Effect of glucose on properties of anodizing film on AZ31B magnesium alloy

The effect of glucose concentration on the properties of anodizing film on AZ31B magnesium alloy was investigated in the electrolyte composed of NaOH, Na2SiO3 and Na2B4O7. The properties and surface morphologies of the anodizing films were studied by voltage-time curves, Cass salt spray test, scanning electron microscopy(SEM), energy dispersion spectrometry(EDS), X-ray diffractometry (XRD), electrochemical impedance spectroscopy(EIS) and potentiodynamic polarization, respectively. The results show that the glucose can effectively suppress spark discharge. In the presence of glucose, a uniform and compact anodizing film with small aperture is obtained. Compared with the anodizing film formed in the electrolyte without glucose, the self-corrosion potential shifts to the positive direction and self-corrosion current density is reduced for the anodizing film formed in the electrolyte with the addition of glucose. The anodizing film formed in the electrolyte with 10 g/L glucose has the excellent corrosion resistance with self-corrosion potential of -1.265 V and self-corrosion current density of 1.55×10-8 A/cm2, respectively.