Electrodeposition of Ni-Mo/TiO2 nanocomposite coatings on low-carbon steels for improving corrosion resistance

Abstract

In this paper, Ni-Mo/TiO2 nanocomposite coatings were successfully deposited from a modified ammonia-citrate bath containing TiO2 nanoparticles. Phase identifications and microstructural characterizations of the as-prepared coatings were obtained by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The corrosion behaviour was evaluated by a potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). It is established that the compact, crack-free Ni-Mo/TiO2 nanocomposite coatings are composed of a Ni-Mo alloy matrix and a TiO2 phase, and both the content of Mo and TiO2 in the obtained composite coatings increase with an increased addition of TiO2 in the plating bath. The Ni-Mo/TiO2 nanocomposite coatings exhibit much nobler Ecorr, lower icorr and larger Rct values than those of the Ni-Mo alloy coating. Among all Ni-Mo/TiO2 nanocomposite coatings, the Ni-Mo/TiO2 coating, deposited from a bath containing 40 mg/L TiO2 nanoparticles, shows the best corrosion resistance.