Letter 8040

Diecast skin blistering 

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We are brass plating Zinc Diecast #3 & #5. We etch in Sulfuric and have success with most parts, on the other hand some parts seem to have excess skin, which blisters in powder coating at 350 F.My question is there a normal thickness or range for this skin or at what point should it be rejected back to diecastor as a casting problem.

Thanks,

Max T. Faeth
plating - Los Angeles, CA, USA

Max,

Even a part that hasn't been buffed shouldn't have a skin like you described. Your diecaster should check his process for even heat distribution in the die as well as his pressure...if it's a pressure casting. As far as plating, I always use a 4 oz/gal Fluoride based acid salt. I also keep the electrocleaner mild and time less than 30 seconds since a smut will form quickly and the copper strike will not adhere.

Jim Conner
- Salisbury, MD

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