In the Arc Spray process, two wires are fed into the spray gun and brought into contact with each other at the nozzle. These emerging wires of the material to be sprayed are then charged and an arc generated between them, which causes the tips of the wires to melt. The point of intersection of these wires is positioned directly in front of a carrier jet of compressed air or nitrogen which is used to atomise and propel the molten material onto the work-piece. A mechanical feed mechanism pushes both wires forward to maintain the arc and the flow of material.Typical feed mechanisms are either electric or pneumatic motor driven and are available in push, pull or push/pull arrangements. The latter being the most reliable and farthest reaching. The molten spray solidifies on the work-piece surface to form a dense, strongly adherent coating suitable for Corrosion Protection or Component Reclamation. Sprayed coatings may also be used to provide Wear Resistance, Electrical and Thermal Conductivity or Free Standing Shapes.
Arc spraying is relatively inexpensive, easy to learn, portable, and fairly simple to maintain. Low particle velocities enable high maximum coating thickness for a given material. Recent advancements in nozzle and torch configurations are providing greater control over coating quality and the spray pattern. With the right equipment, it's possible to produce an elongated spray pattern or to spray components with very small internal diameters. As far as its shortcomings, arc spraying is limited to electrically conductive solid wires and cored wires. The introduction of cored wires has enabled the deposition of complex alloys (such as MCrAlYs) as well as carbide-containing metal alloys that were only attainable using powdered materials as feedstock. The temperature of the arc is controllable to a maximum of approximately 10,000°F. Arcspray equipment can spray any type of materials which have melting points below 10,000°F.
Arc spray is excellent for applications that require a heavy coating deposit. The wire arc system produces a highly concentrated yet relatively wide spray pattern and can spray at extremely high speeds. It also allows the creation of a pseudo-alloy (of mixed metal) coating by feeding two wires of differing metals.
Arc spray systems can be divided into two types, engineering and anticorrosion, there are however units that are versatile enough to competently perform both. Anticorrosion arcspray utilises primarily Zinc, Aluminium and Zinc/Aluminium wires, however other materials may be added in minority or used for a particular environment, temperature or pressure.
Major advantages of the Arcspray Process are that the coatings are available for almost instant use with no drying or curing times and there is no risk of damaging the component. In addition, the deposits possess a higher degree of bond strength then most other thermally sprayed deposits and the use of compressed air and electricity alone mean more economic coatings. Arc spray systems are thermally efficient and, because there is no flame or plasma, little heat is transferred to the part being coated.
Arc sprays versatility enable it to be used today for a diversity of applications ranging from prosthesis coatings, mould (US mold) making, UHF Shielding, sculpture metallising to building timber pest exclusion.