Common Fastener Surface Treatments Compared

Common Fastener Surface Treatments Compared

Surface treatment determines corrosion life, appearance and hydrogen embrittlement risk. Select by environment, cost and assembly needs.

Electroplated Zinc (Blue/Yellow/Black)

Most common, low cost, bright appearance, typically 48-96h salt spray. Suitable for indoor and general outdoor. High-strength bolts need baking after plating to prevent hydrogen embrittlement.

Dacromet (Zinc Flake)

Chrome-free dacromet reaches 500-1000h salt spray with no hydrogen risk, thin coating and heat resistance—ideal for high-strength bolts, outdoor wind, solar and automotive chassis. Downsides: poor conductivity, higher cost, dull gray finish.

Hot-Dip Galvanizing, Black E-Coat, Nickel

Hot-dip galvanizing is thick and robust for power and outdoor steel, but loosens tolerances. Black e-coat is uniform, wear-resistant with good salt spray for furniture and autos. Nickel plating is bright, corrosion-resistant and conductive for electronics and decorative parts.

Selection Advice

Zinc for indoor, dacromet for outdoor high-strength, nickel/e-coat for decorative electronics, hot-dip for thick-corrosion structural steel. Zhuhai Jiali recommends material+coating combinations by service conditions.