New relations between modification degree, swelling and impedance in anticorrosion chitosan-derivative coatings on magnesium alloy AZ31

Environmentally friendly coatings of chitosan-derivatives with natural aldehydes were investigated for corrosion protection of magnesium AZ31 alloy. The derivatives were characterized using FTIR and UV-Vis, and the swelling degree of their films was determined in 3.5 wt% NaCl solution. The coated samples were characterized using scanning electron microscopy, potentiodynamic polarization and electrochemical impedance spectroscopy. The results indicated that, as the modification degree increases, the corrosion current density and the swelling degree decrease, whereas the impedance modulus increases. For the first time it was proposed relations between |Z| and swelling with the modification degree.