Growth behavior of electroless Ni–Co–P deposits on Fe

The electroless Ni–Co–P films were deposited on Fe film in plating baths using sodium hypophosphite as reducing agent and nickel and cobalt sulphates as ion source at pH value of 9 and plating temperature from 60 to 85 °C. The effect of the mol ratio of CoSO4/CoSO4 + NiSO4 in plating bath on the growth behavior of electroless Ni–Co–P films was studied. The electroless Ni–Co–P films were characterized by transmission electron microscopy for the microstructure and thickness, and energy dispersive spectrometer for the composition. The results showed that the electroless Ni–Co–P films can be deposited on Fe films without the step of sensitization and activization; the surface of electroless Ni–Co–P film on Fe is quite even; the more the Co2+ ion in plating bath, the larger the activation energy and the smaller the plating rate of electroless Ni–Co–P films; and the mol ratio of Co/Co + Ni in film is larger than that in plating bath (with the exception of the film deposited in the bath with 0.9 mol ratio of CoSO4/CoSO4 + NiSO4)