Identifying defect size in organic coatings by electrochemical noise, galvanostatic step and potentiostatic step techniques

Organic coating effectively protects metal from corrosion in atmospheric environment. As the coating undergoes degradation in harsh environment enriched with Cl- and at high temperature, there is a need to develop in-situ electrochemical methods to in-field detect the defect size in organic coatings that exposed to atmospheric conditions. This work aims to develop several electrochemical methods including open circuit potential (OCP), electrochemical current noise (ECN), electrochemical impedance spectroscopy (EIS), galvanostatic step and potentiostatic step, and the parameters obtained from each method are compared. Experimental results indicate that, apart from corrosion potential, the other four techniques can effectively detect the defect size in organic coatings by using polarization resistance or charge transfer resistance. Galvanostatic step and potentiostatic step can be used in field corrosion detection due to its concise instrumentation and short measurement time.