Response surface modeling and voltammetric evaluation of Co-rich Cu–Co alloy coatings obtained from glycine baths

• Cu-Co alloy coatings were produced on graphite and steel substrates from glycine baths.
• The reduction of Cu (II) and Co (II) ions in glycine bath depended on the [Co2+] and on the solutions’ pH.
• Response surface methodology verified the influence of the deposition parameters on the chemical composition of the alloy.
• The presence of a Co-rich Cu-Co alloy coating on the steel enhanced the anticorrosive performance of the substrate.
• The porosity of the coating affected the corrosion of the coating/substrate system.

Complexing agents in electrodeposition baths promote the joint deposition of metallic alloys and improve the quality of coatings produced with different chemical composition and interesting properties. The advantages of using glycine as a complexing agent are related to its cost and its environmentally friendly characteristics, producing coatings with high adhesion and good cathodic current efficiency. Cu–Co alloy coatings containing small amounts of cobalt present high magnetic properties. However, an increase in Co content in the alloy may also improve the anticorrosive performance of the coating. This work presents the voltammetric results obtained from experiments performed in solutions containing 0.02 mol L− 1 CuSO4 and 0.50 mol L− 1 glycine and/or different concentrations of CoSO4 at several pH values. Additionally, Cu–Co coatings were electrodeposited on steel substrates and the influences of the deposition parameters current density (j), solution pH (pH) and Co (II) concentration in the bath ([Co2 +]) on the cathodic efficiency (Ef) and the copper and cobalt contents in the coatings (wt.% Cu and wt.% Co, respectively) were evaluated using response surface methodology. The voltammetric results indicated that an increase of [Co2 +] would favor the production of Cu-rich coatings and that a compromise between the parameters pH and [Co2 +] should enable the joint deposition of the metals.