A novel and effective N, S co-doped lignin based carbon dots inhibitor for cold rolled steel in 1.0 M HCl solution

Lignin is an ideal precursor for developing efficient, green, and low-cost carbon dot corrosion inhibitors because it is one of the most abundant sustainable resources. Nevertheless, its potential in this field has not yet been fully exploited. In this paper, a novel type of N, S-doped lignin-based carbon dots (N, S-LCDs) with ultra-high inhibition performance was successfully prepared, using lignin as a precursor and 2-thiazoline-2-thiol as both the nitrogen and sulfur source. It was demonstrated that the N, S-LCDs maintained a high corrosion inhibition efficiency of nearly 90% within the temperature range of 20 to 50 °C, with the maximum efficiency of 97.24% observed at 30 °C. Furthermore, a prolonged immersion test over 72 h confirmed the excellent stability of N, S-LCDs. Characterization results indicated that the synergistic co-doping of N and S is the key to N, S-LCDs superior performance. The adsorption of N, S-LCDs on the cold rolled steel (CRS) surface conforms to the Langmuir adsorption isotherm, and a protective film is formed on the CRS surface through physical and chemical adsorption, thereby effectively inhibiting the corrosion process.