Corrosion in water supply pipe stainless steel 304 and a supply line of helium in stainless steel 316

• Pitting corrosion on outside piping surface of stainless steels 304 and 316 by chlorine action.
• Pitting corrosion is induced by hypochlorite ion in a state of wet/dry conditions.
• One wrong welding procedure in connection pipes: flaws, irregularities, lack of fusion and porosity.
• Corrosion of weld with the formation of rust from the inside of pipe in the water supply system.
• Developing differential concentration cells in the crusts formed on the piping.

A corrosion spreading throughout the 304 stainless steel tubing of a water system to supply various buildings was observed, and also leaks were detected in welding zones. The same place is also crossed by a gas distribution network, with a helium pipe 316 of stainless steel that required periodic repairs more or less every two years, due to the presence of leaks. The tests showed that both types of stainless steel have suffered localized corrosion induced by hypochlorite ion, in a mechanism of dry/wet, and that the welding procedure performed on the 304 stainless steel is unacceptable. Some immediate procedures were undertaken to keep systems running, but recommendations were given for a final resolution of the problems.

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