Pitting corrosion and measuring localized corrosion potential in welds of austenitic stainless steels.

In order to get the fundamental knowledge about the pitting corrosion in austenitic stainless steel welds, some experiments with TIG welds of nine kinds of steels were conducted. The pitting phenomenon occurring in ferric chloride solution was observed minutely, and the localized corrosion potential distribution at the weld was measured to. explain the location where the pitting corrosion is apt to occur. The following results were obtained: There were three types of forms in a weight loss of austenitic stainless steel welds by pitting corrosion in ferric chloride solution. When a delta ferrite phase appeared in weld metals, the pitting corrosion concentrated on the weld metal, and this resulted in a large weight loss. The measurement of the localized corrosion potential distribution revealed that the locations which were likely to be anodic were a slaglike oxide-carbide deposited on the weld metal surface, the interface between the slaglike oxide-carbide and a matrix, and the ripple lines on the weld metal surface.