Electrodeposition of Duplex Ni–B–Zn/Co Composite Coatings

This research article focusses on the Ni–B–Zn/Co composite coatings synthesized via an electrodeposition process. Electrodeposited Ni–B composite coatings have several advantages, such as excellent corrosion as well as wear resistance and high hardness in the as-deposited condition. We studied the influence of Zn/Co addition on microstructure, phase evolution, mechanical (hardness and wear resistance), and corrosion behavior of electrodeposited Ni–B–Zn/Co composite coatings. The Ni–B–Zn/Co composite coatings exhibited significant improvements in microhardness (by 90%) as well as in elastic modulus (by 100%) in comparison with electrodeposited Ni–B coatings. Both scanning electron microscopy (SEM) and x-ray diffraction (XRD) analyses showed significant improvement in grain sizes in Ni–B–Zn/Co composite coatings compared with Ni–B coatings. This grain refinement in composite coatings is primarily attributed to the addition as well as uniform dispersion of Zn/Co within the Ni–B matrix. The Ni–B–Zn/Co coatings exhibited far better corrosion resistance and mechanical properties than Ni–B coatings.