Study of the corrosion behavior of zinc and Zn–Co alloy electrodeposits obtained from alkaline bath using direct current

Abstract

The corrosion behavior of Zn and Zn–Co alloy electrodeposits that were obtained from weakly alkaline glycine solutions has been studied. SEM, EDS and XRD were used to study surface morphology, chemical composition and phase structure of the coatings. Corrosion behavior of Zn and Zn–Co alloy coatings was studied by using potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. The results showed that increasing current density during deposition, increases cobalt content of the coating. It was also shown that increasing current density, up to 15 mA cm −2, decreases the grain size and further increase in current density increases the grain size of the deposit. It was also noticed that corrosion resistance of deposits was highly influenced by the composition and morphology of the coatings. Zn–Co deposit containing 0.89 wt.% Co showed the highest corrosion resistance due to its single phase structure and its finer morphology.