Method of applying a corrosion-proof and wear-resistant coating to a workpiece

摘要

The invention is directed to a method of applying a corrosion-proof and wear-resistant coating to the piston rod of a hydraulic ram which is intended to be used in an underground mine working, or in similar workings. The method comprises the steps of applying a layer of nickel to the piston rod using a currentless nickel-plating process, and then applying a microcracked hard-chromium layer to the nickel layer. The nickel layer is of high density, tensile strength and ductility. Before the application of the microcracked hard-chromium layer, the previously-applied nickel layer is activated electrolytically in a sulphuric acid bath, in order to improve the adhesion of the hard-chromium layer to the nickel layer.