Comparative study of low carbon steel corrosion inhibition in 200 ppm NaCl by amino acid compounds

The amino acid compounds have been tested as corrosion inhibitors for low carbon steel in a 200 ppm NaCl solution using potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS). Potentiodynamic polarization curves showed that these compounds act as cathodic-type inhibitors. Their inhibition efficiency (η) depends on the number of heteroatoms in their structure. This result was confirmed by the electrochemical impedance spectroscopy measurements. In addition, the impedance diagrams were composed of two capacitive loops badly separated. The first loop was attributed to the formation of a protective layer while the second was attributed to the charge transfer resistance. Finally, it is proved that the inhibition performance of Guanine was indeed improved by immersion time and reached a maximum of 96 % at 4 h.