There are a large number of very good reasons why companies like https://www.poeton.co.uk/standard-treatments/plasma-coatings will use a themal spray gun for the application of nickel sulfate or plastic polymers Plasma Spray. In the past the traditional way to apply super heated materials was via an arc welder as this was the only way the high temperature could be achieved. However, this was fine for non flammable material but flammable substances could not be addressed in this way. This was a concern as flammable material needed protective coating more than many other surfaces.
The answer came in the nineteen seventies via the invention of the thermal plasma spray. This superheated material, in most cases a mixture of nickel sulfate and/or polymer composite, was literally fired at the substrates to be covered. The material was heated to a molten/near molten state and then directed onto the surface with the use of a thermal spray gun.
This process is still used today, although it is greatly redefined from forty years ago. The use of the gun is perfect for the specific application to the substrate. The control that the gun offers is ideal as if there are areas that require more coating this can be directed accordingly.