Corrosion inhibition and adsorption behavior of triazoles derivatives on mild steel in 1 M H3PO4 and synergistic effect of iodide ions

Abstract

Corrosion inhibition by 4-amino-1,2,4-triazole, 3-(2-pyridyl)-4-amino-1,2,4- triazole (2-PAT) and 3-(4-pyridyl)-4-amino-1,2,4-triazole (4-PAT) on mild steel in 1 M H3PO4 was investigated by weight loss, potentiodynamic polarization curves, and electrochemical impedance spectroscopy measurements. The results indicate that these compounds act as inhibitors retarding the cathodic corrosion reaction. Adsorption of triazoles derivatives on mild steel surface was also studied to examine basic information on the interaction between the inhibitors and the metal surface. It was found that the inhibitors adsorb on the metal surface following the Langmuir isotherm model. In addition, a synergism effect with KI was studied. It was found that the inhibition efficiency of triazole derivatives increases with iodide ions concentration to achieve 97 % at 5 × 10−4 M of KI. The temperature effect on the corrosion behavior of mild steel in 1 M H3PO4 in the absence and presence of 4-PAT with KI (mixture) was studied in the temperature range from 293 to 333 K. It is noted that the mixture retains its performance in this range. Finally, an adsorption mechanism of triazoles molecules with KI has been proposed and is discussed.