Metal finishing Q&As since 1989

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Need help about hard chrome plating

adv.    

I have a problem in the hard chrome process, specifically trying to apply this process on crankshafts .

1.- I don't get the thickness that I need
2.- there are areas in the crankshaft that have shadows
3.- there are little holes in the deposition

Please help me sorry about the English.

Regards,

EMILIO ARABE CAMACHOI
general manager - SANTA CRUZ, BOLIVIA
2004

I think that conforming anodes is the only way to get uniform coverage on crankshafts. It also allows faster plating because of the closer anode to cathode spacing. Done with great care, you can nearly plate to size, reducing the grind time and cost.

James Watts
- Navarre, Florida
2004

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2004

1. I agree, conforming anodes are the way to go. You will find if designed correctly, the thickness distribution will be a lot more even, reducing subsequent grind time.

2. Again, conforming anodes will solve this.

3. The porosity in the deposit can be attributed to probably one or a combination of 3 things: - if the crankshafts are cast iron, it is inherently porous, allowing ingression of pretreatment chemicals that seep out during plating, contaminating the surface, and not allowing the plating to adhere. - lack of circulation in the bath. The solution should be circulated over the job constantly. - poor precleaning technique. Use a reverse etch of sulfuric/hydrofluoric acid (30 g/l ammonium bifluoride, 450 g/l sulfuric acid) before transferring to the chrome bath. A black smutty surface should appear on the parts if reverse etched correctly.

Trevor Rowlands
Aircraft component manufacturer - Melbourne, Victoria, Australia

adv.