Thermal spraying is a coating technique that sprays a heated material over a surface to cover and protect it. Various materials can be used in thermal spraying, but the three most common are metals, ceramics and plastics; before they are heated, they may be in rod, liquid or powder form. Performing a thermal spray can be done to protect or repair a surface material. One of the biggest advantages of using a thermal spray is that it can deposit a large amount of material very quickly. Unlike other coating methods, thermal spraying does not use volatile organic compounds (VOCs), the coating cools quickly and materials that require high amounts of heat to melt can be used in the spray.
A thermal spray can be created using metal, ceramic or plastic, with the most common being metal and plastic. To create a thermal spray, the material — or feedstock — is placed in a furnace that heats the material until it melts. The feedstock can be added to the furnace as a powder, rod, wire or liquid, though liquid is uncommon.
One benefit to thermal spraying is that it coats a surface material with a protective barrier. For example, a surface coated with a strong metal will become more resistant to wear, heat, abrasions and — if the metal spray resists magnetism — magnetic forces. Another benefit is that a thermal spray can repair surface material. A worn iron bar can be sprayed with iron to fill in the worn sections.
Many coating methods only apply several micrometers of material to a surface, which is not very effective if a lot of material is needed to adequately protect the surface. With thermal spraying, the spray can add up to several millimeters of material at once, which is considerably thicker. This means spraying is normally finished in much less time.
Some coating materials and methods require the use of harmful VOCs that can affect people and the environment, but thermal spraying does not require any VOC use. The thermal spray technique forces materials to cool quickly, which allows the coating to settle in a short amount of time. Metal has a high melting temperature, and many other spraying and coating techniques are unable to melt metal. Thermal spraying is able to produce the high amounts of heat required, which allows operators to use a wider variety of materials.