Polyurethane coatings with corrosion inhibition and color-fluoresence damage reporting properties based on APhen-grafted carbon dots

A dual-functional coating was developed by incorporating carbon dots (CDs) based additives with corrosion sensing and inhibition properties into a polyurethane (PU) matrix. The complex formed between CDs and 1,10-Phenanthrolin-5-amine (APhen) displays not only a bright red color but also fluorescence quenching in the presence of Fe (II) and Fe (III) ions produced during steel corrosion. Electrochemical measurement and molecular simulation results demonstrate that compared with the CDs, APhen, and their mixture, CDs-APhen complex with multiple surface functional groups, chemical bonding, parallel adsorption, and higher binding energy with iron surface can offer a good inhibition effect against steel corrosion in 1 M HCl solution. Subsequently, CDs-APhen was anchored onto sericite (SC) structure and then incorporated into PU coating. A PU coating containing 2 wt.% CDs-APhen@SC demonstrated good barrier property and self-healing performance, which was ascribed to the corrosion inhibition property of CDs-APhen and the layered structure of SC. In addition, the released CDs-APhen complex provided rapid color/fluorescence responses to Fe ions, offering sensitive self-reporting performance during the initial stage of steel corrosion.