Impregnation of zinc parts
Does impregnation on zinc possible before Copper-Nickel-Chrome plating in order to reduce porosity and extend corrosion resistance (reduce blisters)? If yes, which material to use for impregnation? How many salt spray test hour can we get typically?Christian Doucet
- Montreal, QC, Canada
Vacuum impregnation using a thermosetting epoxy resin is a proven technique to make zinc die castings more plateable. It covers up pores that can entrap chemicals that can lead to blisters or post plate corrosion. MIL-STD-276 details the requirements for basic impregnation.
As an alternative, parts can be heavy copper plated followed by buffing or mass finishing. The soft copper will peen over and bridge the pits. Subsequent nickel / chrome plating will then have little, if any, blistering and pitting.
Syracuse, New York