Materials
Why did my stainless weld rust?
Quick answer
Stainless welds rust from iron contamination (steel brushes/discs touching the weld), heat tint left un-treated, or wrong filler for the environment. Fix the tools discipline, pickle or passivate the tinted zone, and match filler (316L for coastal work) — stainless stays stainless when treated like stainless.
The diagnosis sequence
- Rust only at the weld: contamination or heat tint — clean, passivate, done
- Rust everywhere: wrong environment for the grade — 304 near salt spray needs 316 thinking
- Weld rusting differently from parent: mismatched filler — check ER308L vs ER316L vs the actual grade