Copper Plating on Zinc Alloy

Question:

We have a customer who wants our company to copper plate on a zinc alloy (Zamak 3) substrate. We currently cyanide copper plate on steel. What is the process for doing this? P.H.

Answer:

Actually, the plating of zinc alloys is fairly straightforward. Since you are currently using cyanide-based copper plating baths, you are familiar with one of the plating baths required. A standard process for plating copper on zinc alloys is as follows:

• Degrease the part
• Electroclean cathodically (direct or forward)
• Rinse thoroughly
• Dip in a five ml in one liter sulfuric acid solution for 30 sec or until gassing begins
• Rinse thoroughly
• Place parts in a cyanide copper strike bath. The parts must be placed in the strike bath "live." (Current must be on when the rack is placed in the plating tank.)
• Plate at a CD of 25-30 asf for two min. Reduce the current to 10-15 asf and plate for an additional 4-5 min
• Rinse thoroughly
• Dip in a 10 ml/l sulfuric acid solution
• Plate in copper sulfate bath to the desired thickness

I should also add that a number of proprietary non-cyanide alkaline copper plating baths are commercially available. They work well in many applications and allow you to get away from using cyanide-based materials. Vendors of these baths can be found in the Products Finishing Directory and Guidebook, 2004 edition, www.pfonline.com/suppliers.html.