Electroless nickel plating is used to deposit nickel without the use of an electric current. This article provides an overview of the solution composition and characteristics of the electroless nickel bath. It focuses on the metallurgical, mechanical and physical properties of electroless nickel-phosphorus coatings and electroless nickel-boron coatings. The effect of electroless nickel coatings on the fatigue strength of steel is also described. The article includes information on the recommended pretreatment procedures for different ferrous alloys, aluminum alloys, and copper alloys. It presents a detailed account of the equipment and various processesâ€”including bulk and barrel platingâ€”involved in electroless nickel plating, and discusses hydrogen relief methods. The article includes a comprehensive table on nickel plating applications, and concludes with information on electroless nickel coatings on composites and plastics.