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The flame-spray technique was recently developed for application
ofthermoplatic powder coatings. The thermoplastic powder is fluidizedby
compressed air and fed into a flame gun where it is injected througha
flame of propane, and the powder melts. The molten coatingparticles are
deposited on the workpiece, forming a film onsolidification. Since no
direct heating of the workpiece is required, thistechnique is suitable
for applying coatings to most substrates. Metal,wood, rubber, and
masonry can be successfully coated by thistechnique. This technology is
also suitable for coating large orpermanently-fixed objects.
Benefits
There are particular reasons why flame spraying may be selected over
other surface engineering techniques and they are likely to include a
combination of the following:
- The part geometry or the working environment requires manual
spraying - flame spraying offers the easiest and most tolerable
working conditions
- There are cost concerns and the area is large and complex
- The required coating performance is reached with flame spraying
- Dust and fume levels associated with arc spraying are too high
Applications
Flame spraying is widely used were lower coating costs are desired
and a lower coating quality can be tolerated. Some typical applications
include:
- Corrosion protection of structures and components (e.g. bridges,
offshore platforms, LPG bottles) with aluminium or zinc coatings.
Aluminium is more expensive, but has resistance to acidic gaseous
atmospheres (such as those associated with the products of fossil fuel
combustion), as well as neutral solutions, such as salt water. Zinc
has resistance to alkaline corrosion. Flame spraying is also used to
spray corrosion resistant thermoplastic polymer coatings.
- Reclamation of worn shafts, particularly of bearing areas with
materials such as stainless steel or bronze alloys. The coatings
produced are quite porous and lubricants can be absorbed into the
coating, enhancing the performance of the bearing.
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Molding
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