We recently had a 304 stainless steel waterworks fitting that was severely corroded to the point the outlet portion had become completely separated from the clamp. The clamp also showed signs of preferential corrosion on the exterior where the effluent came in contact with the surface as it spilled out of the opening. The contractors use chlorine to purge the water lines after installation. My questions are; How much chlorine content can cause this type of faliure? If while using chlorine tabs to clean lines the tabs become wet and create a gas, can this gas cause the SS to corrode rapidly? If using liquid chlorine products, what % or content can cause corrosion? Thanks for your help.

Thank you for your reply. I have a feeling that this condition happens quite frequently during the process of cleaning water lines where chlorine tablets are used as a disinfectant prior to charging the lines. Is it also possible that when the tablets are not completly disolved, that the combination of chlorine gas and highly chlorinated water will cause the same types of failures if left sitting in the line? I would like to let my customers know that chlorine in any moderately high concentrations are detrimental to all stainless steel products manufactured for use on water systems? Would this be a safe assumption? Cline Reese

What David says is absolutely correct. One of the worst environments that you can expose 300 series stainless steel to is chlorine and chlorides. There ARE other grades of stainless steel that are better. Talk to your steel supplier. The cost may be significantly higher. Passivation before use will be quite helpful, but not enough to prevent corrosion under these conditions.