Application of ordered mesoporous silica nanocontainers in an anticorrosive epoxy coating on a magnesium alloy surface

The optical photographs of samples before and after exposure to 3.5 wt% NaCl solution for 168 h are presented. Before exposure to corrosive environment, the surface of epoxy coating presents wavy morphology. The surface of epoxy-MBT coating occurs lots of hole with the addition of MBT inhibitors, which may become the penetration channel of corrosive electrolyte. With the addition of nanocontainers, the surfaces of these coatings are no macroscopic defects, and the less concentration of nanocontainers, the surface of coatings looks more smooth. Same behavior is observed on the surface of the coatings containing loaded nanocontainers. The surfaces of epoxy coating and epoxy-MBT coating are damaged mostly after 168 h exposure to corrosive environment. They are coarse with lots of distinct holes. However, the surfaces of coatings containing empty nanocontainers present less corrosion hole and look largely intact. These results reveal that the anticorrosion property is improved by addition silica nanocontainers. Interestingly, the surfaces of coatings containing MBT loaded nanocontainers present snowflake-shaped cracks but no corrosive holes. Moreover, the crack reduces with the increase of the concentration of MBT loaded nanocontainers. This phenomenon can be ascribed to the release of MBT inhibitor when microcracks occur on the surface of the loaded nanocontainers encapsulated coatings, which inhibits the generation of corrosion holes. The results demonstrate that the coatings containing MBT loaded nanocontainers have self-healing properties.