Arc spray (sometimes referred to as twin wire arc spray or thermal arc spray) is a process that uses an electric arc to melt wires. The systems push or pull two wires to the gun to be sprayed. The wires are forced together and form an electric arc, melting the wire. Compressed air passes through a nozzle which atomises the molten metal and sprays it onto the work piece. These wires are interchangeable and can be used as one wire zinc, one wire aluminium for example. The higher the current rating of the system, the higher the spray rate. Arc spray is a very good, cost effective method to apply metallic coatings in a very wide range of applications and is one of the most versatile of all of the thermal spray processes. It is a simple process to provide corrosion protection coatings to steel fabrication or is as easily capable to provide engineering coatings to re-build or change the surface properties of the sprayed objects. Changing between anti-corrosion and engineering wires is quite simple. Coatings of zinc, aluminium, steels, copper, bronze and other materials can be sprayed for corrosion protection, engineering reclamation, surface modification and decoration.
The Arc Spray process is known for its low heat input when spraying. Low heating of the substrate makes arc spray useful when it comes to thermally sensitive substrates (e.g. capacitors and electronic components). The low heat input also eliminates the risk of component distortion. The images below show a chocolate egg being subjected to the Arc Spray process. Please note that this was done for demonstrative purposes only and is not to be eaten under any circumstance.
Arc spray systems are commonly considered to be easy to operate and to automate and are offered as "push" or "push/pull" systems. A "push" system pushes the wire to the gun, is lighter and easier to use than a "push/pull" gun and is generally used for engineering applications which use hard engineering wires and have a shorter distance from the machine to the gun (5 metres). "Push/pull" systems are used when a longer distance from the gun to the machine is needed and are typical for anti-corrosion jobs that use soft wires (zinc and aluminium).
Capital costs of arc spraying are typically higher than flame spraying but 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.