A universal strategy for green and in situ synthesis of carbon dot-based pickling solution

Corrosion inhibitors as the most important component play a crucial role in the quality of pickling solution. Carbon dots (CDs) have been demonstrated to be a novel and efficient corrosion inhibitor. However, it is still challenging to prepare a truly green CD inhibitor using a simple and economical approach. Herein, for the first time, a green, in situ , facile, low-cost, high-yield and universal acid oxidation strategy is deliberately developed to massively prepare CD-based pickling solution. Significantly, only a low-cost and easily available saccharide (glucose, soluble starch, fructose or saccharose) is adopted as a single precursor and concentrated H 2 SO 4 functions as both an oxidant for CD preparation and an acid source for pickling solution. The CD-based pickling solution with a specific acid concentration can be obtained within the shortest time of 3 min, which is the fastest preparation method reported to date. The corrosion inhibition efficiency of in situ synthesized CDs even reached approximately 95% for Q235 carbon steel in 0.5 M H 2 SO 4 at a low precursor concentration of 0.26%, which was confirmed by the weight loss test, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) measurement. In addition, according to the analyses of electrochemistry and corrosive surfaces, the inhibition mechanism of CDs is ascribed to the formation of a CD-adsorbed protective film. These findings provide a truly green, in situ and universal approach to rapidly prepare customized CD-based pickling solution with high inhibition efficiency.