Environmentally-safe corrosion inhibitors for the protection of bronzes against corrosion in acidic media [articol]

Abstract

The inhibiting proprieties of two innoxious amino acids (cysteine and phenylalanine) as bronze corrosion inhibitor in a strong acidic solution of 0.2 g/L Na2SO4 + 0.2 g/L NaHCO3 at pH=3 was studied by open-circuit potential measurements, electrochemical impedance spectroscopy and SEM analysis. The impedance measurements revealed that the bronze interface in the absence and in the presence of the amino acids could be suitably represented by a (3RC) equivalent electrical circuit.The magnitude of polarization resistance values determined from the impedance spectra and, consequently, the inhibition efficiencies were found to depend on the structure of amino acids. The anticorrosive efficiencies of the investigated compounds decrease in the order: Cys (96.91 %) > PhAla (52.22 %). SEM analysis of the bronze surface revealed that amino acids inhibit the bronze corrosion process, due to their ability to adsorb on the metallic surface. The results are consistent with the significant increase of impedance in the presence of the organic inhibitors.