Corrosion Protection Properties and Mechanism of Epoxy/Acetic Acid-Doped Polyaniline Coating on Magnesium Alloy.

Abstract

Poly(amidoamine)(PAMAM)/epoxy/acetic acid-doped polyaniline (PAni) coatings were successfully prepared and coated on magnesium alloy substrates. X-ray diffraction pattern, Fourier transform infrared spectroscopy, scanning electron microscopy technique were used to characterize the composition and morphology of acetic acid-doped PAni and composite coatings. The effect of the usage amount of doped PAni on the corrosion protection performance was evaluated with electrochemical measurement in 3.5 wt.% NaCl solutions. Tafel and electrochemical impedance spectroscopy analysis revealed that the addition of 1.0 wt.% doped PAni provided the superior corrosion protection properties. The corrosion protection mechanism was investigated by using electron probe microanalysis test and theoretical physical model. The doped PAni could obviously shrink the pits and made epoxy resin matrix denser by cross-linking and hydrogen bonding. The composite coatings exhibited better corrosion protection properties compared to pure epoxy coating. The in situ generated corrosion products provided anodic corrosion inhibition due to the easier penetration of acetate ions, and better physical barrier mechanism was promoted by the addition of doped PAni.