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Not able to get more than 950 HV hardness in hard chrome plating consistently

December 23, 2005

We are running a Chrome plating bath with the following concentration.
Chromium - 300 g/ml
sulfur - 3.2 g/ml
Temperature - 58 to 60 degree C.

we are using cylindrical components and the material is Inconal.

With this concentration we tried a lot to get 950 HV hardness consistently. We are getting for some components. But not to every components.

So can you please suggest me some methods which can improve the hardness in hard chrome plating? can you tell me the parameters which will affect the hardness of hard chrome plating?

V. Ranga Bhuvana Balaji
Process Shop - Andhra Pradesh

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First of three simultaneous responses --

950 V every time is very close to the limit of what is possible. there's insufficient info in your question to offer any specifics, however, I'd suggest you contact a supplier who offers a boric acid containing catalyst, and follow their specifications as to bath composition, and operating conditions.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2006

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Second of three simultaneous responses --

The hardness of deposits from hard chrome plating solutions change with temperature and current density. I suggest you try operating at a temperature of between 45 and 52 °C.

Don Baudrand
Consultant - Poulsbo, Washington
(Don is co-author of "Plating on Plastics" [on Amazon or AbeBooks affil links]
           and "Plating ABS Plastics" [on Amazon or eBay or AbeBooks affil links])
2006

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Third of three simultaneous responses -- 2006

Hi.

Many things has a affect on the hardness on a chrome deposit.

1.Iron, Cu and trivalent chrome.

2. Temperature is low or to high

3. Concentration chrome to sulfuric is to high

4. Concentration of chrome is to high or low

5. Also if the deposit is not thick enough

And I think 950 HV is good resultant for a batch because a hard chrome deposit have HV range between 800-1100 HV.

Regards

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden