Two vertical 316L stainless steel storage tanks handling phosphoric acid containing chlorides stood for years at 60 C without a problem. Raising the temperature of the acid to 75C led to failure by chloride stress corrosion cracking in three months.
Stress corrosion cracking in the heat affected zone of the circumferential weld due to residual stress, chlorides and acid conditions.
Metallographic section showed typical transgranular, branched cracks through austenite grains, typical of chloride stress corrosion cracking in 316L stainless steel.
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