Studies of different acid doped polyaniline incorporated into epoxy organic coatings on the Mg alloy

The corrosion resistance of acid-doped polyaniline (PANI)/epoxy coating on AZ91D has been investigated. The results show that PANI doped by sulfonylsalicylic acid significantly facilitates the formation of oxide films on the Mg substrate. The oxide films exhibit a double-layer structure. The dense inner layer is mainly composed of Al2O3 and Al sulfosalicylic acid complex, exhibiting stable protection to the substrate. While, the loose outer layer consists of redeposited MgO and Mg (OH)2. These oxide layers result in the pronounced corrosion resistance of the coating/Mg system, of which the impedance modulus still remain 109 Ω·cm2 after 100 days of immersion.