Corrosion Control of Lead in Hydrochloric Acid Solutions by N-phenylcinnamimide and Some of Its Derivatives

The corrosion inhibition of lead in 0.1 M hydrochloric acid (HCl) was investigated in the absence and presence of different concentrations of N-phenylcinnamimide (C15H13NO) and some of its p-derivatives. Weight loss, Tafel polarization, and anodic polarization under constant current (three independent techniques) were used. The weight-loss results showed that the corrosion rate of the lead decreases by increasing the immersion period and the inhibitor concentration. Tafel polarization studies showed that theses inhibitors retard both the anodic and the cathodic reactions through blocking the active corrosion sites on the metal surface. The data of the anodic polarization under constant current showed that as the concentration of the inhibitor increases, the dissolution potential of the lead electrode, the duration time of the dissolution arrest, and the reactivation potential of the arrest were affected. The adsorption of the studied inhibitors on the lead surface obeys the Langmuir adsorption isotherm equation. The inhibition action of the inhibitors was detected from the three techniques and was found to decrease in the order: N-(p-methoxyphenyl)cinnamimide > N-(p-methylphenyl)cinnamimide > N-phenylcinnamimide > N-(p-nitrophenyl)cinnamimide. The inhibition action of all the inhibitors was found to depend on the nature of the attached group in the p-position of the benzene ring.