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Zinc alloy plating

It is widely known that preferable sacrificial anti-corrosive zinc-based plating films for iron, cast iron, and other iron-based materials have a natural potential close to iron though it is less noble than iron. From these perspectives, zinc-nickel alloy plating and zinc-iron alloy plating having excellent anticorrosion property with the potential of zinc controlled by alloying nickel and iron have been commercialized.
Type of plating Features SST white rust SST red rust
Zn-Fe alloy plating Colored chromate 120 H 800 H
Sn-Zn alloy plating Colored chromate 192 H 800 H
Zn-Ni alloy plating
(containing 7 – 10% Ni)
Hexavalent colored chromate 600 H 1200 H
Trivalent colored chromateGreen mark 500 H 1500 H
Zn-Ni alloy plating
(containing 10 – 15% Ni)
Trivalent colored chromateGreen mark 1200 H 3000 H
Adoption examples
Zinc alloy plating
Zinc-nickel alloy plating
(left: trivalent black) (right: trivalent colored)
- In Japanese, “chromate” implies “hexavalent chromium” as was introduced in the section on zinc plating. At present, when trivalent chromium chemical conversion treatment is mainstream, the word “trivalent chromate” is full of contradictions. As a matter of fact, it should be referred to as “trivalent chromium chemical conversion coating or treatment,” but here, the word “chromate” is correspondingly used as an established industry term.

- Zinc-nickel alloy plating has the lowest hydrogen brittleness in zinc and zinc-based alloy plating. It is partly used as a replacement for cadmium plating.