Ordinary primers often peel off new galvanised steel. Short answer: National Paints’ specifier starts galvanised and non-ferrous metal with a thin coat of National Wash Primer, then National Zinc Chromate Primer, one coat of Synthetic Undercoat and one coat of Synthetic Enamel. The specifier gives a total of 140 to 150 microns dry.
The system, coat by coat
| Coat | Product | Dry film per coat |
|---|---|---|
| 1 | National Wash Primer | 5 to 8 µm |
| 2 | National Zinc Chromate Primer | 50 µm |
| 3 | National Synthetic Undercoat | 40 to 50 µm |
| 4 | National Synthetic Enamel Gloss I or II | 40 µm |
| Total given in the specifier | 140 to 150 µm | |
Where it applies
National lists this system under “galvanized and non-ferrous metal”. Typical items include galvanised railings, ducts, gates and sheet metal. For plain structural steel, use one of the National steel systems instead.
Good practice
- Start on a clean, dry surface, and ask for the product data sheets for surface preparation details.
- Keep the wash primer thin; National specifies only 5 to 8 microns.
- Ask for each product’s data sheet for drying times and thinner. We list the thinners we have confirmed in our thinner guide.
Frequently asked questions
Can I use aluminium paint on galvanised steel?
The specifier’s galvanised system ends in Synthetic Enamel, not aluminium paint. If you want a metallic finish, ask us to check the primer compatibility first. See our Aluminium Paint guide.
Step 1: prepare galvanised steel
Galvanising needs its own preparation before any paint. National’s surface preparation guide gives this order for galvanised and aluminium:
- Degrease to remove oil and grease.
- Sand with abrasive paper and solvent to give a key.
- Apply an etch primer: in this system, National Wash Primer.
Each coat in more detail
- Zinc Chromate Primer: the anti-corrosive coat over the wash primer.
- Synthetic Undercoat: builds film and opacity.
- Gloss I or Gloss II: the finish.
How it compares with plain steel
For bare steel, National’s specifier lists Red Oxide Primer twice at 35 microns, two undercoats and one gloss, for 165 to 190 microns in total, under BS 5493. Galvanised steel swaps the primers for a wash primer and one coat of zinc chromate, for 140 to 150 microns. See painting steel with National Paints.
Mistakes to avoid
- Painting straight onto shiny galvanising.
- Building the wash primer thick. It is listed at only 5 to 8 microns.
- Skipping the undercoat. The total film drops below the specified 140 to 150 microns.
Buy in Sharjah and Dubai
Al Tashteb Al Saree is an authorised National Paints retailer. Message us on WhatsApp for Wash Primer, Zinc Chromate Primer, undercoat and enamel.
Sources
- National Paints systems specifier (PDF, via AEC Online)
- National Paints surface preparation guide, Sec. A-2 (PDF)
Retrieved 3 November 2026. The main image is illustrative.
