Azoles as Composite Corrosion Inhibitor for Anti tarnishing of Silver Antiques II. Mechanism of the Azoles for Anti tarnishing of Silver

The normal Raman spectra (NRS) of PMTA, MBO and MBI were measured. Surface enhanced Raman scattering (SERS) was used to study the surface filming processes of these azoles corrosion inhibitors for anti tarnishing of silver, and the interactions between components of composite corrosion inhibitor and silver surface. The mechanism of anti tranishing of silver was also discussed. The experimental results show that there are strong interactions between corrosion inhibitors and silver surface. As constituents of the composite inhibitor with different cycle configuration take on different adsorption directions on the silver surface, much more compact anti tarnishing film is formed. In the pretreatment solution , weak acid pH value is beneficial to the adsorption of corrosion inhibitor and pretreatment time should not be less than 120 min. Under the condition of cathodic polarization with additional potential less than 600mV, in the pretreatment solution and the solution of sodium sulfide, the SERS response ofcomposite corrosion inhibitor becomes stronger as the potential becomes lower. It is proved that the com posite corrosion inhibitor can prevent silver tarnish effectively from corrosion medium.