Effect of variation of the structure of amino acids on inhibition of the corrosion of low-alloy steel in ammoniated citric acid solutions

Abstract

Potentiodynamic polarization, electrochemical impedance spectroscopy, and the new technique electrochemical frequency modulation were used to study the effect of the different structures of three amino acids (tryptophan, tyrosine, and serine) on inhibition of the corrosion of ASTM A213 grade T22 low-alloy steel in ammoniated citric acid solutions. The effects on corrosion inhibition of inhibitor concentration, temperature, and stirring velocity were studied. Thermodynamic data for corrosion and adsorption were calculated and are discussed. The results obtained from the different techniques reveal that the efficiency of inhibition follows the sequence: tryptophan > tyrosine > serine. Inhibition occurs as a result of adsorption of inhibitor molecules by the alloy surface. Adsorption of the inhibitors is a good fit with the Temkin isotherm model. © 2013 Springer Science+Business Media Dordrecht.