Arc Spray Vs. Flame Spray: What’s the Difference?
Metallisation | 8th October 2020
There are two thermal spray or metal spray processes that are commonly suitable for the same applications - arc spraying and flame spraying. You may have heard of these processes at least in passing, but do you really know their similarities and differences and what uses they might have? In this article, we are going to take a look at some of the major differences between arc spray and flame spray, so that you can better understand them when you need either one of them, or both.
With flame spraying, you are using the heat that is generated from the combustion of a mixture of oxygen and a fuel gas, commonly oxy/propane or oxy/acetylene. This gas mixture is ignited to produce a flame that heats the consumable, either a wire or powder. The molten material is atomised and sprayed to build up a coating layer.
Capital costs of flame spraying are typically lower than arc spraying but the running costs are typically higher. The amount of material that can be sprayed by the flame spray process is limited by the size of wire and the material being sprayed.
Arc spraying uses an electric arc as the heat source to melt metallic wires. Similarly to flame, compressed air (or sometimes inert gas) is used to atomise the molten metal. The electric arc is created by charging one wire positive, the other wire negative and forcing the two wires together to create the electric arc. The process is sometimes referred to as twin wire arc spraying.
Capital costs of arc spraying are typically higher than flame spraying by the running costs are normally lower. The amount of material that can be sprayed is limited by the wire diameter and the available power of the machine but higher spray rates are achievable with arc spray.
Why Choose Arc or Flame Spray?
As well as the capital or running costs already mentioned, this decision falls into two primary categories – technical and personal preference.
From a technical viewpoint, some arc spray coatings have a higher bond strength than flame. If your application requires high bond strength, then it will need to be arc but in many cases, the bond strength from a flame spray coating is still in excess of the application needs. For this reason, some applications will specify that coatings must be arc sprayed.
Another technical reason is the availability of power with flame spraying being more portable than arc spray. The final main technical consideration is the require spray rate where arc can be much greater than flame. For example, the maximum spray rate for flame spray zinc is around 32kg/hr compared to arc which could be in excess of 150kg/hr. These are the main technical reasons but there are others that are more application-specific.
From a personal preference perspective, some people just don’t like working with gases and naked flames. If a factory is not used to this, it can require more focus on risk assessments, safety and insurance. Flame spray also requires a little more skill to operate than arc although rarely have we not been able to train the skills required with a day of training.
Arc spray can also be applied at a lower temperature and no flammable gases are required when using it. It is probably the easier option if you are looking to coat large areas at a time. Flame spraying produces less dust and has lower fume levels and is easier to use when you need to coat something that is complex in its geometry.
The Final Finish
Next time you are trying to decide between arc spraying and flame spraying, consider these major differences and see whether there might be an obvious solution for your spraying needs.
If you have any questions about arc spray or flame spray, get in touch and speak to a member of our team today on +44(0)1384 252 464 or send us an email on firstname.lastname@example.org and we will work with you to find the ideal solution for your budget and environment. We look forward to hearing from you.