Thermodynamic properties of 2,5-bis(4-methoxyphenyl)-1,3,4-oxadiazole as a corrosion inhibitor for mild steel in normal sulfuric acid medium

The corrosion rates in the presence of 2,5-bis(4-methoxyphenyl)-1,3,4-oxadiazole (4-MOX) as a steel corrosion inhibitor in 0.5 M sulfuric acid, were measured by the weight loss method, in the range of temperatures from 303 to 343 K. Results obtained revealed that 4-MOX performed excellently as a corrosion inhibitor for mild steel in sulfuric acid media and its efficiency attains more than 96.19% at 8 x 10(-4) M at 333 K. The inhibition was assumed to occur via adsorption of the oxadiazole molecules on the metal surface. The Langmuir adsorption isotherm was tested for their fit to the experimental data. The apparent activation energies, enthalpies and entropies of the dissolution process and the free energies and enthalpies for the adsorption process were determined and discussed. The fundamental thermodynamic functions were used to glean important information about 4-MOX inhibitory behaviour. (c) 2005 Elsevier Ltd. All rights reserved.