Short answer: National Red Lead Primer is an alkyd-based anti-corrosive primer pigmented with red lead, for steel structures in mild to moderately corrosive atmospheres. Degrease the steel, clean it to St 2 or blast it to Sa 2.5, then brush or roll one coat at 30 to 40 microns dry. It covers about 13 to 17.5 m² per litre and takes Synthetic Undercoat after 12 hours at 30°C. Because it contains lead, National’s data sheet says to avoid spraying and to wear a mask if you must.
When to choose Red Lead
National positions Red Lead one step above its everyday Red Oxide Primer: the data sheet lists it for steel structures in mild to moderately corrosive atmospheres, where Red Oxide is listed only for domestic and mildly corrosive ones. Both are alkyds and take the same undercoat and enamels. Choose another primer when the metal is not plain steel or the site is harsher:
| Primer | National lists it for | Colour | m² per litre | Recoat at 30°C |
|---|---|---|---|---|
| Red Oxide | Steel, domestic and mildly corrosive | Red | 14 to 18.5 | 8 to 12 h |
| Red Lead | Steel structures, mild to moderately corrosive | Red-orange | 13 to 17.5 | 12 h |
| Zinc Phosphate | Structural steel, tanks, pipelines, moderately corrosive | Grey | 11.5 | 10 h |
| Zinc Chromate | Steel, galvanised steel, aluminium, brass | Yellow / yellowish green | 14 to 19 | 12 h |
Key facts
| Decorative sheet | Protective sheet | |
|---|---|---|
| Type | Alkyd anti-corrosive primer with red lead pigment, single pack, matt | |
| Volume solids | 53 ± 2% | 51 ± 2% |
| Specific gravity | 1.70 ± 0.05 | |
| Spreading rate | 13 to 17.5 m² per litre | 12 to 17 m² per litre |
| Film per coat | 30 to 40 µm dry (55 to 75 wet) | 30 to 40 µm dry (60 to 80 wet) |
| Drying at 30°C | Touch 3 to 4 h; recoat 12 h; hard 24 h | Touch 5 h; recoat 12 h; hard 24 h |
| Application | Brush or roller preferred; spray only with a protective mask (airless 2100 to 2200 psi, tip 0.015 to 0.020 inch) | |
| Thinning | 5 to 15% | Airless 5 to 10%, air 10 to 15%, brush 10% |
| Thinner | National G.P. Thinner | |
| Flash point | 38°C | |
| Shelf life | 12 months, sealed | 18 months, sealed |
Working safely with a lead primer
- Read the product’s safety data sheet before work; National’s data sheet refers you to it.
- Brush or roll rather than spray, as the data sheet advises. If spraying is unavoidable, wear a suitable protective mask.
- Keep it for steel structures. It is not a primer for indoor household items or anything children handle; for those, Red Oxide or lead-free Eco Enamel over a suitable primer are the National options.
- Store sealed, shaded and away from heat: the flash point is 38°C.
Step 1: prepare the steel
National’s surface preparation guide sets the same order for all steel primers:
- Degrease. Solvent wash and wipe dry with clean rags, or use detergent and rinse with fresh water so no residue stays.
- Clean off rust and mill scale to St 2 (wire brushing, scraping, chipping or sanding of loose scale, rust and old paint) or, for structural work, blast to Sa 2.5 (very thorough blast, near white metal). The guide notes power tools cannot remove tightly adhering mill scale.
- Prime the same day while the surface is clean and dry.
| Grade | Meaning | BS 4232 | SSPC |
|---|---|---|---|
| Sa 3 | Blast to visually clean steel | First Quality | SP-5 |
| Sa 2.5 | Very thorough blast, near white | Second Quality | SP-10 |
| Sa 2 | Commercial blast | Third Quality | SP-6 |
| St 2 | Hand or power tool cleaning of loose material | Less demanding work | |
Step 2: apply the system
- Red Lead Primer, one coat at about 40 microns dry, by brush or roller.
- National Synthetic Undercoat, one coat at about 40 microns, after 12 hours.
- National Synthetic Enamel Gloss I or Gloss II, one to two coats at about 35 microns.
What the data sheet numbers mean
- Coverage = volume solids × 10 ÷ dry film. At 53% solids: 530 ÷ 30 ≈ 17.7 m² per litre; 530 ÷ 40 ≈ 13.3 m² per litre, matching the sheet.
- Wet film to aim for = dry film ÷ volume solids: 40 ÷ 0.53 ≈ 75 microns wet for a 40-micron coat.
- Red Lead is dense (SG 1.70): every 18 litres weighs about 30 kg, well above a typical emulsion. Plan lifting on site.
How much to buy
| Steel area | Red Lead, 1 coat | Undercoat, 1 coat | Gloss II, 2 coats |
|---|---|---|---|
| 50 m² | 2.9 to 3.8 L | 2.9 to 3.8 L | 6.1 to 8 L |
| 100 m² | 5.7 to 7.7 L | 5.9 to 7.7 L | 12.1 to 16 L |
| 250 m² | 14.3 to 19.2 L | 14.7 to 19.2 L | 30.3 to 40 L |
Mistakes to avoid
- Spraying without protection. The data sheet is explicit about avoiding spray.
- Priming galvanised or aluminium. National lists Red Lead for steel only; for non-ferrous metal use Zinc Chromate after an etch primer (see painting galvanised metal).
- Recoating too soon. The sheet gives 12 hours to recoat at 30°C, and touch-dry alone takes 3 to 5 hours.
- Buying too far ahead. The decorative sheet gives a 12-month shelf life.
Frequently asked questions
Red Lead or Red Oxide?
Red Lead is listed for steel structures up to moderately corrosive atmospheres; Red Oxide for domestic and mild conditions, recoats sooner (8 to 12 hours) and keeps longer (18 months). For gates and grilles at home, Red Oxide is the usual choice.
Is it enough for coastal or industrial sites?
National’s specifier uses an epoxy system (300 to 350 microns) for heavy duty, not an alkyd primer. See steel painting systems and ask us for the epoxy products.
Which thinner?
National G.P. Thinner, 5 to 15% by volume depending on the method. See which National thinner to use.
Buy in Sharjah and Dubai
Al Tashteb Al Saree is an authorised National Paints retailer in Bu-Tina, Sharjah. Message us on WhatsApp for Red Lead Primer, undercoat, enamel and G.P. Thinner, or see all National Paints products.
Sources
- National Red Lead Primer, decorative data sheet (PDF)
- National Red Lead Primer, protective data sheet (PDF)
- National Paints surface preparation guide, Sec. A-2 (PDF)
- National Paints systems specifier (PDF)
All via AEC Online, retrieved 4 November 2026. Quantities and weights are our own calculations. The main image is illustrative.
