Investigation Of Corrosion Inhibitive Effect Of Substituted Oxadiazole For Carbon Steel In Hydrochloric Acid Solution

For the requirement of environment protection, development of high-performance, low-toxic inhibitor has become the trend of corrosion inhibitor technology. Nowadays, practical acid inhibitors usually contain atoms with lone-pair electron, such as N, O, S, P, or unsaturated bonds in the molecular structure.Two kinds of green inhibitors, 2,5-bis(2-hydroxyphenyl)-1,3,4-oxadiazole (HPOX) and 2,5-bis(2-hendecyl)-1,3,4-oxadiazole(HOX) containing multi- adsorption center were synthesized. The inhibition effect of HPOX and HOX on the corrosion of carbon steel in hydrochloric acid solution was studied using weight loss measurement, electrochemical polarization curves and impedance spectroscopy. The adsorption of HOX on the surface of carbon steel was confirmed by surface analysis, and thermodynamic adsorption model was used to explain the inhibition mechanism.The synthesis method for oxadiazoles improved was very simple and efficient, which had several advantages just as simple operation, short time, easy purification of product, higher purity and product yields of over 92% compared to traditional synthesis method. Weight loss experimental results showed that HOX with linear branched chain group had good inhibition effect for carbon steel in hydrochloric acid solution with very low concentration, and its inhibition efficiency was superior to HPOX with ring branched chain. In 1mol/L HCl solution at 40℃, inhibition efficiency of HOX at 10mg/L could reach 90%. Under low temperature, HOX could meet for a wide rang of acid medium concentration. At 40℃, in 5mol/L HCl solution containing 60 mg/L HOX, the inhibition efficiency for carbon steel also coulc reach 90%. Electrochemical measurements results showed HOX had significant inhibition effect for both anodic and cathodic corrosion processes of carbon steel. HOX was a mixed-type inhibitor with geometric cover effect and was obeyed the Langmuir's adsorption model. The good shielding effect of long hydrocarbons branched chain lead to excellent inhibition efficiency of HOX. The adsorption free energy of HOX on carbon steel surface was negative, which indicated the absorption was a rapid and intense process.