Surface Treatment
Finish affects rust proofing, appearance and friction — and hydrogen embrittlement risk. Common finishes fall into plating, conversion, coating and hot-dip groups; choose by condition.
| Finish | Group | Feature | Use |
|---|---|---|---|
| Zinc Plating (Clear/Blue/Yellow) | Plating | Good look, basic rust proof, best value | Dry indoor / general outdoor |
| Nickel Plating | Plating | Bright, wear resistant, moderate corrosion | Decorative, electronics |
| Chrome Plating | Plating | Hard, bright, wear resistant | Decorative, tools |
| Tin Plating | Plating | Solderable, conductive | Electronic terminals |
| Gold / Silver Plating | Plating | Excellent conductivity, corrosion | Connectors, premium |
| Zinc-Nickel (Zn-Ni) | Plating | High corrosion, low H2 risk | Automotive chassis, coastal |
| Mechanical Zinc | Plating alt. | Thick coat, no H2 embrittlement | Springs, high-strength parts |
| Passivation | Conversion | Boosts stainless corrosion | Stainless parts |
| Phosphating | Conversion | Holds oil, primer for paint | Pre-paint, locking |
| Blackening / Oxide | Conversion | Decorative, light rust proof | Tools, indoor |
| Trivalent Passivation | Conversion | Eco-friendly, good corrosion | Environmental req. parts |
| Dacromet | Coating | High corrosion, no H2 | Automotive, outdoor |
| Geomet (Zn-Al) | Coating | Eco Dacromet, salt spray | Automotive, high salt |
| Teflon / PTFE | Coating | Low friction, anti-seize | Food, chemical, high temp |
| Nylon Patch | Coating | Lock + corrosion | Vibration environments |
| E-coat | Coating | Even film, good rust proof | Automotive, brackets |
| Hot-dip Galvanizing | Hot-dip | Thick coat, strong rust proof | Outdoor steel, anchors |
| Blasting / Shot Peening | Mechanical | Descale, deburr, roughen | Pre-treatment, pre-paint |
Selection Tips
- Outdoor high corrosion: Dacromet, Geomet or hot-dip galvanizing perform best in salt spray.
- High-strength H2 safety: 10.9 / 12.9 gr prefer Dacromet, mechanical zinc or Zn-Ni; avoid acid pickling + electroplating.
- Vibration locking: pair with nylon patch, locking nuts or PTFE coating.
- Stainless parts: passivation boosts corrosion; plating usually not needed.
- Torque affected by coating: friction differs by finish; verify torque on critical joints.
Common Mistakes
- Zinc ≠ high corrosion: zinc still rusts in salt spray; don't rely on it outdoors.
- Repair damaged coating: scratches speed local rust; use zinc spray for touch-up.
- No acid on high-strength parts: acid descaling can cause H2 embrittlement; avoid on springs & 12.9 gr.
Finish affects torque and locking — state the condition when selecting; salt-spray and coating thickness reports available on request.