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Guide to Fastener Finishes & Corrosion Resistance
When choosing the right fastener for your project, the finish matters as much as size and type — especially for corrosion resistance in different environments.
What is a fastener finish?
A finish is a surface treatment applied to screws, bolts, nuts or washers to improve corrosion resistance, appearance, durability — and sometimes lubricity for easier installation.
Corrosion Resistance Chart
| Finish | Corrosion Resistance | Salt Spray Hours | Best Use |
|---|---|---|---|
| Plain / Uncoated | ❌ Low | < 24 hrs | Dry indoor only |
| Black Oxide | ❌ Very Low | 12–72 hrs | Decorative or dry indoor use |
| Zinc Plated (Silver) | ✅ Moderate | 48–96 hrs | Light-duty indoor |
| Nickel Plated | ✅ Moderate | 48–96 hrs | Decorative / indoor use |
| Black Zinc | ✅ Moderate | 72–120 hrs | Aesthetic indoor use |
| Yellow Zinc / Dichromate | ✅ Moderate+ | 96–120 hrs | Semi-protected environments |
| Stainless Steel G410 | ✅ Moderate | 500–1,000 hrs | Outdoor decking, construction |
| Class 3 Galvanised | ✅ Moderate | 500–1,000 hrs | Roofing, outdoor, construction |
| Zinc Flake (e.g. Geomet®) | ✅✅ High | 1,000–1,500 hrs | Automotive, high-performance |
| Ruspert® R1000 Coated | ✅✅ High | 1,000–1,500 hrs | Exterior, coastal, decking |
| Mechanical Galvanised | ✅✅ High | 1,000–1,500 hrs | Outdoor, construction, structural |
| Class 4 Galvanised | ✅✅✅ Very High | 1,000–1,500+ hrs | Roofing, outdoor, construction |
| Hot-Dip Galvanised | ✅✅ ✅ Very High | 1,000–1,500+ hrs | Outdoor, construction, structural |
| Stainless Steel G304 | ✅✅✅✅ Excellent | 1,500–2,000+ hrs | Outdoor, food-grade, general use |
| Bremick B8® Coating | ✅✅✅ ✅Excellent | 2,000–5,000+ hrs | Roofing, outdoor, construction |
| Stainless Steel G316 | ✅✅✅✅✅ Ultimate | Extreme / marine-grade | Coastal, saltwater, chemical use |
✅ Quick Tips
- Indoors only? Zinc plated, Zinc Yellow or Black Oxide is usually sufficient.
- Outdoor use? Choose Hot-Dip Galvanised, Class 3 / 4, or G304 Stainless steel.
- Coastal or marine? G316 Stainless steel or Bremick B8 for superior resistance.
****Information has been sourced from various companies and has been provided to be used as a guide only
