BLACK CHROME PLATING PROBLEM

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Can any one help me on black chrome plating. Have tried following composition of the bath Cr2O3 (chrome anhydride) 250 gm/ltr Acetic acid 170 ml/ltr cd 150 asf

The problems are:

1) Jet black colour not coming the colour obtained is metallic gray.

2) When attempting brown colour plating (with different cd value) with the solution the brown colour does not come uniformly there are gray patches at high cd areas raising of the temp helps but since acetic acid is not stable at high temp the plating stops taking place.

Some one please help find solution to this problem or suggest some metal acetate which wont affect Cr plating and be stable at high temp.

Thanks,

Viney Chaddha
- Gurgaon, Haryana, India

Are you plating black Chrome on bright Nickel or semibright (Sulphur free) Nickel ? Is your temp control uniform throughout the solution ? Are you oiling parts after plating ? Please post yr situation and maybe I can help.

Khozema Vahanwala
Saify Ind

Bangalore, Karnataka, India

Dear Khozema,

Thank you very much for the response I have tried this in a five litre beaker on a small plate the conditions are :

1) temp is uniform (room temp)
2) plating is attempted on bright nickel
3) there certainly no oil as the cleaning is as follows
a) ultra sonic
b) cathodic cleaning
4) any oil film present may be that of the brighteners and anti pit solutions used in bright nickel but the work piece is thoroughly rinsed after bright nickel

I would be extremely grateful if you can help

Thanks ,

Viney Chaddha
- Gurgaon, Haryana, India

Viney,

You must have a lower temperature 14-15 C degrees. I also suggest you to analyze the trivalent chrome maybe you have to much of hexavalent chrome in your black chrome solution. The ratio between anode and cathode is important 1:2 the anode area shall be more less than cathode area.

Regards,

Anders Sundman
surface finishing engineer
Sweden

It is essential to not have any sulphate present. Add some barium carbonate to ensure no sulphate. Usually processes have other additives such as nitrate, fluoride, boric acid.

Geoff Whitelaw
- Port Melbourne, Vic., Australia

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I wish You could talk on planet earth....apart from that the reason I was looking at this was because I am a designer in Spain and was looking up Black Chrome.............now I am confused...where can I get some good pics ?

Chris Fletcher
designer - Spain

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It's a technical forum for solving plating problems, Chris -- what are you asking us to do, refuse to print the names of the chemicals people ask us for :-)

Ask one of the suppliers of black chrome services or black chrome plating processes for pictures, but be aware that there are several different types for several different purposes, like high absorbtivity for solar collectors, optical black chrome for microscopes and telescopes, decorative black chrome for auto parts, etc. What do you want to plate with black chrome and why? Good luck.

Ted Mooney, P.E.
finishing.com
Brick, New Jersey

October 7, 2008

I am looking for a good formulation or bath composition for black chrome plating. Hope someone can help me thru this..

Macy Melgar
- Makati City, Philippines