Plating the film thickness of which is smaller than 5μm (approximately 0.1 - 0.3μm) is called decorative chromium plating, and that 5μm or larger is called industrial chromium plating or hard chromium plating.
Although most chromium plating comes out of a hexavalent chromium bath, from the perspective of environmental harmony, this is moving toward trivalent chromium or chromium-free plating.
|Type of plating
|Industrial (hard) chromium plating
(hexavalent chromium bath)
|- In order to improve wear resistance, various materials are plated as thick as 5 to hundreds of millimeters. Since microcracks or micropores specific to chromium plating are formed, lubricity is enhanced by using them for oil retention.
||- Hardness Hv = 800 - 1000
|Superhard thermal-resistant chromium plating
(Cr-C alloy plating)
|- Plating is structurally amorphous as is. When it is heat-treated, the hardness is Hv1800.
- Having excellent thermal resistance and wear resistance, it is applied to molds.
|- Hv 1800、
Cross-section SEM photo of hard chromium plating
on flake graphite cast iron
- Chromium-PTFE (Teflon) composite films with chromium-plating-specific microcracks or micropores impregnated with PTFE, which excels in self-lubricity and non-adhesiveness has been commercialized (registered trademark: TEFLOK).
- From the perspective of environmental conservation, nickel-tungsten alloy plating, electroless nickel-silicon carbide composite plating, cobalt-chrome oxide composite plating, Co-Cr2O3 composite plating, and so on have been developed as a replacement for chromium plating.
- For partial repair of wear damage of large machine parts or printing rolls, etc., hard-face retreading chromium brush plating now plays an active part.
[Types of plating]
[Materials & uses]