pH-responsive mesoporous silica nanocontainers based on Zn-BTA complexes as stoppers for controllable release of corrosion inhibitors and application in epoxy coatings

A classical strategy of constructing pH-sensitive release system is to encapsulate mesoporous nanoparticles with insoluble complexes such as copper-benzotriazole (Cu-BTA) complex. In this paper, a new capping material, Zn-BTA complex, was adopted to overcome the promoting effect of Cu2+ ions from the decomposition of Cu-BTA complexes on corrosion of mild steel. Mesoporous silica nanoparticles (MSNs) were synthesized, loaded with BTA and then capped with Zn-BTA complexes as stoppers to form MSN-BTA@Zn nanocontainers. The releasing behaviors of BTA at various pH values were investigated, and it was found that MSN-BTA@Zn could achieve on-command release of BTA in response to decrease of pH caused by anodic reaction of corrosion. MSN-BTA@Zn nanocontainers were introduced to epoxy resin to construct stimuli-responsive coating on mild steel substrate. The composite coating with artificial defects shows a distinct stimuli-responsive performance in 3.5 % NaCl, and the incorporation of MSN-BTA@Zn has no impact on the adhesion of the coating to the substrate. The formation of zinc hydroxide compounds in the cathodic zone of galvanic cell makes contribution to the enhancement of corrosion resistance for the coating.