Electrochemical studies of general and localized corrosion processes

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The primary aim of this research is to develop models to predict the evolution with time of industrially and environmentally important materials corrosion processes. Key areas of interest include corrosion of important materials in high level nuclear waste repositories and gas transmission pipeline steels. The primary goal of an environmental performance assessment model is the demonstration that the chosen scenario will meet the set regulatory goals. The primary goal of an industrial corrosion model is to either demonstrate that the system is fit to remain in service or to optimize the scheduling of maintenance operations for minimal process disturbance. In the majority of these applications oxide films and/or corrosion product deposits on the surface of the materials are the primary defense against corrosion. A thorough understanding of their properties and how they respond with time and exposure environment is essential if their use is to be justified. The primary focus of this proposal is the experimental development of the necessary mechanistic understanding and the determination of the values of essential model parameters. It is proposed that all aspects of localized corrosion processes be studied, from the properties of the films and deposits which must fail for localized processes to initiate, to the development of damage functions for specific corrosion processes, which describe how damage accumulates over the important exposure period. This will be achieved by coupling electrochemical techniques, which have a long history of application to these problems, with a range of novel surface analytical techniques which we have developed or adapted to these applications over the past few years. These include the novel coupling of electrochemical methods and neutron reflectometry and the adaptation of scanning electrochemical microscopy, a technique which can map inhomogeneously distributed corrosion sites.