Corrosion Failure Reasons for Stainless Steel Welded Tube in Lithium Bromide Units

The corrosion failure reasons for 436L stainless steel welded tube of generator and 304 stainless steel welded tubes of absorber in lithium bromide units were analyzed by detection methods of macrograph, microstructure, chemical composition, SEM and EDS analysis. The results show that there were chloride and salt in the 436L welded tubes. The pitting corrosion caused by chloride was the main reason for corrosion and leak of the tubes. The sulfur element near the pits of 304 stainless steel tubes was elevated abnormally, where microbiological corrosion because of sulfur and sulfate happened. The equiaxed grain crystallization processing and laser welding of ferritic stainless steel tube were suggested to improve the quality of weld. Moreover, the welds should be put on the top during installing, and pure water should be used during the test and the tubes should be kept dry during the long-term shutdown.