Flame spray coating is the earliest method of thermal spray coating, utilizing a flame to melt feedstock materials, such as wire or powder. This process involves spraying droplets of molten material onto a workpiece, where they fuse to the surface. Additionally, the flame preheats the workpiece's surface to ensure proper adhesion.

The technique relies on the chemical energy of burning fuel gas to generate the necessary heat, propelling molten particles onto the substrate. While oxy-acetylene is the most common fuel, other gases like propane, propylene, hydrogen, and ethane can also be used.