My immediate thought was Rust-Oleum clear spray, but rustoleum, krylon, and any other alkyd-based paint will react with the zinc and flake off. Primers cover the patina and are therefore not useful. I have not been able to find any other clear paint that would work for this.

Context: This is a decorative application so I'm not sure if this is the right venue. I've added a black patina to galvanized steel pipe using a copper sulfate solution. I need to add a coating to protect the patina and prevent it from yellowing over time.

Any ideas?

  • $\begingroup$ Maybe epoxy paint? $\endgroup$ – Eric S Aug 7 '20 at 13:44

You went the wrong way here. If you want to put a cosmetic finish on galvanized metal, you acid etch it at the factory and have them prime it immediately. Immediately as in they are standing there with sprayguns in hand as the piece comes out of the acid vat. There must be absolutely no patina, oxide, salts, or other tarnish. Then you can paint it on site. Assembly must be carefully planned. No metallic fastening unless 100% isolated with non-conductive materials. This isn't DIY friendly. Most DIY attempts will seriously degrade the galvanizing protection. Zinc coatings need to know which side to protect and which side to sacrifice - and they are easily confused.

  • $\begingroup$ Thanks so much for your comment. In saying this is a decorative application, I meant to convey it is indoor application. The zinc is for decoration (because it is receptive to patina), and not really necessary as a protective coating. $\endgroup$ – Karl Bayer Aug 7 '20 at 16:44

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