Abstract: In a method for electrolytically forming on a metal surface a composite coating having improved hardness and wear resistance, a compound containing phosphorous is added into the plating electrolyte, with the phosphorous content being in a quantity of between about 0.1 to 4.2 g/l with minute particles of a required property suspended therein thereby to coprecipitate a nickel phosphide together with the minute particles, whereby the physical and chemical properties of the composite coating are remarkably improved.

Abstract: Fine particles of a very hard material such as silicon carbide and either a solid lubricant such as carbon fluoride or a lubricant such as a powdered organic high polymer are dispersed in a metal plating solution, and a metal object to be plated is immersed as a cathode, together with a metal rod as an anode, in the plating bath, and then a suitable current is passed through the bath to cause coprecipitation of the fine particles and lubricant in the metal deposit. The plated coating layer thus obtained is electro-polished or chemically or mechanically polished and a given thickness of the metal layer is removed to leave the fine particles as tiny protrusions from the lowered surface. In this way a low-abrasion surface is produced on the metal object.