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.