Copper corrosion inhibition by combined effect of inhibitor and passive film in alkaline solution

The work presents the combined effect of methionine molecules and cuprous oxide passive film on the corrosion inhibition of copper in 1 M NaOH solution by using potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy/energy dispersive X-ray analysis and theoretical calculations. The results reveal that methionine is an effective inhibitor for copper in 1 M NaOH solution and its inhibition efficiency is increased by increasing its concentration. Also, the electrochemical results showed that methionine mainly suppresses the cathodic process as a cathodic-typed inhibitor by adsorption, and the adsorption of methionine can occur on the passive film surface (cuprous oxide) of copper. The adsorbed film of inhibitors combines with the cuprous oxide passive film, and provides a double-layer protection for copper in alkaline solution. Quantum chemical calculation was applied to investigate the inhibition mechanism of methionine, and molecular dynamics simulation was further performed to illustrate the double-layer protection system for copper in alkaline solution.