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How to Repair a Rusted Metal Roof

Metal roofs are known for their energy efficiency, long lifespan and resistance to diverse weather conditions. While metal roofs are generally sealed for protection against corrosion, scratched portions of steel and iron metal roofs can develop rust patches from exposure to oxygen, water and carbon dioxide. Besides appearing dingy, rust weakens a metal roof's structural integrity and increases the roof's susceptibility to water leaks. Immediately repair a rusted metal roof using certain supplies and techniques.

Metal roof maintenance involves removing rust patches.
  1. Scrub the affected portion of the roof with a wire brush to clear away dirt, moss, old paint, flaking roof cement and loose rust. Remove stubborn debris with a metal scraper.

  2. Rinse the metal surface with water to wash away the loosened debris. Dry the metal with paper towels.

  3. Apply naval jelly to the rust as instructed by the product manufacturer. Wear heavy-duty gloves and safety glasses for protection from the chemicals. Leave the naval jelly on the roof for 30 minutes to dissolve the rust.

  4. Flush the metal with water to wash away the naval jelly. Wipe the metal with paper towels until dry.

  5. Examine the metal surface for remaining rust. If some reddish-brown patches persist, rub 80-grit sandpaper diagonally over the metal surface until the rust is completely removed. Follow up with 120-grit sandpaper to smooth the metal surface.

  6. Saturate a clean rag with mineral spirits. Wipe the saturated rag over the metal to prepare the metal surface for paint. Allow the metal to air dry.

  7. Rinse and dry the metal surface. Make sure it is completely free of rust, dirt, oil and any debris.

  8. Apply one coat of rust-resistant primer to the metal surface using a roller brush. Allow the primer to air dry for the amount of time advised by the manufacturer.

  9. Distribute two coats of acrylic paint over the primer. Let the acrylic paint to air dry according to the instructions printed on the can's label.

Warnings

  • Metal roofs are slippery and dangerous to work on when they're icy or wet.
  • Rust can return after 24 hours of applying the naval jelly. Prime and paint the roof quickly to prevent having to redo the entire process.