Waste-derived carbon dots-polymer composite for low-dosage corrosion inhibition of 304L stainless steel in chloride-rich environments

Chloride-induced corrosion significantly shortens the service life of stainless steel in marine and industrial environments, creating a need for effective and eco-friendly inhibitors. In this study, a novel material (TCQDs), composed of a poly(tartaric acid–ethylenediamine) copolymer and carbon quantum dots (CQDs), was developed and evaluated as a green corrosion inhibitor. Banana-peel-derived CQDs were incorporated into the polymer matrix through hydrothermal synthesis and surface activation. The structural and thermal properties were confirmed by FTIR, ¹H NMR, TEM, and TGA, which showed stability above approximately 200 °C. Corrosion inhibition performance for 304 L stainless steel in 3.5% NaCl was assessed using electrochemical and weight loss methods. TCQDs exhibited concentration-dependent inhibition, achieving 89% efficiency at 90 ppm. Polarization studies indicated mixed-type inhibition with a reduced corrosion current density and an efficiency of 91.4%. EIS results revealed increased charge-transfer resistance and larger capacitive arcs. Adsorption followed the Langmuir isotherm (R² ≈ 0.999), with adsorption free-energy ( ∆ 𝐺 𝑜 𝑎 𝑑 𝑠 ) values between −31.0 and −36.3 kJmol −1 . SEM confirmed formation of a smooth protective film. TCQDs inhibit corrosion through combined physisorption and chemisorption, demonstrating high efficiency as a sustainable, low-dosage corrosion inhibitor in chloride-rich environments.