Inhibition effect of amino acid derivatives on the corrosion of brass in 0.6 M aqueous sodium chloride solution

Abstract

The inhibitive effects of three amino acids and their benzenesulphonyl derivatives against the corrosion of brass in 0.6 M aqueous sodium chloride solution have been studied using potentiodynamic polarization and electrochemical impedance spectroscopy. The amino acids used are glycine (I), L (-) aspartic acid (II) and L (-) glutamic acid (III) and their corresponding benzenesulphonyl derivatives IV, Vand VI. The inhibition efficiency of these compounds increases in the order I< II< III for amino acids and the same trend is followed for benzenesulphonyl derivatives. Compound VI is found to be the best inhibitor. The inhibition efficiency of VI with 4 ×10^-5M concentration is the highest, which reaches 81.2- 85.5%. It has been observed that introduction of C₆H₅-SO₂- group increases the inhibition efficiency of the amino acids by 14-33% due to (a) higher molecular size (b) <img src='/image/spc_char/pi.gif' border=0> - electron contribution of the benzene ring and (c) presence of more active adsorption sites.