APPLICATIONS OF EXTREME-VALUE THEORY IN CORROSION ENGINEERING

In the context of corrosion engineering it is often natural to be conc erned with extreme events. This is because, firstly, it is these extre me events that often lead to failure and, secondly, it may only be pos sible to measure the extremes, with much of the underlying measurement s by their very nature unobservable. Statistical methods relating to e xtreme value theory can be used to model and predict the statistical b ehaviour of extremes such as the largest pit, thinnest wall, maximum p enetration or similar assessment of a corrosion phenomenon. These tech niques can be applied to the single largest value, or to a given numbe r of the largest values, measured over individual areas or coupons; or to all values exceeding a given threshold. The data can be modeled to account for dependence on environmental conditions, surface area exam ined, and the duration of exposure or of experimentation. The applicat ion of a selection of these techniques is demonstrated on data from in dustry and from laboratory experiments.