In-situ observation and kinetics study on shrinkage defect corrosion of ductile iron in NaCl solution

The corrosion propagation and kinetics of shrinkage defects in ductile iron in NaCl solution were investigated by in-situ observation based on time-lapse microscopy and confocal laser scanning microscopy. Immersion experiments reveal that shrinkage defects endure notably harsher corrosion compared to the matrix, exhibiting an average depth increase of 52.38 mu m within a single day. The depth loss rate, a crucial indicator for corrosion kinetics, inversely correlates with the square root of immersion time, underscoring the substantial role of shrinkage defects in expediting early-stage corrosion. The corrosion process predominantly involves longitudinal extension, with sharply shaped defects experiencing the most significant depth increases.