"303 and 17-4 machined parts in seawater"

Question:

"We've noted pitting on small turned parts made from 303 and 17-4 welded to or associated with a 304 tank that is exposed to seawater and air daily. The problem has not been notice in cooler climates, but has been seen in warm climates. The affected parts are also close to a bronze bushing. The 304 tank perfoms well."

Answer:

Not a lot to go on here; however, I am assuming that you are referring to atmospheric exposure. If so, the 17-4PH should exhibit somewhat less resistance to pitting than 304SS, based on its less chromium and nickel content. 303 stainless steel may be pitting at sulfur includions, based on its high sulfur content. Galvanic corrosion should not play a material role in corrosion in atmospheric service. I may be able to help more, provided with additional details.

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