The positive contribution of Cr2O3 reinforcing nanoparticles to enhanced corrosion and tribomechanical performance of Ni–Mo alloy layers electrodeposited from a citrate-sulfate bath

Abstract

The service lifetime and efficiency of the engineering materials can be enhanced by adopting an appropriate surface modification strategy. This work has endeavored to finish the surface of St37 steel by electrodeposited Ni–Mo alloy layers strengthened by various levels of suspended Cr2O3 nanoparticles in the bath, i.e., 0–8 g/L, to obtain high corrosion and tribomechanical performance. The phase structure, morphology, chemistry, and roughness of the surfaces were assessed by XRD, FESEM, EDS, and AFM, respectively. Corrosion performance of the developed films was measured using OCP, EIS, and potentiodynamic polarization techniques, as well as long-term immersion in the corrosive NaCl medium. Vickers microhardness tester and ball-on-disk tribometer were employed to evaluate the tribomechanical behavior of the coatings. While there is no change in the phase structure of the Ni–Mo alloy layer with the included Cr2O3 nanoparticles, the nanocomposite layers show a more compact and rougher surface. The microhardness of the alloy coating was enhanced by approx. 30 % with the inclusion of the 8 g/L Cr2O3 nanoparticles in the electrolyte. An increase in polarization resistance of the nanocomposite layers compared to alloy one, by 16 kΩ, demonstrated the improvement in the corrosion protection performance with the included nanoparticles. The Ni–Mo–Cr2O3 nanocomposite layers offered lower COF and wear mass loss than the Ni–Mo alloy layer, irrespective of Cr2O3 loadings. The surface modification of mild steels by the Ni–Mo–Cr2O3 nanocomposite films can promote their service lifetime and efficiency in severe industrial applications.