Estudo e caracterização do efeito de alguns inibidores de corrosão para o cobre através da espectroscopia raman intensificada por superfície (SERS) e ensaios eletroquímicos

Abstract

The interaction between imidazole (Imid) or 4-methylimidazole (4-MeImid) with a copper surface has been characterized by means of SERS, weight loss and electrochemical experiments as a function of applied potential (E) and corrosive medium composition. Coadsorption of Imid and ImidH+ (imidazolium) has been demonstrated for the first time by SERS spectra acquired in a wide E and pH window. Surface spectra have also shown that only the neutral 4-MeImid adsorbs on the electrode while 4-MeImidH+ adsorbs as an ionic pair with Cl- . Cyclic voltammetry, chronoamperometry and weight loss measurements are in excellent agreement with spectroscopic data. The combination of both micro and macroscopic techniques has allowed us to determine that the inhibitor’s mechanism of interaction changes from chemisorption in cathodic polarization to physisorption near the EOC to soluble complex formation in anodic polarization. These results allowed us to determine that both Imid and 4-MeImid are cathodic inhibitors but their protection efficiency is quite poor when E ≥ EOC. Our data indicate that 4-MeImid is a better inhibitor for copper than Imid, in acidic media. Finally, our results have allowed to clarify literature disagreements and the low inhibition performance of these azoles through a coherent explanation of the mechanism of azole/Cu interaction.