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  for Metal Finishing since 1989
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Zero defects in plating aluminum

I am experiencing the problem of blisters in plating Aluminum with Copper to the tune of 2.5%. The cycle is as follows Hot Caustic-Rinse-Nitric dip- Alzincate 20% x 1 min -Rinse-Nitric dip- Alzincate 20% x 1 min -Rinse-Cyanide copper strike at 9 volts x 1 min - Copper plate at normal voltage How can I reduce the rate of defects? I have understood following parameters to be key factors in adhesion. Are there any more?

1. Quality of Degreasing of Alu.
2. Quality of Activation of Al.
3. Bonding of Al. (High or low thickness of Alzincate layer)

How to ascertain that the alzincate layer formed is adherent & uniform? The opinion in visual inspection differs from person to person. Can we establish 100% quantified process control over this "bonding" process? Persons having practical experience - please help.

S Sudhanshu
Industrialist - Aurangabad, Maharashtra, India
2004

The words "hot Caustic" bothers me. You would probably be better off with an alkaline cleaner. The difference is less sodium hydroxide in the formula. Another possibility of problems is poor rinse water quality. Since we have no information on the tank makeups, operating conditions or frequency of analysis, it is impossible to provide anything more than guesses. One of your vendors should be able to provide you a complete operations sheet, which if you follow exactly, you should not have too many problems.

James Watts
- Navarre, Florida
2004