Research on the causes of pitting corrosion of 201 stainless steel plate

The surface of the 201 stainless steel plate has high corrosion resistance due to the formation of a dense chromium oxide film. However, local spot corrosion is difficult to avoid. Pitting damage has great concealment and sudden, especially in petroleum, chemical, nuclear power and other fields, pitting corrosion is easy to cause pipe wall perforation, make a lot of oil and gas leakage, and even cause fire, explosion and other disasters.

Since the 1930s, human exploration of stainless steel pitting nucleation mechanism has never been interrupted. But the initial location of pitting has always been considered "random and unpredictable." The research of Ma Xiuliang and other scientists shows that the local dissolution of manganese sulfide under certain medium conditions originates from the interface between it and the "tumor", and gradually expands into the material. The results also show that the local dissolution rate of manganese sulfide is different due to the nano-oxide octahedron. On this basis, the research team, in collaboration with Professor Peijun Hu of Queen's University Belfast, determined that the oxide nano-octahedron, which has strong activity and is easy to quickly dissolve the surrounding manganese sulfide, has the characteristics of metal ions as its outer surface, similar to "malignant tumor"; In contrast, the less active nanooctahedron has oxygen ions as its outer surface, similar to a "benign tumor." This discovery provides direct evidence to reveal the starting position of manganese sulfide dissolution in the early stage of stainless steel pitting corrosion, and raises people's understanding of the pitting mechanism of 201 stainless steel plate from the previous micron scale to the atomic scale.