Tropical atmospheric corrosion of galvanized steel, in a light urban atmosphere in the San José valley of Costa Rica

Costa Rica imports most of the metallic materials it uses. In construction, Galvanized Steel (GS) is one of the most used elements in urban areas, where atmospheric corrosion is the main problem of its environmental deterioration. The area of greatest population and economic activity in Costa Rica is the San José Valley, which has a tropical monsoon climate with low pollution, defined under ISO 9223 as light urban. The present study of the atmospheric corrosion of the GS, proposes a high correlation for simple linear models, with climatic parameters as main components and SO₂ as secondary component. Seasonality and sampling sites are partially significant at the beginning of the oxidation process, but this effect is damped over time. The average corrosion rate after 2 years is in the order of 0.4 $\mu$m y^-1, which represents a low level (C2 according to ISO 9223). Complex annual corrosion models, such as those indicated by ISO 9223, overestimate the real corrosion value.

Keywords: atmospheric corrosion, galvanized steel, mathematical modelling, monsoonal climate, air pollutants, rain, time of wetness.