Electrochemical Studies on Zero VOC Coated Steel through Atmospheric Exposure and REAP Test in the Laboratory

The application of coatings for control the degradation of materials has been historically used since ancient civilizations, but usually the coating systems take a long time to show the physical evidence of corrosion on coated metals, so the evaluation of coatings in aggressive atmospheres and with a rapid way has been the dream of the experts and users through the time. Cabinete standard tests have been developed as a quality control for coatings, including salt fog, climate chamber or artificially damage conditions.

The paint systems utilized for the study were zero volatile organic or water base paints with Zinc phosphate content. The electrochemical measurements were made before and after the potentiostatic test using the electrochemical techniques of Corrosion Potential (E_corr), Linear Polarization Resistance (LPR), Electrochemical Impedance Spectroscopy (EIS) and the Polarization Curves. For the evaluation of the atmospheric exposed coatings they were retired at different times and applied the electrochemical tests in the laboratory and returned to the exposure rack. For the application of the Rapid Electrochemical Assessment of Paints (REAP), the galvanic current was registered during the potentiostatic conditions providing an excellent parameter for the qualification of paint systems, while a degradability parameter for the paint systems can be calculated from the LPR results that can be compared with results from atmospheric exposure.