THE EFFECT OF HEAVY METAL IONS ON THE LOCALIZED CORROSION

8/7/2019 THE EFFECT OF HEAVY METAL IONS ON THE LOCALIZED CORROSION

http://slidepdf.com/reader/full/the-effect-of-heavy-metal-ions-on-the-localized-corrosion 1/36

THE EFFECT OF HEAVY METAL IONS ON THE

LOCALIZED CORROSION BEHAVIOR OF STEELS1

Anees U. Malik, Mohammad Mobin, Ismail Andijani,

Fahd Al-Muaili and Mohammad Al-Hajri

Saline Water Desalination Research Institute

Saline Water Conversion Corporation (SWCC)P.O.Box 8328, Al-Jubail 31951, Saudi Arabia.

E-mail: [email protected]

SUMMARY

The localized corrosion is the most serious problem encountered in a processing plant

such as desalination and power plants. The carryover of metal ions by the liquid,

aerosol and vapors appears to be the primary cause of corrosion in evaporators,

distillate system, boiler tubes, turbines, distillate pipelines and other systems of

desalination and power plants. The deposition of carryover heavy metals/oxides on

steel components in MSF desalination or power plants is a common problem and

reported by many authors. The deposits may initiate localized attack in the form of

pitting or crevice corrosion. The pits act as initiators of stress corrosion in the form of

stress corrosion cracking, corrosion fatigue or intergranular corrosion and result in

the failure of components. However, this aspect has been given little attention and is

least understood yet has great relevance to seawater desalination and power plants.

Keeping in view the above facts, a research project entitled, “The effect of heavy metal

ion on the localized corrosion behavior of steels” was formulated by the Corrosion

Department of R&D Center Al-Jubail.

The project contains the results of an investigation concerning with the effect of heavy

metal ions, e.g., Cu, Ni and Zn on the localized corrosion behavior of carbon steel and 316L under different experimental conditions. The work of the project was divided into

five major tasks, namely, literature survey; material and equipment acquisition;

immersion test under static condition; immersion test under dynamic condition; and

electrochemical studies.

Immersion tests of 1, 6 and 12 months duration were carried out to determine the

effect of metal ions on the corrosion rate of steels. The effect of Si a light non-metallic

1Issued as Technical Report: TR. 3804/APP 96010 in March, 2005.



element has been specifically studied. The important experimental conditions, which

include the nature of aqueous medium, metal ion concentration, temperature, pH and

flow condition, have been taken into account. In general, there is a negligible effect of

metal ions on the corrosion rate of 316L in presence of 50 ppb, 1 ppm and 100 ppm

concentration in either seawater or distillate water under different experimental

conditions. The effect of metal ions on the corrosion rate of carbon steel is quite

pronounced and follows interesting trends. The results from immersion tests show a

decrease in the corrosion rates of carbon steel in distillate water containing higher

concentration of Cu and Ni under both static and dynamic conditions. In seawater, a

higher concentration of Cu is detrimental under dynamic condition. The presence of Zn

in the aqueous medium influences the corrosion behavior of steel differently than that

of Cu and Ni. A higher concentration of Si in seawater, under dynamic condition,

effectively decreases the corrosion rate.

Electrochemical techniques like free corrosion potential, potentiodynamic polarization

and polarization resistance measurements and AC impedance have been used to

investigate the role of heavy metal ions on the corrosion behavior of carbon steel and

SS 316L. The instantaneous corrosion parameters as obtained by electrochemical

techniques show an increase in corrosion rates with increasing metal ion

concentrations. Under controlled laboratory conditions, there is no evidence of

localized attack in presence of different concentrations of metal ions.

1. INTRODUCTION

Corrosion is the major cause of component or material failure in desalination and

power plants. Though one or more forms of corrosion are involved during corrosionfailure in desalination plants general and pitting corrosion are more common modes of

failures [1]. In seawater processing systems, if dissolved oxygen and pH are under

control, general corrosion is the predominant mode of attack on conventional

construction materials such as carbon steel. This form of corrosion is easily

controllable and is desirable in the sense that it permits predictive estimates of service

life. Pitting, the most detrimental form of attack, is often responsible for the corrosion

failures of components in desalination and power plants. In process plants, it accounts

at least 90% of metal damage by corrosion [2]. Though there are several causes of



pitting, the attack of certain aggressive anions on the protective oxide film on the metal

appears to be most widely referred to in the corrosion literature [3,4]. Stainless steels

particularly austenitic lose their protectivity in presence of chloride ions and undergo

pitting. Steels invariably undergo pitting under stagnant or low fluid velocity

conditions [5, 6, 7]. Contact with heavy metal ions such as copper is another cause

which has been attributed to pitting of steels [8]. This aspect has been given little

attention and is least understood yet has great relevance to seawater desalination and

power plants [9]. A number of cases have been reported regarding the copper induced

pitting corrosion of iron and galvanized pipes and tanks in recirculating hot water

system [10-13]. A copper concentration of 0.1 mg/l was found to be sufficient to cause

accelerated attack.

In multistage flash (MSF) desalination plants, as a result of condenser tube corrosion,

the re-circulating brine has high copper content. This can deposit in the flash chambers

and accelerate the corrosion of steel due to high Cu/Fe local cell action [14]. In a AISI

316L distillate line from an MSF desalination plant, green deposits of copper rich oxide

were found, on removing the deposits, deep pits were observed. The pitting was

attributed to carryover copper from the heat exchanger by the distillate [15].

The frequent deposition of copper oxide in the distillate system has been reported in the

MSF desalination plants of Abu Dhabi [16]. The presence of high concentration of

copper in the distillate was due to the deterioration of protective copper oxide during

the start up following outage.

In steam turbines, the deposits along the steam path resulting from boiler carryover are

most problematic. These deposits are detrimental to efficiency, and can have a drastic

effect on turbine reliability because of increased thrust loading and possibility of stress

corrosion cracking of steam path components from high levels of salts/metal oxide

carryover. A study of the corrosion related problems in steam generating equipment

indicates that while 26% of the failures are attributed to pitting, 57% are caused by the

deposition blades [17]. These deposits are formed from high dissolved and suspended

slit carry over of steam.

Besides copper, silicon compounds like SiO2 or Na2SiO3 form important constituent of

turbine deposits. As SiO2, it is non-aggressive but may possibly act synergistically to



enhance the corrosion effect of other elements or compounds. Na2SiO3 has been found

very effective in controlling corrosion of carbon steel by many investigators and the

optimum quantity of Na2SiO3 required to suppress the corrosion has been cited as less

than 10 ppm [18]. In unbuffered solutions, Na2SiO3 is effective as corrosion inhibitor

for iron by inhibiting anodic dissolution of the metal [19]. The compound Na2SiO3

dissociates in water solution to form SiO2 and NaOH and could be very aggressive to

some material such as Ti alloys and steam rotor alloys [20].

The present investigation concern with the effect of heavy metal ions such as Cu, Ni

and Zn on the localized corrosion behavior of carbon steel and AISI 316L under

different experimental conditions. The effect of silicon a light non-metallic element

has been specifically studied. The important experimental conditions which include

the nature of aqueous medium, metal ion concentration, pH and flow conditions have

been taken into account. Immersion tests and electrochemical techniques have been

employed to study the effect of heavy metal ions on the corrosion behavior of steels.

The results of the study shall provide important information about the role of heavy

metal carryover on the failure of desalination and power plant components.

2. EXPERIMENTAL DETAILS

The corrosion behavior of steels in presence of heavy metal ions were studied by

carrying out experiments under different sets of conditions. The conditions are as

follows:

Steels used for testing : Carbon steel, AISI 316L

Aqueous test media : Distillate water, filtered raw seawater

Heavy metal ions : Cu, Ni, Zn (effect of Si, a light non-metallicelement was specifically studied)

Metal ion concentration in : 100 ppm, 1 ppm, 50 ppb

the test media

pH of the test media : 4 (moderately acidic), 6.5 (neutral) and 8.5

(basic)

Temperature : 25 oC

Flow condition : Static, dynamic

Duration of immersion test : 1, 6 and 12 months



under static condition

Duration of immersion test : 1 month

under dynamic condition

Both immersion (weight loss measurements) and electrochemical techniques were used

to determine the effect of heavy metal ion on the corrosion behavior of steels.

2.1 Immersion Tests

2.1.1 Preparation of Specimens

Commercially available carbon steel and 316L were used for immersion tests.

Coupons of dimension 2.4 x 2.4 x 0.3 cm were cut from the sheet. The coupons were

machined and abraded on 180 grit SiC paper to simulate the near service condition. To

hold the specimens, a hole of 1.5 mm dia. was made near the edge. The abraded

coupons were washed, degreased with ethyl alcohol and dried up. The composition of

steels as analyzed by optical emission spectrometer is given in Table 1.

2.1.2 Preparation of Test Solution

The test solutions were made up with distillate water and filtered raw seawater. The

composition of Arabian Gulf seawater is given in Table 2 [21]. The solutions

containing 100 ppm, 1 ppm and 50 ppb of Cu, Ni, Zn and Si, respectively were

prepared in distillate water and filtered raw seawater using Analar grade BDH

chemicals. The pH of the solutions was adjusted using NH4OH and CH3COOH. For the

test solutions made up with distillate water a pH of 4, 6.5 and 8.5 was maintained

whereas for the test solutions made up with seawater a pH of 8.5 was maintained. The

test solutions containing Si was prepared using Na2SiO3 and stored in plastic

containers. In case of Si the test solution pH was not maintained to 6.5 to avoid theprecipitation at higher concentration.

2.1.3 Immersion Test Procedures

Immersion tests were conducted in accordance with ASTM designation G31-72

(Reapproved 1990) which entitled, “Laboratory Immersion Corrosion Testing of

Metals”. After taking the initial weight and dimensions, the coupons were hanged in

the test solution containing varying concentration of metal ions with the help of nylon

thread. A blank experiment, in absence of heavy metal ions, was also carried out for



comparison purpose. In order to avoid galvanic and crevice corrosion, the coupons

were loosely tied with the nylon threads. The immersion tests were carried out under

both static and dynamic conditions. Under static condition, the test runs were of 1, 6

and 12 months duration whereas under dynamic condition the runs were of 1 month

duration. After completion of the immersion test, the specimens were taken out and

cleaned following ASTM designation G1-90 which entitled, “Standard Practice for

Preparing, Cleaning and Evaluating Corrosion Test Specimens” and observed for any

localized attack. The average corrosion rate was determined by the following

relationship:

Where K = Constant, 3.45 x 106 for mpy

W = Mass loss in g, to nearest 1 mg

A = Area in cm2 to the nearest 0.01 cm2

T = Time of exposure in hours to the nearest 0.01 h

D = Density in g/cm3

2.2 Electrochemical Tests

The electrochemical tests like free corrosion potential, potentiodynamic and

polarization resistance measurements and electrochemical impedance were carried out

to investigate the effect of heavy metal ions on the corrosion behavior of steel. The

electrochemical tests were carried out on Solartron AC Impedance System which

comprised of 1250 B frequency response analyzer with blank front panel and 1287

electrochemical interface unit. The experiments were carried out using a corrosion cell

from EG & G model K0047 with saturated calomel electrode (SCE) as reference and

graphite rod as counter electrode.

2.2.1 Preparation of Specimens

Circular specimens with 1.5 cm diameter were punched from 3 mm thick carbon steel

and 316 L sheets. A nichrome wire was soldered to one face of the specimens for the

electrical connection and the specimens were then mounted in epoxy resin to provide

crevice free mount. The exposed circular face was ground to 180 grit SiC paper. The

ground specimens were washed, degreased and dried up.

2.2.2 Preparation of Test Solution

DxT xA

xW K rateCorrosion =



The procedure for the preparation of test solutions for electrochemical tests was similar

to that adopted for immersion tests.

2.3 Free Corrosion Potential Measurements

The free corrosion potential measurements of carbon steel and SS 316L were carried

out in both distillate water and filtered raw seawater for a period of 1 month. The

measurements were carried out in presence and absence of metal ions at room

temperature under static condition. The change in voltage against SCE used as

reference electrode, was plotted vs time.

2.4 Potentiodynamic Polarization Measurements

Potentiodynamic polarization measurements were carried out using a scan rate of 0.166

mV/s commencing at a potential above 250 mV more active than stable open circuit

potential. To observe the effect of a particular metal ion in a given medium,

potentiodynamic curves were obtained using the same specimen under similar

experimental condition except a periodic change in metal ion concentration. However,

before starting the polarization scan at each concentration, the specimen was stabilized

for about 1 hour for attaining a steady state which was shown by a constant potential.

2.5 Polarization Resistance Measurements

Polarization resistance measurements were conducted at a scan rate of 0.166 mV/s with

starting and final potential corresponding to -15 mV to + 15 mV vs open circuit

potential, respectively. The maximum current range was 0.1µ A. All the

measurements were completed on the same day with the same specimen. However,

metal ion concentration was periodically changed and before starting the measurements

at each concentration, the specimen was left for about 1 hr for attaining a steady state

which was indicated by a constant potential.

2.6 AC Impedance Measurements

The electrochemical impedance measurements were performed under potentiostatic

conditions at the free corrosion potential. Amplitude sine wave signal was 10 mV over



the frequency range of 1 KHz to 1 mHz with five points per decade. All the ac

impedance measurements were performed before polarization resistance

measurements. However, before each measurement the specimen was left to attain a

constant potential.

3. RESULTS

3.1 Immersion Tests (weight loss measurements)

The corrosion rates of carbon steel and 316 L in presence and absence of metal ions

under different experimental conditions, as obtained by weight loss measurement

technique are given in Tables 3-10. The results for carbon steel and SS 316L are

summarized separately.

3.1.1 Carbon Steel

Tables 3-6 show the effect of metal ions on the corrosion rate of carbon steel in both

distillate and filtered raw seawater at different pH at 25 oC. In absence of metal ions,

the corrosion rate of carbon steel in distillate water (under both static and dynamic

conditions) and filtered raw seawater (under static condition) are almost the same.

However, in filtered raw seawater, under dynamic condition, there is a large increase in

the corrosion rate of carbon steel. The effect of different metal ions on corrosion rate of

carbon steel is described as follows:

(1) Effect of Copper

In distillate water, under static condition, the presence of 50 ppb and 1 ppm of copper

at both pH 6.5 and 8.5, appears to have negligible effect on the corrosion rate of carbon

steel. However, under dynamic condition there is a large increase in corrosion rate in

presence of 50 ppb and 1 ppm of copper. The highest corrosion rate of 28 mpy is

noticed in presence of 1 ppm of copper. A lowering in the corrosion rate is noticed at

100 ppm of copper concentration under both static and dynamic conditions. In filtered

raw seawater, under static condition, the corrosion rate increases slightly with

increasing copper ion concentration. However, under dynamic condition a large

increase in corrosion rate is observed only in presence of 100 ppm of copper, at other

concentrations, there is no appreciable change in the corrosion rates.

(2) Effect of Nickel



The presence of nickel in both distillate water and seawater has almost similar effect to

that of copper on the corrosion rate of carbon steel. In distillate water, the highest

corrosion rate of 33 mpy is observed in presence of 50 ppb of nickel under dynamic

condition, this is followed by a corrosion rate of 21 mpy in presence of 1 ppm of

nickel. Both under static and dynamic conditions, a lowering in corrosion rate is

observed only in presence of 100 ppm of nickel. In seawater, under static condition

though there is a slight increase in corrosion rate with increasing metal ion

concentration, there is no significant effect under dynamic condition.

(3) Effect of Zinc

In distillate water, under static condition, except for 100 ppm of zinc ion concentrationwhich indicated an increase in the corrosion rate, there is no appreciable effect of zinc

on the corrosion rate of carbon steel. Under dynamic condition, corrosion rate is

almost unaffected in presence of all the three concentration of zinc. In seawater, under

static condition, the presence of zinc has no significant effect on the corrosion rate of

carbon steel. However, under dynamic condition there is a decrease in the corrosion

rate in presence of zinc at all the three selected concentrations.

(4) Effect of Silicon

The effect of silicon, a light non-metallic element, on the corrosion rate of carbon steel

was specifically studied. The silicon solution in distillate water and seawater were

specially made and kept in plastic containers. The immersion tests were also carried

out in plastic vessels. In both distillate and seawater, under static condition, presence

of silicon appears to have no significant effect on the corrosion rate of carbon steel.

However, under dynamic condition, the corrosion rates appear to decrease with

increasing Si concentration.

3.1.2 SS 316L

Tables 7-10 show the effect of metal ions on the corrosion rate of SS 316L in both

distilled water and filtered raw seawater at different pH at 25 oC. The results are

obtained under static condition. SS 316L is unaffected in distilled water (pH 6.5) and

seawater (pH 8.5) for an immersion period of 1, 6 and 12 months duration. The effect

of different metal ions on the corrosion behavior of 316L is summarized as follows:



(1) Effect of Copper, Nickel, Zinc and Silicon

In general, there is negligible effect of metal ions on the corrosion rate of 316L in

presence of 50 ppb, 1 ppm or 100 ppm concentration at pH 4, 6.5 or 8.5 for an

immersion period of 1, 6 or 12 months duration in both distilled water and seawater.

3.2 Electrochemical Studies

3.2.1 Free Corrosion Potential (E corr ) Measurements

Figures 1 to 9 show time vs free corrosion potential plots for carbon steel and SS 316L

immersed in distilled water (pH 6.5) and filtered raw seawater (pH 8.5) in presence and

absence of heavy metal ions under static condition. The results for carbon steel and SS

316L are summarized separately.

3.2.1.1 Carbon Steel

The free corrosion potential of carbon steel in distilled water, in absence of metal ions,

for the first 2 hrs is about -550 mV vs SCE; this is followed by an increase in potential

till a stable potential range of -650 to -750 mV is reached. However, in seawater

without metal ions, a potential of -650 mV is reached during the first 2 hrs, this is

followed by an increase in potential till a stable potential range of -700 to -800 mV is

reached. The results of the effect of heavy metal ions on the free corrosion potential of

carbon steel in both distilled water and seawater are summarized as follows:


Figures 1 and 2 show potential vs time plots for carbon steel in distilled water and

seawater containing 0, 1 and 100 ppm copper. In distillate water containing 1 ppm Cu,

a positive shift in Ecorr is noticed for the first 24 hours only whereas in presence of 100ppm Cu, a pronounced positive shift in Ecorr is noticed for a time period extending 17

days. In seawater, though, there is no significant effect of the presence of 1 ppm Cu

on the Ecorr of carbon steel, the presence of 100 ppm Cu slightly shifted the E corr in

noble direction and a potential below-650 mV is maintained for the time period

extending 17 days.




In distillate water a significant ennoblement in Ecorr is observed in presence of both 1

and 100 ppm nickel (Figure 3). An initial decrease in negative potential was observed

in presence of both 1 and 100 ppm nickel, this is followed by a constant noble

potential. However, in presence of 1 ppm Ni after a time period extending 16 to 17

days, an increase in negative potential is observed till a potential equal to the potential

of carbon steel in absence of nickel is reached. In seawater, the effect of nickel on the

potential of steel is not much pronounced. In presence of both 1 and 100 ppm nickel

the potential is reached to above - 600 mV on the first day of immersion (Figure 4).

(3) Effect of Zinc

The Ecorr vs time plots for carbon steel in distilled water and seawater containing 0, 1

and 100 ppm zinc is shown in figures 5 and 6. In distillate water, though the potential

of carbon steel in presence of 100 ppm zinc is slightly below the potentials of carbon

steel, there is no significant effect of zinc on the Ecorr of carbon steel in both distilled

water and seawater.

(4) Effect of Silicon

Figure 7 shows the potential vs time plots for carbon steel in seawater containing 0, 1

and 100 ppm silicon. Though, there is no effect of presence of 1 ppm silicon on theEcorr of carbon steel, a major positive shift in Ecorr is observed in presence of 100 ppm

of silicon.

3.2.1.2 SS 316L


Figure 8 shows the potential vs time plots for SS 316L in distillate water containing 1

and 100 ppm copper. An increase in copper ion concentration shifts the Ecorr of 316L in

more noble direction.


Figure 9 shows the potential vs time plots for SS 316L in distillate water containing 1

and 100 ppm nickel. After an initial negative shift in Ecorr , the increasing nickel ion

concentration appears to shifts the Ecorr of 316L in more noble direction.

3.2.2 Potentiodynamic Polarization Measurements



Figures 10 to 15 show potentiodynamic curves for carbon steel in distilled water and

seawater containing different concentrations of metal ions. The values of corrosion

potential, Ecorr and corrosion current, Icorr for carbon steel in distilled water and

seawater in presence of 0, 50 ppb, 1 ppm and 100 ppm metal ions, as computed from

potentiodynamic curves, are given in Table 11. In general, though there is no

significant effect of the presence of 50 ppb and 1 ppm of metal ions on the E corr and Icorr

values, the presence of 100 ppm of metal ions in both distillate water and seawater has

pronounced effect on the Ecorr and Icorr values. In presence of 100 ppm of Cu and Ni an

increase in Icorr values is observed whereas in presence of 100 ppm Zn a reverse trend is

observed.

3.2.3 Polarization Resistance Measurements

The polarization resistance measurements were carried out on carbon steel immersed in

distilled water containing 0, 50 ppb, 1 ppm and 100 ppm of copper and nickel,

respectively. The measurements were carried out on duplicate samples. Typical

polarization resistance plots are shown in figures 16 to 19. Table 12 lists the

polarization resistance values, R p computed from linear polarization plots. The results

from the polarization measurements show a negative shift in Ecorr and lowering in R p

values with increasing copper and nickel ion concentration in the distilled water.

3.2.4 AC Impedance Studies

The effect of heavy metal ions on the corrosion behavior of carbon steel in distilled

water was studied by electrochemical impedance spectroscopy (EIS). The technique is

unique as it allows the quantitative study of corrosion behavior of low corroding

systems which is not entirely possible by conventional dc techniques. Parameters such

as solution resistance, R S, polarization resistance, R P and interfacial capacitance, C

evaluated from EIS proved to be useful in studying corrosion kinetics and associated

interfacial phenomenon.

Nyquist curves were obtained to study the effect of heavy metal ions on the corrosion

behavior of carbon steel. Nyquist plot is obtained by plotting the imaginary impedance

(Z”) against real impedance (Z’) at each excitation frequency. At high frequency, the

impedance is almost entirely created by solution resistance (R P +R S). The R P



(inversely proportional to the corrosion rate of exposed metal surface) is the difference

between low frequency limit and high frequency limit.

Figures 20 to 23 show Nyquist plots for carbon steel in distilled water containing

varying concentration of heavy metal ions. The results obtained from Nyquist plots are

listed in Table 13. Though a well defined semicircle characteristics of Nyquist plot is

lacking, the computed values of R P show a decreasing trend with increasing metal ion

concentration. The result is in conformity with the values of R P obtained from dc

experiment (linear polarization resistance measurements).

To observe the effect of metal ion concentration with time, the ac impedance

measurement of carbon steel in distilled water containing 100 ppm nickel was extended

for 1 month. The results are summarized in Table 14.

4. DISCUSSION

The effect of heavy metals like Cu, Ni and Zn and a non-metal Si on the corrosion

behavior of carbon steel and 316L was studied in the pH range of 4 to 8.5 at room

temperature under both static and dynamic conditions. Carbon steel shows a complex

dependence of corrosion rate on pH. In near neutral pH range (5 <pH<9), pH no more

plays a direct role in corrosion [22]. The major reaction governing corrosion in most

practical application in this pH range is the reduction of oxygen present in the solution.

Therefore, under static condition, the pH range under study is not expected to play a

significant role in corrosion and any change in the corrosion behavior of steel may be

expected to be brought about by presence of metal ions in the solution. However,

under dynamic condition in addition to the presence of metal ions the agitation of

solution and presence of solids in the solution may also affect the corrosion rate. The

changes in seawater chemistry and that of biological activities in the test solution with

time and addition of heavy metal ions were not monitored, as these parameters under

the experimental conditions designed for this study are not expected to affect the

corrosion behavior significantly. Further, the monitoring of these parameters were

beyond the scope of project objectives as the main aim of this study was to establish a

baseline data considering the effect of heavy metal ions on the localized corrosion

behavior of steel, if present in test solution. The important parameters affecting

corrosion rate under experimental conditions of this study are well documented and



supported by relevant reference [22]. In case of steel, in presence of dissolved oxygen,

the corrosion process is controlled by cathodic diffusion and solution agitation is

expected to cause an increase the corrosion rate. The presence of fine suspended solid

particles in the solutions may also cause an increase in corrosion rate due to their

movement over the steel surface. This is evident from the results of immersion studies

for carbon steel, in absence of metal ions, in pH range of 6.5 to 8.5 under dynamic

condition. The corrosion rate in distillate water is unchanged whereas in seawater there

is a large increase in corrosion rate.

Considering the results of immersion test for 316L there is negligible or no effect of the

presence of metal ions on the corrosion rate in both distilled water and seawater in the

pH range of 4 to 8.5. However, the effect of metal ions on the corrosion rate of carbon

steel is quite pronounced and follows interesting trends. Under experimental

conditions the presence of Cu and Ni in both distillate water and seawater has similar

effect on the corrosion rates. In distillate water, a higher concentration of Cu and Ni

result in a decrease in corrosion rate under both static and dynamic conditions whereas

a lower concentration of Cu and Ni considerably increases the corrosion rate under

dynamic condition. In seawater, a higher concentration of Cu is detrimental under

dynamic condition.

An increase in corrosion rate of carbon steel in presence of Cu and Ni can be explained

on the basis of occurrence of two cathodic reactions whereas a lowering in corrosion

rate may be explained on the basis of formation of a stable protective barrier over the

steel surface by the deposited metal. In presence of dissolved oxygen and metal ions

the anodic and cathodic reaction may be written as follows:

Anodic reaction: Fe→ Fe2+ + 2 ē (1)

Cathodic reaction: (Cathodic reactions in pH range of 6.5 to 8.5 are reduction of O 2 and

the metal ions)

½ O2 + H2O + 2 ē → 2OH- (2)

M++ + 2 ē → M (3)



Since during metallic corrosion, the total rate of oxidation equals to total rates of

reduction, the dissolution rate of steel equals to the reduction rates of O2 and metal ions

and hence the initial corrosion rate of carbon steel in presence of metal ions is expected

to increase. After reduction of the metal ions the resulting metal get deposited over the

steel surface and form a barrier which is likely to protect the steel from further

corrosion. The extent of protection offered to the steel shall depend upon the ability of

the deposited metal to form a stable protective barrier and nature of protection offered

to steel surface. The deposited Cu and Ni protect the steel cathodically. In aqueous

medium containing high concentration of Cu and Ni a stable protective barrier is more

likely to be formed and hence a lowering in corrosion rate is observed. In presence of

lower concentration of metal ions the observed increase in corrosion rate is due to

absence of a stable protective barrier. In seawater the observed increase in corrosion

rate in presence of 100 ppm Cu under dynamic condition is due to erosive action of

fine suspended solid particles on the barrier film.

In presence of Zn, the corrosion rate of carbon steel in distillate water under both static

and dynamic conditions is unaffected except at higher concentration of metal. Since

Zn is anodic to steel, under the given experimental conditions, it is unlikely to get

reduced and deposit over steel surface and thus decrease the subsequent rate of

corrosion. However, it may remain in the solution in the ionic form affecting the

conductivity of the test solution. The observed increase in corrosion rate in presence of

100 ppm of Zn may be accounted due to the increase in the conductivity of the

solution. In seawater, with increasing metal ion concentration a lowering in corrosion

rate under dynamic condition is probably due to limited transfer of dissolved O2 from

bulk solution to the surface. The presence of higher concentration of Si in the aqueous

medium appears to be effective in lowering down in the corrosion rate of carbon steelunder dynamic condition. The effectiveness of Na2SiO3, under dynamic condition, in

lowering down the corrosion rate of carbon steel has already been established [18].

The results of immersion tests find support from free corrosion potential

measurements. The Ecorr of carbon steel in distillate water and seawater is in the range

of -650 to -750 mV and -700 to -800 mV vs SCE, respectively. In distillate water

containing 100 ppm of Cu and Ni a positive shift is E corr is noticed which is maintained

for a considerable period of time. A positive shift in Ecorr is indicative of the protection



offered to steel surface. In seawater containing 100 ppm of Cu and Ni the shift is not

much significant. The presence of Zn in the aqueous medium does not affect the Ecorr

significantly whereas the presence of 100 ppm Si in seawater shifts the Ecorr

considerably in noble direction. For 316L also an increasing concentration of metal

ions in the aqueous medium appears to shift the Ecorr in noble direction.

The corrosion parameters obtained from potentiodynamic and linear polarization

measurements show an increase in Icorr and lowering in R p values, respectively with

increasing Cu and Ni ion concentrations indicating an increase in corrosion rate of

carbon steel with increasing metal ion concentration in the aqueous medium. The

parameters measured by the above techniques are instantaneous and the increase in

instantaneous corrosion rate with increasing metal ions concentration is expected and

can be explained on the basis of occurrence of two cathodic reactions (Equ. 2 and 3).

5. CONCLUSIONS

(1) Under controlled laboratory conditions the results from immersion and

electrochemical tests show no evidence of localized attack on carbon steel and

316L in presence of different concentration of heavy metal ions.

(2) The results from immersion tests in the pH range 4 to 8.5 at room temperature

show no effect of metal ions on the corrosion rate of 316L.

(3) The effect of metal ions on the corrosion rate of carbon steel in the pH range of

6.5 to 8.5 at room temperature is quite pronounced and follows interesting

trends.

(4) The presence of Cu and Ni in the aqueous medium produces almost similar

effect on the corrosion behavior of carbon steel.

(5) The corrosion rate of carbon steel in distilled water containing higher concentration of Cu and Ni decreases under both static and dynamic conditions.

In seawater, however, a higher concentration of Cu is detrimental under

dynamic condition.

(6) The presence of Zn in the aqueous medium influences the corrosion behavior of

steel differently than that of Cu and Ni.

(7) A higher concentration of Si in seawater, under dynamic condition, effectively

decreases the corrosion rate of carbon steel.





Table 3. Effect of Copper on the Corrosion Rate of Carbon Steel at Different pH

Under Static and Dynamic Condition at 25oC

Corrosion Rate (mpy)Aqueous Test

Medium

pH Flow

Condition

Ion

Concentration 1 Month 6 Month 12 Month

Distillate Water 6.5 Static Nil 2.669 2.305 2.309" 6.5 Static 50 ppb 2.776 2.416 2.306

" 6.5 Static 1ppm 3.324 0.092 2.012

" 6.5 Static 100ppm 0.724 0.049 0.032

" 8.5 Static 50 ppb 2.838 3.043 2.738

" 8.5 Static 1ppm 0.771 3.006 3.246

" 8.5 Static 100ppm 0.890 0.102 1.212

" 6.5 Dynamic Nil 2.088

" 6.5 Dynamic 50ppb 13.523

" 6.5 Dynamic 1ppm 28.059

" 6.5 Dynamic 100ppm 0.478Filtered Raw

Seawater

8.5 Static Nil 2.668 1.757 1.836

" 8.5 Static 50ppb 2.811 2.392 1.907

" 8.5 Static 1ppm 2.623 2.375 2.208

" 8.5 Static 100ppm 3.366 4.574 4.499


" 8.5 Dynamic 50ppb 17.819


" 8.5 Dynamic 100ppm 27.527

Table 4. Effect of Nickel on the Corrosion Rate of Carbon Steel at Different pHUnder Static and Dynamic Condition at 25

oC

Corrosion Rate (mpy)Aqueous Test Medium pH

Flow

ConditionIon Conc.

1 Month 6 Month 12 Month

Distillate Water 6.5 Static Nil 2.669 2.305 2.309

" 6.5 Static 50 ppb 2.636 2.421 2.763

" 6.5 Static 1ppm 3.035 3.007 3.274

" 6.5 Static 100ppm 0.110 0.039 0.006

" 8.5 Static 50 ppb 3.311 2.654 2.691

" 8.5 Static 1ppm 3.429 0.085 2.656

" 8.5 Static 100ppm 1.328 0.050 0.028" 6.5 Dynamic Nil 2.088

" 6.5 Dynamic 50ppb 32.9822

" 6.5 Dynamic 1ppm 21.0646

" 6.5 Dynamic 100ppm 1.2971

Filtered Raw Seawater 8.5 Static Nil 2.668 1.757 1.836

" 8.5 Static 50ppb 2.638 1.889 1.719

" 8.5 Static 1ppm 2.851 2.032 1.772

" 8.5 Static 100ppm 4.181 2.840 2.933

" 8.5 Dynamic Nil 18.917 - -

" 8.5 Dynamic 50ppb 16.273

" 8.5 Dynamic 1ppm 18.179" 8.5 Dynamic 100ppm 18.450



Table 5. Effect of Zinc on the Corrosion Rate of Carbon Steel at Different pH Under

Static and Dynamic Condition at 25oC

Corrosion Rate (mpy)Aqueous Test Medium pH

Flow

ConditionIon Conc.

1 Month 6 Month 12 Month

Distillate Water 6.5 Static Nil 2.669 2.305 2.309" 6.5 Static 50 ppb 2.514 2.069 1.999

" 6.5 Static 1ppm 2.552 2.129 1.973

" 6.5 Static 100ppm 4.980 7.518 4.746

" 8.5 Static 50 ppb 2.971 2.565 2.237

" 8.5 Static 1ppm 2.455 2.958 2.324

" 8.5 Static 100ppm 3.864 3.012 0.052


" 6.5 Dynamic 50ppb 0.737


" 6.5 Dynamic 100ppm 2.043

Filtered Raw Seawater 8.5 Static Nil 2.668 1.757 1.836" 8.5 Static 50ppb 2.126 2.062 2.050

" 8.5 Static 1ppm 2.387 1.917 1.639

" 8.5 Static 100ppm 2.135 2.185 2.435


" 8.5 Dynamic 50ppb 12.584


" 8.5 Dynamic 100ppm 10.615

Table 6. Effect of Silicon on the Corrosion Rate of Carbon Steel at Different pH

Under Static and Dynamic Condition at 25oC


MediumpH

Flow

Condition

Ion


Distillate Water 6.5 Static Nil 2.669 2.305 2.309

" 8.5 Static 50 ppb 2.789 2.842 3.099

" 8.5 Static 1ppm 2.790 2.216 2.748

" 8.5 Static 100ppm 3.583 2.653 3.030


" 6.81 Dynamic 50ppb 3.412


" 8.19 Dynamic 100ppm 1.377Filtered Raw

Seawater

8.5 Static Nil 2.668 1.757 1.836

" 8.5 Static 50ppb 3.721 1.975 1.844

" 8.5 Static 1ppm 2.259 1.918 1.608

" 8.5 Static 100ppm 1.817 1.591 1.854


" 7.94 Dynamic 50ppb 16.937

" 8.10 Dynamic 1ppm 17.289

" 8.64 Dynamic 100ppm 10.158



Table 7. Effect of Copper on the Corrosion Rate of 316L at Different pH Under Static

Condition at 25oC


Medium

pHFlow

Condition

Ion Concentration

1 Month 6 Month 12 MonthDistillate Water 6.5 Static Nil - - -

" 6.5 Static 50 ppb - .0006 .0016

" 6.5 Static 1ppm .0039 - .00175

" 6.5 Static 100ppm - - .0003

" 8.5 Static 50 ppb - - -

" 8.5 Static 1ppm - .0059 .0009

" 8.5 Static 100ppm - .00198 -

" 4 Static Nil - - -

" 4 Static 50ppb - .00385 -

" 4 Static 1ppm - .00286 -

" 4 Static 100ppm - .00393 -Filtered raw

seawater 8.5 Static Nil 0.0059 .00132 .00165

" 8.5 Static 50ppb .0318 .0023 .00067

" 8.5 Static 1ppm - .0016 .00032

" 8.5 Static 100ppm .0155 .003 .00066

Table 8. Effect of Nickel on the Corrosion Rate of 316L at Different pH Under

Static Condition at 25oC


Medium pHFlow

Condition

Ion


Distillate Water 6.5 Static Nil - - -

" 6.5 Static 50 ppb - .0066 .00255

" 6.5 Static 1ppm - .00745 .0009

" 6.5 Static 100ppm .00410 .0067 .0003

" 8.5 Static 50 ppb .01563 .00391 .0003

" 8.5 Static 1ppm .00421 .00537 -

" 8.5 Static 100ppm .00835 .00535 .0003


" 4 Static 50ppb .00784 .00599

" 4 Static 1ppm - .00469 -

" 4 Static 100ppm .011995 .00644 .0009

Filtered raw

seawater 8.5 Static Nil 0.0059 .00132 .00165

" 8.5 Static 50ppb .0099 .00096 .0003

" 8.5 Static 1ppm .006 - .0003

" 8.5 Static 100ppm .006 .0006 .0003



Table 9. Effect of Zinc on the Corrosion Rate of 316L at Different pH Under Static

Condition at 25oC


MediumpH

Flow

Condition

Ion

Concentration1 Month 6 Month 12 Month


" 6.5 Static 50 ppb .00766 .00639 -

" 6.5 Static 1ppm .00171 .00589 .0006

" 6.5 Static 100ppm .0222 .00635 .0029

" 8.5 Static 50 ppb - .00303 -

" 8.5 Static 1ppm .01519 .00435 .0003

" 8.5 Static 100ppm .02005 .00358 -


" 4 Static 50ppb .00638 .00486 -

" 4 Static 1ppm .0125 .00466 -" 4 Static 100ppm .01945 .00504 -

Table 10. Effect of Silicon on the Corrosion Rate of 316L at Different pH Under Static

Condition at 25oC


MediumpH

Flow

Condition

Ion

Concentr

ation. 1 Month 6 Month 12 Month


" 5.3 Static 50 ppb - .0032 -

" 6.0 Static 1ppm - .0032 .0003

" 9.5 Static 100ppm .00797 .00197 .0003

Filtered Raw

Seawater

8.5 Static Nil 0.0059 .00132 .00165

" 8.1 Static 50ppb - .0006 .00172

" 8.1 Static 1ppm - .0006 .0006

" 8.6 Static 100ppm - .0014 .0010



Table 11. Values of Ecorr and Icorr for carbon steel in distillate water and seawater as obtained

by potentiodynamic polarization curves at room temperature

Alloy Medium Heavy Metal

ion

Metal in

Concentration

pH Ecorr (V) ICorr (Amp/cm2)

Carbon

steel

Distilled

water

Copper Nil 6.5 -0.453 6.788 x 10-6

” ” ” 50 ppb ” -0.469 8.528 x 10-6

” ” ” 1 ppm ” -0.471 7.371 x 10-6

” ” ” 100 ppm ” -0.002 2.046 x 10-5

” Seawater ” Nil 8.5 - -

” ” ” 50 ppb ” -0.756 8.360 x 10-6

” ” ” 1 ppm ” -0.751 5.529 x 10-6

” ” ” 100 ppm ” -0.750 4.891 x 10-5

” Distilled

water

Nickel Nil 6.5 -0.310 5.585 x 10-6

” ” ” 50 ppb ” -0.375 7.390 x 10-6

” ” ” 1 ppm ” -0.406 9.333 x 10-6 ” ” ” 100 ppm ” -0.659 2.817 x 10

-4

” Seawater ” Nil 8.5 - -

” ” ” 50 ppb ” -0.729 1.274 x 10-5

” ” ” 1 ppm ” -0.740 8.204 x 10-6

” ” ” 100 ppm ” -0.547 9.427 x 10-6

” Distilled

water

Zinc Nil 6.5 -0.466 8.022 x 10-6

” ” ” 50 ppb ” -0.478 7.765 x 10-6

” ” ” 1 ppm ” -0.494 1.134 x 10-5

” ” ” 100 ppm ” -0.488 5.146 x 10-6

” Seawater ” Nil 8.5 -0.718 1.142 x 10-5

” ” ” 50 ppb ” -0.767 7.222 x 10

-6

” ” ” 1 ppm ” -0.772 2.377 x 10-6

” ” ” 100 ppm ” -0.733 4.502 x 10-7

Table 12. Values of corrosion potential, Ecorr and polarization resistance, RP as computed by

linear polarization resistance at room temperature and pH 6.5

Results

Sample -I Sample -IIAlloy Medium Heavy

Metal ion

Metal ion

concentration Ecorr (V) RP (ohm-cm2) Ecorr (V) RP (ohm-cm2)

Carbon

steel

Distilled

water

Copper Nil -0.505 3.14 x 104

-0.431 7.46 x 104

” ” ” 50 ppb -0.528 2.57 x 104

-0.472 2.79 x 104

” ” ” 1 ppm -0.675 7012 -0.476 1.09 x 104

” ” ” 100 ppm -0.737 666 -0.735 1141

” ” Nickel Nil -0.473 4.17 x 104

-0.464 5.84 x 104

” ” ” 50 ppb -0.485 4.18 x 104

-0.483 5.08 x 104

” ” ” 1 ppm -0.547 1.91 x 104

-0.510 2.04 x 104

” ” ” 100 ppm -0.655 780 -0.656 881



Table 13. AC impedance results for carbon steel and SS 316L in distilled water (pH 6.5) containing

varying concentration of heavy metal ions

Results

Sample -I Sample -IIAlloy Medium

Heavy

Metalion

Metal ion

concentration

RP (ohm-cm2)

Ecorr (V) RS(ohm-cm2)

RP (ohm-cm2

Ecorr (V) RS(ohm-cm2)

Carbonsteel

Distilledwater

Copper Nil 4641 -0.513 - 6014 -0.437 -

” ” ” 50 ppb 2895 -0.550 - 5305 -0.473 -

” ” ” 1 ppm 2462 -0.691 - 2999 -0.501 -

” ” ” 100 ppm 285 -0.738 - 602 -0.736 -

” ” Nickel Nil 4741 -0.473-

4460 -0.468-

” ” ” 50 ppb 4557 -0.491 - 4286 -0.487 -

” ” ” 1 ppm 2191 -0.560 - 3532 -0.515 -

” ” ” 100 ppm 328 -0.655 - 410 -0.658 -

316 L ” Copper Nil 2.85 x 106

-0.0276- -

” ” ” 50 ppb 4.76 x 10

6

-0.0609 - -” ” ” 1 ppm 1.25 x 106 -0.0469 - -

” ” ” 100 ppm 2.37 x 106 -0.1266 -

Table 14. The Values of Ecorr and Rp with time as obtained by ac impedance

Results

Sample -IAlloy Medium Time (days)

Ecorr (V) Rp (ohm-cm2)

Carbon steel Distilled water

containing 100 ppm Ni

1 (immediately) -0.081 1.79 x 106

1 (after 3 hours) -0.069 8230

2 -0.155 7473

6 -0.485 4477

7 -0.231 12542

9 -0.207 14971

10 -0.258 21883

14 -0.116 84134

15 -0.119 38111

16 -0.154 31027

17 -0.330 9766

20 -0.495 257922 -0.378 9843

23 -0.345 36429

27 -0.369 15265

28 -0.372 10638

29 -0.378 49667

30 -0.388 2222



Figure 1. Ecorr vs time plot for carbon steel immersed in

distillate water (pH = 6.5) containing different

concentration of copper


seawater (pH = 8.5) containing different

concentration of copper

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

100

200

0 5 10 15 20 25 30 35 40

Time (Days)

Potential (mv) vs SCE

1 ppm Cu

100 ppm Cu

0 ppm Cu

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

0 10 20 30 40 50 60

Time (Days)


1 ppm Cu100 ppm Cu0 ppm Cu




distilled water (pH =6.5) containing different

concentration of nickel

Figure 4 Ecorr vs time plot for carbon steel immersed in


concentration of nickel

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

100

0 5 10 15 20 25 30 35

Time (Days)


100 ppm Ni1 ppm Ni0 ppm Ni

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

0 10 20 30 40

Time (Days)


100 ppm Ni1 ppm Ni0 ppm Ni




distilled water (pH = 6.5) containing different

concentration of zinc



concentration of zinc

-900

-800

-700

-600

-500

-400

-300

-200

-100

00 5 10 15 20 25 30 35

Time (Days)


1 ppm Zn100 ppm Zn0 ppm zn

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

0 10 20 30 40

Time(Days)


100 ppm Zn1 ppm Zn0 ppm Zn





concentration of silicon

Figure 8. Ecorr vs time plot for 316L immersed in distilled

water (pH = 6.5) containing different concentrationof copper

-900

-800

-700

-600

-500

-400

-300

-200

-100

0

100

0 10 20 30 40

Time (Days)


1 ppm Si100 ppm Si0 ppm Si

0

50

100

150

200

250

0 10 20 30 40 50 60

Time (Days)


100 ppm Cu1 ppm Cu



Figure 9. Ecorr vs time plot for 316L immersed in distilled

water (pH = 6.5) containing different concentration

of nickel

Figure 10. Potentiodyanmic curves for carbon steel in distilled water

(pH=6.5) in presence of Cu

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

0 10 20 30 40

Time (Days)


1 ppm Ni

100 ppm Ni



Figure 11. Potentiodyanmic curves for carbon steel in seawater (pH=8.5)

in presence of Cu


(pH=6.5) in presence of Ni



Figure 13. Potentiodyanmic curves for carbon steel in seawater (pH=8.5)

in presence of Ni


(pH=6.5) in presence of Zn



Figure 15. Potentiodyanmic curves for carbon steel in seawater

(pH=8.5) in presence of Zn

Figure 16. Polarization resistance curves for carbon steel in distilled water

(pH=6.5) containing different concentration of Cu



Figure 17. Polarization resistance curves for carbon steel (sample II) in

distilled water (pH=6.5) containing different concentration of

Cu

Figure 18. Polarization resistance curves for carbon steel (sample II) in

distilled water (pH=6.5) containing Ni



Figure 19. Polarization resistance curves for carbon steel in distilled

water containing Ni

Figure 20. Nyquist plot for carbon steel in distilled water (pH 6.5)

containing different concentration of Cu



Figure 21. Nyquist plot for carbon steel (Sample II) in distilled water (pH

6.5) containing different concentration of Cu

Figure 22. Nyquist plot for carbon steel in distilled water (pH 6.5)

containing different concentration of Ni



Figure 23. Nyquist plot for carbon steel (sample II) in distilled water (pH

6.5) containing different concentration of Ni



REFERENCES

1. Malik, A.U., Kutty, P.C.M., Andijani, I.N. and Al-Fozan, S.A., (1994), Materials

Performance and Failure Evaluation in SWCC MSF Plants, Desalination, 97, 171.

2. Asphahani, A.I. and Silence, W.L., (1987), Metal Hand Book: ASME Publication.

Vol. 13., p. 113.

3. Szklarska-Smialowska, Z., (1986), Pitting Corrosion of Metals, NACE, Houston.

4. Uhlig, H.H. and Revie, R.W., (1985), Corrosion Control - An Introduction to

Corrosion Science and Engineering, John Wiley & Sons, 3rd Edi., New York.

5. Sandricks, A.J., (1979), Corrosion of Stainless Steels, John Wiley & Sons, 3rd

Edi., New York.

6. Szklarska-Smialowska, Z., (1987), Industrial Problems Treatment and Control

Techniques, Pergmon Press, Oxform.

7. Malik, A.U., Kutty, P.C.M., Andijani, I.N. and Ahmed, S., (1992), The Influence

of pH and Chloride Concentration on the Corrosion Behavior of AISI 316 L Steel

in Aqueous Solution, Corrosion Science, 33, 1809.

8. Internal Corrosion of Water Distribution System: Cooperative Research Report,American Water Work Association and DVGW-for Schungsteus, (1985), USA, p.

191.

9. Schrieber, C.F., (1986), Measurement and Control Related Corrosion and Scales

in Water Desalination Installation in “Measurement of Control in Water

Desalination”, Editor, Noam Lior, Elsevier, Amsterdam, p. 427.

10. Kenworthy, L. (1943), The Problems of Copper and Galvanized Iron in Water

System, J. Inst. Metals, 69, 67.

11. Guise, H., (1971), Dissolved Copper Effect on Iron Pipe, J. AWWA, 63, 79.

12. Treweek, G.P., Trusell, R.R. and Pomeroy, R.D., (1978), Copper Induced

Corrosion of Galvanized Steel Pipe, in Proc. 6th Water Technology Conference,

Louisoille, AWWA, Denver, Colo.13. Grrasha, L., Rinse, W. and Davis, M., (1981), Corrosive Effect of Dissolved

Copper on Galvanized Steel, Phase-II, Internal Report, Metropolitan Water

District of S.C.

14. Khan, A.H., (1986), Desalination Processes and Multistage Flash Distillation

Practice, Elsevier, Amsterdam, p. 442.

15. Malik, A.U. and Al-Sofi, M..AK., (1995), Private Communication .

16. Al-Sums, E.A., Aziz, S., Al-Radif, A., Said, M.S. and Heikel, O., (1994), Vapor

Side Corrosion of Copper Base Condenser Tubes of the MSF Desalination Plants

of Abu Dhabi, Desalination, 97, 109.

17. Otaker Jonas, (May 1989), Developing Steam Purity Limits, Power, N.Y.

18. Malik, A.U., Asrar, N., Andijani, I. N., and Haiy, M. A. A., (2003), “CorrosionPrevention of Steel Structure with sodium Silicate”, in Proc. WSTA Sixth Gulf

Water Conference, Riyadh, Saudi Arabia, March 8-12, Vol. II, p. 363.

19. Armstrong, R.D, Peggs, L. and Walsh, A., (1994), “Behavior of sodium silicate

and sodium phosphate (tribasic) as corrosion inhibitor for iron”, J. Applied

Electrochemistry, 24, 1244.

20. Steam Turbine Blades: Consideration in Design and a Survey of Blade Failure,

(1981), Tech. Report, EPRI, Research Project 912-1, CS-1967, Palo Alto.

21. Malik, A.U., Andijani, I. N., Jamaluddin, A.T.M. and Shahreer A., (2004),

Crevice corrosion behavior of high alloy stainless steels in a SWRO pilot Plant,

Desalination, 171, 289-298.

22 Metal Handbook (1987) ASM International Vol 13, Corrosion 9th Edition P

Date post:	08-Apr-2018
Category:	Documents
Upload:	naren57
View:	220 times
Download:	0 times

THE EFFECT OF HEAVY METAL IONS ON THE LOCALIZED CORROSION

Documents