Metal finishing Q&As since 1989

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Hardness of hexavalent chrome

Can anyone tell me where to find values for the hardness of electroplated hexavalent chrome? I need values according to the Vickers, Knoop, and Rockwell C scales.

Tammy Utzler
- Johnstown, Pennsylvania
1999

The hardness for the electroplated hexavalent chromium is between 450 Hv and 1200 Hv --depends on the conditions of your process (current density, temperature, concentrations and bath contamination).

JosÈ Francisco Costa
- RiomeÈPortugal
1999

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Hi Tammy,

I do believe Jose's range to be a little wide open. We have numerous chrome tanks with conventional sulphate catalyst, mixed sulphate/fluoride catalyst and proprietary non-etch catalyst. The hardness is checked monthly on all types and is always in the 900-1100 Hv range. While it may be possible to plate as low as 450 Hv I believe you would have to be operating way outside recommended parameters. Converting one hardness number to a different scale is not a recommended practice as each hardness test was developed for specific applications. But if you must, ASTM E140 has conversion tables. Also anything you can find on hardness by Jack Horner or Sur-Fin proceedings will give more in depth information

Rick Richardson, MSF
Dayton, Ohio
1999