Metal spraying (often referred to as thermal spraying) is a surface coating process where metals and ceramics are applied to the surface of a component. This creates a protective layer that improves performance and extends the life of the underlying material.
Thermal spraying is widely used to protect ferrous metals from corrosion and to modify surface properties, such as improving wear resistance or thermal conductivity. Its applications are extensive, covering a broad range of industries and requirements.
You can explore a selection of these in our solutions section. If your specific application isn’t listed, it doesn’t mean we can’t help – our team is always happy to discuss your requirements and find the right approach for you.
The Processes
All methods of thermal spraying involve the projection of small molten or softened particles onto a prepared surface where they adhere and form a continuous coating. To create the molten particles, a heat source, a spray material and an atomisation/projection method are required. Upon contact, the particles flatten onto the surface, freeze and mechanically bond, firstly onto the roughened substrate and then onto each other as the coating thickness is increased.
Metal spray equipment falls into four main categories:
- Flame Spray
- Arc Spray
- Plasma Spray
- High Velocity Oxygen Fuel (HVOF).
A fifth more recent process is Laser Cladding.
Gas fuel* and oxygen flame (*commonly propane or acetylene).
Wire or powder or ceramic rods
Compressed air (wire flame)
In this process, gas fuel and oxygen are combined and ignited to create a high-temperature flame. The coating material (either in wire or powder form) is then introduced into the flame. For wire flame spraying, the wire is melted and a stream of compressed air breaks the molten metal into fine particles, which are sprayed onto the component surface. Thicker wire typically allows for a higher spray rate. For powder flame spraying, the powder particles (metal or ceramic) are heated and softened in the flame. These particles are then propelled at speed through a nozzle and deposited onto the surface, forming the coating.
In twin wire arc spray, two wires are fed into the spray gun and electrically charged - one positive and one negative. When they meet, they create an arc that melts the wire tips. Compressed air then breaks up the molten metal and propels it onto the component surface. Wire can be fed using push, pull, or push/pull systems, depending on the setup. Higher current systems, such as 350A or 700A, allow for greater spray rates, making the process more efficient for larger or demanding applications.
Plasma arc
Powder (ceramic, metal, plastics)
Via plasma jet
Plasma is a gas that has been heated to such a high temperature that it becomes ionised and electrically conductive. In plasma spraying, this is created by an electric arc inside the spray gun, producing a focused plasma jet. Powder is fed into this jet, where it softens before being propelled onto the surface at high speed, forming a well-bonded coating. Because the heat is concentrated within the jet, the component itself remains relatively cool.
Fuel (liquid or gas) and oxygen flame
Powder (metal)
Via the flame
The fuel (liquid kerosene in our system) is mixed with oxygen and ignited. The combustion gases pass through a converging/diverging nozzle and accelerate to around 1,500m/sec. The powder is injected into the accelerated flame where it softens and gathers speed. The high impact speed of the particles produce a highly adherent, dense coating structure.
Fuel (liquid or gas) and oxygen flame
Powder (metal)
Via the flame
In this process, fuel is mixed with oxygen and ignited, much like standard HVOF spraying. Here, kerosene is typically used as the main fuel, with hydrogen added to stabilise the flame and allow for a more controlled combustion zone. Nitrogen is often introduced to increase gas velocity while lowering the temperature, which helps limit heat transfer to the component. The resulting gases are forced through a specially designed nozzle to create a supersonic flow. Powder is then injected into this high-speed stream, where it softens and accelerates before striking the surface. The high impact speed of these particles forms a dense, strongly bonded coating.
High power laser beam
Powder (metal)
Via laser beam
This process utilises a precisely focused high power laser beam to create a weld pool into which a metallic powder is applied. The powder, which is carried by a stream of inert shielding gas, is blown co-axially through the laser beam.
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