If left untreated in the aluminum melt, alkali and alkaline earth metals will affect the physical properties of aluminum products, particularly the ductility. Even in trace quantities, these metals degrade the properties of most aluminum alloys, causing cracking and corrosion. Sodium (Na) is by far the biggest alkaline metal contaminant, and calcium (Ca) the major alkaline earth metal contaminant. Sodium and calcium are traditionally removed in the casthouse via the direct injection of chlorine gas into molten aluminum in the holding furnace. However, chlorine is a hazardous and highly corrosive material. Increased emphasis on health, safety, and the environment have accelerated efforts to find substitutes for the extremely hazardous and highly corrosive chlorine gas in treating molten aluminum.
展开▼
