Can 316L stainless steel rust?
Yes. No stainless grade is stainless forever. 316L has a much higher chloride threshold than 304, but it still corrodes where chlorides concentrate, where deposits hold moisture against the surface, or where the passive film is damaged and has no oxygen to rebuild itself.
The three realistic failure paths
Chlorides trapped in a crevice under a sealant or a fixing; salt and dust deposits left unwashed on a sheltered elevation; iron contamination from carbon steel tools, scaffolding or swarf.
How the risk is designed out
Detail joints so water drains and dries, avoid open crevices, keep carbon steel away from stainless, and specify a wash cycle the building can actually sustain.
Tea staining is not failure
Brown surface discolouration is a stain on the passive film, not structural corrosion. It is removed with a mild acid cleaner and does not require panel replacement.
After welding or heavy site cutting, passivation restores the chromium oxide layer. Skipping it is the most common reason a new facade stains within its first year.
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