Home » Zinc-Flake Coatings – Quick Selection Guide
(GEOMET / DACROMET / GEO-BLACK / etc.)
Zinc-Flake Coatings – Quick Selection Guide
1) Summary Comparison Table
| Coating System | Typical Types / Grades | Appearance / Color | Salt Spray (ISO 9227 NSS) | Typical Thickness | Topcoat Options | Notes |
|---|
| GEOMET 321 | 321, 321H, 321 Plus | Silver-gray metallic | 480-720 h (no red rust) | 6-12 μm | Organic lubricated topcoat optional | Most common general-purpose GEOMET; excellent fastener coating |
| GEOMET 500 | 500A, 500B, 500 + Topcoat | Silver-gray; slightly darker than 321 | 720-1000 h | 8-12 μm | Integrated lubricant in many variants; additional topcoat optional | Better friction control; used in automotive / structural |
| GEOMET 720 | 720, 720A | Silver-gray | 1000-1500 h+ | 8-12 μm | Optional | High corrosion resistance; heavy-duty applications |
| DACROMET 320 | 320L, 320D | Silver / dull gray | 600-720 h | 7-12 μm | Yes (for friction tuning) | Older system; some regions restrict Cr(VI) versions |
| DACROMET 500 | 500L, 500B | Medium gray | 720-1000 h | 8-12 μm | Yes | Higher performance DACROMET; Cr-free versions available |
| GEO-BLACK® | GEO-BLACK C / D / Plus | Black (matte to semi-gloss) | 720-1000 h depending on system | 6-15 μm | Usually required; defines gloss + friction | Black aesthetic version of GEOMET family |
| Zinc-Flake + PTFE Topcoats | GEOKOTE, Dri-To-Coat, black PTFE | Silver, black, or graphite-like | 1000-1500+ h | 10-18 μm | Required (PTFE/fluoropolymer) | Low-friction, chemical-resistant |
| Zinc-Al + Organic Hybrid | ZF hybrid coatings (various suppliers) | Silver, dark gray | 600-1200 h | 8-15 μm | Optional | Economical alternative systems |
2) Detailed Quick-Selection Table (Use for Choosing the Right Coating)
A. Appearance / Aesthetic Requirements
| Requirement | Recommended Coating | Why |
|---|
| Silver-gray standard fastener finish | GEOMET 321 / DACROMET 320 | Widely accepted, economical |
| Premium high-uniformity silver | GEOMET 500 | Better smoothness & friction control |
| Black finish | GEO-BLACK or GEOMET 321 + black topcoat | Stable color + corrosion resistance |
| Very dark / graphite appearance | PTFE black topcoat | Smooth feel & chemical resistance |
B. Corrosion Resistance Targets
| Required NSS Hours | Recommended System |
|---|
| ≥ 480 h | GEOMET 321, DACROMET 320 |
| ≥ 720 h | GEOMET 500, DACROMET 500, GEO-BLACK |
| ≥ 1000 h | GEOMET 720, GEOMET 500 + topcoat, PTFE systems |
| ≥ 1500 h | GEOMET 720 + high-performance topcoat |
C. Friction / Torque-Tension Requirements
| Requirement | Recommended System |
|---|
| Standard fasteners | GEOMET 321 + lubricant topcoat |
| Controlled μ = 0.10-0.18 | GEOMET 500A / 500B |
| Controlled μ = 0.12-0.20 (black) | GEO-BLACK + friction topcoat |
| Very low friction | Zinc-flake + PTFE topcoat |
D. Thickness Selection
| Typical Thickness | Where Used |
|---|
| 6-10 μm | Standard bolts, nuts, washers, clips |
| 8-12 μm | Structural bolts, chassis components |
| 10-18 μm | Severe corrosion or heavy-duty assemblies |
| 12-25 μm | PTFE-enhanced / multi-layer systems |
3) Quick Decision Guide
If you need…
- Lowest cost zinc-flake → DACROMET 320 or GEOMET 321
- Black coating (OEM-friendly) → GEO-BLACK
- Best corrosion resistance → GEOMET 720
- Stable friction (automotive) → GEOMET 500
- Very low friction / chemical resistance → Zinc-flake + PTFE
- Chromium-free requirement → All modern GEOMET systems + Cr-free DACROMET versions
