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).