Other materials that can be used in an electroless plating process are silver, gold, tin, copper, zinc, chrome, cadmium, palladium, and rhodium. Besides nickel, gold, copper, silver, and palladium are all quite common. Gold plated objects are given a thin layer of gold across the surface of a different metal. The purpose of this is usually to provide electronics with a layer that is both corrosion resistant and conductive.
Silver plating can be found in electronics as well and makes a cheaper alternative to gold. The main problem with silver is that it does not oxidize so it will not perform well in humid environments. The high conductivity of copper makes it an obvious choice for appropriate applications. Palladium offers unmatched bath stability, but it is rare and therefore quite expensive to source.
Electroplating (electrically charged) processes use a wider variety of metals; from tin to zinc to chrome to cadmium and rhodium. To add conductivity, tin is usually combined with other metals like copper before plating takes place. Zinc is used to prevent oxidation of the plated metal. Not only that, but zinc is used in processes where small parts are plated together in large groups. Chrome plating leaves a polished finish, but it can be expensive and it requires more electrical current than other metals.
While electroless cadmium plating is possible, it is not common because the metal can be a hazard to the environment. This has made it very controversial among manufacturers. Rhodium plating (electroless) is used on precious metals, particularly for jewelry.
Electroless plating, sometimes referred to as autocatalytic plating, is a basic chemical reaction. Essentially what happens is that the metal that is intended to coat the part is submerged in an aqueous solution or bath. After being introduced to this solution, the metal begins to react. Hydrogen is released and metal ions produce a negative surface charge that causes the solution to bond to the metal.
In contrast to this, electroplating is powered by a current that reduces cations of the chosen material from the solution. The result is a coating or thin layer of metallic material. The purpose of electroplating is generally to protect from abrasion, add aesthetic qualities or add a desired property not already present in that part. In some cases, electroplating can even be used to increase the thickness of small parts.