ELECTROLESS NICKEL-PLATING - INFLUENCE OF MIXED-LIGANDS

Electroless nickel plating has been studied from acidic bath solution containing ethylenediamine and/or sodium potassium tartrate as complex ing agents at various pH, temperatures and concentrations of sodium hy pophosphite. Ni-P alloys with various amounts (1-18%) of phosphorus ar e obtained under different plating and bath conditions. Cyclic voltamm etric studies of the bath solution revealed that the extent of complex ation 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 diffractio n studies revealed the existence of multiphase Ni-P, Ni3P2 and Ni5P2 f ilms on the surface. Working conditions are optimised to get good qual ity deposits with high plating rate at sufficiently low temperature fr om a stable plating bath solution.