Oil well steel (N-80) and mild steel Corrosion inhibition by fatty acid oxadiazoles for

Three long chain fatty acid oxadiazoles namely 2-undecane-5-mercapto-1-oxa- 3,4-diazole (UMOD), 2-heptadecene-5-mercapto-1-oxa-3,4-diazole (HMOD) and 2 -decene-5-mercapto-1-oxa-3,4-diazole (DMOD) were synthesized in the laborat ory and were evaluated as corrosion inhibitors for mild steel in 15% HCl at 105 +/- 2 degreesC by weight loss method. Inhibition tests were also carri ed out on N-80 steel under similar conditions in 15% HCl containing 5000 pp m of UMOD. The results obtained indicated that oxadiazole derivatives are g ood corrosion inhibitors. UMOD was found to be the best corrosion inhibitor . It exhibited 94% inhibition efficiency for N-80 steel and 72% inhibition efficiency for mild steel. Potentiodynamic polarization studies carried out at room temperature on mil d steel in 15% HCl, containing 500 ppm of oxadiazole derivatives and on N-8 0 in 15% HCl containing 500 ppm of UMOD showed that all the investigated co mpounds are of mixed type inhibitors. The adsorption of all the oxadiazoles was found to obey Temkin's adsorption isotherm. (C) 2001 Elsevier Science B.V. All rights reserved.