Electrodeposition and corrosion characterization of epoxy/polyaniline coated AZ61 magnesium alloy

Abstract

An epoxy with 7% polyaniline (PANI) powder coating by electrostatic deposition is proposed to enhance the corrosion resistance of AZ61 magnesium alloys. The coating thickness is varied from 85 to 130 microns, and the results are compared to the corrosion resistance of epoxy coated and uncoated AZ61 magnesium alloy. The surface characterization and corrosion behaviour of AZ61 magnesium alloy + epoxy/PANI coating are examined using X-ray photoelectron spectroscopy, salt spray test, potentiodynamic test and Fourier transform infrared spectroscopy. It is observed that the polymer coating protects the base metal against corrosion and the corrosion resistance increases with coating thickness. The corrosion rate of the uncoated, 130 µm coating thickness of epoxy coated and epoxy/PANI coated AZ magnesium alloy is observed to be 0.5379, 0.0869 and 0.0372 mm/year, respectively. The corrosion resistance of epoxy/PANI coating is superior to the epoxy coating. The increase in corrosion resistance of the epoxy/PANI coated AZ61 alloy is attributed to the physical insulation and suppression of magnesium dissolution.