12/17/2023 0 Comments Painnt applicationSecond is the lower film build on inside corners and recesses. This is caused by increased electrostatic attraction in these areas. First is the higher film build on outside corners, edges and around cutouts. Because of this “wraparound” effect, electrostatic applicators are especially suitable for coating tubular products. Not only are the charged coating droplets attracted electrostatically to the front surfaces of these products, they also wrap around and, in some cases, completely coat back surfaces. Charged paint particles are attracted electrostatically to the surfaces of the products to be finished, which are usually at ground potential. It relies upon the attraction of opposite electrical charges. In air-assisted airless spraying, compressed air provides additional atomization and pattern control for application of viscous, high-solids coatings, allowing use of lower fluid pressures and paint temperatures.Įlectrostatic spraying equipment (Read: Benefits of electrostatic sprayers) charges coating droplets as they pass or contact an electrode. The increased use of high-viscosity, high-solids coatings requires painters to use higher temperatures and higher fluid pressures to atomize paint. Furthermore, lower pressure reduces overspray and eliminates the cloud of vapor associated with conventional spraying.Īir-assisted airless spraying units add compressed air to airless spray. Because of the low atomizing air pressures, coating droplet velocities are low enough to lessen blowback. Newer, specially designed HVLP spray guns, using compressed air from conventional sources, can replace air-atomizing guns. This not only reduces the tendency to condense atmospheric moisture but also stabilizes the evaporation of solvent from the coating droplets. The use of heated air lessens the cooling associated with air and airless atomization. High-volume low-pressure spraying originally relied on turbines supplying high volumes of low-pressure, heated air to HVLP spray guns. It also compensates for seasonal changes in ambient temperatures. Consequently, finishing with hot airless spray equipment reduces air pollution and decreases the amount of coating residue requiring disposal. Higher-viscosity paints using less solvent can be sprayed. The coating viscosity, amount of solvent required and overspray are commensurately reduced. Thus, hot airless spraying can apply paint at lower fluid pressure. Heating the coatings applied by airless spray using in-line heaters has the same effect as adding solvents-it lowers viscosity. This accounts in part for the higher transfer efficiency. Only their own momentum (not compressed air) propels the droplets. Unlike air-atomized spraying where compressed air imparts a greater velocity to coating droplets, causing overspray and blowback, airless spraying lessens overspray and blowback. The viscosity of the paint, the size of the orifice and hydraulic pressure determine the speed at which the fluid emerges from the gun. Upon emerging from the orifice, the tremendous internal pressure causes the paint stream to blow apart into atomized droplets. Airless spraying forces paint under pressure through a small orifice in the gun, atomizing it in the same manner as a nozzle attached to a garden hose atomizes water.
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