Effect of Polyacrylic Acid Additives on Anodic Oxidation Film on Magnesium Alloy

In order to further improve the corrosion resistance of the anodic oxidation film on magnesium alloy, polyacrylic acid (PAA) was added into the base electrolyte containing sodium hydroxide (NaOH), sodium silicate (Na2SiO3) and terephthalic acid (PTA) as the main components to prepare anodic oxidation film on the surface of AZ91D magnesium alloy. The effects of polyacrylic acid on the morphology, phase composition and corrosion resistance of the anodic oxidation film on magnesium alloy were analyzed by optical microscope, scanning electron microscope (SEM), X - ray diffraction (XRD) and electrochemical analyzer. Results showed that adding polyacrylic acid into the electrolyte during the anodic oxidation of magnesium alloy could increase the oxidation voltage, inhibit arc discharge, reduce the number of micropores on the film, increase the density and thickness of the film, affect the phase composition of the film, and therefore improve the film’s corrosion resistance.