Thermal metal spraying

Thermal metal spraying is often used as an alternative to galvanising. Many fabrications are often unsuitable for galvanising as they may be too large or intricate to be immersed or they have a strict tolerance on the coating thickness. The process is also ideal for the more delicate jobs where distortion or warping could occur if galvanised.

Thermal metal spraying is a term used to describe a technique in which melted (or heated) metallic materials are sprayed onto a surface. The metallic material can be heated either electrically (plasma or arc) or by chemical means (combustion flame).

Thermal spraying can provide a thickness of coatings ranging from 20 micrometres to several millimetres and can be accurately controlled either manually or automatically. 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 semi-molten state and accelerated towards substrates in the form of micrometre-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/delicate substances.

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What are other advantages of thermal metal spraying?
  • Very little heat is generated during the application which means there is no risk of thermal distortion.
  • The low heat input eliminates the risk of thermal metallurgical degradation.
  • There is no cooling down or curing period so items can usually be immediately handled after application.
  • Sealed hollow section fabrications may be treated without the need for ‘venting’ due to the non immersion process.
  • The coating thickness can be accurately controlled meaning the amount applied can be varied from place to place to provide extra protection in critical areas.
  • There is no limit to the size of article which can be treated.
  • The application needn’t be restricted to in works, and can be conducted on site.
  • Metal spraying is used to restore corrosion protection on damaged areas of welded galvanised steel.

Here at Surface Technik we are regularly working to specifications that are employed by both national and international organisations which use thermal spray as the first layer of protection. These specifications are often approved and used for the MOD, Railtrack, The highways agency and local Water authorities.