"316L in contact with Phosphoric Acid + NaOH"

Question:

"Does anyone have experience of the susceptibility to corrosion of 316L SS to the cycling presence of phosphoric acid followed by low/intermediate conc. sodium hydroxide solution. Some of our cold formed thin plate (3-5mm) SS components have shown some pitting/holes in this environment (up to 80C/180F) although no discolouration has been seen. Can the acid/alkaline rinse be the cause? The solutions would only be present for 60minutes per day. The remainder of the time the atmosphere would be dry at 60C."

Answer:

With the plate being so thin, you might want to investigate whether the pinholing is occurring at non-metallic inclusions. 316SS, otherwise should resist both environments, based on your stated conditions.

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