Underpaint Corrosion Modelling

T. Machado Amorim, and C. Allély
ArcelorMittal Research and Development, Automotive Products Center, Maizières les Metz, France

Underpaint corrosion is one of the most important degradation modes for galvanized steel sheets employed in automotive and building industry. Simplified systems (metal coated with thin polymer layer) under corrosion situations have been studied in the past few years and it is now widely accepted that one of the mechanisms responsible for the paint disbonding is cathodic delamination.

In this work, a mathematical model has been developed to simulate the transient propagation of the cathodic delamination on a simplified zinc-polymer coated model system placed in stationary corrosion conditions.

The results in terms of delamination rate and pH evolution in the confined zone obtained from this 2D model are in good agreement with literature data and experimental trials.