Corrosion of metals in the tropics

Abstract

Abstract The atmospheric corrosion of a few common metals has been studied at more than twenty sites in Nigeria and at some others under various conditions of atmospheric humidity and salinity. Contrary to general belief, corrosion is not generally higher under tropical conditions than in temperate climates. Where there is no industrial pollution, the governing factor is airborne salt and while in very saline atmospheres steel may corrode as much as 8 g./dm. 2 /month, in very humid areas free from high salinity the rate may be less than 0.1. The rate of corrosion of ferrous metals varies little between wet and dry seasons or between day and night. Atmospheric salinity has been measured by various methods and at many places; the corrosion of ferrous metals and zinc is proportional to the rate of deposit of salt on a damp textile surface. The corrosion of steel in tropical tidal waters is twice as fast in tidal as in continuous immersion, and in the former case can be as high as 12 g. dm. 2 / month.