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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
- Riome»Portugal
1999



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 [affil link] 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




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