Study of corrosion behavior of the biodegradable chitosan-polyvinyl alcohol coatings on AA8011 aluminum alloy

Biodegradable and environment-friendly chitosan-Polyvinyl alcohol (PVA) composite with different weight % (0.1, 0.5 and 1) of PVA have been prepared by using blending/mixing method. The obtained composites were coated on AA8011 aluminum alloys by dip coating method for the first time. The coatings were studied using SEM, AFM and FTIR analysis. Potentiodynamic polarization analysis and the electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of the coatings. The results showed that by adding PVA, wettability of the chitosan coating increases and the adhesion strength of the coating increases from 2.1 MPa to 2.7 MPa. However, increasing the wettability reduces the corrosion resistance. In addition, PVA acts as an anodic inhibitor and improves the corrosion resistance of the chitosan coating. Therefore, PVA has a dual effect on the corrosion behavior of chitosan coatings. Maximum corrosion resistance occurs in the sample containing 0.5 wt% PVA. Corrosion behavior of chitosan 0.5 wt% PVA in a long time showed that the coating can behave as a self-healing coating. Formation of a complex between PVA and Al ions was studied using of UV-vis analysis. The mechanism of the self-healing effect of chitosan-PVA coating was suggested.