Cysteine-modified graphene oxide as an efficient corrosion inhibitor for brass: Experimental and computational insights

Graphene oxide (GO), renowned for its exceptional properties, has emerged as a promising material for corrosion-resistant applications. L-Cysteine (L-Cys), an eco-friendly and non-toxic corrosion inhibitor, was covalently grafted onto GO flakes via epoxy ring-opening, targeting carbon‑carbon bonds in epoxy groups to preserve the hydrophilic oxygen-containing functional groups. The successful functionalization was confirmed through SEM, FTIR, XRD, and UV–vis spectroscopy analyses. Electrochemical impedance spectroscopy and polarization measurements were employed to evaluate the corrosion inhibition performance of the GO@L-Cys composite. At an optimal concentration of 100 ppm, the modified GO demonstrated an inhibition efficiency of approximately 90 % in protecting brass from corrosion, significantly outperforming unmodified GO (65 %). Surface characterization revealed the absence of corrosion pits and the formation of a flower-like nanoparticle layer, attributed to L-Cys complexation with copper atoms. The uniform dispersion of the GO@L-Cys composite on the brass surface further enhances cathodic protection. Additionally, Monte Carlo simulations and non-covalent interaction (NCI) analyses supported the experimental results, confirming strong interactions between L-Cys and the brass surface. These findings indicate that the GO@L-Cys composite is a highly effective corrosion inhibitor for brass alloys, particularly in aggressive environments.