Removing faulty electroless nickel coatings from nonferrous metals - using electrolyte which does not attack substrate

摘要

The aq. bath contains sulphuric acid and citric acid, pref. together with phosphoric acid, to give a density of 1.532-1.714 (1.637) g/cm2 at 20 degrees C. The bath is pref. employed at 20-60 degrees C using a current density of 10-30 (20)A/dm2. Used on Cu or Cu alloy substrates, e.g. brass, with complex shape, where mechanical removal of the coating of Ni, contg. 3-12 wt.% P, is difficult. As soon as the substrate is exposed a passive layer is obtd. on the surface of the substrate; and when all the Ni-P is dissolved the current is reduced virtually to zero.