Catalytic activity of iron, nickel, and nickel-phosphorus in electroless nickel plating

The catalytic activity for electro-oxidation of hypophosphite and electroless Ni plating on Fe, Ni and electrolessly plated Ni (with 2.2-2.9% phosphorus) was investigated in an ammoniacal solution of p H 8.8 at 50 deg C by potential measurements and linear sweep voltammetry from --0.3 to 0.92 V vs. SCE. Cathodic polarization of any of the substrates (in 0.1M H sub 2 SO sub 4 ) before testing or permeation of hydrogen through Fe foils during testing reduced the incubation time for electroless plating, increased anodic dissolution of the substrates in the passive region and increased the hypophosphite electro-oxidation on Ni and Ni--P at potentials of thermodynamic stability for nickel oxides or hydroxides. The Ni--P substrate exhibited significantly higher activity than pure Ni, in a similar manner to the effect of cathodic polarization. The effect of cathodic polarization and H is associated with the electrochemical reduction of surface oxides, whereas the higher activity of Ni--P deposits (as compared to that of pure Ni) is explained by the lower protectivity of surface oxides on these deposits. 19 ref.--AA