Electrochemical and surface analysis investigation of corrosion inhibition performance: 6-Thioguanine, benzotriazole, and phosphate salt on simulated patinas of bronze relics

Organic heterocyclic corrosion inhibitors play a crucial role in the non-destructive protection of excavated bronze relics exposed to the atmosphere. However, the current selection of corrosion inhibitors, additives, and dosage requires further investigation. This study involves a comprehensive preparation simulation of electrode materials and atmospheric corrosion electrolytes. The corrosion inhibition performance of 6-thioguanine (6-Tg) and traditional benzotriazole (BTA) inhibitors at pH = 7.5 is explored. Analytical techniques such as potentiodynamic polarization, EIS, XRD, XPS, and SEM-EDS were employed to analyze the characteristics of the research electrode materials. Surface analysis reveals that 6-Tg forms a protective corrosion inhibition film on the surface of the covered patina electrode, influencing the transition of Cu2(OH)3Cl to the more stable Cu2(OH)2CO3 crystal. Electrochemical results demonstrate that, after 600 h in the corrosion solution containing 0.1 g/L of 6-Tg, the corrosion potential and corrosion current reach 0.244 V and 4.9 μA cm−2, respectively. Upon adding 1.2 g/L of NaH2PO4, the polarization resistance and inhibiting efficiencies reach 15.6 kΩ cm2 and 99%, resulting in a synergistic corrosion inhibition effect and passivation potential shift from −0.6 V to 0.2 V region.