Corrosion Failure Reasons for Welded Joint of Stainless Steel Pipeline for Nitrate Transport

Chemical composition analysis, field emission scanning electron microscopy, energy spectrum analysis were used to study the corrosion failure reasons for nitric acid transportation pipeline welds. The results showed that intergranular corrosion occured mainly in the weld heat affected zone of 304 stainless steel pipe, and knife-line corrosion occured along the heat affected zone. Carbon content of the tee joint material was higher than the standard value, leading to the material in the heat affected zone more likely to be sensitized and to form coarse grains during the welding process, resulting in a decline of the material's corrosion resistance. Carbon content was the key factor influencing the nitric acid corrosion resistance of 304 stainless steel weld joint, high carbon content led to stainless steel sensitizing in heat affected zone during welding process, reducing the corrosion resistance of the material.