Influence of Thermal Treatment on the Electrochemical Properties of Ni+Mo Composite Coatings in an Alkaline Solution

The Ni+Mo composite coatings were prepared by electrodeposition under the galvanostatic conditions ( j dep = -300 mA cm -2 ) from the nickel bath containing molybdenum powders of different granulation (3-7 μm, <150 μm, <100 nm). Thermal treatment of the obtained coatings was conducted in the argon atmosphere. The surface morphology of the coatings was studied using a scanning electron microscopy (SEM). Chemical composition of the electrodeposits was determined by X-ray fluorescence spectroscopy (XRF). Phase composition investigations were conducted by X-ray diffraction (XRD) method. Investigations of hydrogen evolution reaction (HER) and electrochemical corrosion resistance were carried out in 5 M KOH solution. It was found that for the Ni+Mo thermally treated coatings the decrease in activity towards the HER was observed. Simultaneously these coatings are more corrosion resistant than Ni+Mo as-deposited coatings. The reasons for the electrochemical properties of these coatings have been discussed.