How to finish black oxide metal

Written by debbie tolle
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How to finish black oxide metal
Finished black oxide metal (and overgrown garden and wrought iron railings image by Stephen Gibson from

Black oxide is used on metals that are prone to rust. It is particularly applied to steel and iron, but is also used on other metals. You can apply black oxide to most metals that you have at your home to stop or prevent rusting, such as metal sheds, posts and wrought iron. Preparation is the key for the successful bonding process of black oxide to metal and the final finish coat.

Skill level:

Things you need

  • Wire brush
  • Steel wool
  • Rags
  • Paintbrush
  • 4-inch foam roller pad or larger
  • 4-inch roller frame or larger
  • Paint tray
  • Black oxide
  • Exterior, oil base primer for metal
  • Exterior, oil base direct to metal paint
  • Paint thinner

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    Applying Black Oxide

  1. 1

    Wire brush the surface of your metal to remove any flaking paint or rust build-up. A wire brush will quickly scrape off all loose particles. Follow the wire brushing by using steel wool to sand the surface of your metal as smooth as possible.

  2. 2

    Use a slightly damp cloth to remove sanding dust, dirt and grime from the surface of the metal. Water from a slightly damp cloth will quickly evaporate while you are wiping down your metal and not cause problems with the black oxide.

  3. 3

    Thoroughly stir black oxide, then with a paint brush or roller apply an even coat over the entire metal surface. Do not apply black oxide too heavily or it will run.

  4. 4

    Allow the black oxide to dry for a maximum of 24 hours or by the recommended amount of time required by the manufacturer. When black oxide is completely dry the surface of the metal, including rust, will turn black. Apply a second coat to any areas that you may have missed and let it dry. Follow the application of black oxide with a cover coat of paint.

    Finishing Black Oxide

  1. 1

    Apply a coat of exterior, oil-based primer made for metals, to provide a strong bonding surface for a cover coat of paint. Using a primer will prolong the life of your paint. Thoroughly wash your paintbrush with paint thinner. You cannot use water to clean a paintbrush used in oil-based products.

  2. 2

    Wait for the primer to dry before you apply a cover coat. Some primers will completely dry within two hours. Read the label on the primer, and follow the manufacturer's requirements before you paint.

  3. 3

    Paint the surface of your primed black oxide metal with direct-to-metal paint. Use a paintbrush for areas that you cannot access with a roller. On larger areas, use a foam roller. A foam roller will make the metal look as if it has been sprayed. Allow your cover coat to dry, then apply a second coat if necessary.

Tips and warnings

  • Tint your primer the same colour as the paint. Tinting primer will eliminate the need for a second coat of paint.
  • If your oil base paint is too thick or tacky when you apply it, add approximately 1/4 cup of paint thinner per quart of paint.
  • Some black oxide coatings do not require the use of primer before painting, and you can use an exterior acrylic latex paint for a cover coat instead of paint specifically made for metals.

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