Analysis on Intergranular Corrosion of Direct Drinking Water Pipe Used in 22OkV Substation

Intergranular corrosion is a kind of chemical or electrochemical corrosion on the metallic materials grain boundary. Owing to the higher impurity content in the inner grain of metal materials, the grain boundary would be more susceptible to corrosion than the inner one. After corrosion, the metal surface still maintains a certain metallic lustre, while the intergranular bonding force is significantly weakened and the mechanical properties are greatly reduced, which seriously affects the safety and reliability of the metallic components. In this paper, the cracked direct drinking water pipe used in a 220kV substation was investigated by means of macromorphology inspection, chemical composition analysis, scanning electron micrograph analysis, microstructure analysis and energy spectrum analysis. The result showed that intergranular corrosion was the main cause of cracking of the direct drinking water pipe and the chloridion in the medium further accelerated the corrosion of the pipe. In addition, targeted preventive measures were put forward in order to improve the intergranular corrosion resistance of the direct drinking water pipe and avoid the similar corrosion failure.