Robert D. Klassen

Atmospheric corrosivity modeling — a review

The corrosion of metals exposed to the atmosphere is expensive to our societies in terms of aesthetics, safety and functionality. The factors that influence atmospheric corrosivity are reviewed as well as classification schemes, and statistical and mechanistic models. The mechanistic models and experiments revealed that corrosion rates can vary dramatically between locations that are only meters apart. Another implication is that the most influential step in the corrosion process was the deposition rate of corrodent, i.e. aerosols or gaseous pollutants. Thus the principles of mass transfer and deposition of pollutants and aerosols, namely convection and turbulent diffusion, can form a theoretical framework for interpreting and predicting atmospheric corrosivity. The implications for the design of structures is that local corrosivity rates can be predicted based on simulated airflow patterns. Analysis to date has revealed that: (i) smaller objects can be expected to corrode faster because of a greater capture efficiency of salt aerosols; (ii) objects exposed to faster wind speeds and aerosols will corrode faster; and (iii) objects in the lee of prevailing winds from an aerosol source will corrode faster than objects on the windward side of an aerosol source.