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. (C) 2019 Elsevier B.V. All rights reserved.