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Speckles problem in acid tin plating

I am doing acid tin plating on zinc base die cast and facing problem of "speckles" or we can say small embossed dot of tin plating appear on surface ,can any body solve my problem?
thanks,

Tariq Malik
employee - Pakistan
October 15, 2008

For your problem, a picture would help. Also you need to list your exact process and your controls.
Zinc base die cast leaves a lot of unknowns. Which alloy? It makes a difference.
Otherwise, we will all be guessing and frequently suggestions are answered with "I am already doing that".

James Watts
- Navarre, Florida
October 17, 2008

October 22, 2008

James
my process is
chemical degreasing
electrical degreasing (anodic then cathodic)
dipping (sulfuric acid 0.5-1 %)
copper cyanide
neutralization (optional)
acid tin
our zinc alloy are Zamak5 and zamak 3
thanks,

Tariq Malik
- Pakistan

Dear tariq,
You should provide a barrier layer of nickel in between copper & tin.

Gulshan sachdeva
handicrafts Exports - Moradabad, Uttar Pradesh, India
December 17, 2008

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