The substituted 1,3,4-oxadiazoles: a new class of corrosion inhibitors of mild steel in acidic media

The effect of a new class of corrosion inhibitors, namely 2,5-disubstituted-1,3,4-oxadiazoles, on the corrosion of mild steel in 1 M HCl and 0.5 M H2SO4 have been investigated by Various corrosion monitoring techniques. Results obtained reveal that these compounds are very good inhibitors and behave better in 1 M HCl than 0.5 M H2SO4 Potentiodynamic polarisation studies clearly reveal the type of inhibitor. The oxadiazoles acts on the cathodic reaction without changing the mechanism of the hydrogen evolution reaction. Changes in impedance parameters (R-t and C-dl) are indicative of adsorption of the oxadiazole on the metal surface leading to the formation of a protective film which grows with increasing exposure time. The adsorption of oxadiazole derivatives on the mild steel surface in both acidic media follows a Langmuir adsorption isotherm. (C) 1999 Elsevier Science Ltd. All rights reserved.