Analysis of electrochemical noise obtained from pure aluminium in neutral chloride and alkaline solutions

The present work involves the analysis of electrochemical noise obtained from pure aluminium during breakdown of the oxide film in aqueous neutral chloride solution and hydrogen evolution in alkaline solution. Since the noise data involve information on such stochastic processes as uniform corrosion, breakdown of the oxide film and hydrogen evolution, they were analysed based upon a stochastic theory: the plot of the cumulative probability numerically calculated was first transformed from the domain of the frequency of events to the mean free time domain and then, the Weibull probability plot was constructed by fitting Weibull distribution function to the calculated cumulative probability. Finally, the conditional event generation rate was numerically determined as a function of time. From two linear regions in one Weibull probability plot, it was concluded that breakdown of the oxide film and hydrogen evolution, respectively, were clearly distinguished from uniform corrosion in the Weibull probability plot. In addition, the roles of anion additives in breakdown of the oxide film and hydrogen evolution were also discussed in terms of the distribution of the mean free time and the conditional event generation rate.