Coatings can be applied in a variety of ways, from e-coating to a brush. With all these options, why use traditional paint?
Unless you are a large manufacturer, many of the powder or vapor deposition methods of coating may be out of your reach for cost reasons. Painting your product not only offers many cost advantages in terms of capital investment, but can also lower the per-piece cost. For the sake of this article, we will consider “painting” to be the wet application of coatings via spray methods.
Spraying paint offers many advantages over the other forms of industrial coating. Low initial cost, fast application, high transfer efficiency and others we will discuss in this article. Keep in mind that there are always exceptions to the rules, and this discussion is not exhaustive.
Spraying a coating on a product can be as simple and low cost as a gravity or siphon feed spray gun in a simple cross draft spray booth. For the small job shop that doesn’t spray every day, this offers the lowest initial cost and the most flexibility in the coatings that can be applied. High build primers, corrosion resistant coatings, CARC, DTM and other coatings can all be applied with a simple change of needle/nozzle sizes.
Clean air can make the difference
That being said, a small investment in clean air can make a world of difference. Using a well maintained air source and
multi-stage filtration will ensure that the air going through the spray gun is the cleanest possible. Using an up-to-date booth with clean filters will keep finish defects to a minimum. Where you put your booth is also of consequence. Taking in air from your sanding operation will corrupt your finish before it gets started. A distributor specializing in industrial finishing can not only help assure proper air quality and application methods, but can also design an environmentally friendly and efficient layout using your current production footprint.
When higher volumes or higher viscosities rule out the use of cup guns, one may turn to pressure feed systems. Pressure feed systems consist of a pressure feed spray gun and a supply source. These may vary from a simple pressure pot to a multi-source diaphragm pump fed manifold. The benefits of such a system include longer spray times for larger products, the ability to spray higher viscosity coatings, and quick color/coating changes if properly set up.
When higher transfer efficiency and speed are called for, air-assisted airless can be employed. AA is similar to pressure fed systems however, the gun handles higher pressures and the pump is usually of a piston operated type. AA is used to bridge the gap between traditional airless systems, which apply paint in a very expeditious manner, but finish quality may suffer; and low pressure air spray or HVLP applications. AA is a hybrid technology reaping the benefits of both air spray (high finish quality) and airless (high speed and high transfer efficiency).
Electrostatic wet spray
When metal substrates are being painted, electrostatic wet spray may be an option. Although the initial cost is higher than the aforementioned processes, the per piece cost benefits can be significant. Electrostatic painting encompasses a variety of coating methods. For purposes of this discussion we will stick with wet e-static spray methods. Your choice of waterborne or solvent-borne material has had little impact on the choice of coating methods up until now. For e-static, the principal technologies used differ based on this choice. Direct charge methods are used for solvent borne materials, and indirect charge methods for waterborne (the use of various safety equipment can sanction the use of direct charge systems for waterborne, but this is outside the scope of this article). E-static offers better transfer efficiency than air spray or HVLP systems and has the added benefit of wrapping around complex profiles, thus increasing speed.
With all the choices available to today’s manufacturers, wet spray coating offer the most flexible means by which to coat your products while offering state-of-the-art technology and environmental benefits.
Contact your local industrial spray specialist for more information on the aforementioned technologies and which might be the best choice for your operation. n
Dale Stitt is North American sales manager for Anest Iwata (Cincinnati, OH), a manufacturer of air compressors and spray equipment. He can be reached at 800-440-0282, or by visiting anestiwata.com.