Hiding power, yield and efficiency of powder coatings
Generally, efficiency is very high in electrostatic powder coatings because of recycling possibility.
Hiding power of powder coatings is depended in two important factors:
Density and particle size
Hiding power of FamPowder Powder Coatings is as follows:
-Smooth colors with thickness 50 – 70 micron; every one kilogram powder on the smooth surfaces 10 – 12 M².
– Sand-tex colors with thickness 50 – 70 micron; every one kilogram powder on the smooth surfaces 8-10 M².
– Textured colors with thickness 80 – 100 micron; every one kilogram powder on the smooth surfaces 6-8 M².
– Hammer-tone colors with thickness 90 – 120 micron; every one kilogram powder on the smooth surfaces 6-8 M².
Note: the above numbers are based on recycling consumption on the smooth surfaces and taken in laboratory calculations and in complicated surfaces with angles definitely will change.
Powder Coating Applying Efficiency
When spraying powder by the electrostatic gun, some powders are adhered to the substrate surface and some fall down on the booth ground. Ratio of adhered to powder which fall down is called Powder Coating efficiency.
Pressure & Air Speed in the gun
More air speed causes low efficiency and accumulating powder in the corners and angles. Powder particles are directed to the component and adhered to the component by the help of electrostatic absorption. If the particles movement towards the component is done very fast more than enough, the powder particles hit to the component severely and fall down on the ground. The particles don’t have opportunity to adhere to the component because of the high energy in the air. In general, the less air speed the more adhesion efficiency and less waste.
Gun Distance from Object
Powders will not stick to the object and fall down if the gun distance is more than recommended. On the other hand if the gun distance is less than recommended, the powders will overcharge because of insufficient voltage and high ampere thus the powders will run away and ejected or causes orange peel problem. Ideal relative distance for manual gun is vary depending gun nozzle, object, manual or automatic gun and application but usually it is 15cm-20cm from objects experimentally.
Utilizing suitable spraying nozzle
Powder coating spraying gun can be equipped with different various nozzle.
Angle nozzles (spraying corners) have high speed transferring powders properties and large width spraying. These kinds of nozzles with more wastes are generally suitable for some powders such as Metallic, Hammer-Tone, Textured and pattern coatings. Round nozzles (spraying round) can be applied as standard in most cases. These kinds of nozzle are offered in different sizes and dimensions. It is recommended to test the nozzle according to their shape and size to get the best result after consulting your gun supplier.
The Negative effect of humidity and heat
Heat and humidity within the working environment can have significance negative effect on spraying and Powder Coating layer quality. Any change in these factors will directly effect on the powder flow in the gun, production efficiency, and cabin filters life and also powder electrical charge.
More heat will change the powder physical/chemical properties and high humidity will cause agglomeration problem. On the other hand very dry environment reduce electrostatic charging capabilities and coating layer. So it is recommended environmental relative humidity adjusted between 50–60 and heat around 25°C.
Object Good Earthing
Good earthing is one of the important factors in electrostatic spraying equipment. This maximizes the avoidance of high voltage discharge and the possibility of resultant electrical sparks. Without effectively earthing the spray gun, negative charges will accumulate and powder will then pass through the gun without being charged. The powders will not adhere to the surface. The electrical resistance between the object & earthing should be always less than 1 Million OHM.
Particle Size & Grading
Particle size grading will directly effect on the layer of the powder and also its waste volume.
The powders will move very slow in pistole and pump with very soft and small particle size and cause low movement of electrons and high powder waste amount and charges. On the other hand big particle size grading will cause high weigh not adhere to the surface and pouring on the cabin floor and causing problem in Farade case in high voltage.
So, Particle size grading should be in standard limit not very small and not very big.
In general, all the cheap powder coatings are in big particle size grading and special heavy weight without standard because of their technical problem. These powders are low in coating with much waste amount, ultimately after final calculation in spite of its low price they will be calculated more expensive than the standard powders with high quality.
Comparison between New Paint & Recycled Paint
The most important powder coating advantages is its possibility to recycle.
%95 paint are recycled and enter the production cycle again if we consider low powder waste amount in filter and hanging. The transfer efficiency amount should be determined to access the recycled paint. It is clear that the paint transfer is in accordance with the paint applying method and earthing and also how to keep the spraying equipment such as (Pistol, Nasal, and hose). Inadequate earthing can easily be recognized by little or no powder accumulation to decrease transfer efficiency.