Corrosion resistance and mechanisms of Nd(NO3)3 and polyvinyl alcohol organic-inorganic hybrid material incorporated MAO coatings on AZ31 Mg alloy

This work reports the design and preparation of novel organic (polyvinyl alcohol, PVA)-inorganic (neodymium nitrate, Nd(NO 3 ) 3 ) hybrid coatings on micro-arc oxidation (MAO) coating for magnesium (Mg) alloy corrosion protection . X-ray diffractometer , X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy , field emission scanning electron microscope , Energy Dispersive X-ray spectrometer and surface roughness were applied to characterize the chemical composition and surface morphology of the coatings. The corrosion resistance of the coatings was evaluated by electrochemical and salt spray tests. The results suggested that the formation of PVA-Nd 3+ and PVA-Mg 2+ complexes promoted the enrichment of Nd 3+ on the surface, and thereby improved the sealing quality and compactness of the coating. Interestingly, when the coating was damaged, the Nd 3+ ions were transformed to their carbonates and covered the active sites, and thus exhibiting self-healing function. Further, the corrosion resistance of PVA-Nd 3+ modified MAO composite coating on AZ31 Mg alloy was improved.