Electrochemical characterization of non-chromate surface treatments on AZ80 magnesium

Surface treatments were applied to AZ80 magnesium alloy (8%Al–92%Mg) within non-chromate environments to develop its anti-corrosion characteristics. The non-chromate process involved chemical conversion using a phosphate and hydrofluoric acid (HF) coating, followed by anodizing. The chemical conversion generated good adhesion between the substrates and the anodic film. The anodizing process formed a 30 μm-thick film on the surface of the AZ80. Electrochemical properties were obtained using Pourbaix diagram, polarization, and EIS (Electrochemical impedance spectroscopy) analyses to characterize the effects on the treated AZ80. Tafel polarization and models of equivalent circuits revealed that the corrosion rate of anodized AZ80 was reduced from 14.44 to 0.28 mpy with passive-film resistance increasing from 428 to 54,200 Ω.