Abstract

A. N. Alneami and A. S. Fouda

The dissolution of aluminium in hydrochloric acid and in sodium hydroxide is influenced by the addition of pyrrole, 2-methyl pyrrole and pyrrole 2-carboxyaldehyde. This influence is studied by the thermometric technique. The results show that all compounds investigated are adsorbed on the metal surface, in their cationic form in acid medium, but in its molecular form in alkaline medium. The reaction rate was found to be proportional to the absolute value of Hammett constant (σ) which describes the ability of the substiluents to change the electron density on the pyrrole ring. The degree of coverage θ of the adsorbed inhibitors is determined from the RN value data, and it was found that the results obey the Langmiur adsorption isotherm. Thermodynamic parameters for the adsorption process were determined and discussed.

Inhibition;Aluminium; Hydroxide

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