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Zinc sulphate treatment of cast ductile iron

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I am seeking a method to protect cast Ductile Iron parts for use in high temperature, high humidity enviroment, close to the ocean. 316 Stainless is usually specified but I have been told that a treatment with zinc sulphate may be superior to even 316. How could this be so? The items are cast into the outside of concrete walls.

Ernest Comerford
- Brisbane, Queensland, Australia

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This sounded intriguing, but in searching the Internet and reference books back to the early 1960's, I was unable to find such a treatment. Perhaps someone was thinking of a zinc chromate-containing primer?

If the parts are already installed, and assuming high temperature refers to ambient conditions, I recommend a good cleaning (using a phosphoric acid rust remover if necessary), followed by a zinc-rich epoxy primer and a polyurethane topcoat.

Ken Vlach
- Goleta, California

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