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Anomalous Electrochemical Phenomena during Corrosion of Aluminium in NaOH Solutions at Low Cathodic and Anodic Polarization

S.A. Awad and S.S. Mahmoud

Department of Chemistry, University College for Girls, Ain Shams University, Heliopolis

 

Abstract: The rates of corrosion of aluminium in aqueous 0.03 to 0.4 M-NaOH solutions were measured at 20°C, under imposed cathodic as well as anodic current densities up to 160 цA cm-2. The rates were determined from the loss in mass of aluminium, as well as by measuring the volume of evolving hydrogen. The results were in contradiction with the fundamentals of electrode kinetics. Thus, within certain current density range, the cathodic reaction (viz. hydrogen evolution) is retarded by cathodic currents, and activated by anodic currents. On the other hand, the anodic reaction is accelerated with cathodic currents, and inhibited with anodic ones although the surface is active. To avoid breakdown of electrode kinetics, it is suggested that the entities initiating the cathodic and anodic reactions originate simultaneously from the surface metal atoms. A surface equilibrium is always established between the charged entities and the neutral metal atoms. Pronounced changes in the surface pattern at low polarization lead to anomalous electrochemical phenomena.

Full paper in Portable Document Format: 472a88.pdf

 

Chemical Papers 47 (2) 88–92 (1993)

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