Influence of Mechanical Attrition on Protective Properties of Anomalous Electrodeposited Ni-Co Alloys

Ni-Co alloys with different compositions were electrodeposited from additive-free Watt’s type electrolytes utilizing mechanical-assisted electrodeposition. SEM, XRD, microhardness, and potentiodynamic polarization tests were used to investigate the effects of mechanical attrition speed and electrolyte composition on electrodeposits. Increased attrition speed resulted in reduced Co content in films with fcc crystal structure and raised Co content in hcp crystal structures. The microhardness values raised significantly, while the corrosion resistance was reduced by applying mechanical attrition. In order to choose the best electrodeposit, the C factor—a ratio of hardness to corrosion current density—is introduced. Based on the C factor, the deposits with 4 at% (Co/Co + Ni) in electrolyte and attrition speed of 600 rpm were selected as the best condition, which resulted in an alloy with a smooth and reflective surface containing 32 at% (Co/Co + Ni) with a hardness of 480 HV and corrosion current density close to that of pure nickel electrodeposits.