Naslov
Electrochemical and surface properties of aluminium in citric acid solutions

Autori
Šeruga, Marijan ; Hasenay, Damir

Izvornik
Journal of Applied Electrochemistry (0021-891X) 31 (2001), 9; 961-967

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
aluminium; citric acid; corrosion; oxide film; surface processes

Sažetak
The electrochemical and surface properties of aluminium in 0.05 M citric acid solutions of pH 2-8 were studied by means of open circuit potential (OCP), potentiodynamic polarization and potentiostatic current-time transient measurements. The OCP reached a steady-state value very slowly, probably due to the slow rate of detachment of surface complexes into the solution. Aluminium exhibits passive behaviour in citric acid solutions of pH 4-8. Tafel slopes bc were characteristic for hydrogen evolution on aluminium covered by an oxide film. The corrosion kinetic parameters Ecorr, icorr and ba suggest that surface processes are involved in the dissolution kinetics, especially in the pH range 3-6. Current-time transient measurements confirm that, in citric acid solutions of pH 3-6, the dissolution is controlled by surface processes, i.e. by the rate of detachment of surface complexes, while in solutions of pH 2, 7 and 8 dissolution is under mass-transport control. The addition of fluoride ions to citric acid changes the controlling steps of the dissolution process. Citrate and fluoride ions compete for adsorption sites at the oxide surface, and adsorption of these ions is a competitive and reversible adsorption.

Izvorni jezik
Engleski

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