Novel smart stannate based coatings of self-healing functionality for AZ91D magnesium alloy

Smart stannate based coatings were used for improving the corrosion resistance of AZ91D alloy. The proposed coatings characterize with their safety compared with the process involving toxic chromate. They are also industrially applicable and economically attractive where only two steps are needed for the coating preparation and the chemicals used are just a diluted tin-oxide solution. The electrochemical behavior and the self-healing characteristics due to stannate coatings on Mg substrate has been evaluated in 3.5% NaCl solution. Polarization measurements, electrochemical impedance spectroscopy, SEM–EDS analyses were performed to assess the performance of the coatings in NaCl and to determine the optimum conditions for self-healing ability. Results showed that stannate coatings improve the resistance to localized corrosion and micro-cracks due to formation of tin oxide-rich magnesium hydroxide layer. It was confirmed that stannate are promising coatings provide a self-healing functionality for Mg substrate that heal the pitting zones and auto-repair the micro-cracks.