Accelerated test methods for evaluation of WB coating system comprising of epoxy primer and polyurethane top coat

In corrosion protection study, it is important to develop economically attractive test method for mitigation of corrosion damage of coated structure. Faster predication of protective behavior of any coating is a big challenge for the coating industries. In present work, in-house waterborne anticorrosive coating system was selected for study. The corrosion protection of coating evaluated as per ISO12944-C3-High which includes salt spray ISO 9227, 480h and quick condensation test ISO6270, 240h. The exposure period was extended up to 1000 h for further monitoring of deterioration of selected coating system. In view of early predication of coating performance, different accelerated test exposure condition were designed in laboratory, such as; thermal aging in distilled water 50°C and 80°C, chemical immersion H2SO4 and NaOH, wet-dry cycle and thermal cycling. The corrosion protection properties of coating exposed to ISO 12944-C3-High environment was compared against the lab designed test method using electrochemical impedance spectroscopy EIS technique. The deterioration rate of coating was measured by evaluating polarization resistance Rp, water uptake w and break point frequency Fb. The coated specimens after exposure were also evaluated for loss of adhesion strength. Results showed that thermal aging in distilled water at 80°C is the most severe exposure condition as coating system loses its protective behavior in relatively short period.