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Zinc-nickel plating is a process by which a layer of a zinc-nickel compound is deposited on a substrate metal. The use of zinc-nickel alloy helps protect these other materials while adding to their aesthetic desirability. This alloy is applied to other metals using various electroplating techniques, including barrel plating and rack plating.
The basic process for zinc-nickel plating is electroplating. This technique uses a chemical bath and an electric system with an anode and a cathode. Zinc and nickel plates must be dissolved in a chemical bath before they can form a plate of a zinc and nickel compound. Solutions can be either highly acidic or highly basic and are commonly made out of either a chloride or cyanide.
Once the zinc and nickel are dissolved, electricity is applied to the system. On one end of the tank is the anode, through which electricity enters the system. On the other end is the cathode, through which electricity exits the system. Zinc and nickel ions are generally negatively charged and attracted to the positively charged cathode. Over time, they stick to the cathode and zinc-nickel plating is formed.
The zinc-nickel plating that is formed through the electroplating process is usually made up of more zinc than nickel. The amount of zinc in the compound is usually between 85% and 95%, while the remainder of the compound is nickel. This alloy is stronger and more durable than zinc alone.
Zinc-nickel plating can be done in barrels or in racks. In both of these processes, the material that is to be plated with the zinc-nickel alloy is placed in an electrified solution. The zinc-nickel plating is grown on the surface of the material as in traditional electroplating.
Barrel plating is frequently used to plate many small parts at once. It can be used to coat any size substrate with the alloy as long as the substrate can tumble freely within the barrel. The barrel is rotated a various rates. Faster rotational rates produce a zinc-nickel plating that is more uniform.
Racks can also be used to hang substrate materials that require zinc-nickel plating. The materials are lowered into the electrified chemical solution where the zinc-nickel plate forms. The areas on the substrate by which it is hung do not receive plating. Zinc-nickel plating accomplished by this method is not as uniform as the plating that comes from the barrel plating process.