Corrosion Reason and Safeguard Measures for Hastelloy C22 Heat Exchanger

Aiming at the leaking accident of coil of Hastelloy C22 heat exchanger in methyl methacrylate equipment, we analyzed the reason in detail by means of chemical composition analysis, SEM, EDAX and so on. The results show that the leaking accident of coil of Hastelloy C22 heat exchanger was caused by improper welding. On the grain boundary of heat affected zone between base metal and precipitated phase, high Mo content carbide which will cause the priority corrosion of low Cr, Mo material surrounding it was precipitated, leading to intergranular corrosion and leakage. The precipitation of high Mo content carbide on grain boundary can be eliminated by solution treatment and fast cooling, sequentially, intergranular corrosion leakage induced by sulfuric acid will be avoided.