Why HVLP is the Preferred Choice for Painting Metal
HVLP spray guns utilise a High Volume of air at a Low pneumatic Pressure in order to transfer paint or other fluids to a surface. The integrated turbine is similar to types used in vacuum cleaners, but rather than sucking in air, it blows warm air with the liquid towards the substrate. HVLP is often the preferred choice for painting metal mainly because it has a higher transference rate than older technological spray painting systems. Transfer efficiency is defined as the percentage of paint leaving the gun that results in coating the intended surface rather than being dissipated into the air.
The aim of any spray gun is to atomise liquid which effectively breaks it up into tiny particles, so this paint atomisation simply converts liquid paint into a mist of spray. As a rule, the smaller the droplet size, the more uniform the coating. Factors influencing the size of the liquid droplets and the effectiveness of atomisation include the size of the spray gun tip and level of air pressure.
Proper atomisation is essential for achieving a good finish when re-spraying architectural metalwork. Poor atomisation will lead to a number of problems such a coating that resembles orange peel or an uneven surface. When used by experienced sprayers, HVLP guns are an impressive way of covering a multitude of surfaces ranging from cars to the metal framework on shop fronts.
What are the Advantages of Using the HVLP Method of Spray Painting?
There are many advantages to using HVLP spray painting. Conventional spray guns use very high air pressure to force paint through the tip at such high velocities that some droplets bounce back off the surface into the air rather than sticking to the substrate. This transfer inefficiency is not only a waste of paint, it can also end up coating unwanted surfaces.
1. HVLP systems have about a 30% better transference rate of paint to surface than other spray guns. This is because the paint particles leave the gun at about half the velocity of other types of spray painting systems. Consequently, most of the material is actually transferred to the desired surface rather than becoming airborne.
2. A higher transference rate means less waste and therefore, it is a less expensive technique for coating surfaces.
3. A reduction of airborne paint particles equals less air pollution, so HVLP is often chosen for painting metal because it is a more environmentally friendly option.
4. A lower level of VOCs (Volatile Organic Compounds) is both healthier for the paint sprayer as well for staff in a commercial building being sprayed and other members of the public.
5. Since the atomisation occurs at a slower speed than some other methods of spraying, HVLP offers more finesse with less over-spray, therefore it is easier to be accurate.
6. However, it is still a fast way of coating substrates simply because it is so efficient.
7. An HVLP also applies good paint coverage, so a gun can reach recesses as well as flat surfaces which makes it versatile.
8. This versatility makes an HVLP system ideal for a huge range of architectural metalwork as well as other items. It is ideal for shop fronts, roller shutters, doors, fascias and office furniture.
9. A wide array of finishes such as metallic coatings can be used including any RAL or BS colour. In fact, paint is not the only coating that can be sprayed with this application. An HVLP paint sprayer can be used with both water-based and solvent-based type coatings. The system can spray primer, contact adhesives, varnish, lacquer and vinyl fluids to name a few.
10. With any type of coating an HVLP is renowned for offering a high quality finish (if used by an experienced sprayer).
11. HVLP systems are lightweight, compact and therefore portable which makes on-site paint spraying an easy option.
12. Furthermore, the method can be used on exteriors or in an interior setting which is another reason HVLP is the preferred choice for painting metal.
Dos and Don’ts of HVLP Spraying / HVLP Paint Spraying Tips
• Do mix the correct ratio of air and liquid coating. Too much coating and not enough air will result in the paint not having enough body, fill or durability. Excess air will blow the coating everywhere but the surface that needs to be coated.
• Do spray paint evenly in an elliptical shape for best results.
• Don’t use halogenated hydrocarbon solvents in an HVLP spray painting system.
• Don’t put cleaning agents like trichloroethane or methylene chloride through an HVLP spray gun.
• Do use more thinner as well since the warm air produced by the HVLP turbine dries the paint slightly and this can lead to a finish resembling orange peel.
• Do employ a professional sprayer if possible because atomisation is not as fine as air spray guns, so an experienced hand is needed for an even finish.
• Do make sure the air supply is turned off when the HVLP gun is not being used (and relieve the pressure).
As long as guidelines are adhered to, HVLP is the preferred choice for painting metal by many professionals who rely on an efficient method for achieving a smooth top coat.