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)

Cyclic test

UV radiationSalt spray Weather-o-mete

Thermal cycleCCT

Acceleration

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

①

②

③

①

②

③

①

②

③

Thank you!