Corrosion protection of magnesium alloy AZ31 by coating with poly(ether imides) (PEI)

The present investigation evaluates the commercially available class of poly(ether imides) for corrosion protection of Mg alloys. This class of polymer is used in a wide field of applications like automotive, aerospace, medicine and electronics where it shows beneficial properties. The coatings were applied by dipping to the metal surface as porous and non-porous layers. The corrosion resistance of the coatings and the degradation behaviour were investigated by electrochemical impedance spectroscopy (EIS) as well as under environmental conditions like salt-spray and climate test. Furthermore the resulting polymer coating was qualified by ATR-IR and IR-microscopy. Surprisingly the results indicate that the porous type of coating has lower degradation rate than the dense coating, which was related to hydrogen release without damaging the coating and the interface.