Corrosion in Caustic Soda in Mineral Processing Operations

Because of the high cost of energy, hydrometallurgy is frequently preferred to smelting to extract metals from ores. Many of these processes involve leaching of the metal with an acid, often sulfuric acid. However, there are some processes that use alkaline leachates, such as sodium hydroxide. Hot alkaline solutions present somewhat different corrosion problems to acidic ones and this paper presents data on the corrosion performance of metals and polymers in hot alkaline solutions. Some case histories from the mineral processing industry are used to demonstrate the importance of correct material selection in these corrosive solutions.