Abstract
The inhibition of aluminium corrosion in oxalic acid solution by three cationic surfacants was studied using potentiostatic and potentiodynamic polarization. It was found that the addition of any of the three used surfacants resulted in a decrease of the corrosion current, demonstrating the inhibition nature of these surfactants. The inhibition efficiency increases with increasing surface concentration as well as the number of ethylamine units. The results obtained are discussed in view of the adsorption of surfacant molecules on the aluminium surface. It was found the adsorption of surfacant molecules on the aluminium surface follows the Languir adsorption isotherm. The effect of temperature on the inhibition efficiency was also studied. The results indicate that the inhibition efficiency decreases with increasing temperature. The activation energy of the system increases with the addition of surfacant; on the other hand, it was found that the addition of surfacant shifts the pitting potential of aluminium toward the active direction, indicating the accelerating effect on pitting corrosion. This finding is discussed in view of the effect of surfacant addition on the interfacial tension at the passive film/solution interface.