Which paint should I use on metal?
Which paint should I use on metal?
Remove the rust, apply a rust-inhibiting primer the same day, then an alkyd or a direct-to-metal acrylic.
Paint on steel is a barrier, and corrosion continues under any breach in it — so the outcome is decided almost entirely by preparation. Loose scale, mill scale and oil all have to come off, and the metal has to be primed while it is still bright, because a freshly abraded steel surface flash rusts within hours in humid air and even that invisible film undermines adhesion. Aluminium and galvanised steel are different problems: aluminium regrows an oxide instantly and needs an etch primer or a self-etching product, and zinc reacts with alkyd binders. For anything outdoors, the film thickness matters as much as the product: two proper coats do far more than one heavy one, which sags and skins over uncured paint.
The options, ranked
| Option | Good at | Bad at |
|---|---|---|
| Zinc phosphate primer | The standard anticorrosive primer for steel; the pigment actively inhibits corrosion rather than just covering it. | Needs sound, clean, dry metal to work as intended. |
| Epoxy primer | The toughest barrier available and the right choice for severe exposure and for tightly adhered rust. | Two-pack, has a pot life, and chalks in sunlight so it needs a topcoat. |
| Direct-to-metal (DTM) acrylic | Primer and topcoat in one for light-duty interior work, and low odour. | Not a substitute for proper preparation and primer on anything that gets wet. |
| Rust converter | Converts residual oxide in pits that abrasive cannot reach into a stable, paintable compound. | Only works on rust, needs the right topcoat over it, and is not a substitute for removing loose scale. |
Technique that changes the outcome
- Degrease first, then remove rust to bright metal or firmly adhered oxide
- Prime the same day, and do not touch the bare metal with bare hands
- Build the film in two or three thin coats rather than one thick one
- Pay attention to edges and welds, where paint pulls thin and corrosion starts
What goes wrong
- Painting over loose rust or mill scale
- Leaving primed metal unfinished outdoors for months; most primers are not UV-stable
- Ordinary primer on galvanised steel or bare aluminium
Compiled practical guidance rather than a published standard. Product formulations vary by brand and market, so read the label — and where the work is structural, electrical or gas, the regulations that apply where you are govern rather than anything here.
Other paint questions
| For | Use |
|---|---|
| Previously painted wood | Clean it, key it and spot-prime bare areas — and find out first whether the existing paint is oil or water based. |
| Bare wood | Knotting solution on the knots, a wood primer, then your topcoat — and prime end grain twice. |
| Plastic | Any paint, provided an adhesion promoter goes on first — and on polypropylene or polyethylene, the promoter is not optional. |
| Kitchens | A scrubbable acrylic eggshell or satin on the walls — and for cabinets, degrease, prime and use a proper cabinet enamel. |
| Bathrooms | A moisture-resistant acrylic in a satin or eggshell sheen with a mould inhibitor — but ventilation, not paint, is the actual fix. |
| Ceilings | A flat matt emulsion — and if there is a water stain or nicotine, seal it with a shellac-based stain block first. |
| Tiles | Tile paint over an epoxy or adhesion primer on a thoroughly degreased and abraded glaze — and expect a limited life in a shower. |
| Fences | A penetrating stain or fence treatment rather than a film-forming paint — and let new pressure-treated timber weather first. |
| Floors | Two-pack epoxy on concrete after a moisture test and a proper grind; floor-grade varnish or floor paint on timber. |
| Radiators | A radiator enamel — water-based acrylic ones no longer yellow, which ordinary gloss on a hot surface always will. |
| Exterior masonry | A breathable mineral or masonry paint — and on an old solid wall, breathability matters more than any durability claim. |
| Galvanised metal | A mordant wash, a self-etch primer or a purpose-made acrylic primer for galvanising — ordinary oil-based primer peels off in sheets. |
| UPVC | A uPVC-specific paint or an adhesion promoter with an acrylic topcoat — and avoid dark colours, which can distort the frame. |
Common questions
- Which paint should I use on metal?
- Remove the rust, apply a rust-inhibiting primer the same day, then an alkyd or a direct-to-metal acrylic.
- What should I avoid?
- Painting over loose rust or mill scale Leaving primed metal unfinished outdoors for months; most primers are not UV-stable Ordinary primer on galvanised steel or bare aluminium
Related pages
- Which paint goes over previously painted wood? Clean it, key it and spot-prime bare areas — and find out first whether the existing paint is oil or water based.
- Which paint should I use on bare wood? Knotting solution on the knots, a wood primer, then your topcoat — and prime end grain twice.
- Which paint sticks to plastic? Any paint, provided an adhesion promoter goes on first — and on polypropylene or polyethylene, the promoter is not optional.
- Which paint should I use in a kitchen? A scrubbable acrylic eggshell or satin on the walls — and for cabinets, degrease, prime and use a proper cabinet enamel.
- Which paint should I use in a bathroom? A moisture-resistant acrylic in a satin or eggshell sheen with a mould inhibitor — but ventilation, not paint, is the actual fix.
- Which paint should I use on a ceiling? A flat matt emulsion — and if there is a water stain or nicotine, seal it with a shellac-based stain block first.
- Which paint can I use on tiles? Tile paint over an epoxy or adhesion primer on a thoroughly degreased and abraded glaze — and expect a limited life in a shower.
- Which paint should I use on a fence? A penetrating stain or fence treatment rather than a film-forming paint — and let new pressure-treated timber weather first.
- Which paint should I use on a floor? Two-pack epoxy on concrete after a moisture test and a proper grind; floor-grade varnish or floor paint on timber.
- Which paint should I use on radiators? A radiator enamel — water-based acrylic ones no longer yellow, which ordinary gloss on a hot surface always will.
- Which glue works on metal? Glue and adhesive
- Which drill bit should I use for metal? Drill bit
- Which blade cuts metal? Blade
Sources
- Typical range compiled from manufacturer specifications — At One Place