How To Paint Metal?
QUICK ANSWER
Paint metal by removing all rust with sandpaper or a wire brush, cleaning the surface with a degreaser, applying a rust-inhibiting primer (Rust-Oleum Rusty Metal Primer or Stops Rust), then painting with a metal-rated topcoat. Two thin coats provide better coverage than one thick coat.
Painting metal is fundamentally different from painting wood or drywall. Metal does not absorb paint at all; everything happens at the surface. The right primer is the most important factor since it converts rust, blocks new rust, and provides a surface paint can bond to. The wrong approach leaves you with peeling paint and rust bleeding through within months. Here is the method that produces durable results.
What metal needs paint?
Common painted metals: steel (most outdoor furniture, fences, gates, metal doors), wrought iron (railings, gates, decorative items), cast iron (radiators, decorative items), aluminum (siding, gutters, some furniture), and galvanized steel (specific prep needed, see separate article). Each has slightly different prep requirements. Steel is the most common and most rust-prone. Aluminum needs less rust treatment but still needs primer for paint adhesion. Cast iron is durable and paint adheres well after sanding rust spots.
How do you prep metal?
Remove all loose rust, flaking paint, and dirt with a wire brush, sandpaper (60 to 80 grit), or angle grinder with a wire wheel for severe cases. Sand smooth any sharp edges or pitting. For badly rusted metal, treat with a rust converter (Rust-Oleum Rust Reformer chemically converts rust to a paintable surface) before priming. Wipe down with mineral spirits or a degreaser to remove oils, dust, and surface contaminants. The metal must be completely clean and dry before primer goes on.
What primer and paint should you use?
Use a rust-inhibiting primer designed for metal: Rust-Oleum Stops Rust Primer, Rust-Oleum Clean Metal Primer, or Sherwin-Williams DTM Acrylic Primer. For severely rusted metal, use Rust-Oleum Rusty Metal Primer which is formulated to bond over residual rust. For topcoat, use a paint specifically rated for metal: Rust-Oleum Stops Rust, Krylon Rust Tough, or Sherwin-Williams Pro Industrial. Spray paints work well for furniture and decorative items; brush-on paints work for larger or detailed surfaces.
How do you handle rust?
For light surface rust: sand off, prime with rust-inhibiting primer, paint normally. For moderate rust with some pitting: wire brush thoroughly, treat with rust converter, prime, paint. For severe rust with thinning metal or holes: address structural integrity first (may require welding or replacement). For metal that will be repeatedly exposed to moisture (outdoor furniture, fences), use a 2-part epoxy paint for maximum durability. Re-prime and repaint metal showing any rust as soon as you notice it, before the rust spreads.
Painting metal is mostly about rust management and primer selection. Remove all rust, clean thoroughly, apply rust-inhibiting primer, finish with metal-rated topcoat. Two thin coats outperform one thick coat. For severely rusted metal, use specialized products designed for that situation. Watch for and treat any new rust spots immediately since rust spreads under paint and causes peeling. Done right, painted metal lasts 5 to 15 years outdoors.
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