Lesson 9 — Painting metal surfaces

Tools and materials

• Magnet
• Wire brush, abrasive paper/pads
• Degreaser
• Metal primer suited to the metal
• Topcoat suitable for metal (and for heat, for radiators)
• PPE: glasses, gloves, FFP2/FFP3 mask

Preparation checklist

• Turn radiators off and let them cool completely before working.
• Protect walls and floors beneath.

Safety precautions

• Old paint on metal (railings, radiators) may contain lead — test before abrading.
• Wear eye protection when wire brushing — particles fly.
• Never use heat guns or torches on old coatings that may contain lead.

Step by step

1. Identify the metal with a magnet and by appearance.
2. Degrease the surface.
3. Remove loose paint and rust with a wire brush or abrasive until you reach firm, sound material.
4. Feather edges of sound paint.
5. Wipe clean and allow to dry.
6. Apply the correct primer straight away to bare ferrous metal, before new rust forms.
7. Galvanised or aluminium: use a primer the maker states is suitable for that metal — ordinary primers may not stick.
8. Apply the topcoat in thin, even coats, brushing along the length; work radiator fins from the top down with a radiator brush or small roller.
9. Let it dry as the data sheet says; apply a second coat if required.

Common mistakes and how to avoid them

• Painting over loose rust — it carries on spreading underneath.
• Using an ordinary primer on galvanised metal — peeling.
• Painting a warm radiator — poor finish and blistering.

Troubleshooting

• Rust spots return: preparation wasn't back to sound metal — repeat.
• Paint peeling from new galvanised: wrong primer; strip loose paint, use a galvanised-suitable primer.

Final quality check

• All rust treated
• Even coverage, no runs
• Radiator off-cool until paint data sheet times are met