N, S-Doped carbon dots from camellia oleifera shells and 2-aminothiazole as a heat-resistant corrosion inhibitor for citric acid pickling of cold rolled steel

Abstract

Citric acid (H3C6H5O7) pickling is an eco-friendly and efficient route for rust removal from metals. However, most reported inhibitors for this process are organic compounds with potential ecotoxicity, and the application of biomass-derived carbon dots (CDs) in this context remains unexplored. Herein, low-toxicity and highly adaptable doped CDs (COS-ATCDs) using camellia oleifera shells (COS) and 2-aminothiazole (2-AT) were first synthesized. It exhibits great fluorescence and corrosion inhibition performance. When the concentration is as low as 100 mg L−1, the corrosion inhibition efficiency for cold rolled steel (CRS) reaches nearly 90%, whereas COS-CDs only achieve 30% at 20 °C. Most importantly, even at 80 °C, COS-ATCDs can still maintain a highly efficient inhibitory effect by increasing the concentration. The introduction of 2-AT can strengthen the interfacial interaction between the Fe substrate and COS-CDs, enhancing compactness and corrosion resistance of the adsorption layer. This work provides both experimental evidence and mechanistic insights to guide the rational design of high-performance, environmentally sustainable corrosion inhibitors for green pickling uses.