A corrosion map of Australia: Principles and implications

A multi-scale model of corrosion has been developed. This model looks at the process that control corrosion across scales from 10⁹m to 10 ^-3m. The processes range from those that control the formation of marine aerosols and their transport across the Australian continent to processes controlling the deposition and retention of aerosol salts on metal surfaces. The model predicts the state of a surface each three hours for a year. The "states" include wet from rain, wet from the wetting of hygroscopic salts and dry. Empirical relationships derived from chamber tests are then used to estimate the incremental corrosion over 3 hours for each state. A geographic information system is then used to integrate the model components together and develop a salinity and a corrosion map of Australia. At the continental scale the map illustrates that salinity levels and thus corrosion rates are much higher on Australia's southern coasts compared to the northern coasts. At the local scale it illustrates how coastal landforms such as capes and headlands can produce major variation in salinity levels and corrosion rates. The effect of variation in the intensity of rain events from northern Australia to southern Australia is also highlighted. The intense rains of the Australian tropics effectively clean exposed metal surfaces reducing the corrosion rate.