Two elements are widely used in coatings as inorganic substituents in 'hybrid' molecules: silicon and fluorine. Although both impart some similar properties, such as low friction, high thermal, chemical and weathering resistance, their chemistry and modes of use are very different. The use of silicon as a binder has already been discussed in the recent column on hybrid coatings; here the focus is on the use of fluorochemicals both as binders and as surface-modifying additives.
Almost all fluorochemicals derive from the same original mineral, fluorspar (also known as fluorite). Global production exceeds 4 million tonnes per year, with the major part coming from China and Mongolia. Much is used directly in the production of steel and ceramics, the remainder being converted into various fluorochemicals and fluoropolymers.
The total volume of fluorochemicals produced worldwide is estimated at 2 million tonnes, with a value of more than $11.5 BN. Fluorochemicals are extremely versatile and find their way into many unrelated applications. Table 1 shows some of their main uses, but a comprehensive list would be very much longer.