Magnesium is an alkaline earth metal that is never found in nature on its own. Instead, the element is found in seawater, carbon ores, dolomite, carnalite, and other minerals. Thus, the production of the metal in order to create the cutting edge magnesium sheet products begins as soon as the minerals and seawater is harvested. There are two important ways that the elemental magnesium is extracted from nature before it can be used in creating other products.
Electrolysis
This method is most commonly used to extract the magnesium from its most abundant source, seawater. The goal is to extract magnesium hydroxide from the seawater, not the elemental magnesium. The seawater is concentrated into brine and then dried and dissolved in hydrochloric acid. The reaction creates magnesium chloride, which is evaporated to produce a salt. The salt is then heated to melting point. It can conduct electricity in this state. The electricity passed through the molten salt separates it into elemental magnesium and elemental chlorine. The chlorine becomes a gas and the magnesium is left over.
To work, the raw materials must contain an oxide or chloride, making seawater not the only source suitable for electrolysis. The process also works on extracting the magnesium from rock minerals.
Thermal Reduction
Industrial minerals are an increasingly significant component of B.C.’s mineral wealth. The most economically significant industrial minerals produced are: magnesite, white calcium carbonate, limestone, silica, dimension stone, gypsum, sulphur, construction aggregate and crushed rock. The mineral magnesium compounds, such as that bonded with dolomite, are extracted using thermal reduction. Extreme high heat is required and process is much more costly than electrolysis, the preferred extraction method. The mineral compound is heated at such a high heat until they separate into their own compound couplings. The magnesium couples with oxygen to make magnesium oxide and the calcium bonds with the leftover oxygen to create calcium oxide or lime. These compounds are further reduced using heat and silicon to extract the magnesium in the form of a vapor. Then, it is condensed by reactor to ready for refining.
The heat required to facilitate the reduction is so high that a vacuum is needed to lower the reaction temperatures. There are three ways to perform a thermal extraction:
- Pidgeon process
- Bolzano process
- Magnatherm process
At the end of the extraction processes, the magnesium is in a crystal-like form. It is melted once again, refined to further extract impurities and then pure magnesium is ready to turn into sheets.