Synthesis and properties of a novel Ni–Co and Ni–Co/ZrO2 composite coating by DC electrodeposition

Ni–Co and Ni–Co/ZrO2 composite coatings have been synthesized via a single-step direct current (DC) electrodeposition route as a protective coating. The influences of electrodeposition current density, time and ZrO2 concentration on structural, composition and properties of Ni–Co coating were investigated. All coatings present compact, crack-free and nodular-like morphology in a nanocrystalline structure. Some aggregations still exist in the coating. The preferred orientation of these coatings changed from (200) to (111) texture with a fcc structure. The amount of Co in Ni–Co matrix slightly decreases as current density and time increases. The Co and ZrO2 content in Ni–Co/ZrO2 matrix increase with the increasing of ZrO2 concentration in bath. Less than 60 min is beneficial for low roughness of Ni–Co/ZrO2 coating. Current density, deposition time and ZrO2 embedded in metallic matrix affect the hardness of Ni–Co alloy. Ni–Co/ZrO2 coating has enhanced hardness compared to Ni–Co ones. Although they might not exhibit the best corrosion resistance in the initial immersing stage, Ni–Co/ZrO2 composite coating obtained at 2–4 A dm−2 with 5–10 g L-1 ZrO2 presents the better corrosion resistance and desirable performance stability during the long-term immersion process in aggressive media. The Ni–Co/ZrO2 coating exhibits promising advantages as a protective coating. •Ni–Co and Ni–Co/ZrO2 composites was fabricated by single-step DC electrodeposition.•Effects of current density and zirconia particles on Ni–Co alloys were evaluated.•Morphology, phase structure, crystallite size and surface characteristics were studied.•Hardness and corrosion resistance were optimized for best protective performance.•2–4 A dm−2 and 5–10 g L−1 ZrO2 was the suitable parameters for high corrosion resistance and service stability.