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How to Paint Rusted Metal

By Jim Dugan
Professional Contractor & DIY Expert

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Before you try to paint rusted metal, seal the existing oxidation, or it will inevitably bleed through. No one manufactures a 100 percent reliable paint that can permanently block rust. When professionals paint rusted metal, they seal it with a certain type of priming agent, formulated with special chemicals that prevent the oxidation from showing through. To generate a lasting finish, follow the same tactic.

Cleaning the Rusted Metal

Before you can paint over rusted metal, you must add a primer. Unfortunately, the primer won’t stick to layers of flaking rust. Scrape as much of this off of the metal as you can, using a wire brush. Before priming or painting rusted metal, wash the surface. For best results, use a cleanser that has a degreasing agent.

Prime Over Rust

If you paint rusted metal without priming it, peeling will follow. If you prime over rusted metal, using plain latex primers, bleed-through will result. The only way to permanently seal rust is to apply a zinc chromate or iron oxide primer. Once the rust is primed, you may paint it.

Painting Over Rust

You can paint rusted metal if it has been prepped with the right primer. It doesn’t matter if you need to paint rusted steel, rusted iron, rusted aluminum or failing rusted galvanized metal; use the same prep technique for each. Paint over rusted metal, using an oil-based finish that is compatible with iron oxide primer. Do not paint over rusty metal, using latex paint as it is not compatible with oil-based iron oxide primer.