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
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
I do believe Jose's range to be a little wide open. We have numerous chrome tanks with conventional sulfate catalyst, mixed sulfate/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 E 140 has conversion tables. Also anything you can find on hardness by Jack Horner or Sur-Fin proceedings will give more in depth informationRick Richardson, MSF
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