The gradual deterioration of material by chemical processes, such as oxidation or attack by acids; if caused by an atmospheric effect, a form of weathering. Of great significance is the corrosion due to the combined effects of atmospheric temperature, humidity, and suspended impurities, for example, the rusting of iron, the direct effects upon a surface wetted by acid water, or, indirectly, the rotting of wood caused by the action of fungi or bacteria in the soil and in enclosed spaces. Compare corrasion, erosion.