Abstract Leakage occurred in stainless steel pipes conveying a 30% KOH solution in an electrolytic hydrogen production unit after one year of service. The leakage pipe consisted of straight pipe and elbows by welding. This study aims to determine the cracking failure causes based on non-destructive testing, visual observation, fracture surface analysis, microstructure investigation, chemical composition and mechanical properties, and residual stress measurement. The cracking failure was attribut