Eight compounds prepared by modification of epoxidized linseed oil and oleic acid with aniline, p-chloro-aniline, p-toluidine and p-anizidine, were tested as corrosion inhibitors. The test coupons were mild steel and the environment consisted of 0.05N HCl at 70°C or mixed vapours of gasoline and HCl. In HCl, the percentage inhibition ranged from 26.0 to 59.5% for linseed oil and from 88.0 to 94.5% for oleic acid derivatives. In the gas phase, the ranges were from 70.3 to 85.98 and from 62.5 to 74.0%, respectively. The values obtained for two commercial inhibitors tested under the same conditions were 34.5 and 91.7% in HCl and 57.0 and 64.0% in the mixed vapours. The results conformed with a simple Langmuir model and with predictions based on NMR measurements, basicity values (pKa) and Hammett constants. A ranking of the compounds according to percentage inhibition agreed with the order of increasing electron density on the nitrogen atom in these compounds |
