Thermal spraying techniques are coating processes in which melted or heated materials are sprayed onto a surface. The feedstock, i.e. the coating precursor, is heated by electrical or chemical means. Thermal spraying provides thick coatings – the thickness range is approximately 20 micrometers to several mm, depending on the process and feedstock – over a large area at high deposition rate as compared to other coating processes such as electroplating, physical and chemical vapor deposition. Coating materials available for thermal spraying include metals, alloys, ceramics, plastics and composites. They are fed in powder or wire form, heated to a molten or semimolten state and accelerated towards substrates in the form of micrometer-size particles. Combustion or electrical arc discharge is usually used as the source of energy for thermal spraying. Resulting coatings are made by the accumulation of numerous sprayed particles. The surface may not heat up significantly, allowing the coating of flammable substances.