To paint galvanised metal, clean it, prime it with an Etch Primer that bites the zinc surface, then topcoat with High Gloss Enamel. Galvanised sheet, palisade and roofing are coated in zinc, which is smooth and non-porous, so ordinary primers and paint slide off. An etch primer is the key step. This guide covers new versus weathered galvanising and the full system.
Why does galvanised metal need an etch primer?
Galvanised metal needs an etch primer because its zinc coating is smooth and non-porous, so paint has nothing to grip without one. Etch Primer chemically micro-etches the zinc to create a key and a bonding layer. A red oxide or wall primer laid straight onto shiny galvanising peels off in sheets, taking the topcoat with it. This is the single most common reason painted palisade and galvanised roofs fail.
Can you paint over galvanised metal?
Yes, you can paint galvanised metal once it is clean and etch-primed. New, shiny galvanising is the trickiest because its surface is at its most non-porous; weathered galvanising that has dulled outdoors takes paint a little more readily, but still needs an etch primer for a lasting bond. Never rely on the topcoat alone to stick to zinc.
Do you need to weather new galvanising first?
No, you do not need to leave new galvanising to weather for months if you use an etch primer. The old advice to let galvanising weather for a year came from the days before etch primers, when paint needed the zinc to dull and oxidise first. An etch primer removes that wait by chemically keying the surface, so new galvanising can be degreased, etch-primed and painted straight away. What matters is removing the oily passivation film, not waiting for the weather to do it.
New vs weathered galvanising
New galvanising is smooth and often carries an oily passivation layer; weathered galvanising has dulled and oxidised. For new galvanised metal, degrease thoroughly to remove the oily film, then etch-prime. For weathered galvanising, wash off chalky white zinc salts and dirt, let it dry, then etch-prime. Either way the Etch Primer is what guarantees adhesion; the cleaning just gives it a sound surface to work on.
How to paint galvanised metal step by step
- 1. Clean and degrease. Wash off dirt, oil and zinc salts; rinse and let it dry fully.
- 2. Remove any rust. If the zinc has worn through to rusting steel, strip the rust with Rust Remover and spot-treat those areas.
- 3. Etch-prime. Apply one to two thin coats of Etch Primer, letting each dry.
- 4. Topcoat. Finish with two coats of High Gloss Enamel for a hard, weatherproof surface.
How long does paint last on galvanised metal?
Over a proper etch primer, enamel on galvanised metal lasts about 5 to 10 years before it needs a maintenance coat, longer than on bare steel because the zinc keeps protecting the metal underneath. The paint fails early only where the etch primer was skipped or the surface was not degreased. Because galvanising itself resists rust, a painted galvanised gate or roof that is touched up at chips holds its finish for a long time. Inspect the cut edges and drilled holes, where the zinc is broken, and touch those up first.
Galvanised roofs and palisade fencing
Galvanised roofs and palisade take the same etch-prime-then-enamel system, with extra care on coverage. Palisade and mesh have far more surface area than their footprint suggests, so budget more primer and paint than the flat measurement implies. For a full galvanised or metal roof, a sprayable anti-rust primer such as ZP4 speeds the job; see the guide to painting a metal, IBR and corrugated roof.
Common galvanised painting mistakes
The two mistakes that ruin a galvanised paint job are skipping the etch primer and painting over the oily passivation film. Paint straight onto shiny new zinc and it peels within months, no matter how good the topcoat. Miss the degrease and the etch primer itself will not bond to the oily film left from galvanising. Get those two right — degrease, then etch-prime — and the rest of the job behaves like painting any metal.
What about cold galvanising?
Cold galvanising is a high-zinc coating used to re-protect welds and bare steel spots, not a decorative topcoat. It restores zinc protection where hot-dip galvanising has been cut, drilled or welded. After cold galvanising a repair, treat it like galvanised metal: etch-prime, then enamel, so the colour and weather protection match the rest of the surface.
Sizes and price
Etch Primer and High Gloss Enamel come in 5 litre (L) and 20 L. Coverage runs about 1 L per 8 to 12 square metres (m²) per coat on smooth sheet, less on palisade. Prices sit on the product pages and the full price list.
Where to buy
Shop Etch Primer, High Gloss Enamel and Rust Remover with national delivery, or visit our paint shops in Table View, Cape Town and Edenvale, Johannesburg. Trade line: +27 84 985 6141. See the full metal paint guide.
