Initial corrosion protection of Zn-Mn alloys electrodeposited from alkaline solution

Abstract

The effects of a deposition current density (c.d.) on the corrosion behaviour of Zn-Mn alloy coatings, deposited from alkaline pyrophosphate solution, were investigated by atomic absorption spectrophotometry (AAS), X-ray diffraction (XRD), atomic force microscopy (AFM), optical microscopy, electrochemical impedance spectroscopy (EIS) and measurement of corrosion potential (E(corr)). XRD analysis disclosed that zinc hydroxide chloride was the main corrosion product on Zn-Mn coatings immersed in 0.5 mol dm(-3) NaCl solution. EIS investigations revealed that less porous protective layer was produced on the alloy coating deposited at c.d. of 30 mA cm(-2) as compared to that deposited at 80 mA cm(-2).