Colloquia

Summary

The corrosion of naval helicopters is accelerated by their use in saline environments; a material's environment influences its corrosion rate.

The specifics of this interaction can be logged by sensors such as relative humidity and temperature, as well as solution and polarization resistances. The latter is a direct method to measure corrosion. This way, relations between the environment and the corrosion rate can be established. However, the polarization resistance sensors deteriorate and the quality of data output declines as a consequence. Also, the cost of their recurring replacement must be considered. Therefore, the Royal Netherlands Aerospace Centre (NLR) seeks a method to measure corrosion without using degrading sensors.

A literature review is conducted to lay the theoretical foundation and previously proposed corrosion prediction models are explored. Consecutively, the measured sensor data is used to study corrosion behaviour. Included are examinations of the sensor calculations from raw data.

Influences of environmental parameters (salt, temperature and relative humidity) on the solution and polarization resistances are clarified by an experiment using different amounts and types of salt.

This report finds an empirical corrosion prediction model based on parameters measured by non-degrading sensors. To include the effect of salinity, this model features the definition of a salt parameter, which estimates the amount of salt present on the surface. The model predicted corrosion under various conditions with an overall accuracy of ±70%.

In addition, the degradation-entropy generation (DEG) methodology and the Buckingham-Pi theorem are applied in the context of corrosion, while possibilities for another predictive model are explored.