Pitting behaviors of low-alloy high strength steel in neutral 3.5 wt% NaCl solution based on in situ observations

Pitting behaviors of a low-alloy high strength steel in neutral 3.5 wt% NaCl solution were investigated by in situ laser confocal microscopy and scanning electron microscopy observations. The detailed pitting morphology evolutions with time are presented. Pitting initiation sites at the oxide, sulfide, and composite inclusions and pitting growing morphologies were observed. The relationship between the pit diameter, inclusion type, and area is illustrated. A mathematical model of the pitting growth kinetics surface was established based on the in situ measurements, and the changes in the pitting shape are well simulated. Finally, pitting initiation mechanisms for the three types of inclusions and a model for pitting process are proposed.