How Does Flame Spray Work?
Metallisation | 1st October 2020
When you need to apply a thermal spray coating, a popular option available to you is flame spray. This is used for a variety of purposes and it has numerous benefits, as we are going to see below. In this article, we are going to discuss flame spray, including how it works and what you might want to use it for, as well as when it is a better option than other kinds of thermal spray. Understanding all that could help you to have a better sense of what it can do for you.
What Is Flame Spray?
Wire flame spray is a thermal spray coating where a metal wire is melted and sprayed to produce a metallic coating. Another variant of the process is powder flame spray where a metal or ceramic powder is used instead of a wire.
Flame spray is a tool often used in the application of corrosion protection or engineering coatings. Corrosion coatings are commonly applied by flame spray to architectural steel (balconies, fences, gates etc.) through to structural steel and marine coatings on ships, wind turbines, monopiles and offshore oil platforms. Typical spray materials include zinc, aluminium or alloys of these two elements. Decorative coatings of bronze and copper for example are also commonly applied by the flame spray process. The use of flame spray for engineering coatings is a little more specialised but common coating materials include babbitt for bearings, steels and molybdenum. Alumina coatings are commonly powder flame sprayed as thermal barrier coatings.
How Does Flame Spray Work?
An oxygen/fuel flame is created by mixing the gases, passing the mixture through a nozzle and igniting the mixture to make a high-intensity flame. The wire or powder is fed into the flame which melts the metal or ceramic. Compressed air then atomises the molten metal or the softened ceramic and projects it onto the item being sprayed.
The coating bonds to the surface being sprayed mechanically so the surface is commonly roughened by grit blasting. The coating layer builds, typically from a minimum of around 50 microns up to potentially several mm. Most corrosion coatings would not exceed 500 microns. Some engineering coatings could be several mm thick.
The Advantages of Flame Spray
Wire flame spray is most commonly compared to arc spray and there are several processes where either process is used. As a general rule, flame spray is more cost-effective to buy (lower capital cost) but the running costs are greater than with arc, mainly due to higher gas/oxygen costs. This makes flame spray ideal for smaller or less frequent operation.
For some applications, for example, spraying aluminium for a corrosion coating, flame spray can also have a higher deposit efficiency, e.g. it uses less wire than arc spray so it can be possible that even though the fuel costs are higher than arc spray, the overall coating cost may be lower.
Wire flame spray systems are very flexible for working around large sites and areas where 3 phase electricity is not readily available. It is commonly used for example to apply corrosion protection coatings in oil refineries.
The power flame spray process is a cost-effective solution to apply ceramic coatings. Ceramic coatings are commonly applied by the plasma spraying process with much higher capital costs. Several applications, like thermal barrier coatings onto exhaust manifolds, can often be applied to an acceptable quality level with a powder flame spray system, making it an accessible tool for high-end hobbyists and entry/mid-level motorsports teams.
There is a little more skill required to operate and maintain a flame spray system compared to arc spray but these skills are easily taught by our training team. A familiarity of working with compressed gases is also a benefit to our customers using flame spray systems.
The Final Finish
As you can see, flame spray is a useful solution with a wide range of advantages that make it the perfect thermal spray solution. We have mentioned that there is often some cross-over of applications between flame and arc spray. Our technical sales team are on hand to understand your application and help you choose the right solution. First and foremost, it has to be the right technical solution and then any budget constraints are review. Contact a member of our team.
Thanks to our near one hundred years of experience within the metal coating industry (we sold our first flame spray system in 1922), we’ve become the UKs leading developer, manufacturer and worldwide supplier of a full range of metal spraying equipment such as flame spray equipment and consumables. If you have any questions or need advice; get in touch today on +44 (0)1384 252 464 or send us an email on email@example.com. We look forward to hearing from you.
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