Cathodic behavior of pure Al in sulfate media

• N. Benzbiria^1,2, T.T.M. Tran³, M.W. Kendig⁴, M. Zertoubi² and W. Qafsaoui¹

¹ Laboratoire de l’Eau et de l’Environnement, Faculté des Sciences d’El Jadida, BP 20, 24000 El Jadida, Morocco
² Laboratoire Interface Matériaux et Environnement, Faculté des Sciences AïnChock, BP 5366 Maârif, Casablanca, Morocco
³ Sorbonne Université, CNRS, Laboratoire Interfaces et Systèmes Electrochimiques, 4 place Jussieu, F-75005, Paris, France
⁴ Kendig Research Associates LLC, 496 Hillsborough, Thousand Oaks, CA 91361, USA

Abstract: The cathodic behavior of Al in 0.5 M Na₂SO₄ solution was studied by electrochemical methods. It was shown that the reduction of Fe(CN)₆^3- was difficult when an oxide layer was formed on the electrode surface during 1 h immersion in 0.5 M Na₂SO₄ solution due to the poor ionic and electronic conductivities of Al hydroxides. This reaction required a high cathodic overpotential on Al surface pre-treated at –2 V/SCE Al and was kinetically more difficult in comparison to platinum. Rotating disk electrode measurements showed that oxygen reduction reaction (ORR) was controlled by kinetics on both Al pre-treated at –2 V/SCE and oxidized Al cathodic dissolution was controlled by the supply of OH^– ions through H₂ evolution and by ORR on both oxidized Al electrode and the Al surface pre-treated at –2 V/SCE. Polarization curves obtained at different pH values showed that no dissolution behavior was observed at pH 5, whereas in neutral and alkaline solutions, OH^– ions production induced chemical dissolution of the hydroxide layer. In O₂ supersaturated solution, it was shown that ORR kinetics were slightly favored.

Keywords: aluminum, oxide film, cathodic corrosion, sulfate solution, polarization curves

Int. J. Corros. Scale Inhib., 2019, 8, no. 2, 385-410 PDF (1 283 K)
doi: 10.17675/2305-6894-2019-8-2-17

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