Activation of pure Al in an indium-containing electrolyte - an electrochemical noise and impedance study

The activation of aluminium in an acidic indium-containing electrolyte has been studied using electrochemical noise measurements. The average pit-growth rate, measured under freely corroding conditions, was comparable in the presence and absence of indium. However, pit growth times were considerably higher in the presence of indium. The initial breakdown process followed a pseudo-first order process with a rate constant almost a factor of two greater in the case of the indium-containing solution. Analyses of the current-noise data in the frequency domain yielded spectral noise plots, which agreed well with impedance spectra measured under similar conditions. Good agreement was also obtained between R-n, which is defined as the ratio of the standard deviation in the potential noise signal to the standard deviation of the current noise signal, and the zero frequency limit of the impedance. (C) 2000 Elsevier Science Ltd. All rights reserved.