Electrochemical behaviour of aluminium in concentrated NaOH solutions

The corrosion-dissolution characteristics of pure aluminium were studied in a 4M NaOH electrolyte by steady state techniques and voltammetric analysis. Delineated steady state polarization curves show that aluminium exhibits a passive state at both 25 degrees C and 60 degrees C. Kinetic parameters for aluminium oxidation and hydrogen evolution are consistent with those obtained in a KOH electrolyte. New information is provided by voltammetric experiments: the existence of a sharp passivation peak was demonstrated in the very negative range of potential. Such curves underline the effect of impurities contained in NaOH which increase the corrosion current. In aluminate containing electrolyte, kinetics for both partial reactions are reduced and an oscillatory phenomenon is observed at the active to passive transition. (C) 1999 Elsevier Science Ltd. All rights reserved.