New synthesized 5-phenyl-2H-tetrazole as corrosion inhibitors of steel in 1 M HCl solution in the presence of salts

Corrosive solutions in the acidic domin are more and more encountered in industry [1]. Inhibitors are generally used in these processes to control the metal dissolution [2]. Most of the well-known acid inhibitors are organic compounds containing nitrogen, sulphur and oxygen atoms [3]. The tested inhibitor, namely 5-phenyl-2H-tetrazole was synthesized according to a described experimental procedure. Therefore, benzaldehyd (1) in reaction with NH2OH was converted to benzaldoxime (2). The obtained compound was dehydrated by aceticanhydride to give benzonitrile (3). Then, 5-phenyl-2H-tetrazole (4) was prepared by [2+3] cycloaddition reaction between (3) and NaN3.The molecular structure of this compound is shown below. In these research work, we studied the inhibition of corrosion of steel in 1M HCl by 5-phenyl-2H-tetrazole by weight loss, electrochemical polarization and impedance spectroscopy (EIS) methods. The addition of salt in the presence of 5-phenyl- 2H-tetrazole, indicated that, the rate of corrosion decreased. . The adsorption of inhibitors on the steel surface is found to obey the frumkin adsorption isotherm model. EIS measurements show that the increase of the transfer resistance with the inhibitor concentration. The rate of corrosion of steel in 1M HCl without the5-phenyl-2H-tetrazole increases with the increase of the temperature range from 298 to 3530K, but with the tetrazole compounds, the rate of corrosion of steel decrease.