Structural, magnetic and corrosion properties of electrodeposited cobalt-nickel-molybdenum alloys

Soft-magnetic ternary Co-Ni-Mo films were electrodeposited from a sulphate-citrate bath at pH 4.0 at a constant deposition rate of 2.5 μm h−1. Both nickel and molybdenum incorporations in the ternary alloy were restrained in order to achieve low coercivity and maximum saturation magnetisation. 11-15 wt% Ni and 7-13 wt% Mo were considered the most appropriate percentage ranges for actuation applications in MEMS of the coatings. Deposits were silvery bright and showed low roughness. A nanometric grain size of ∼8 nm was deduced from the X-ray diffractograms. A comparative corrosion study of Co, Co-Mo, Co-Ni and Co-Ni-Mo films was also carried out. Corrosion data demonstrated that small amounts of nickel in the deposits did not cause an Ecorr shift towards more positive values but decreased the corrosion rate.