Influence of size and proximity of paint coating defects on corrosion behavior of carbon steel plates

For paint-coated steel structures, corrosion tends to propagate not only from individual coating defects but also from a plurality of adjacent coating defects that, by interacting with each other, accelerates the corrosion process. However, the influence of size and proximity of the coating defect on corrosion behavior is ambiguous and unclear. In this research, combined cyclic corrosion tests were conducted over a prolonged period using paint-coated steel plates with single and two adjacent circular defects. The test results indicate that the mean and maximum corrosion depths increased when a single defect of the coated steel plate was larger. The corrosion growth rate for specimens with two adjacent circular defects was greater than the one with a single defect. Furthermore, in order to clarify the electrochemical mechanism between two adjacent circular defects, time-dependent corrosion current was measured using a model specimen with these defects.