Electroless nickel plating of metals, plastics, or ceramics - using periodically replenished bath kept an constant density

摘要

The bath contains nickel salt, sodium citrate, NH4Cl, NH4OH, sodium hypophosphite, a water-soluble polyhydroxy benzene, and a copper salt, with an initial density of 1.075-1.116 g/cm3, esp. 1.099 g/cm3 which remains at this value during plating. The initial density is pref. achieved by adding Na2SO4 as a dummy salt, and during plating, part of the bath is automatically and periodically removed at short time intervals and replaced by a replenishing soln. (R) and water to keep the density at 1.099. For Ni coating of a metal substrate, the latter is pref. first exposed as a cathode to a voltage of 8-12V for 2-10 seconds. Used e.g. for small or large relay poles made of metal sheet, or for substrates with a complex shape.