Interfacial effects of –NH2 and –Cl functional groups on the copper corrosion inhibition by 2-mercaptobenzothiazole

Inhibition efficiency follows MBTH-6-NH 2 ≪ MBTH < MBTH-6-Cl. • A new approach is proposed to evaluate anodic and cathodic inhibition efficiencies. • Adsorption energy alone cannot explain inhibition performance. • Organic inhibitor layers regulate interfacial reaction kinetics and surface electronic structure. By combining experimental techniques with density functional theory (DFT) calculations, we investigate the interfacial corrosion inhibition behavior of 2-mercaptobenzothiazole (MBTH) and its –NH 2 and –Cl substituted derivatives on Cu surfaces. The inhibition efficiencies follow the order MBTH-6-NH 2  < MBTH < MBTH-6-Cl. At 5 × 10 −4 M, MBTH and MBTH-6-Cl exhibit high efficiencies of 95.5% and 97.8%, respectively, whereas MBTH-6-NH 2 shows a lower efficiency of 76.3%. The formation and characteristics of inhibitor layers on copper are confirmed by SEM, AFM, ATR-FTIR, and contact angle measurements. DFT calculations reveal that the adsorption energies of the inhibitors on Cu (111) at various coverages do not correlate with the experimental efficiencies, indicating that adsorption strength alone cannot account for the inhibition mechanism. Instead, the efficiency trend is governed by the influence of inhibitor layers on interfacial electrochemical reactions. The MBTH-6-NH 2 -covered Cu (111) surface exhibits enhanced oxygen reduction activity due to stronger O 2 and H 2 O adsorption, facilitated by hydrogen bonding with the –NH 2 group. Moreover, the reduced work function and lower Cu escape energy promote interfacial charge transfer and copper dissolution. These results demonstrate that regulation of interfacial reaction kinetics and surface electronic structure by organic inhibitor layers is critical for copper corrosion inhibition. Download: Download high-res image (99KB) Download: Download full-size image