Chloride distribution model and corrosion map of structural steels for tropical climate in Thailand

Tropical climate generally causes long-period of high temperature, relative humidity, and frequent monsoon rainfalls. In combination with airborne salinity, tropical countries usually experience severe corrosion of steel structure. Chloride is a major marine aerosol accelerating corrosion. A study on chloride distribution within 0-5 km from the sea was conducted at three coastal regions in Thailand: upper Gulf of Thailand, southern Gulf of Thailand, and Andaman coasts. It is revealed that chloride deposition rates are exponentially decaying functions of distance from the sea. The chloride deposition rate at the coast is ranked from low to high as upper Gulf of Thailand < Andaman < southern Gulf of Thailand. Sea wind also contributes to chloride deposition rate based on run of wind (ROW) parameter. In this work, both correlative functions of chloride deposition rate with either sea wind speed during prevailing sea wind period or annual monthly ROW are compared. Furthermore, corrosion map constructed from chloride raster layer is presented and validated. A web application of Thailand corrosion map from this work is launched for public access to corrosion rate of carbon steel (SS400) and weathering steel (Corten-B). The chloride distribution model based on run of wind parameter can be applied to coastal regions with varying seasonal wind characteristic for example California, Florida, Italy, Malaysia, and South Korea.