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Corrosion Inhibition Efficiency in Relation to Micellar Interaction Parameters of Cationic/Nonionic Surfactant Mixtures for Carbon Steel Pipelines in 1 M HCl Solution

The effect of different nine molar mixed ratios of didecyl dimethyl ammonium chloride as a cationic surfactant and nonyl phenol ethoxylate (e.o. = 9) as a nonionic surfactant, on the inhibition behavior of carbon steel have been examined using the weight loss and the potensiodynamic methods. The results show that these mixed cationic/nonionic surfactant mixtures (II to X) can be used to inhibit the corrosion of steel pipelines in the petroleum acid job. The surface active properties of the used surfactant mixtures were calculated using the surface tension measurements and the critical micelle concentration (CMC) values. The micellar interaction parameters of the investigated mixtures were calculated using the data of CMC. From the corrosion results it was found that, the maximum synergistic effect was obtained by the mixtures VIII (30%C + 70%N) and IV (70%C + 30%N). They exhibited inhibition efficiency expressed by the rate of corrosion as 5.15 and 1.53 miles per year respectively, at 400 ppm. The positive synergistic behavior of these mixtures pronounced the better results than which obtained by the individual inhibitors (cationic or nonionic alone). At the same time the maximum micellar interaction parameter was obtained by the mixtures VIII and IV (−1.85 and −1.80, respectively). These results justified the strong relationship between the corrosion inhibition efficiency and the micellar interaction parameters of the mixed surfactants which used as an organic corrosion inhibitors.