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PROBLEMS FACED IN CHLORIDE ZINC PLATING

I am a electroplating chemist and handling a chloride zinc plating line, plating automotive components of castings and sheet metals. I am facing a problem of "discoloration of green passivation" after 2 or 3 days of plating. I've thoroughly given carbon, zinc dust [on eBay or Amazon] treatment for any organic/inorganic impurities. Now the solution is perfectly alright in Hull cell test. The discoloration is coming only in green passivation and not in blue or yellow. I am following strictly the parameters recommended by the supplier of the passivations. Can any one help me in diagnosing this problem.

Thanks in advance,

Rummy Cai
- Chennai, India
2003

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2003

Dear Rummy Cai,

The problem isn't as rummy as it sounds :). You need to start with yr plating bath. Reduce the addition of R Brightener to minimum levels and increase dosage of M to ensure total dissolution of the R in the bath. After that please rinse copiously to ensure that no brightener film remains on the part before passivation. I do hope you have a strong Nitric dip prior to Green ?

Khozem Vahaanwala
Saify Ind

Bengaluru, Karnataka, India