Flame spray coating is the earliest form of thermal spray coating. It uses a flame to melt a feedstock, either wire or powder, then spray droplets of molten material onto the workpiece where it fuses to the surface. The surface of the workpiece is also preheated using the flame.
Flame spraying uses the chemical energy of burning fuel gas to generate heat and then propel the molten particles toward the substrate. Oxy-acetylene is the most common fuel, but a variety of other gases can be used including propane, propylene, hydrogen and ethane.
Flame spraying is often used on workpieces that are too large to heat in an oven. Although advanced methods like plasma spraying and HVOF are increasingly used for demanding operations, flame spray is still popular because of the lower costs of equipment and processing. It can be used for applying a variety of different coatings including polymers and ceramics as well as metals.