Evaluation of Coating Performance
IMCS 2008 International Marine Coating Summit
Pukyong National University
Jin-Hwan Park
Lab. of Organic Coatings & Corrosion Control
2008. 10. 30
Contents
1. Introduction
2. Weathering test
3. Acceleration
4. Evaluation of Coating Performance
5. E I S
6. Data analysis
Introduction
Passivation film
Organic coating
Steel
H2O H2O H2OH2O H2OH2O H2O O2 O2
Be, maintain highly dielectric property
Highly chemical-resistance
Low moisture absorption and transfer rate
Optimum
coating thickness
Weathering test
Outdoor Spray-on
Appropriate environment condition for seeing the tendency characteristic against the
infrastructure or the paint exposed to oceanic environment
Coating evaluation hour is caught long
Acceleration
NORSOK M-501(Surface Preparation and Protective Coating)
- Paints, thermally sprayed metallic coatings, Passive fire protective coatings
Exposure cycle
Performance requirements for protective paint systems for offshore and
related structures
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
UV / Condensation
ISO 11507
Salt spray
ISO 7253
Low-temp.
Exposure at
(-20±2) ˚C
The exposure cycle used in this procedure lasts a full week(186h)
Evaluation of Coating Performance
- Corrosion creep from scribe: less than 3.0 mm
- Blistering (ISO 4628-2): Rating 0
- Chalking (ISO 4628-6): Max. rating 2
- Rusting (ISO 4628-3): Rating 0
- Cracking (ISO 4628-4): Rating 0
- Adhesion (ISO 4624): Min 5.0MPa and max. 50% reduction from original value.
- Overcoatable without mechanical treatment obtaining minimum adhesion of 5MPa.
Acceptable criteria
E I S
- Do not disturb the electrode properties
- Quantitative analysis of coating performance
E I S
Electrochemical Impedance Spectroscopy
complex resistance occurred by resistance, capacitor, inductor
when flowing alternating current across an electrochemical cell
The ratio of potential and current is the impedance of the cell (Z)
at the chosen frequency, according to Ohm’s law
)sin(
sin
0
0
tI
tV
I
VZ
A spectrum obtained by varying the frequency of the applied signal
Electrochemical Cell Display
Reference
electrodeCounter
electrode
Working
electrode
Electrochemical interface
Coating
E I S
Frequency Response Analyzer
Equipment
E I S
Re
Cc
Rp
Rct
Cdl
Equivalence circuit of organic coating
Cc : coating capacitance
Rp : Pore resistance
Cdl : double layer capacitance
Rc : Charge transfer resistance
SteelOrganic
coating
Real Part(ohm)
Ima
gin
ary
Pa
rt(o
hm
)coating
interface
Nyquist Plot
Re Rp Rct
Re
Cc
Rp
Rct
Cdl
Defected
organic coating Data calculationMeasurements
of E I S
Data analysis
Corrosion, effectiveness and life of surface coatings can be investigated
SteelOrganic
coating
5 10 15 20 25
-1100
-1000
-900
-800
-7009mm diameter hole
180um
280um
650um
800um
6mm diameter hole
180um
280um
650um
800um
Cycle (days)
Pote
nti
al
V
S S
.C.E
(m
V)
Possibility of corrosion
Full Cathodic protection
Data analysis
Steel
Organic
coating
Polarization scan
Of organic coatingData diagram
Prediction of corrosion possibility
Prediction of corrosion
possibility
Real Part(ohm)
Imag
inary
Part
(oh
m)
Nyquist PlotBode plot
frequency
R
Data analysis
Characteristic Impedance aging organic coating
4 6 8 10
Poor Aging begins Good Excellent
Coating impedance, Log Z(Ω•cm2 ) at 0.1Hz
Bode plot
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