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Zinc -Cobalt Plating Difficulties

We are switching over from Cadmium to "Zinc-Cobalt" plating for aluminum (both machined & Die-cast) components. Subsequent treatment is Black OR Olive-Drab passivation. We find inconsistency in plating quality like weak adhesion, shade variation, patches, etc.? Any clues from an experienced guy ?

Pramod Bapat
- PUNE, Maharashtra, INDIA
2001

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Acid or alkaline bath? Are you using the correct conversion coating for this bath? Is the black non-silver?

  
Tom Pullizzi
Falls Township, Pennsylvania
2001

Dear Mr Pramod Bapat,

We do a competent job on all the processes you require but would recommend that you get in touch with a competent supplier of plant and equipment and try to do the job yourself in-house. As we are too far away in Bangalore to make us viable logistically, self help is the best help. Scout around Poona for a better plater if you have spare parts to scrap for trials and retrials.

In my humble opinion plating on Aluminium diecastings is one of the most difficult jobs to do and is a combo of a science and art. Its next to impossible to find a witch doctor cum scientist posing as a plater, and you'd better get ready to become one yourself if you want to accomplish this.

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India

2001

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2007

Dear Reader,
I saw your letter.I can under stand your problem. Please give carbon treatment to the bath.Then dummied your bath for 6 hours at high current(5amp/dm2). then continue your process it will help you in great manner.we also faced the same problem past one year ago.we also did the same.now a days there is no problem.

Good Luck,

P.KARTHIKEYAN
- Bangalore, Karnataka, India