An Alternative Approach to Modeling Corrosion

The traditional approach to corrosion modeling is relatively straightforward. Corrosion is expressed as a rate of penetration per year and failure is defined when a critical loss of section is predicted to have occurred. Such an approach is well suited to applications involving ships and pipelines where a small local leak can lead to more widespread problems.  However, if this approach is applied to civil structures then it generally proves to be overly conservative and does not reflect the actual properties of a structure. Civil structures, such as reinforced concrete elements, suspension bridges and steel frame buildings, are usually not affected by global failure due to a local event.

This paper describes the development of an alternative approach that takes into account the overall variability in the environment and exposure conditions during the corrosion process. This generates a basic data set that can be employed to represent the natural variability in extent and severity of corrosion occurring on a structure. This was collated into cumulative frequency curves for several common metallic systems and a Weibull distribution fitted to the data. The model has been verified against several different types of structures and the results confirm that compared to the traditional approach, the predictions generated by this method are less conservative, more realistic and greatly improve confidence in the prediction of service lives.