Corrosion characteristics of natural and industrial brines

Saline waters are classified according to standard ASTM D 1129, based on the content of dissolved salts: brackish water 2 to 5 g/l , seawater ∼ 35 g/l and brines with more than 30 g/l. Natural brines include geothermal; those produced by oil wells, by seawater desalination plants, production of salts: NaCl, KCl, MgCl ₂; of hypersaline, inland - seas like the Dead Sea, Israel and Jordan and the Great Salt Lake, USA, both sources of minerals. Industrial brines comprise those used for refrigeration and cooling containing CaCl ₂ or NaCl; for food preservation, for tanning of hides. They are corrosive because of their content of salts and dissolved gases: H ₂S, NH ₃, CO ₂, O ₂. In diluted brines the concentration of dissolved oxygen (DO) varies from 4 to 6 mg /I; in saturated brines e.g. Dead Sea with 280 g/l of salts, low DO of 0.1 mg/l, prevents corrosion of steel, but when hygroscopic salts are deposited on metal surfaces corrosion appears beneath these deposits. Industrial plants which operate steel equipment in brines processing suffer from localized corrosion such as erosion-corrosion, pitting and galvanic corrosion. Plastic materials are degraded by physicochemical mechanisms of absorption, swelling, aging and erosion.