What Is an EP Primer
EP primer (epoxy primer, EP primer) is a two-component priming material based on an epoxy resin and an isocyanate or polyamide hardener. After polymerisation it forms a dense, virtually impermeable film with exceptional adhesion to steel, galvanised steel, aluminium, and plastic.
How It Differs from Other Primers
EP vs Acrylic Primer
- Epoxy: higher adhesion, better moisture resistance, does not absorb water
- Acrylic: easier to sand, fills irregularities, less expensive
- Choice: epoxy — first coat on bare metal; acrylic — filling primer applied on top
EP vs Acid Primer (Wash Primer)
- Acid primer (1K, phosphoric acid): chemically etches metal, creates micro-roughness — applied to bare metal under epoxy
- Epoxy: applied over acid primer or directly onto prepared bare metal
- They MUST NOT be mixed into a single layer — only applied in sequence
Where Epoxy Primer Is Mandatory
- Bare metal — after sandblasting, grinding down to bare metal, or welding
- Corrosion-affected areas — repaired sections where rust was present
- Sills and underbody — areas with heightened moisture exposure
- Galvanised steel — the only primer with reliable adhesion to zinc
- Aluminium — for aluminium body panels (bonnet, doors)
- New-vehicle systems — during factory body preparation from scratch
EP Primer Application Procedure
- Surface preparation — sanding P80–P150, degreasing with anti-silicone
- Optional: apply wash primer (acid primer) — 1 thin coat, flash time 15–30 min, do NOT sand
- Mix EP: paint + hardener (usually 4:1 or 3:1 by volume)
- Apply 2 coats of EP with a flash time of 15–20 min between coats
- After partial cure (1–2 h): sand with P240–P400 before applying acrylic filling primer
Important: Epoxy primer must not be dry-sanded — use wet sanding or a dust-extraction orbital sander only. When heated it releases harmful isocyanates.
Recoat Window and Matting
EP primer has a "recoat window" — typically 30 min to 8 h after application. If the window has passed, sanding is required. After full cure (24+ h) inter-coat adhesion decreases.
Popular EP Primers on the Ukrainian Market
- PercoTop CS980 2K Epoxy Binder — industrial system, excellent adhesion to metal
- PercoTop CS911 2K DTM Binder — DTM (Direct To Metal), can be applied without sanding to a clean surface
- Standox Epoxy Primer — premium option for bodywork repair
❓ Frequently asked questions
How many coats of EP primer are needed?▾
Typically 2 coats. The first is an adhesion coat (thin, 25–30 µm), the second is a build coat (30–50 µm). In areas with high corrosion risk (underbody, sills) 3 coats can be applied.
Can you paint directly over EP primer?▾
Yes, but only after the surface has been sanded and an acrylic filling primer is used between the primer and the topcoat. Painting directly over sanded EP is only suitable when the system specifically allows it (certain DTM systems).
What is the difference between EP primer and acid primer?▾
Acid primer (wash primer) — 1K, thin, chemically etches metal, cannot be sanded. Epoxy primer — 2K, thicker film, sandable, provides anti-corrosion protection. They are applied in sequence: acid primer first, then EP on top.
Where can I buy EP primer in Ukraine?▾
UA-Pro offers a wide range of epoxy primers by PercoTop, Standox, and other brands with delivery across all of Ukraine. Order online or by phone at +380993040007.
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