Intelligent anti-corrosion and corrosion detection coatings based on layered supramolecules intercalated by fluorescent off-on probes

The metallic engineering structures were commonly covered and protected by the anti-corrosion coatings. The early corrosion under the coatings and at the defects was concealed. Once the corrosion was visible to the naked eye, it indicated that the corrosion has developed seriously. Therefore, it was practical significant to detect the early corrosion of the metal under the coatings and at the defects. The formation of iron ions and anodic acidification were the characteristics of local corrosion process. Based on this fact, iron ions and protons responsive fluorescent on-off probes Rhodamine B Acylhydrazone (RBA) were prepared for the detection of corrosion. In the prepared supramolecules of RBA/LDHs, RBA intercalated and was loaded between layered double hydroxide (LDHs) to protect RBA from premature exposure to corrosive environment and fluorescence quenching. When corrosive Cl− was presented, the RBA loaded by LDHs exchanged with Cl− in corrosive environment, and RBA was released, and Cl− intercalated and was loaded between layers of LDHs. Therefore, the response to corrosion factors and release of RBA were realized, and was accompanied by the capture of Cl− and treatment of corrosion region. In the epoxy coatings, RBA/LDHs indicated the occurrence of corrosion and accurately locate the corrosion site and coating defects in form of fluorescence. Simultaneously, the sheet morphology and dispersion distribution of RBA/LDHs enhanced the shielding performance of the coatings.