Letter 39024

Not able to get more than 950 HV hardness in hard chrome plating consistantly [India] 

December 23, 2005

We are running a Chrome plating bath with the folloing concentration.
Chromium - 300 g/ml
Sulphur - 3.2 g/ml
Temperature - 58 to 60 degree celcius.

we are using cylindical components and the material is inconal.

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

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

V. Ranga Bhuvana Balaji
Process Shop - Andhra Pradesh

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, SC, USA

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 degrees Celcius.

Don Baudrand Don Baudrand, Consultant   Poulsbo, WA. USA

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 hardchrome deposit have HV range between 800-1100 HV.

Regards

Anders Sundman     surface finishing engineer Sweden

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