Coating thickness / corrosion resistance (neutral salt spray) / cost / remarks
Screw surface treatment is a commonly used processing method for screws, which can not only improve the surface brightness of screws, but also improve the performance of screws.
| Screw surface treatment process | Coating thickness | Corrosion resistance (neutral salt spray) | Cost | Remark |
| Oxidation black | about 1um oxide layer | 1-3 hours | low | |
| black nickel, white nickel | Copper: 0.5-1um Nickel: 2-10um | 6-12 hours | middle | Re-plating products above 10um |
| white zinc, blue zinc | Zinc: 2-10um | 6-12 hours | middle | |
| green zinc | Zinc: 2-10um | 8-20 hours | middle | Due to the limited use in the industry, only one sample from one manufacturer was collected, which is not representative. |
| black zinc | Zinc: 2-10um | 20-40 hours | middle | |
| Color zinc | Zinc: 3-15um | more than 48 hours | middle | |
| Electrophoresis black | The coating is about 15um | More than 100 hours | High (less than stainless iron and stainless steel) | |
| Dacromet | Coating about 5-40um | More than 100 hours | High (less than stainless iron and stainless steel) | Poor coating uniformity |
| 304 stainless steel | / | more than 48 hours | High | Surface cleaning |
| stainless iron | / | about 20 hours | High (less than stainless steel) | Surface cleaning |
