Electroless Nickel Plating—Influence of Mixed Ligands

SUMMARYElectroless nickel plating has been studied from acidic bath solution containing ethylenediamine and/or sodium potassium tartrate as complexing agents at various pH, temperatures and concentrations of sodium hypophosphite. Ni-P alloys with various amounts (1–18%) of phosphorus are obtained under different plating and bath conditions. Cyclic voltammetric studies of the bath solution revealed that the extent of complexation of nickel ions with the complexing agents is in the order of EDA > SPT > EDA & SPT. The functional properties of Ni-P alloys are found to depend on structure, composition and post-treatments. The high % in P in the alloy gave a high corrosion resistance. The X-ray diffraction studies revealed the existence of multiphase Ni-P, Ni3P2 and Ni5P2 films on the surface. Working conditions are optimised to get good quality deposits with high plating rate at sufficiently low temperature from a stable plating bath solution.