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Cleaning procedure for chromium cobalt alloy to be Hard Chromed

Need information about cleaning procedure for Hard Chrome plating chromium cobalt alloy stainless steel.

Lynn Staggs
plating shop - Memphis, Tennessee, USA
2004

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Degrease in alkaline cleaner, vapor degreaser or by hand wiping with solvent. Reverse current 1-2 minutes, 6 volts in chromic acid, start plating at 0 volts and ramp up over several minutes to full plating current. No problem.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004

I think Jeffrey is right if your chrome solution has some fluoride. Otherwise, I think that it would be safer not to reverse etch and go to the conventional Woods activation or a variant of such. I hope Jeffrey or others have a saying regarding this.

Guillermo Marrufo
Monterrey, NL, Mexico
2004

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Guillermo,

We have done lots of hard chrome on 3xx, 4xx and PH grades of stainless, and the short reverse etch followed by ramp up has always worked. We have never needed to use Wood's nickel strike. Our chrome bath is a sulphate/boric acid catalyst, no fluoride. I have used Wood's nickel on stainless alloys before nickel or copper plating, and it usually works okay, although it has not been 100% reliable.

The question was asked about cobalt containing alloys, but I am certain that from a plating standpoint there is no difference between cobalt and nickel.

Merry Christmas

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2004

My 2 cents worth. 3xx and 4xx series do not need a strike. High nickel alloy parts work much better with a Woods strike.

James Watts
- Navarre, Florida
2004

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2004

The reference to chromium cobalt alloy seems to me likely to mean the 28%Cr + 6%Mo + incidental elements totaling several %, and balance Co. ASTM F75 is a typical spec. Material is for surgical implants as there is effectively zero reaction between it and human body liquids. It is not a stainless steel - it contains close enough to no iron.

Would electroplaters among you see any problem hard chroming this alloy?

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.