Nickel is used in many food processing systems and equipment because it resists corrosion, and is will not react with the chemicals in food. Nickel is very passive and does not tarnish or "rust." It is also used in jewelry that contacts skin all day long. Some people have a reaction to it, but some people have a reaction to brass and silver, too, so it isn't accurate to say nickel is poisonous. The metal salts used in nickel plating are moderately poisonous, but the end user (the player) doesn't get near those. Once the plating is applied, the deposited metal is perfectly safe. (The same is true for silver and gold plating which have cyanide in the plating bath. The cyanide does NOT become part of the metal layer.) Copper is sometimes plated before nickel for corrosion protection and to make the nickel adhere to the base metal better. Before the advent of plastic car parts, steel was plated with copper, then nickel, then chrome. The copper was the base coating because it sticks to almost anything. Next came nickel for corrosion protection and because it sticks well to copper. Last in the sandwich was chrome for looks.