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The synergistic effect of benzotriazole (BTAH) and molybdate on the inhibition of copper tarnish was studied in this paper. The antitarnish treatment of copper was conducted with BTAH solution containing molybdate. The surface morphology observation and composition analysis were investigated by SEM with energy dispersive X-ray (EDX) spectroscopy. The addition of molybdate improved the protection of BTAH significantly. The BTAH + molybdate treated copper specimen has higher N concentration in its surface. The structure of the protective film was studied by XPS and AES measurements. It was characterized to be a complex of Cu(I)BTA. The antitarnish effect is certified by the formation of the protective Cu(I)BTA film. Molybdate does not participate in the formation of the protective film. The presence of molybdate promotes the passivation of copper. This facilitates the stabilization of the cuprous oxide film, and strengthens the adsorption of BTAH.

Methionine (MET) is non-toxic and easily biodegradable so that it is an alternative corrosion inhibitor in the water treatment and industrial pickling process. In this article, the inhibition behavior of MET combined with cetrimonium bromide (CTAB) and cetylpyridinium bromide (CPB) for copper corrosion in 0.5 M HCl solution has been investigated by using the electrochemical impedance spectroscopy (EIS), cyclic voltammetry, and polarization curve methods. It shows that combination of MET with CTAB or CPB improves the inhibition performance effectively, and produces strong synergistic inhibition effect. The combined inhibitors suppress cathodic reaction and shift the corrosion potential toward more negative values. The mixed CTAB/MET has a better synergistic effect compared with the mixed CPB/MET. The quantum chemical parameters were calculated by PM3 semiempirical quantum method. The better synergistic inhibition between MET and CTAB is attributed to their stronger electrostatic interaction.

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