Plating is typically divided into two categories, depending on the presence of electric current. In electroless plating, electric current is not used; in electroplating, electric current is used. Both processes tend to be more effective than vacuum metallization at producing metallic coats with strong adhesion, although plating tends to be more dangerous.
Electroless plating is often used to deposit nickel or copper metal onto plastic substrates. First, the surface of the plastic is etched away using an oxidizing solution. Because the surface becomes extremely susceptible to hydrogen bonding as a result of the oxidizing solution, typically increases during coating application. Coating occurs when the plastic component (post-etching) is immersed in a solution containing metallic (nickel or copper) ions, which then bond to the plastic surface as a metallic coating.
In order for electroplating (or electrolytic plating) to be successful, the plastic surface must first be rendered conductive, which can be achieved through basic electroless plating. Once the plastic surface is conductive, the substrate is immersed in a solution. In the solution are metallic salts, connected to a positive source of current (cathode). An anodic (negatively charged) conductor is also placed in the bath, which creates an electrical circuit in conjunction with the positively charged salts. The metallic salts are electrically attracted to the substrate, where they create a metallic coat. As this process happens, the anodic conductor, typically made of the same type of metal as the metallic salts, dissolves into the solution and replaces the source of metallic salts, which is depleted during deposition.