METHOD OF MAKING AN ARTICLE HAVING A LAYER OF A NICKELPHOSPHORUS ALLOY AND COATED WITH A PROTECTIVE LAYER

摘要

A protective layer is developed on a workpiece coated with a nicke- phosphorous alloy by treatment in an aquous solution of chromic acid. The work is treated electrolytically with periodic current reversal at a frequency of 0.1-50 Hz, a current density of 0.2-1.0 A/sw.dm and a cathode: anode pulse duration of 0.05-20. The process produces a black wear resistance finish with a reduced energy input. Process times are also relatively low.