnO containing ZRPs in a 35 wt NaCl environmentand characterize the associated mechanisms Different elec-trochemical microscopy techniques were used in this workincluding electrochemical and localized scanning vibratingelectrode spectroscopy technique
2 Experimental Design
21 Materials and Preparation The 1008 steel samples wereused in this work All the samples were mechanically grindedwith different grit sizes of SiC papers to 1200 used assubstrate coatedwith the developed paint Before applicationthey were degreased with acetone and ethanol solution inan ultrasonic bath to remove the impurities and rinsedthoroughly with double distilled water and dried in the air
PAni emeraldine base (PAni EB) molecular weight ca65000 was supplied by the Aldrich Chemical Company Allthe other chemicals were obtained from Aldrich in analyticalgrade purity Conductive PAni emeraldine salt (PAni ES) wasprepared by dispersing 10 g PAni EB in 250ml of 1molsdotdmminus3ethanolic solution of phenylphosphonic acid and stirring
overnight Then the PAni ES product was filtered washedwith distilled water air-dried and subsequently groundunder liquid nitrogen to give powders oflt20120583mparticle size
Zinc-rich primer used in this work (Amercoat 68HS)is a commercial polyamide cured epoxy resin pigmentedwith zinc dust pigment purchased from PPG industries Itis composed of epoxy base hardener and zinc dust whichcontains approximately 80 zinc in dry film with 70 plusmn 3volume solids Zinc oxide nanoparticles (lt130 nm) 40wtdispersed in ethanol was purchased from Aldrich ChemicalCompany whose density is 125 gml plusmn 005 gml at 25∘CTwo paints are designed PAni-ZRP and PAni-ZnO-ZRPFor PAni-ZRP paint conductive PAni powder synthesizedabove was added in the premixed ZRP coating componentby 02 wt under agitation until fully mixed For PAni-ZnO-ZRP paint 01 wt PAni powder and 03 wt nano-zincoxide powders were added accordingly to the premixed ZRPsystem under agitation until fully mixed Coatings were thenpainted by high pressure spraying on prepared panels Theaverage dry coating thickness was detected in the range of170ndash180 um
22 Testing Environments and Methods
221 Coating Characterization and Weight Loss Test Afterthe prepared samples were completely dry contact angletest was applied to check the tendency of water uptake onthe coating surface according to ASTM D7334 [29] Four-pin conductivity tester was applied to check the percolationcondition of various coating systems Weight loss test wasdesigned to check the cathodic reaction of zinc particles andformation of zinc oxide products in coating interface Thecoated samples (in duplicate) were taped at the back side andedges leaving the tested area of 1 cm times 1 cm and then wereimmersed in 35 wt NaCl solution over a period of 120 daysat room temperature Before and after being immersed all thesamples were weighted to check the weight loss conditionsThe surface morphology of the specimens was observed byField Emission Scanning Electron Microscope (SEM) at abeam energy of 5 keV accompanied by energy-dispersive X-ray spectroscopy (EDS) In addition pH of the electrolyte wasmonitored from time to time
222 Electrochemical Spectroscopy Technique MeasurementsThe EIS tests were conducted using Gamry Reference 600Potentiostat instrument Three-electrode system was appliedfor electrochemical tests steel samples serving as workingelectrode saturated calomel electrode (SCE) as the referenceelectrode and platinum mesh as counterelectrode In EISan alternating current signal with a frequency range from100 kHz to 10mHz and amplitude of 10mV was applied tothe working electrode at the corrosion potential Besidesopen circuit potential (OCP) was also recorded in each studysystem to check the electrochemical status All the tests areset at room temperature over a period of 120 days in 35 wtNaCl to simulate chloride neutral corrosive environmentDuplicate samples are considered for each test to verify therepeatability
International Journal of Spectroscopy 3
Computer
35wt NaCl
Test cell
SCEreferenceelectrode
Counterelectrode
Workingelectrode
Potentiostat
Sample
(a)
Carbon steel with a thin coating
Pt-Ir microelectrode
Calibration wire Sample
To electrometer andlock-in amplifier
Vertical vibrationamplitude 30 m
Ionic current flow fromsite of electrochemicalactivity
(b)
Figure 1 Illustration diagram of EIS test system (a) and SVET Scanning System (b)
SVET was tested by VersaScan Electrochemical Scan-ning System The SVET microelectrode applied was a PtndashIrmicroelectrode (Microprobe Inc) with a 10 120583m diametertip The vibrating separation of the microprobe was around100 120583m above the samples with the amplitude 20120583m alongthe 119883 and 119884 directions A platinum wire circle was usedas the reference and counterelectrodes when performingthe calibration process The ZRP samples (1 times 1 cm2) wereprotected by a polyester tape to make the exposed area of3 times 3mm2 to be the scanning area An artificial scratchwas introduced to half of the scanning area to simulatethe galvanic couple of ZRPs and steel substrate The probewould move across with a 31 times 31 scan generating a 961-point mesh across the surface Scans were initiated 10 safter immersion and repeated every half an hour All of theSVET measurements were performed in duplicate at OCP in001 wtNaCl solutionThe experimental setup for these twoelectrochemical tests are shown in Figure 1
3 Results and Discussion
31 Coating Characterization and Weight Loss Test Thetest result of coating surface hydrophobicity is shown inFigure 2 PAni-ZRP and PAni-ZnO-ZRP exhibited a muchlarger contact angle value than the commercial ZRP whichindicates both two coatings are more hydrophobic thanzinc-rich primer coating This property would postpone the
activation time of zinc particles after being immersed insodium chloride solution in agreement with the previousstudy [8] Comparing these two coatings the addition ofzinc oxide nanoparticles does not change the coating surfacehydrophobic property so much just a little bit of ignorableincrease Itmakes sense that the surface property of zinc oxideparticle is similar to zinc particle (spontaneous oxides on thesurface) The main factor would be conductive polyanilinemaking the surface more hydrophobic The resistivity 120588holds an opposite relationship with conductivity which canindicate the Zn-to-Zn connection condition of ZRPs Thesmall amount of conductive PAni improved the Zm-to-Zncondition of the ZRP which has been discussed in previousstudy [8] while the addition of nano-ZnO particles inPAni-ZRP increased the dry coating resistivity with largederivation probably because of the addition of ZnO and thecombination of ZnO and PAni which counteract the effect ofconductive polyaniline in ZRP
The results of solution pH and sample weight loss wereplotted in Figure 3 for PAni-ZRP with and without ZnOnanoparticles The pH for 35 wt NaCl solution is 639 ThepHevolution of these two systems is similar over time a quickincrease during the first 5 d followed by a slow increase till120 dThe increase of pH is due to the cathodic reaction listedin the following
12O2 +H2O + 2119890
minus 997888rarr 2OHminus (1)
4 International Journal of Spectroscopy
50
60
70
80
90
PAni-ZnO-ZRPPAni-ZRPZRP
Con
tact
angl
e (de
gree
)
(a)
100
200
300
400
500
600
700
PAni-ZnO-ZRPPAni-ZRPZRP
Coa
ting
resis
tivity
(o
hm cm
)
(b)
Figure 2 Contact angle (a) and coating resistivity 120588 (b) of PAni-ZRP and PAni-ZnO-ZRP
0 20 40 60 80 100 12060
65
70
75
80
85
90
pH
Time (day)PAni-ZRPPAni-ZnO-ZRP
(a)
0 10 20 30 40 50 60minus07
minus06
minus05
minus04
minus03
minus02
minus01
00
01W
eigh
t los
s (w
t)
Time (day)PAni-ZRPPAni-ZnO-ZRP
(b)
Figure 3 Solution pH and weight loss of sample PAni-ZRP and PAni-ZRP-ZnO over time
Later due to alkaline environment the corrosion of Zn maybe related to the following equations This makes the secondperiod exhibit a slowly increasing pH
The weight loss was negative meaning the formed zinc oxideproducts were compact and adhesive in the coating matrixpH value of coating PAni-ZRP is larger than PAni-ZnO-ZRPindicating the more reaction of zinc particles In additionthis agrees with the weight loss data PAni-ZRP gains more
weight than PAni-ZnO-ZRP Hence the addition of nano-ZnO in PAni-ZRP presents a slower zinc cathodic activa-tion
The surface morphologies of PAni-ZRP and PAni-ZnO-ZRP before test and after 60 d of immersion are shown inFigures 4 and 5 respectively The surface morphology ofcoating PAni-ZnO-ZRP is more uniform and has less poresthan PAni-ZRP (Figure 4) And after 60 d of immersionthe coating surface was covered by zinc oxide products theoxide products of PAni-ZnO-ZRP are more compact Thecross-sectional SEM images after 60 d and 120 d are shown inFigure 6 Zinc particles at the inner coating matrix were also
International Journal of Spectroscopy 5
20 m
(a)
20 m
(b)
Figure 4 Surface morphologies of PAni-ZRP (a) and PAni-nano-ZnO-ZRP (b) before test
40 m
(a)
0
20
40
60
80
100
SiC ClOZn
0203
193
467
335
PointAtomic percent (norm)
(b)
40 m
(c)
0
20
40
60
80
100
SiC ClOZn
0405
186
501
303
PointAtomic percent (norm)
(d)
Figure 5 Surface morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 d
reacted for PAni-ZRP after 60 d of immersion (Figure 6(a))The zinc oxide layer formed on PAni-ZnO-ZRP coating ismore compact than PAni-ZRP comparing Figure 5(a) and5(c) And the EDS mapping was conducted at the coatingmatrix by scanning an area of 40 120583m times 40 120583m (above thesteel substrate) Notably even before test the oxygen contentwas approximately 10 wt at the zinc particle surface becauseof the presence of native zinc oxide The EDS mappingsof element of Zn O Cl and Fe were detected to trackthe waterions transportation and cathodic reaction of zinc
particles in coatingsteel interface (Figure 7) Before 20 dthe mass percent of element O and Cl in coating PAni-ZRP is higher than PAni-ZnO-ZRP indicating that water andions transported to the coating PAni-ZRP interface quickerthan PAni-ZnO-ZRP This shows that the addition of nano-zinc oxide may reduce the passing routes of waterions andimproves the coating barrier performance in agreement withpublished literature [30] In addition a small amount of ironwas detected for PAni-ZRP at 120 d showing an localizedattack of substrate corrosion
6 International Journal of Spectroscopy
100 m
(a)
100 m
(b)
100 m
(c)
100 m
(d)
Figure 6 Cross-sectional morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 days (a amp c) and 120 days (b amp d)
0
40
50
60
70
80
90
100
120202
Mas
s per
cent
()
05
ZnOCl
Fe
Time (day)
(a)
0
40
50
60
70
80
90
100
Mas
s per
cent
()
12020205Time (day)
ZnOCl
(b)
Figure 7 EDS mapping of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at different immersion time
International Journal of Spectroscopy 7
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07O
CP (V
ver
sus S
CE)
Time (day)
(a)
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07
OCP
(V v
ersu
s SCE
)
Time (day)
(b)
Figure 8 OCP changes over time for PAni-ZRP (a) and PAni-ZnO-ZRP (b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
(a)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
QＩＲＣ
RＩＲＣ
(b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
W＞Ｃ
(c)
Figure 9 Electric equivalent circuits (EECs) models applied for EIS data fitting
32 OCP and EIS Results and Discussion OCP can be cor-related to the anticorrosion performance stages of ZRP [2]Three main periods were differentiated in the ZRPrsquos lifetimeafter immersion in 3 NaCl solution (a) the ldquoactivationrdquoperiod corrosion potential shifts to cathodic values (b) in asecond period the electrode potential shifts to more anodicvalue and then reached the limit of CP (c) at the thirdperiod the corrosion potential is out of the CP range andthe coating provided barrier protection depending on theformed zinc oxide products and coating morphology Thechanges of OCP of PAni-ZRP and PAni-ZnO-ZRP coatingswere detected after being immersed in 35 wtNaCl solutionfrom time to time The OCP for steel 1018 was tested beingminus860mV versus SCE which will be the limit potential ofeffective CP range That is when OCP is more anodic thanminus860mV the cathodic protection provided by zinc particlesdisappears [31] As shown in Figure 8 OCP increased slightlyover time after 5 d immersion for the two coating systems Butthe potential is still inOCP range lower thanminus860mV versusSCE which is the corrosion potential of bare steel used in thiswork
Interestingly the OCP presents a decreasing period intwo different slopes at initial 5 d immersion except the sharpincrease for PAni-ZRP a faster slope and a slower slope inagreement with the published work [2] The higher slope isrelated to the activation of zinc particle and increasing arearation of ZnFe and the slower decreasing slope was dueto the increasing contact resistance between zinc particlesLater the formation of zinc oxide productsmade the potentialshift towards anodic value Comparing these two coatingsystems PAni-ZnO-ZRP coating system has more stable
OCP than PAni-ZRP during the initial period The sharpincrease in OCP value for PAni-ZRP is because of the quickand accumulated formation of zinc oxide in coating interface
The EIS results were fitted using equivalent electricalcircuits (EECs) models to get valuable parameters related tocoating evolution as shown in Figure 9 These EEC modelshave been used in many published studies related to ZRPs[32ndash34] 119877119904 represents the electrolyte resistance 119876119888 and 119877119888represent the constant phase element (CPE) and the resis-tance of the coating respectively 119876oxi and 119877oxi represent theCPE and the resistance of the zinc oxide products while 119876dland 119877ct represent the CPE of the double layer and the chargetransfer resistance respectively119882dif represents the Warburgimpedance CPE elements are typically applied in the EISfitting procedure to characterize the surface roughness atthe interface [35] or to describe the frequency dependenceof nonideal capacitive behavior [36] The impedance of theWarburg diffusion element 119885119908 follows
119885119908 = 120590 (1 minus 119895) 120596minus12 (4)
where 120590 is the Warburg coefficient in units of Ωsdotcm2sdotsminus12The CPE impedance is calculated using the following [35]
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
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Submit your manuscripts atwwwhindawicom
International Journal of Spectroscopy 3
Computer
35wt NaCl
Test cell
SCEreferenceelectrode
Counterelectrode
Workingelectrode
Potentiostat
Sample
(a)
Carbon steel with a thin coating
Pt-Ir microelectrode
Calibration wire Sample
To electrometer andlock-in amplifier
Vertical vibrationamplitude 30 m
Ionic current flow fromsite of electrochemicalactivity
(b)
Figure 1 Illustration diagram of EIS test system (a) and SVET Scanning System (b)
SVET was tested by VersaScan Electrochemical Scan-ning System The SVET microelectrode applied was a PtndashIrmicroelectrode (Microprobe Inc) with a 10 120583m diametertip The vibrating separation of the microprobe was around100 120583m above the samples with the amplitude 20120583m alongthe 119883 and 119884 directions A platinum wire circle was usedas the reference and counterelectrodes when performingthe calibration process The ZRP samples (1 times 1 cm2) wereprotected by a polyester tape to make the exposed area of3 times 3mm2 to be the scanning area An artificial scratchwas introduced to half of the scanning area to simulatethe galvanic couple of ZRPs and steel substrate The probewould move across with a 31 times 31 scan generating a 961-point mesh across the surface Scans were initiated 10 safter immersion and repeated every half an hour All of theSVET measurements were performed in duplicate at OCP in001 wtNaCl solutionThe experimental setup for these twoelectrochemical tests are shown in Figure 1
3 Results and Discussion
31 Coating Characterization and Weight Loss Test Thetest result of coating surface hydrophobicity is shown inFigure 2 PAni-ZRP and PAni-ZnO-ZRP exhibited a muchlarger contact angle value than the commercial ZRP whichindicates both two coatings are more hydrophobic thanzinc-rich primer coating This property would postpone the
activation time of zinc particles after being immersed insodium chloride solution in agreement with the previousstudy [8] Comparing these two coatings the addition ofzinc oxide nanoparticles does not change the coating surfacehydrophobic property so much just a little bit of ignorableincrease Itmakes sense that the surface property of zinc oxideparticle is similar to zinc particle (spontaneous oxides on thesurface) The main factor would be conductive polyanilinemaking the surface more hydrophobic The resistivity 120588holds an opposite relationship with conductivity which canindicate the Zn-to-Zn connection condition of ZRPs Thesmall amount of conductive PAni improved the Zm-to-Zncondition of the ZRP which has been discussed in previousstudy [8] while the addition of nano-ZnO particles inPAni-ZRP increased the dry coating resistivity with largederivation probably because of the addition of ZnO and thecombination of ZnO and PAni which counteract the effect ofconductive polyaniline in ZRP
The results of solution pH and sample weight loss wereplotted in Figure 3 for PAni-ZRP with and without ZnOnanoparticles The pH for 35 wt NaCl solution is 639 ThepHevolution of these two systems is similar over time a quickincrease during the first 5 d followed by a slow increase till120 dThe increase of pH is due to the cathodic reaction listedin the following
12O2 +H2O + 2119890
minus 997888rarr 2OHminus (1)
4 International Journal of Spectroscopy
50
60
70
80
90
PAni-ZnO-ZRPPAni-ZRPZRP
Con
tact
angl
e (de
gree
)
(a)
100
200
300
400
500
600
700
PAni-ZnO-ZRPPAni-ZRPZRP
Coa
ting
resis
tivity
(o
hm cm
)
(b)
Figure 2 Contact angle (a) and coating resistivity 120588 (b) of PAni-ZRP and PAni-ZnO-ZRP
0 20 40 60 80 100 12060
65
70
75
80
85
90
pH
Time (day)PAni-ZRPPAni-ZnO-ZRP
(a)
0 10 20 30 40 50 60minus07
minus06
minus05
minus04
minus03
minus02
minus01
00
01W
eigh
t los
s (w
t)
Time (day)PAni-ZRPPAni-ZnO-ZRP
(b)
Figure 3 Solution pH and weight loss of sample PAni-ZRP and PAni-ZRP-ZnO over time
Later due to alkaline environment the corrosion of Zn maybe related to the following equations This makes the secondperiod exhibit a slowly increasing pH
The weight loss was negative meaning the formed zinc oxideproducts were compact and adhesive in the coating matrixpH value of coating PAni-ZRP is larger than PAni-ZnO-ZRPindicating the more reaction of zinc particles In additionthis agrees with the weight loss data PAni-ZRP gains more
weight than PAni-ZnO-ZRP Hence the addition of nano-ZnO in PAni-ZRP presents a slower zinc cathodic activa-tion
The surface morphologies of PAni-ZRP and PAni-ZnO-ZRP before test and after 60 d of immersion are shown inFigures 4 and 5 respectively The surface morphology ofcoating PAni-ZnO-ZRP is more uniform and has less poresthan PAni-ZRP (Figure 4) And after 60 d of immersionthe coating surface was covered by zinc oxide products theoxide products of PAni-ZnO-ZRP are more compact Thecross-sectional SEM images after 60 d and 120 d are shown inFigure 6 Zinc particles at the inner coating matrix were also
International Journal of Spectroscopy 5
20 m
(a)
20 m
(b)
Figure 4 Surface morphologies of PAni-ZRP (a) and PAni-nano-ZnO-ZRP (b) before test
40 m
(a)
0
20
40
60
80
100
SiC ClOZn
0203
193
467
335
PointAtomic percent (norm)
(b)
40 m
(c)
0
20
40
60
80
100
SiC ClOZn
0405
186
501
303
PointAtomic percent (norm)
(d)
Figure 5 Surface morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 d
reacted for PAni-ZRP after 60 d of immersion (Figure 6(a))The zinc oxide layer formed on PAni-ZnO-ZRP coating ismore compact than PAni-ZRP comparing Figure 5(a) and5(c) And the EDS mapping was conducted at the coatingmatrix by scanning an area of 40 120583m times 40 120583m (above thesteel substrate) Notably even before test the oxygen contentwas approximately 10 wt at the zinc particle surface becauseof the presence of native zinc oxide The EDS mappingsof element of Zn O Cl and Fe were detected to trackthe waterions transportation and cathodic reaction of zinc
particles in coatingsteel interface (Figure 7) Before 20 dthe mass percent of element O and Cl in coating PAni-ZRP is higher than PAni-ZnO-ZRP indicating that water andions transported to the coating PAni-ZRP interface quickerthan PAni-ZnO-ZRP This shows that the addition of nano-zinc oxide may reduce the passing routes of waterions andimproves the coating barrier performance in agreement withpublished literature [30] In addition a small amount of ironwas detected for PAni-ZRP at 120 d showing an localizedattack of substrate corrosion
6 International Journal of Spectroscopy
100 m
(a)
100 m
(b)
100 m
(c)
100 m
(d)
Figure 6 Cross-sectional morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 days (a amp c) and 120 days (b amp d)
0
40
50
60
70
80
90
100
120202
Mas
s per
cent
()
05
ZnOCl
Fe
Time (day)
(a)
0
40
50
60
70
80
90
100
Mas
s per
cent
()
12020205Time (day)
ZnOCl
(b)
Figure 7 EDS mapping of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at different immersion time
International Journal of Spectroscopy 7
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07O
CP (V
ver
sus S
CE)
Time (day)
(a)
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07
OCP
(V v
ersu
s SCE
)
Time (day)
(b)
Figure 8 OCP changes over time for PAni-ZRP (a) and PAni-ZnO-ZRP (b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
(a)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
QＩＲＣ
RＩＲＣ
(b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
W＞Ｃ
(c)
Figure 9 Electric equivalent circuits (EECs) models applied for EIS data fitting
32 OCP and EIS Results and Discussion OCP can be cor-related to the anticorrosion performance stages of ZRP [2]Three main periods were differentiated in the ZRPrsquos lifetimeafter immersion in 3 NaCl solution (a) the ldquoactivationrdquoperiod corrosion potential shifts to cathodic values (b) in asecond period the electrode potential shifts to more anodicvalue and then reached the limit of CP (c) at the thirdperiod the corrosion potential is out of the CP range andthe coating provided barrier protection depending on theformed zinc oxide products and coating morphology Thechanges of OCP of PAni-ZRP and PAni-ZnO-ZRP coatingswere detected after being immersed in 35 wtNaCl solutionfrom time to time The OCP for steel 1018 was tested beingminus860mV versus SCE which will be the limit potential ofeffective CP range That is when OCP is more anodic thanminus860mV the cathodic protection provided by zinc particlesdisappears [31] As shown in Figure 8 OCP increased slightlyover time after 5 d immersion for the two coating systems Butthe potential is still inOCP range lower thanminus860mV versusSCE which is the corrosion potential of bare steel used in thiswork
Interestingly the OCP presents a decreasing period intwo different slopes at initial 5 d immersion except the sharpincrease for PAni-ZRP a faster slope and a slower slope inagreement with the published work [2] The higher slope isrelated to the activation of zinc particle and increasing arearation of ZnFe and the slower decreasing slope was dueto the increasing contact resistance between zinc particlesLater the formation of zinc oxide productsmade the potentialshift towards anodic value Comparing these two coatingsystems PAni-ZnO-ZRP coating system has more stable
OCP than PAni-ZRP during the initial period The sharpincrease in OCP value for PAni-ZRP is because of the quickand accumulated formation of zinc oxide in coating interface
The EIS results were fitted using equivalent electricalcircuits (EECs) models to get valuable parameters related tocoating evolution as shown in Figure 9 These EEC modelshave been used in many published studies related to ZRPs[32ndash34] 119877119904 represents the electrolyte resistance 119876119888 and 119877119888represent the constant phase element (CPE) and the resis-tance of the coating respectively 119876oxi and 119877oxi represent theCPE and the resistance of the zinc oxide products while 119876dland 119877ct represent the CPE of the double layer and the chargetransfer resistance respectively119882dif represents the Warburgimpedance CPE elements are typically applied in the EISfitting procedure to characterize the surface roughness atthe interface [35] or to describe the frequency dependenceof nonideal capacitive behavior [36] The impedance of theWarburg diffusion element 119885119908 follows
119885119908 = 120590 (1 minus 119895) 120596minus12 (4)
where 120590 is the Warburg coefficient in units of Ωsdotcm2sdotsminus12The CPE impedance is calculated using the following [35]
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
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4 International Journal of Spectroscopy
50
60
70
80
90
PAni-ZnO-ZRPPAni-ZRPZRP
Con
tact
angl
e (de
gree
)
(a)
100
200
300
400
500
600
700
PAni-ZnO-ZRPPAni-ZRPZRP
Coa
ting
resis
tivity
(o
hm cm
)
(b)
Figure 2 Contact angle (a) and coating resistivity 120588 (b) of PAni-ZRP and PAni-ZnO-ZRP
0 20 40 60 80 100 12060
65
70
75
80
85
90
pH
Time (day)PAni-ZRPPAni-ZnO-ZRP
(a)
0 10 20 30 40 50 60minus07
minus06
minus05
minus04
minus03
minus02
minus01
00
01W
eigh
t los
s (w
t)
Time (day)PAni-ZRPPAni-ZnO-ZRP
(b)
Figure 3 Solution pH and weight loss of sample PAni-ZRP and PAni-ZRP-ZnO over time
Later due to alkaline environment the corrosion of Zn maybe related to the following equations This makes the secondperiod exhibit a slowly increasing pH
The weight loss was negative meaning the formed zinc oxideproducts were compact and adhesive in the coating matrixpH value of coating PAni-ZRP is larger than PAni-ZnO-ZRPindicating the more reaction of zinc particles In additionthis agrees with the weight loss data PAni-ZRP gains more
weight than PAni-ZnO-ZRP Hence the addition of nano-ZnO in PAni-ZRP presents a slower zinc cathodic activa-tion
The surface morphologies of PAni-ZRP and PAni-ZnO-ZRP before test and after 60 d of immersion are shown inFigures 4 and 5 respectively The surface morphology ofcoating PAni-ZnO-ZRP is more uniform and has less poresthan PAni-ZRP (Figure 4) And after 60 d of immersionthe coating surface was covered by zinc oxide products theoxide products of PAni-ZnO-ZRP are more compact Thecross-sectional SEM images after 60 d and 120 d are shown inFigure 6 Zinc particles at the inner coating matrix were also
International Journal of Spectroscopy 5
20 m
(a)
20 m
(b)
Figure 4 Surface morphologies of PAni-ZRP (a) and PAni-nano-ZnO-ZRP (b) before test
40 m
(a)
0
20
40
60
80
100
SiC ClOZn
0203
193
467
335
PointAtomic percent (norm)
(b)
40 m
(c)
0
20
40
60
80
100
SiC ClOZn
0405
186
501
303
PointAtomic percent (norm)
(d)
Figure 5 Surface morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 d
reacted for PAni-ZRP after 60 d of immersion (Figure 6(a))The zinc oxide layer formed on PAni-ZnO-ZRP coating ismore compact than PAni-ZRP comparing Figure 5(a) and5(c) And the EDS mapping was conducted at the coatingmatrix by scanning an area of 40 120583m times 40 120583m (above thesteel substrate) Notably even before test the oxygen contentwas approximately 10 wt at the zinc particle surface becauseof the presence of native zinc oxide The EDS mappingsof element of Zn O Cl and Fe were detected to trackthe waterions transportation and cathodic reaction of zinc
particles in coatingsteel interface (Figure 7) Before 20 dthe mass percent of element O and Cl in coating PAni-ZRP is higher than PAni-ZnO-ZRP indicating that water andions transported to the coating PAni-ZRP interface quickerthan PAni-ZnO-ZRP This shows that the addition of nano-zinc oxide may reduce the passing routes of waterions andimproves the coating barrier performance in agreement withpublished literature [30] In addition a small amount of ironwas detected for PAni-ZRP at 120 d showing an localizedattack of substrate corrosion
6 International Journal of Spectroscopy
100 m
(a)
100 m
(b)
100 m
(c)
100 m
(d)
Figure 6 Cross-sectional morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 days (a amp c) and 120 days (b amp d)
0
40
50
60
70
80
90
100
120202
Mas
s per
cent
()
05
ZnOCl
Fe
Time (day)
(a)
0
40
50
60
70
80
90
100
Mas
s per
cent
()
12020205Time (day)
ZnOCl
(b)
Figure 7 EDS mapping of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at different immersion time
International Journal of Spectroscopy 7
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07O
CP (V
ver
sus S
CE)
Time (day)
(a)
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07
OCP
(V v
ersu
s SCE
)
Time (day)
(b)
Figure 8 OCP changes over time for PAni-ZRP (a) and PAni-ZnO-ZRP (b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
(a)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
QＩＲＣ
RＩＲＣ
(b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
W＞Ｃ
(c)
Figure 9 Electric equivalent circuits (EECs) models applied for EIS data fitting
32 OCP and EIS Results and Discussion OCP can be cor-related to the anticorrosion performance stages of ZRP [2]Three main periods were differentiated in the ZRPrsquos lifetimeafter immersion in 3 NaCl solution (a) the ldquoactivationrdquoperiod corrosion potential shifts to cathodic values (b) in asecond period the electrode potential shifts to more anodicvalue and then reached the limit of CP (c) at the thirdperiod the corrosion potential is out of the CP range andthe coating provided barrier protection depending on theformed zinc oxide products and coating morphology Thechanges of OCP of PAni-ZRP and PAni-ZnO-ZRP coatingswere detected after being immersed in 35 wtNaCl solutionfrom time to time The OCP for steel 1018 was tested beingminus860mV versus SCE which will be the limit potential ofeffective CP range That is when OCP is more anodic thanminus860mV the cathodic protection provided by zinc particlesdisappears [31] As shown in Figure 8 OCP increased slightlyover time after 5 d immersion for the two coating systems Butthe potential is still inOCP range lower thanminus860mV versusSCE which is the corrosion potential of bare steel used in thiswork
Interestingly the OCP presents a decreasing period intwo different slopes at initial 5 d immersion except the sharpincrease for PAni-ZRP a faster slope and a slower slope inagreement with the published work [2] The higher slope isrelated to the activation of zinc particle and increasing arearation of ZnFe and the slower decreasing slope was dueto the increasing contact resistance between zinc particlesLater the formation of zinc oxide productsmade the potentialshift towards anodic value Comparing these two coatingsystems PAni-ZnO-ZRP coating system has more stable
OCP than PAni-ZRP during the initial period The sharpincrease in OCP value for PAni-ZRP is because of the quickand accumulated formation of zinc oxide in coating interface
The EIS results were fitted using equivalent electricalcircuits (EECs) models to get valuable parameters related tocoating evolution as shown in Figure 9 These EEC modelshave been used in many published studies related to ZRPs[32ndash34] 119877119904 represents the electrolyte resistance 119876119888 and 119877119888represent the constant phase element (CPE) and the resis-tance of the coating respectively 119876oxi and 119877oxi represent theCPE and the resistance of the zinc oxide products while 119876dland 119877ct represent the CPE of the double layer and the chargetransfer resistance respectively119882dif represents the Warburgimpedance CPE elements are typically applied in the EISfitting procedure to characterize the surface roughness atthe interface [35] or to describe the frequency dependenceof nonideal capacitive behavior [36] The impedance of theWarburg diffusion element 119885119908 follows
119885119908 = 120590 (1 minus 119895) 120596minus12 (4)
where 120590 is the Warburg coefficient in units of Ωsdotcm2sdotsminus12The CPE impedance is calculated using the following [35]
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
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Submit your manuscripts atwwwhindawicom
International Journal of Spectroscopy 5
20 m
(a)
20 m
(b)
Figure 4 Surface morphologies of PAni-ZRP (a) and PAni-nano-ZnO-ZRP (b) before test
40 m
(a)
0
20
40
60
80
100
SiC ClOZn
0203
193
467
335
PointAtomic percent (norm)
(b)
40 m
(c)
0
20
40
60
80
100
SiC ClOZn
0405
186
501
303
PointAtomic percent (norm)
(d)
Figure 5 Surface morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 d
reacted for PAni-ZRP after 60 d of immersion (Figure 6(a))The zinc oxide layer formed on PAni-ZnO-ZRP coating ismore compact than PAni-ZRP comparing Figure 5(a) and5(c) And the EDS mapping was conducted at the coatingmatrix by scanning an area of 40 120583m times 40 120583m (above thesteel substrate) Notably even before test the oxygen contentwas approximately 10 wt at the zinc particle surface becauseof the presence of native zinc oxide The EDS mappingsof element of Zn O Cl and Fe were detected to trackthe waterions transportation and cathodic reaction of zinc
particles in coatingsteel interface (Figure 7) Before 20 dthe mass percent of element O and Cl in coating PAni-ZRP is higher than PAni-ZnO-ZRP indicating that water andions transported to the coating PAni-ZRP interface quickerthan PAni-ZnO-ZRP This shows that the addition of nano-zinc oxide may reduce the passing routes of waterions andimproves the coating barrier performance in agreement withpublished literature [30] In addition a small amount of ironwas detected for PAni-ZRP at 120 d showing an localizedattack of substrate corrosion
6 International Journal of Spectroscopy
100 m
(a)
100 m
(b)
100 m
(c)
100 m
(d)
Figure 6 Cross-sectional morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 days (a amp c) and 120 days (b amp d)
0
40
50
60
70
80
90
100
120202
Mas
s per
cent
()
05
ZnOCl
Fe
Time (day)
(a)
0
40
50
60
70
80
90
100
Mas
s per
cent
()
12020205Time (day)
ZnOCl
(b)
Figure 7 EDS mapping of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at different immersion time
International Journal of Spectroscopy 7
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07O
CP (V
ver
sus S
CE)
Time (day)
(a)
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07
OCP
(V v
ersu
s SCE
)
Time (day)
(b)
Figure 8 OCP changes over time for PAni-ZRP (a) and PAni-ZnO-ZRP (b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
(a)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
QＩＲＣ
RＩＲＣ
(b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
W＞Ｃ
(c)
Figure 9 Electric equivalent circuits (EECs) models applied for EIS data fitting
32 OCP and EIS Results and Discussion OCP can be cor-related to the anticorrosion performance stages of ZRP [2]Three main periods were differentiated in the ZRPrsquos lifetimeafter immersion in 3 NaCl solution (a) the ldquoactivationrdquoperiod corrosion potential shifts to cathodic values (b) in asecond period the electrode potential shifts to more anodicvalue and then reached the limit of CP (c) at the thirdperiod the corrosion potential is out of the CP range andthe coating provided barrier protection depending on theformed zinc oxide products and coating morphology Thechanges of OCP of PAni-ZRP and PAni-ZnO-ZRP coatingswere detected after being immersed in 35 wtNaCl solutionfrom time to time The OCP for steel 1018 was tested beingminus860mV versus SCE which will be the limit potential ofeffective CP range That is when OCP is more anodic thanminus860mV the cathodic protection provided by zinc particlesdisappears [31] As shown in Figure 8 OCP increased slightlyover time after 5 d immersion for the two coating systems Butthe potential is still inOCP range lower thanminus860mV versusSCE which is the corrosion potential of bare steel used in thiswork
Interestingly the OCP presents a decreasing period intwo different slopes at initial 5 d immersion except the sharpincrease for PAni-ZRP a faster slope and a slower slope inagreement with the published work [2] The higher slope isrelated to the activation of zinc particle and increasing arearation of ZnFe and the slower decreasing slope was dueto the increasing contact resistance between zinc particlesLater the formation of zinc oxide productsmade the potentialshift towards anodic value Comparing these two coatingsystems PAni-ZnO-ZRP coating system has more stable
OCP than PAni-ZRP during the initial period The sharpincrease in OCP value for PAni-ZRP is because of the quickand accumulated formation of zinc oxide in coating interface
The EIS results were fitted using equivalent electricalcircuits (EECs) models to get valuable parameters related tocoating evolution as shown in Figure 9 These EEC modelshave been used in many published studies related to ZRPs[32ndash34] 119877119904 represents the electrolyte resistance 119876119888 and 119877119888represent the constant phase element (CPE) and the resis-tance of the coating respectively 119876oxi and 119877oxi represent theCPE and the resistance of the zinc oxide products while 119876dland 119877ct represent the CPE of the double layer and the chargetransfer resistance respectively119882dif represents the Warburgimpedance CPE elements are typically applied in the EISfitting procedure to characterize the surface roughness atthe interface [35] or to describe the frequency dependenceof nonideal capacitive behavior [36] The impedance of theWarburg diffusion element 119885119908 follows
119885119908 = 120590 (1 minus 119895) 120596minus12 (4)
where 120590 is the Warburg coefficient in units of Ωsdotcm2sdotsminus12The CPE impedance is calculated using the following [35]
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
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Submit your manuscripts atwwwhindawicom
6 International Journal of Spectroscopy
100 m
(a)
100 m
(b)
100 m
(c)
100 m
(d)
Figure 6 Cross-sectional morphologies of PAni-ZRP (a amp b) and PAni-nano-ZnO-ZRP (c amp d) after 60 days (a amp c) and 120 days (b amp d)
0
40
50
60
70
80
90
100
120202
Mas
s per
cent
()
05
ZnOCl
Fe
Time (day)
(a)
0
40
50
60
70
80
90
100
Mas
s per
cent
()
12020205Time (day)
ZnOCl
(b)
Figure 7 EDS mapping of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at different immersion time
International Journal of Spectroscopy 7
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07O
CP (V
ver
sus S
CE)
Time (day)
(a)
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07
OCP
(V v
ersu
s SCE
)
Time (day)
(b)
Figure 8 OCP changes over time for PAni-ZRP (a) and PAni-ZnO-ZRP (b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
(a)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
QＩＲＣ
RＩＲＣ
(b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
W＞Ｃ
(c)
Figure 9 Electric equivalent circuits (EECs) models applied for EIS data fitting
32 OCP and EIS Results and Discussion OCP can be cor-related to the anticorrosion performance stages of ZRP [2]Three main periods were differentiated in the ZRPrsquos lifetimeafter immersion in 3 NaCl solution (a) the ldquoactivationrdquoperiod corrosion potential shifts to cathodic values (b) in asecond period the electrode potential shifts to more anodicvalue and then reached the limit of CP (c) at the thirdperiod the corrosion potential is out of the CP range andthe coating provided barrier protection depending on theformed zinc oxide products and coating morphology Thechanges of OCP of PAni-ZRP and PAni-ZnO-ZRP coatingswere detected after being immersed in 35 wtNaCl solutionfrom time to time The OCP for steel 1018 was tested beingminus860mV versus SCE which will be the limit potential ofeffective CP range That is when OCP is more anodic thanminus860mV the cathodic protection provided by zinc particlesdisappears [31] As shown in Figure 8 OCP increased slightlyover time after 5 d immersion for the two coating systems Butthe potential is still inOCP range lower thanminus860mV versusSCE which is the corrosion potential of bare steel used in thiswork
Interestingly the OCP presents a decreasing period intwo different slopes at initial 5 d immersion except the sharpincrease for PAni-ZRP a faster slope and a slower slope inagreement with the published work [2] The higher slope isrelated to the activation of zinc particle and increasing arearation of ZnFe and the slower decreasing slope was dueto the increasing contact resistance between zinc particlesLater the formation of zinc oxide productsmade the potentialshift towards anodic value Comparing these two coatingsystems PAni-ZnO-ZRP coating system has more stable
OCP than PAni-ZRP during the initial period The sharpincrease in OCP value for PAni-ZRP is because of the quickand accumulated formation of zinc oxide in coating interface
The EIS results were fitted using equivalent electricalcircuits (EECs) models to get valuable parameters related tocoating evolution as shown in Figure 9 These EEC modelshave been used in many published studies related to ZRPs[32ndash34] 119877119904 represents the electrolyte resistance 119876119888 and 119877119888represent the constant phase element (CPE) and the resis-tance of the coating respectively 119876oxi and 119877oxi represent theCPE and the resistance of the zinc oxide products while 119876dland 119877ct represent the CPE of the double layer and the chargetransfer resistance respectively119882dif represents the Warburgimpedance CPE elements are typically applied in the EISfitting procedure to characterize the surface roughness atthe interface [35] or to describe the frequency dependenceof nonideal capacitive behavior [36] The impedance of theWarburg diffusion element 119885119908 follows
119885119908 = 120590 (1 minus 119895) 120596minus12 (4)
where 120590 is the Warburg coefficient in units of Ωsdotcm2sdotsminus12The CPE impedance is calculated using the following [35]
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
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SpectroscopyAnalytical ChemistryInternational Journal of
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Submit your manuscripts atwwwhindawicom
International Journal of Spectroscopy 7
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07O
CP (V
ver
sus S
CE)
Time (day)
(a)
0 1 2 3 4 5 20 40 60 80 100 120
minus11
minus10
minus09
minus08
minus07
OCP
(V v
ersu
s SCE
)
Time (day)
(b)
Figure 8 OCP changes over time for PAni-ZRP (a) and PAni-ZnO-ZRP (b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
(a)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
QＩＲＣ
RＩＲＣ
(b)
Rs
Qc
Rc
R＝Ｎ
Q＞Ｆ
W＞Ｃ
(c)
Figure 9 Electric equivalent circuits (EECs) models applied for EIS data fitting
32 OCP and EIS Results and Discussion OCP can be cor-related to the anticorrosion performance stages of ZRP [2]Three main periods were differentiated in the ZRPrsquos lifetimeafter immersion in 3 NaCl solution (a) the ldquoactivationrdquoperiod corrosion potential shifts to cathodic values (b) in asecond period the electrode potential shifts to more anodicvalue and then reached the limit of CP (c) at the thirdperiod the corrosion potential is out of the CP range andthe coating provided barrier protection depending on theformed zinc oxide products and coating morphology Thechanges of OCP of PAni-ZRP and PAni-ZnO-ZRP coatingswere detected after being immersed in 35 wtNaCl solutionfrom time to time The OCP for steel 1018 was tested beingminus860mV versus SCE which will be the limit potential ofeffective CP range That is when OCP is more anodic thanminus860mV the cathodic protection provided by zinc particlesdisappears [31] As shown in Figure 8 OCP increased slightlyover time after 5 d immersion for the two coating systems Butthe potential is still inOCP range lower thanminus860mV versusSCE which is the corrosion potential of bare steel used in thiswork
Interestingly the OCP presents a decreasing period intwo different slopes at initial 5 d immersion except the sharpincrease for PAni-ZRP a faster slope and a slower slope inagreement with the published work [2] The higher slope isrelated to the activation of zinc particle and increasing arearation of ZnFe and the slower decreasing slope was dueto the increasing contact resistance between zinc particlesLater the formation of zinc oxide productsmade the potentialshift towards anodic value Comparing these two coatingsystems PAni-ZnO-ZRP coating system has more stable
OCP than PAni-ZRP during the initial period The sharpincrease in OCP value for PAni-ZRP is because of the quickand accumulated formation of zinc oxide in coating interface
The EIS results were fitted using equivalent electricalcircuits (EECs) models to get valuable parameters related tocoating evolution as shown in Figure 9 These EEC modelshave been used in many published studies related to ZRPs[32ndash34] 119877119904 represents the electrolyte resistance 119876119888 and 119877119888represent the constant phase element (CPE) and the resis-tance of the coating respectively 119876oxi and 119877oxi represent theCPE and the resistance of the zinc oxide products while 119876dland 119877ct represent the CPE of the double layer and the chargetransfer resistance respectively119882dif represents the Warburgimpedance CPE elements are typically applied in the EISfitting procedure to characterize the surface roughness atthe interface [35] or to describe the frequency dependenceof nonideal capacitive behavior [36] The impedance of theWarburg diffusion element 119885119908 follows
119885119908 = 120590 (1 minus 119895) 120596minus12 (4)
where 120590 is the Warburg coefficient in units of Ωsdotcm2sdotsminus12The CPE impedance is calculated using the following [35]
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
International Journal ofInternational Journal ofPhotoenergy
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
16 times 104
12 times 104
80 times 103
40 times 103
00
00 16 times 10412 times 10480 times 10340 times 103
Zrea (ohm cＧ2)
PAni-ZnO-ZRP Day 60 Day 120PAni-ZRP Day 60 Day 120
minusZi
mag
(ohm
cＧ2)
(c) Third stage
Figure 10 EIS diagrams of PAni-ZRP and PAni-ZnO-ZRP at different stages
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
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Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
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Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
SpectroscopyAnalytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
MaterialsJournal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
BioMed Research International Electrochemistry
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Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
International Journal of Spectroscopy 9
Table 1 EIS fitting parameters of PAni-ZRP and PAni-ZnO-ZRP
(a) Day 1 fitted using EEC shown in Figure 9(a)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 791 times 10minus7 062 874 times 104 784 times 10minus6 049 142 times 105PAni-ZnO-ZRP 728 times 10minus8 074 107 times 105 109 times 10minus6 051 623 times 105
(b) Day 2 fitted using EEC shown in Figure 9(b)
Coating system 119884119888 (Ssdots119899sdotcmminus2) 119899119888 119877119888 (Ωsdotcm2) 119884oxi (Ssdots119899sdotcmminus2) 119899oxi 119877oxi (Ωsdotcm2) 119884dl (Ssdots119899sdotcmminus2) 119899dl 119877ct (Ωsdotcm2)PAni-ZRP 127 times 10minus7 077 1051 182 times 10minus6 043 156 times 105 134 times 10minus5 058 218 times 105PAni-ZnO-ZRP 160 times 10minus8 075 7789 202 times 10minus8 048 429 times 105 457 times 10minus5 072 235 times 105
(c) Days 20 60 and 120 fitted using EEC shown in Figure 9(c)
Day 20 520 times 10minus7 071 1526 641 times 10minus5 032 5441 12057Day 60 278 times 10minus6 059 1679 266 times 10minus6 087 5466 29798Day 120 979 times 10minus7 065 1186 554 times 10minus5 035 5260 76884
PAni-ZnO-ZRPDay 20 369 times 10minus6 059 280 824 times 10minus5 039 878 10402Day 60 570 times 10minus6 056 3902 12 times 10minus4 042 895 10475Day 120 441 times 10minus7 070 3196 120 times 10minus4 020 6680 41375
time constants were observed in Nyquist diagram at thevery beginning fitted by EEC shown in Figure 9(a) Initiallycoating PAni-ZnO-ZRP has larger119877119888 and119877ct than PAni-ZRPThis confirms the above immersion test results and SEMEDSresults Pigments in the paint would induce pores andnanostructure powders can fill in these pores to formuniformpaint interface When being immersed in corrosive environ-ment it would prevent the transportation of electrolyte andcorrosive ions Then quickly after 2 d three time constantswere observed and EEC shown in Figure 9(b) was used to fitthe dataThe semicircle at high frequencies was related to theorganic coatingmatrix the semicircle at medium frequencieswas associated with the native zinc oxides and the one atlow frequencies was considered to represent the activationof the zinc particles when the electrolyte diffused throughzinc oxide to reach the metallic zinc surface At this stage thecoating PAni-ZnO-ZRP has larger 119877119888 and 119877ct than PAni-ZRP(Tables 1(a) and 1(b)) which explains the slower cathodicactivation of zinc particles
Over time Nyquist diagram presents a circuit with twotime constants combined with a small diffusion signal tail forboth two coatings (Figure 10(b)) which was fitted using EECshown in Figure 9(c)The diffusion signal appeared when thecoatingwas covered by compact zinc oxide productsNotablyfor PAni-ZnO-ZRP the diffusion-controlled mechanismsrsquotransport processes were recognized earlier in time (Day 8)than for PAni-ZRP (Day 10) Over 120 days (Figure 10(c))the diffusion signal becamemore obvious and the impedanceincreased Comparing with PAni-ZRP PAni-ZnO-ZRP haslarger 119877ct but smaller diffusion coefficient 120590 (Table 1(c)) It
makes sense that for PAni-ZRP the assumption of zinc par-ticles is faster than PAni-ZnO-ZRP confirmed from weightgain data in Figure 3(b) This formed more zinc corrosionproducts which made the diffusion of oxygen much moredifficult The higher 119877ct for PAni-ZnO-ZRP with slowlyincreasing 119877119888 indicated the cathodic reaction of zinc particlesslow and stable compared with PAni-ZnO
For EIS results resistance 119877119905 at different frequencies werealso extracted from bode modulus plots which provided thevisual ideas of coating interface properties as discussed inmany literatures [23 24 37] For both two coating systemsthree stageswere obtained during 120 days of immersion (Fig-ure 11) which agrees with OCP results First the activationstage was characterized by a dramatically decreasing coatingresistance Then it is the competition stage characterized byan increasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing resistance for PAni-ZnO-ZRP
It is interesting that PAni-ZRP and PAni-ZnO-ZRPshowed a very different performance during the initial fewdays (Figure 12) For PAni-ZRP the first decreasing stage(0ndashDay 3) was combined by two repeat pattern substagesThe first substage is from the beginning to 4 h when theimpedance dropped dramatically at all frequencies related toactivation of zinc particles After 4 h till 15 h the impedanceincreased due to the formation of zinc oxides Then theimpedance was kept stable till 51 h This is considered as thefirst substage Similarly the impedance dropped drasticallyagain followed by increasing impedance From 57 h to 68 hthe impedance at frequencies lower than and including 10Hz
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
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Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
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ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
10 International Journal of Spectroscopy
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 2 4 20 40 60 80 100 120Time (day)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 11 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) over 120 days
0 12 24 36 48 60 72 84 96Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(a)
0 12 24 36 48 60 72Time (hour)
106
105
104
103
102
100 （Ｔ
10（Ｔ
1（Ｔ
01 （Ｔ
001 （Ｔ
(ohm
cＧ2)
Rt
(b)
Figure 12 119877119905 value at various frequencies of PAni-ZRP (a) and PAni-ZnO-ZRP (b) at initial stage
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
International Journal ofInternational Journal ofPhotoenergy
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
SpectroscopyAnalytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
MaterialsJournal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
BioMed Research International Electrochemistry
International Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
International Journal of Spectroscopy 11
was stable while the one at medium and high frequenciesdecreased and was then stable This was considered as thesecond substage These two substages were correlated to theactivation of zinc particle in this coating interface indicatingthat this process is not stable In regard of PAni-ZnO-ZRPthree substages were observed the fast decreasing that isfirst 4 hours of immersion After 4 h to 25 h the impedancedecreased at a slower speed while after 25 hours 119877119905 slightlyincreased It can also be seen that for the initial stage PAni-ZnO-ZRP has larger and more stable impedance comparedwith PAni-ZRP This analysis indicated that the activationof zinc particles occurred much more slowly which needslocalized electrochemical technique to study
33 SVET Results and Discussion
331 SVET Data Analysis Methodology After SVET teststhe potential density was transferred to a current densitydisplayed in a three-dimensional (3D) map The currentmapping shows the spatial distribution of the current densityas a function of the (119909 119910) position in the scan region onZRPs In addition the contour map of the current densitiesis at the bottom of the 3D map Considering the signalof current in the mapping the negative current value iscorrelated with cathodic reaction mainly occurring on steelsurface while the positive current values are correlated withanodic reaction that occur at the zinc primer surface SVETmaps have been collected during 60 h of immersion for eachsample The total cathodic and anodic currents have beencalculated at the scanning area to obtain the evolution of totalcurrent density over time which has been applied in analysisof a massive amount of local ionic current distribution datamaps [38] The total anodic current density 119868119860 and cathodicionic current density 119868119862 are calculated by integrating thecurrent density 119894119911 distribution across the scan area at differenttimes as shown in
where 119909max 119909min 119910max and 119910min are the coordinates ofthe scanning area The evolutions of 119868119860 and 119868119862 have beencalculated to compare these two coatings It should be noticedthat SVET is not always able to capture all of the localizedcurrents [12] It has been reported that SVET may not detectthe activity occurring under the scanning plane if the galvanicinteraction of the anodic and cathodic microsites occurslocally on the sample surface and the circulation of cationsand anions is concentrated essentially below the scan planeThe imbalance of anodic current and cathodic current hasbeen discussed in [12 33 39] To check this value the totalcurrent was calculated following
119868int = 119868119860 minus 119868119862 (7)
332 SVET Results and Discussion The SVET current den-sity maps together with contours for PAni-ZRP and PAni-ZnO-ZRP are presented in Figures 13 and 14 respectively asa function of immersion time The characteristic parameters119868int 119868119860 119868119862 are shown in Figure 15 For PAni-ZRP the anodiccurrent was observed at zinc-rich primer and cathodic cur-rent was detected on the steel surface after 6 h of immersionindicating the activation of zinc cathodic protection Thecurrent 119868119860 119868119862 increased fast during the following 24 h Thenthe current decreased and few anodic peaks were obtainedon the ZRP surface For PAni-ZnO-ZRP anodic peaks wereobserved on ZRP surface at 6 h same as PAni-ZRP relatedto the activation of zinc particles The current 119868119860 119868119862 slightlyincreased during initial few hours and became homogeneousafter 8 h However this continuity disappeared after 24 hAnodic bumps were obtained at the ZRP surface especiallyat 60 h
The characteristic parameters showed totally differentbehaviors for these two coatings Four different stages wereobserved fromFigure 15The sacrificial cathodic reactionwasactivated with a quick increase of 119868119860 and 119868119862 till 30 h Thisperiod is related to the cathodic reaction of zinc particlesduring activation stageThe formation of zinc oxide productsmade the current decrease similar to these two coatings ForPAni-ZnO-ZRP the third stage occurred during 30 h to 48 hwhen 119868119860 and 119868119862 remained stable Later 119868119860 and 119868119862 increasedagain which is not seen for PAni-ZRP The sudden increaseof current and anodiccathodic peak obtained at 60 h may berelated to the combination of PAni and ZnO whichmay forma 119901-119899 junction allowing the electrons to transport in onlyone direction in paint film [9] Interestingly PAni-ZnO-ZRPpresents much smaller current value during 60 h of immer-sion compared with PAni-ZRP This further proves that theaddition of ZnO in PAni-ZRP makes the cathodic reactionof zinc particles slower What is more 119868119860 and 119868119862 in PAni-ZnO-ZRP decreased at earlier time than PAni-ZRP afterforming zinc oxide products in coatingmatrix indicating thatZnOnanostructured particles improve coating barrier withinreduction of passing routes used by electrolyte and corrosiveions
As discussed above three stages were observed by bothOCP and EIS analysis First the activation stage was char-acterized by decreasing 119877ct Then the cathodic activationformed zinc oxide corrosion products in the coating matrixconfirmed using SEMEDS which increased the Zn-to-Zncontact resistance But Zn-to-Fe area ratio is also increasedaccompanied with the transportation of electrolyte and ionsThis is considered as the competition stage characterizedwitha decreasing 119877ct and an increasing diffusion resistance After60 d the stable stage was attained with a constant 119877ct exceptDay 120 and an increasing diffusion resistance
ZRP provides two protection mechanisms barrier pro-tection and CP The barrier protection was demonstratedthrough immersion tests and surfacemorphologiesThe SEMdata show that the addition of nano-zinc oxide powders incoating matrix tends to produce less pores uniform coatinginterface resulting in much larger initial 119877119888 value from EISfitting data Besides a diffusion-controlled process appearedearlier than observed for PAni-ZRP which further proves
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
International Journal ofInternational Journal ofPhotoenergy
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
Figure 13 SVET current density maps for PAni-ZRP at different immersion time
that the addition of ZnO improved the coating interfacemorphologies In regard of CP effect over 120 days ofimmersion these two coatings are still in CP effective periodthrough OCP test Both EIS and SVET results show that theaddition of nano-ZnO makes the cathodic activation of zincslower and more stable In our previous study conductivepolyaniline improved the Zn-to-Zn connection conductionof zinc-rich primer referred to as percolation conditionwhich is critical for CP period That is why over 120 daysZRP added with PAni are still in CP period Considering the
addition of nano-ZnO it does not improve the percolationcondition but it filled in the pores caused by zinc and PAniparticles which improves barrier performance The uniformcoating interface plus the good Zn-to-Zn connection helps toslow cathodic reaction of zinc confirmed by EIS and SVETresults Another proposed mechanism is that ZnO andorZn2+ can interact with PAni and change its morphology intocompact clusters on the metalpolymer interface which hasbeen detected using localized electrochemical test SVETThiswould facilitate formation of passive layer and hereby prevent
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
International Journal ofInternational Journal ofPhotoenergy
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
Figure 14 SVET current density maps for PAni-ZnO-ZRP at different immersion time
further corrosion [12] But this needs further continuingstudy
4 Conclusion
Effect of zinc oxide nano particles on corrosion performancehas been studied in conductive polyaniline containing zinc-rich primer using Electrochemical Impedance Spectroscopy(EIS) and localized electrochemical Scanning Vibrating Elec-trode Technique (SVET) The results showed that the addi-tion of nano-zinc oxide particles increased coating barrier
performance And nano-ZnO in coating matrix made thecathodic reaction of zinc more stable and slower furtherto increase the effective cathodic protection period Thecombination of PAni and ZnO was confirmed by SVET test
For both two coating systems three stages were obtainedduring 120 days of immersion First the activation stagewas characterized by a decreasing charge transfer resistance119877ct Then it is the competition stage characterized by anincreasing ZnFe area ratio and increasing zinc contactresistance After 60 d the stable stage was obtained with aslightly increasing diffusion resistance
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
International Journal ofInternational Journal ofPhotoenergy
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
SpectroscopyAnalytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
MaterialsJournal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
BioMed Research International Electrochemistry
International Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
14 International Journal of Spectroscopy
0 10 20 30 40 50 60
minus400
minus300
minus200
minus100
0
100
200
300
400
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(a)
0 10 20 30 40 50 60
minus60
minus40
minus20
0
20
40
60
Time (hour)
(AmiddotcＧ
minus2)
I
IAICIＣＨＮ
(b)
Figure 15 Characteristic parameters of SVET results above the scratched PAni-ZRP (a) and PAni-ZnO-ZRP (b) in 001 wt NaCl solution
Conflicts of Interest
The authors declare that there are no conflicts of interestregarding the publication of this paper
References
[1] D Pereira J D Scantlebury M G S Ferreira and M EAlmeida ldquoThe application of electrochemical measurementsto the study and behaviour of zinc-rich coatingsrdquo CorrosionScience vol 30 no 11 pp 1135ndash1147 1990
[2] C M Abreu M Izquierdo M Keddam X R Novoa andH Takenouti ldquoElectrochemical behaviour of zinc-rich epoxypaints in 3 NaCl solutionrdquo Electrochimica Acta vol 41 no 15pp 2405ndash2415 1996
[3] H Marchebois M Keddam C Savall J Bernard and STouzain ldquoZinc-rich powder coatings characterisation in artifi-cial sea water EIS analysis of the galvanic actionrdquo ElectrochimicaActa vol 49 no 11 pp 1719ndash1729 2004
[4] P J Kinlen Y Ding and D C Silverman ldquoCorrosion protec-tion of mild steel using sulfonic and phosphonic acid-dopedpolyanilinesrdquo Corrosion vol 58 no 6 pp 490ndash497 2002
[5] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgressin preparation processing and applications of polyanilinerdquoProgress in Polymer Science vol 34 no 8 pp 783ndash810 2009
[6] N Y Abu-Thabit and A S H Makhlouf ldquo17 -Recent advancesin polyaniline (PANI)-based organic coatings for corrosion pro-tectionrdquo inHandbook of Smart Coatings forMaterials ProtectionA S H Makhlouf Ed pp 459ndash486 Woodhead Publishing2014
[7] A Meroufel C Deslouis and S Touzain ldquoElectrochemicaland anticorrosion performances of zinc-rich and polyaniline
[8] X Li D Yang and H Castaneda ldquoEffect of different oxidationstates of polyaniline on anticorrosion performances ofmodifiedzinc rich primerrdquo in CORROSION 2016 NACE International2016
[9] A Mostafaei and F Nasirpouri ldquoEpoxypolyaniline-ZnOnanorods hybrid nanocomposite coatings Synthesis character-ization and corrosion protection performance of conductingpaintsrdquo Progress in Organic Coatings vol 77 no 1 pp 146ndash1592014
[10] S Sathiyanarayanan S S Azim and G Venkatachari ldquoCorro-sion protection of magnesium ZM 21 alloy with polyaniline-TiO2 composite containing coatingsrdquo Progress in Organic Coat-ings vol 59 no 4 pp 291ndash296 2007
[11] S Sathiyanarayanan S S Azim and G Venkatachari ldquoPrepa-ration of polyaniline-Fe2O3 composite and its anticorrosionperformancerdquo Synthetic Metals vol 157 no 18-20 pp 751ndash7572007
[12] A Alvarez-Pampliega S V Lamaka M G Taryba et al ldquoCut-edge corrosion study on painted aluminum richmetallic coatedsteel by scanning vibrating electrode andmicro-potentiometrictechniquesrdquo Electrochimica Acta vol 61 pp 107ndash117 2012
[13] C F Glover R Subramanian and G Williams ldquoIn-coatingphenyl phosphonic acid as an etch-primer corrosion inhibitorsystem for hot dip galvanized steelrdquo Journal ofThe Electrochem-ical Society vol 162 no 9 pp C433ndashC441 2015
[14] M Kendig F Mansfeld and S Tsai ldquoDetermination of the longterm corrosion behavior of coated steel with AC impedancemeasurementsrdquo Corrosion Science vol 23 no 4 pp 317ndash3291983
[15] J Titz G H Wagner H Spaehn M Ebert K Juettnerand W J Lorenz ldquoCharacterization of organic coatings on
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
International Journal ofInternational Journal ofPhotoenergy
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
SpectroscopyAnalytical ChemistryInternational Journal of
Hindawiwwwhindawicom Volume 2018
MaterialsJournal of
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
BioMed Research International Electrochemistry
International Journal of
Hindawiwwwhindawicom Volume 2018
Na
nom
ate
ria
ls
Hindawiwwwhindawicom Volume 2018
Journal ofNanomaterials
Submit your manuscripts atwwwhindawicom
International Journal of Spectroscopy 15
metal substrates by electrochemical impedance spectroscopyrdquoCorrosion vol 46 no 3 pp 221ndash229 1990
[16] F Mansfeld and C H Tsail ldquoDetermination of coating deterio-ration with EIS I Basic relationshipsrdquo Corrosion vol 47 no 12pp 958ndash963 1991
[17] CH Tsai and FMansfeld ldquoDetermination of coating deteriora-tion with EIS part II development of a method for field testingof protective coatingsrdquo Corrosion vol 49 no 9 pp 726ndash7371993
[18] J R Macdonald ldquoImpedance spectroscopy old problems andnew developmentsrdquo Electrochimica Acta vol 35 no 10 pp1483ndash1492 1990
[19] CGOliveira andMG S Ferreira ldquoRanking high-quality paintsystems using EIS Part I Intact coatingsrdquoCorrosion Science vol45 no 1 pp 123ndash138 2003
[20] C G Oliveira and M G S Ferreira ldquoRanking high-qualitypaint systems using EIS Part II Defective coatingsrdquo CorrosionScience vol 45 no 1 pp 139ndash147 2003
[21] X M Li B Faber B Minch and H Castaneda ldquoAnalysisof soft coating corrosion performance on carbon steel usingelectrochemical impedance spectroscopyrdquo Corrosion vol 70no 6 pp 615ndash626 2014
[22] B R Hinderliter S G Croll D E Tallman Q Su and G PBierwagen ldquoInterpretation of EIS data from accelerated expo-sure of coated metals based on modeling of coating physicalpropertiesrdquo Electrochimica Acta vol 51 no 21 pp 4505ndash45152006
[23] M Mahdavian and M M Attar ldquoAnother approach in analysisof paint coatings with EIS measurement Phase angle at highfrequenciesrdquo Corrosion Science vol 48 no 12 pp 4152ndash41572006
[24] Y Zuo R Pang W Li J P Xiong and Y M Tang ldquoTheevaluation of coating performance by the variations of phaseangles inmiddle and high frequency domains of EISrdquoCorrosionScience vol 50 no 12 pp 3322ndash3328 2008
[25] E Akbarinezhad M Bahremandi H R Faridi and F RezaeildquoAnother approach for ranking and evaluating organic paintcoatings via electrochemical impedance spectroscopyrdquo Corro-sion Science vol 51 no 2 pp 356ndash363 2009
[26] X Li and H Castaneda ldquoCoating studies of buried pipe in soilby novel approach of electrochemical impedance spectroscopyat wide frequency domainrdquo Corrosion Engineering Science andTechnology vol 50 no 3 pp 218ndash225 2015
[27] S Li ldquoMonitoring corrosion using vibrational spectroscopictechniquesrdquo in Intelligent Coatings for Corrosion Control pp673ndash701 Butterworth-Heinemann Boston Mass USA 2015
[28] H S Isaacs ldquoThe measurement of the galvanic corrosionof soldered copper using the scanning vibrating electrodetechniquerdquo Corrosion Science vol 28 no 6 pp 547ndash558 1988
[29] A International Standard Practice for Surface Wettability ofCoatings Substrates and Pigments by Advancing Contact AngleMeasurement ASTM International Conshohocken Pa USA2013
[30] S K Dhoke and A S Khanna ldquoStudy on electrochemicalbehavior of nano-ZnO modified alkyd-based waterborne coat-ingsrdquo Journal of Applied Polymer Science vol 113 no 4 pp2232ndash2237 2009
[31] H Marchebois S Joiret C Savall J Bernard and S TouzainldquoCharacterization of zinc-rich powder coatings by EIS andRaman spectroscopyrdquo Surface and Coatings Technology vol 157no 2-3 pp 151ndash161 2002
[32] J S Francisco V R Capelossi and I V Aoki ldquoEvaluation ofa sulfursilane anticorrosive pretreatment on galvannealed steelcompared to phosphate under a waterborne epoxy coatingrdquoElectrochimica Acta vol 124 pp 128ndash136 2014
[33] A G Marques and A M Simoes ldquoEIS and SVET assessment ofcorrosion resistance of thin Zn-55 Al-rich primers Effect ofimmersion and of controlled deformationrdquo Electrochimica Actavol 148 pp 153ndash163 2014
[34] S Sathiyanarayanan S Syed Azim and G Venkatachari ldquoCor-rosion protection coating containing polyaniline glass flakecomposite for steelrdquoElectrochimicaActa vol 53 no 5 pp 2087ndash2094 2008
[35] C H Hsu and F Mansfeld ldquoConcernng the conversion ofthe constant phase element parameter Y0 into a capacitancerdquoCorrosion vol 57 no 9 pp 747-748 2001
[36] S Skale V Dolecek and M Slemnik ldquoSubstitution of theconstant phase element by Warburg impedance for protectivecoatingsrdquo Corrosion Science vol 49 no 3 pp 1045ndash1055 2007
[37] I Sekine K Sakaguchi and M Yuasa ldquoEstimation and predic-tion of degradation of coating films by frequency at maximumphase anglerdquo Journal of Coatings Technology vol 64 no 810 pp45ndash49 1992
[38] R M Souto Y Gonzalez-Garcıa A C Bastos and A MSimoes ldquoInvestigating corrosion processes in the micrometricrange A SVET study of the galvanic corrosion of zinc coupledwith ironrdquo Corrosion Science vol 49 no 12 pp 4568ndash45802007
[39] M Yan V J Gelling B R Hinderliter D Battocchi D ETallman andG P Bierwagen ldquoSVETmethod for characterizinganti-corrosion performance of metal-rich coatingsrdquo CorrosionScience vol 52 no 8 pp 2636ndash2642 2010
TribologyAdvances in
Hindawiwwwhindawicom Volume 2018
Hindawiwwwhindawicom Volume 2018
International Journal ofInternational Journal ofPhotoenergy
Hindawiwwwhindawicom Volume 2018
Journal of
Chemistry
Hindawiwwwhindawicom Volume 2018
Advances inPhysical Chemistry
Hindawiwwwhindawicom
Analytical Methods in Chemistry
Journal of
Volume 2018
Bioinorganic Chemistry and ApplicationsHindawiwwwhindawicom Volume 2018
