High-Solids Epoxy Anti-Corrosion Primer
A solvent-borne, two-component (2K) epoxy primer for steel and aluminium substrates in aggressive industrial environments. The high solids content (>70% by volume) reduces VOC emissions while maintaining excellent adhesion, corrosion resistance, and topcoat compatibility. This guide covers Part A (pigment/binder component) formulation; Part B is a standard polyamide hardener.
Target Application
Industrial anti-corrosion primer for steel structures, marine, and oil & gas applications
Key Properties
- Volume solids >70%
- Excellent adhesion to blast-cleaned steel (Sa 2.5)
- ISO 12944 Category C4/C5 suitable
- Topcoat compatible with polyurethane and epoxy topcoats
Ingredient List
| INGREDIENT | % |
|---|---|
| Bisphenol A/F Epoxy Resin (80% in xylene) | 35.0% |
| Mixed Aromatic Solvent (Solvesso 100) | 10.0% |
| n-Butyl Acetate | 5.0% |
| Wetting & Dispersing Agent (pigment) | 1.5% |
| Anti-settling Agent (organoclay) | 0.5% |
| Defoamer | 0.3% |
| INGREDIENT | % |
|---|---|
| Zinc Phosphate Pigment | 12.0% |
| Titanium Dioxide (rutile, R-type) | 10.0% |
| Barium Sulphate (extender) | 8.0% |
| Talc (fine grade) | 6.0% |
Percentages are by weight unless otherwise noted. “q.s.” = quantity sufficient to reach 100%.
Manufacturing Process
- 1
Charge epoxy resin and solvents into the mill base vessel under slow stirring.
- 2
Add wetting/dispersing agent and mix for 10 minutes.
- 3
Pre-gel organoclay in a portion of solvent (10:1 solvent:clay by weight), then add to main vessel.
- 4
Add pigments and extenders in order: zinc phosphate, then TiO2, then fillers. Mix between each addition.
- 5
Grind to Hegman 5–6 (25–50 µm) using a bead mill or three-roll mill. Check grind gauge.
- 6
Let-down with remaining binder and solvent. Mix for 20 minutes.
- 7
Add defoamer last. Adjust viscosity to 85–95 KU with solvent if required.
- 8
Filter through 100 µm bag filter into final containers.
- 9
Mix Part A with Part B at the recommended mix ratio (consult hardener TDS — typically 4:1 or 5:1 by volume). Allow 20–30 minutes induction time before application.
Regulatory Notes
- VOC content of the mixed, ready-to-use paint must comply with applicable regulations — EU Directive 2004/42/EC Category A/j (one-pack performance coatings) or local equivalents
- Xylene: classified H226, H312, H315, H319, H332, H335 under CLP — ensure SDS and label reflect current classification
- Zinc phosphate: confirm REACH registration status; note discussions around zinc compounds as PBT substances
- For marine applications: IMO Resolution MSC.215(82) PSPC requirements apply — additional documentation and application records required
Formulator Tips
- Zinc phosphate loading of 10–15% by weight of total formulation gives optimal corrosion protection without sacrificing adhesion
- Induction time (sweat-in time) after mixing Parts A and B is critical — skipping it leads to adhesion failure
- Pot life at 23°C is typically 4–6 hours for polyamide-cured systems — plan application accordingly
- Apply at DFT (dry film thickness) of 60–80 µm in a single coat; excessive DFT causes solvent retention and delayed cure
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