Dissolutions of Inclusions in Low-Alloy Steel Exposed to Chloride-Containing Environments

Abstract The role played by non-metallic inclusions in the nucleation of pitting corrosion in low-alloy steels is determined by the detailed analysis of the inclusions in an AISI 1536 steel and their behavior on exposure to ferric chloride and sodium chloride solutions at various pH values. It is found that the sulfide phases of the inclusions are preferentially dissolved in all cases, leading to disintegration of these inclusions. Otherwise, there is evidence that sulfide-free inclusions can behave cathodically with respect to the steel matrix, leading to localized attack of the matrix. A scheme for categorizing the inclusion attack is proposed.