Electrodeposition of Zn-Mn alloy coating on the surface of power fittings and evaluation of its corrosion resistance
Zn coating is one of the most commonly used anti-corrosion coating,which can act as a sacrificial anode to provide good cathodic protection for power fittings.The electrodeposited Zn alloy coatings can further improve the corrosion resistance,and provide more effective protection for electric fittings.To investigate the effects of MnSO4·H2O content in the plating bath on the Zn-Mn alloy coating,the X-ray diffraction(XRD),scanning electron microscopy(SEM),potentiodynamic polarization curve and electrochemical impedance spectroscopy(EIS)were employed to analyse the phase composition,micromorphology and corrosion resistance,respectively.The results show that the Zn-Mn alloy coating has obvious passivation characteristics in 3.5 wt.%NaCl solution.The corrosion current density of Zn-Mn alloy coating is lower than that of pure Zn coating,and the electrochemical impedance value of Zn-Mn alloy coating is bigger than that of pure Zn coating.When the MnSO4·H2O is 33.8 g/L,the optimized Zn-Mn alloy coating(Zn-Mn Ⅱ)exhibits a flat and dense surface topography and owns a high Mn content in the coating,resulting in the best corrosion resistance.