This study aims at investigating the effect of inhibitor response order on anticorrosion properties of AA2024 with coating system. The inhibitor response order was constructed by adding different inhibitor in sol-gel primer or epoxy top coating of the coating system. Nanocontainers of graphene oxide/layered double hydroxides (GO/LDHs) were loaded with 2-mercaptobenzothiazole (MBT) and vanadate separately to get the inhibitors of GO/LDHs-MBT and GO/LDHs-VOx, which were used in this work. The protection performances of the coating systems with different inhibitor combination and different inhibitor response order were investigated. The best protective coating system is composed of sol-gel coating with GO/LDHs-MBT and epoxy coating with GO/LDHs-VOx. It is contributed to inhibitor combination and a proper response order of the inhibitors. When filiform corrosion occurs, MBT anions from the sol-gel coating are close to the alloy and they inhibit the corrosion in anodic areas immediately, and then vanadate anions from the out and thick epoxy coating reduce the kinetics of the cathodic oxygen reduction reaction. Response order enhances the corrosion protection properties provided by inhibitor combination, which gives a promising way to design good anticorrosive coating system.
Inhibitor-doped sol–gel coatings for corrosion protection of magnesium alloy AZ31
