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 H2S O4 have been investigated by Various corrosion monitoring techniques. Resul ts obtained reveal that these compounds are very good inhibitors and behave better in 1 M HCl than 0.5 M H2SO4 Potentiodynamic polarisation studies cl early reveal the type of inhibitor. The oxadiazoles acts on the cathodic re action without changing the mechanism of the hydrogen evolution reaction. C hanges 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 protec tive film which grows with increasing exposure time. The adsorption of oxad iazole derivatives on the mild steel surface in both acidic media follows a Langmuir adsorption isotherm. (C) 1999 Elsevier Science Ltd. All rights re served.