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Method for checking quality of zinc plated parts

2007

We use zinc plated M.S parts in our product. All these parts are plated by our vendor using cyanide plating bath. Recently we have observed lot of products in FG wherein Rusting has started in M.S parts which are plated. These parts are only 3 months old.

We are unable to trace reason for corrosion.

Basically to avoid this in future, what must be quality check at our end for plated parts. We usually do salt spray test every week and we have not found single problem since 7 months in the results.

Is there any immediate / fast test apart from salt spray to detect passivation quality of zinc plated components ?

Z.R Desai
Engineer - Baroda, Gujarat, India

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2007

Dear Mr Desai,
I feel SST is not a very dependable method of checking the quality as the results vary much.
There are many causes of corrosion and its difficult to pin point at some of them since you have not given the details.
But, I think, controlling the quality will be much better than checking the quality. What I suggest is have a meeting with your vendor and a good electroplating chemical supplier and make a good procss sequence for plating along with in process quality checks. Then regularly audit the vendor for these quality checks as well as process control. If your vendor use good process control, then your problems will be reduced automatically.

Regards,
Mangesh Kulkarni.
Chemetall-Rai India Limited

Mangesh Kulkarni
- Pune, INDIA