Corrosion of Metals in Tropical Environments^★

This paper discusses the corrosion of Aston process wrought iron when exposed to five natural environments in the tropics. Data are reported covering an exposure period of eight years during which the metal was immersed at mean tide and continuously in fresh water and in the sea. Data are presented also from atmospheric exposures including both marine and inland atmospheres. Results indicate that corrosion (measured by weight loss) in fresh water is about equal to that which occurs at mean tide, while corrosion proceeds at the greatest rate during continuous immersion in the sea. Millscale on wrought iron accelerates pitting most severely on metal immersed continuously in the sea, although to a lesser degree than structural steel similarly exposed. It is suggested further that during the earlier exposure of wrought iron and mild steel to tropical water there is little difference in the rates at which the two metals corrode. After eight years, however, the steel shows a significantly greater weight loss. The corrosion of metallic couples of wrought iron and carbon steel in both fresh water and sea water is discussed. 4.2.7