Titanium is widely used in specific applications due to its high strength, low density, and good chemical stability. Titanium is as strong as steel but much less dense. It is therefore important as an alloying agent with many metals including aluminium, molybdenum, and iron. These alloys are mainly used in aircraft, spacecraft, and missiles because of their low density and ability to withstand extremes of temperature.
To make titanium you need magnesium.
Despite it being one of the most abundant elements in the earth’s crust, titanium is very expensive, because the production of pure metallic titanium is very complex.
Titanium can't be extracted by reducing the ore using carbon as a cheap reducing agent. The problem is that titanium forms a carbide, TiC, if it is heated with carbon, so you don't get the pure metal that you need. The presence of the carbide makes the metal very brittle.
The world needed an alternative reducing agent to produce titanium. In the case of titanium, the reducing agent is magnesium. This process known as the Kroll process was invented in 1940 by William J. Kroll in Luxembourg.
William Kroll expected his process to be superseded within five years, however today the Kroll process remains and dictates the way titanium is produced.
In the Kroll process, the TiCl4 is reduced by liquid magnesium to give titanium metal.
The Kroll process is the dominant technology for the production of titanium metal, as well as driving the majority of the world's production of magnesium metal.
There is no substitute for magnesium in the Kroll process.
There is no net zero titanium without net zero magnesium.
The world is ready for green metals.