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Application of molecular probe to investigate surface structure of metal passivator on copper

Copper sulfide (Cu2S) contaminant is semi-conductive. Its formation and migration to insulating paper and oil caused insulation breakdown. Addition of benzotriazole derivatives as metal passivator slows down the corrosion process, as the metal passivator produces a protective layer on the copper surface, which prevents the reaction between corrosive sulfur and copper. But the surface structure of this impermeable film is still unknown. Herein we reported our investigation on the orientation of metal-passivator complex on copper surface by means of molecular probe. Ageing experimental study with different steric and electronic groups in benzotriazole skeleton indicated that the second position of the molecule was sensitive to steric effect, suggesting end-on orientation preferable. Subsequently, SEM-EDX revealed the relative amount of copper sulfide on copper surface. Moreover, FTIR represented the characteristic wavenumber of C=O, C=N moiety and benzene skeleton of passivator-copper complex. XPS analysis delivered the organic elemental composition of the protective layer.