Studies of electrochemical corrosion of low alloy steel under epoxy coating exposed to natural seawater using the WBE and EIS techniques

摘要

The electrochemical corrosion of 907A low alloy steel under epoxy coating exposed to natural seawater was investigated by the wire beam electrode (WBE) and electrochemical impedance spectroscopy (EIS) techniques, and the correlations of the current distribution and the EIS characteristics for local defect areas of the coating were discussed. It was found that there were close corresponding relationships among the potential distribution, the current distribution and the EIS characteristics in the whole or local areas of the WBE. Each electrode of the WBE had a distinctive electrochemical corrosion characteristic during the coating degradation process. The EIS characteristics of the WBE were dominated by the substrate corrosion process of the most serious coating defect. Polarity reversals of the single electrodes under epoxy coating can be found, but the causes of the phenomena were different from each other.