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Anti-Corrosion Surface Coatings for Screws: Zinc, HDG, Dacromet & Black Oxide
Compare fastener plating and protective finishes. Salt spray test hours (ASTM B117), outdoor durability, hydrogen embrittlement risks, and cost efficiency.
Corrosion Resistance Ratings (Salt Spray ASTM B117)
| Coating Method | Coating Thickness | Salt Spray Hours to Red Rust | Primary Application |
|---|---|---|---|
| Black Oxide | 1 - 2 µm | 24 - 48 hours (indoor with oil) | Indoor machinery, optical tools |
| Electro-Zinc Plated (Clear/Yellow) | 5 - 12 µm | 72 - 120 hours | General indoor hardware, automotive brackets |
| Hot-Dip Galvanized (HDG) | 45 - 65 µm | 500 - 1,000+ hours | Outdoor infrastructure, telecom towers, solar framing |
| Dacromet / Geomet (Zinc Flake) | 10 - 15 µm | 1,000 - 1,500+ hours | Automotive chassis, marine hardware, wind turbines |