How do I paint a radiator or metal surface?

Radiators expand and contract every time the heating runs, and they reach temperatures that ordinary paint is not designed for. Both the primer and the topcoat need to be appropriate or the finish fails within a season.

Safety

What you'll need

• Metal primer
• Radiator paint
• Sandpaper
• Degreaser
• Small roller and brush (optional)

Step by step

1. Turn the heating off and let it go completely cold.Not warm. Paint on a warm radiator dries too fast, brushes badly and releases fumes. This can take several hours.
2. Clean it thoroughly with a degreaser.Radiators collect dust and airborne grease. Paint over that and it peels regardless of the primer.
3. Sand the whole surface lightly.It keys the existing finish so the primer can grip. Remove any flaking or rust back to sound metal.
4. Treat any rust before priming.Rust spreads under paint. Sand back to bare metal and use a rust-inhibiting primer on those areas.
5. Apply a primer suitable for metal.Ordinary wall primer will not adhere. A dedicated metal or radiator primer is the step that determines whether the finish lasts.
6. Use paint designed for radiators.It is formulated to tolerate heat cycling without yellowing or cracking. Ordinary gloss yellows noticeably within a year on a radiator.
7. Apply thin coats with a small roller and brush.Roller for the flat faces, brush for edges and between fins. Two thin coats are far better than one thick one, which runs and sags.
8. Leave it to cure fully before turning the heating on.Check the product instructions — often several days. Heating it too early can cause the finish to soften, blister or smell strongly.

Tips

• A radiator can be removed and painted flat, which gives a far better finish and lets you reach the back — but it requires draining and refitting.
• Radiator brushes with a long angled handle reach behind and between fins, which is otherwise almost impossible.
• Painting a radiator the same colour as the wall makes it far less visually prominent than a white radiator against colour.

Common mistakes

• Painting a warm radiator — The paint dries too fast to brush out, leaving marks, and the fumes are unpleasant. Let it go completely cold.
• Using ordinary emulsion or gloss — Neither tolerates the repeated heat cycling. Emulsion flakes and gloss yellows badly within a year.
• Skipping the metal primer — Paint does not adhere reliably to metal without it, and the finish flakes at the first knock.

Questions people ask