How to Put Black Oxide on Steel

By J. Lang Wood
Black oxide, a distinctive appearance, rust
industrial_30 image by Aleksandr Popov from

Steel is used extensively in a variety of products from gun metal to hobby crafts. Unfortunately, steel is vulnerable to rusting, which discolors the product and deteriorates the material. Blackening, or adding a black oxide finish to the steel, helps prevent steel from rusting by creating a chemical reaction on the metal surface. This coating inhibits rusting and allows for additional paint finishing that will not be undermined by the rusting process. Black oxide can be finished by a cold process that can be done at room temperature.

any rust, the black oxide process
drahtbürste image by Frank-Peter Funke from

Remove any rust with a wire brush or sandpaper. The cold black oxide process requires that you start with clean parts.

Clean the steel pieces carefully to remove dust, solvent and oil residues. Mix a mild detergent and water solution and gently wash all metal surfaces with a soft cloth. Wipe dry.

Prepare the black oxide solution as directed on the package.

Immerse the steel parts into the tank of black oxide finish chemicals.

Allow the chemicals to penetrate the steel surface. Read package directions to determine length of immersion for specific materials.

Fill the rinsing tank with plain water. The tank should be large enough to fully immerse the parts that will be rinsed.

Remove parts from the chemical solution with tongs and place them into the rinsing tank. Allow the parts to set for 10 minutes, moving the parts around with tongs to ensure that all metal surfaces get a thorough rinsing.

Remove parts and allow them to dry thoroughly.

Coat with penetrating sealer using a brush or by dipping into the sealer. Shake off excess sealer. Allow to dry thoroughly.

Apply primer and paint as desired