Corrosion Inhibition of Mild Steel in 1 M Hydrochloric Acid by 2,5-Bis(2-Aminophenyl)–1,3,4-Oxadiazole

Abstract

The inhibition effect of a new class of organic inhibitors (e.g., 2,5-bis(2-aminophenyl)–1,3,4-oxadiazole [2-APOX]) on the corrosion of mild steel in molar hydrochloric acid (HCl) was investigated. The inhibitor was synthesized and its inhibiting action on the corrosion was studied through weight loss and various electrochemical techniques. Potentiodynamic polarization studies clearly revealed the fact that 2-APOX is a mixed-type inhibitor. Changes in impedance parameters (charge-transfer resistance [Rt] and double-layer capacitance [Cdl]) were indicative of adsorption of 2-APOX on the metal surface, leading to the formation of a protective film that grew with increasing exposure time. The 2-APOX appeared to function through the general adsorption mode following the Langmuir adsorption isotherm model. Effect of temperature on the corrosion behavior of mild steel in 1 M HCl with addition of 80 mg/L of 2-APOX was studied in the temperature range from 25°C to 60°C. The associated activation corrosion and free adsorption energies were determined. This inhibitor is considered a noncytotoxic substance.