With the exception of zinc plated parts, all zinc die-castings are processed as follows: preclean, mill, copper strike, and copper plate.

Preclean: A two step process to remove most synthetic, petroleum, vegetable, and animal based fluids used in die-casting and machining operations.
Mill: A controlled removal of the outer layer of die-cast. This process can remove flash, surface die-cast blisters, and modify dimensions if necessary. This step is essential to improve the adhesion of the subsequent copper plating.
Copper Strike: The copper strike is a specially formulated copper solution designed to provide excellent adhesion to the die-cast surface. The thickness of the strike is approximately 50 millionths of an inch.
Copper Plate: The copper plate seals the zinc to protect it from environmental exposure. Also, copper is used to modify dimensions. After the minimum thickness is achieved, we often add more copper to build dimensions. A thick, continuous copper plate is essential to protect the part from subsequent plating solutions which are corrosive to raw zinc.
Final Plate: After copper plating, the parts may safely be plated in nickel, tin, EN, etc.