Corrosion inhibition of carbon steel in chloride solutions by some amino acids

Abstract

The corrosion inhibition of carbon steel was investigated in stagnant naturally aerated chloride solutions using amino acids as environmentally safe corrosion inhibitors. The corrosion rate was calculated in the absence and presence of the corrosion inhibitor using the polarization technique and electrochemical impedance spectroscopy. The experimental impedance data were fitted to theoretical data according to a proposed electronic circuit model to explain the behavior of the alloy/electrolyte interface under different conditions. The corrosion inhibition process was found to depend on the adsorption of the amino acid molecules on the metal surface. Cysteine, histidine, phenylalanine and arginine have shown remarkably high corrosion inhibition efficiency. The corrosion inhibition efficiency was found to depend on the structure of the amino acids. The mechanism of the corrosion inhibition process is based on the adsorption of the amino acid molecules on the active sites of the metal surface. Results obtained from potentiodynamic polarization indicated that the inhibitors are mixed-type inhibitor.