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 mum 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 similar to8 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 E-corr shift towards more positive values but decreased the corrosion rate. (C) 2005 Elsevier B.V. All rights reserved.