Powder coating is a process in which a powder is sprayed, in a sealed spray booth, over a typically metal product or item. The product is then heated to a specific overall temperature of the item for the powder to melt which creates a solid, even, thicker coating of a protective film. There are also liquid coating options, so why would anyone choose the powder version over the more traditional liquid coatings?
Well, we here at C Tek choose to powder coat certain products for a variety of reasons. They are more durable coating materials. Powder coatings can produce thicker and specialty coatings of color, texture, and finish options. It also less of a serious environmental impact on the area surrounding the workshop using the material to coat their products. The curing and drying process goes smoother than with the liquid coating options. Finally, the percentage of material that gets utilized is higher than other coating methods
The durability of powder coating is superior to most other types of coatings. Once cured and hardened, the powder coating is extremely tough and can protect against abrasion, chipping, impact, chemicals, and weather. It is the perfect choice for anything marine-based as well because it can withstand up to hundreds of hours of direct salt spray without showing any signs of wear or even fading in their brilliantly vibrant color options.
Because of the way that powder coatings are produced, they can make a much wider range of specialty coatings and finishes. They can be completely smooth or pitted to varying degrees and even textured to increase traction or grip. Also, they come in a vast array of super vibrant color options that do not fade even under severe situational exposers to many different things that would otherwise destroy a liquid coating.
When it comes to performing the coatings, liquid coatings include a variety of VOCs or Volatile Organic Compounds that are highly regulated materials especially for workplaces that use them often or even daily. They have to pay for permits that only allow them to release so many VOCs from their shop in a given period of time with hefty fines for those who go over on the release of these compounds.
Other environmental impacts include no need for primer or hazardous waste disposal. The primer is interesting as well since many items that get powder coatings are aluminum which would otherwise require a highly toxic chrome primer before a typical liquid coating could be applied and hold correctly. The chrome is carcinogenic and just all-around bad news for those employees tasked with using and applying the aluminum primer material. As far as hazardous waste, when it comes to liquid coatings you have all the masking materials and overspray covered items that need to be disposed of properly because of the number of solvents required to apply the liquid coatings to the product. It is a large amount and is full of VOCs which, again, are very bad for the environment in many different ways.
The curing and drying process of powder coatings requires much fewer materials to produce the proper conditions. To cure powder coatings, all you need is some even heat throughout the product itself or an oven in the case of liquid suspended powder coating applications. These are when you have the powder seeped in a liquid suspension and dip the product into the mixture and then heat cure for about 10 minutes, or more depending on product size and thickness of the material. Also, for a powder application, you only need a light air exchange that can even be processed inside of a workshop. While liquid coatings require you to have a well-ventilated spray area and another well-ventilated booth with filters on the air exchanges to absorb all those nasty VOCs, fumes from all the solvents, and other harmful byproducts. They also need to be cooked in an oven that has a high air exchange rate which requires much more power, man-hours during extended dry times, and also other cost draining equipment. Plus, it needs to vent outside in a non-frequented area to limit employee exposure to the harmful chemicals released during the drying and curing process of liquid coatings.
Also, because of all the added ventilation products needed for curing liquid coatings the amount of ventilation and other materials plus the extended drying times necessary means that each drying period costs more and takes longer to produce equivalent products. You have to regularly replace filters on the ventilation system because they become clogged with solvent fumes and VOCs. All these hidden costs make powder coatings much more attractive as an option for most applications.
The amount of liquid material that gets wasted in the application process is excessive. You have overspray and the fact that it has to be cut with solvents to put apply it in the proper form for the maximum coating features. With liquid coating you produce a lot of oversprays, you cover masking materials with the coating material, and lose some to hose lines and other transporting equipment. With powder coating, you are using a pneumatic sprayer to drift a layer of powder onto the heated product so it melts on contact and can even be used with an electrostatic application. This is where electrically charged ions of powder coating material are sprayed over an opposingly charged metal product so that the two are electrically attracted to each other and very little material does not end up on the product. Plus, the little bit of material that doesn’t end up on the product can be meticulously cleaned up and reused again with the same coating batch. This means that nearly 100% of powder coating material is utilized in the application procedure.
Liquid coatings require a lot of extra equipment that is not necessary and also takes more material to produce equivalent products. There are many drawbacks to using a liquid over powder coating product, but what are the drawbacks to using powder or liquid? That’s right, there are a few areas where liquid coatings are the better option to coat a product, and here are the main drawbacks to powder coatings and how it can be inferior to liquid applications in some situations:
Since powder coatings require the product to be evenly heated for the coating material to properly melt and become one continuous material, the substrate materials of products are somewhat limited. Typically, smaller metal products are the best candidates for application processes, you can also apply it to some plastics, medium density fiberboard, fiberglass, and a few others as well. As long as it will not melt, warp, or burn when added to the curing oven’s excessive heat for a short period, then it will be okay to use powder coatings. For all other substrates, a liquid coating is needed to properly protect it from the elements and actions around it when in use.
Powder coatings, when applied, tend to be of larger thicknesses due to the lack of control on how much material lands on the product with each pass over with the sprayer. With a liquid coating application, you can spray it in much thinner thicknesses and still evenly coat it, you just use a finer spray and fewer pass overs with the spray gun. Liquids can be applied in thicknesses of less than 6 mm, which is nearly impossible with the two ways in which powder is applied. With a sprayed powder, it comes out in varying densities and melts instantly to the products surface creating an even coating only as the powder turns liquid and slowly levels out the thin areas with some of the thicker ones. With a liquid suspended powder application in which you dip the product is powder in a liquid suspension, you cannot control the amount that sticks or pools up in lower areas on the surface. You are just more hard-pressed to produce an even, thin, and smooth surface coating using powder over liquid coatings.
With the way you need to clean up the spray booth meticulously to resupply the powder to limit waste but also to change between color applications because you do not want two different powder materials for the coatings to mix or it is essentially rendered useless. If you collect every grain when you are done or ready to switch up finishes, colors, or any other powdered coating, then you save yourself by recycling the material and not wasting any. This takes man-hours. So, if you needed to create a product with multiple colors you will need to clean the booth out between each color or finish and then apply the next one once the first is done curing. The amount of human hours involved in the process begins to build up and become not so cost-effective as liquid coatings in some situations. The liquid is quick and easy to change over and requires little to no remasking or cleanup between coatings.
When it comes to anything large or thick, it is harder to apply powders because you need bigger oven space for curing and drying and/or need to heat the item evenly hot enough for the powder application process. Plus, for liquid suspension applications, the dipping pool needs to be large enough to evenly dip and remove the product evenly for an even coating to occur. So, either way, it is not easy to use powder. If the item being coated is larger than your typical curing oven and also too big to be evenly dipped, then you will need to use a liquid coating in most situations.
Both the liquid and powder coatings require a spray gun and spray booth of some sort. So, they are evenly priced up to that point. Even the material itself is evenly priced, although you do need to purchase solvents for the application process of liquid, it doesn’t add up to the initial startup costs of powder coating operations. This is mostly because a curing oven is more expensive than a high air exchange ventilation system. The ovens also take more electricity to power to the proper heats to transfer their heat fully to the typical metal products, so they heat up to the desired temperature. These start-up building costs for the overall operation often limit operations needing to produce coated items to use liquid setups, since they are much cheaper to begin using and therefore you recoup your investment quicker.
As you now know, it costs more to start powder coating than a liquid coating, but in the much longer run it can even out or even become cheaper due to the smaller amounts of material losses incurred in the process. There are many situations where both could be used equally as well, but there are also many situations where the powder is preferred because it is a bit stronger, brighter, will hold color and finish longer, and is easy to apply. In other situations, liquid coatings are best used due to a large area needed application and it will not fit in a curing oven, or it needs a thinner coating due to a tolerance fitting or other reason and the powder cannot coat that thinly.
There are many reasons to use either one, but we at C Tek offer the means and opportunity plus if your product is of the right variety, then powder coatings are the superior coating material when applied perfectly which also takes some experience and expertise that is only learned through trial and error, unfortunately. Luckily our technicians have earned their stripes, so to speak, and are professionals at applying this material or setting up application operations for businesses. So, if you get the opportunity then try the powder coating, it may make a product more marketable for a whole host of reasons and expand its possible usage areas which also widens a product’s market. All these reasons are great positives to the powder coating concept and increase the reasons you should come see us at C Tek Solutions and let us go over your individual needs to produce a proper coating plan. Then, we can set that plan up for you to begin your own coating operations or use ours.
When deciding to choose powder coatings, we always compare it with liquid paints. In this regard, we will consider the benefits and limitations of powder coatings. Liquid paint and powder coating have many differences both in production and application. Apart from quality, the pros and cons of powder coating are also related to the following.
Below, we have listed the benefits and limitations of powder coating compared to liquid paint.
Powder coating contains no solvents and is 100% solid, this is why it is environmentally friendly. Powder helps reduce the health hazard to operators.
The fact that powder coating contains no solvents makes it much less prone to conflagration compared to liquid paint.
Powder coating enjoys high viscosity and is 100% solid so it can be easily produced in much greater thicknesses compared to conventional liquid coatings without runs or drips.
The system and equipment in spraying of powder coating is designed in a way that the powder which does not adhere to the substrate will enter the spray cycle again and is recovered and reused. This minimizes wastage and prevents sewage residue.
Powder coatings have better physical and mechanical properties and are much harder and more durable than conventional paint. This quality is one of the important factors in evaluating powder coatings and is very effective compared to liquid paint.
Powder coatings can be applied in a wide range of colors and textures that are not readily achievable through conventional liquid coating methods. Some examples are: leather, hammer tone, sand texture, wood effect, metallic, and crocodile skin. Powder coatings can be formulated for both protective and decorative applications. The final finish achieved by the powder material ranges from matte to glossy. The variety in the aesthetics of powder coatings is essential in its evaluation and in choosing it over liquid paint. In fact, many industries have chosen only powder coatings because of this quality.
Considering that the production process and blending of powder coatings is carried out in molten form, it is not possible to change the color after production. Whereas in liquid paint we can change the color in all the stages, even when applying the paint, by adding pigment paste.
Powder coatings are 100% solid and because of this, with a minimum amount of application the initial thickness is formed and it contains no volatile components. This makes it impossible to have thicknesses less than 25 microns. Whereas in liquid paint, we have paint thinner and it is possible to have a lower percentage of solids, film thickness can even be as low as 10 microns.
The spray equipment and method of application of powder coatings make coating only possible in spray chambers. Substrates must be charged and after having been coated, enter a curing oven heated up to 200 degrees. Considering these conditions, it is not possible to coat and cure large substrates.
Powder coatings only dry and cure in temperatures above 180 degrees. Whereas liquid paints are varied and could dry up even in room temperature.
Considering the method of application and conditions of charging the substrate, as well as the fact that the substrate needs to be cured up to 180 degrees, it is not possible to coat non-metal substrates.
Powder coatings can be applied to non-metal substrates too. In fact they have been commercially applied, in high volume, to MDF (medium density fiberboard) for over 20 years. Some coaters use UV curable powder coatings, others use low temperature thermosets that can cure as low as 130 degrees.
Taking into consideration the benefits and limitations of powder coatings, and the selected product to be coated, you can evaluate whether coating metals with liquid paint or powder is more suitable for you. Taking into account the many benefits of powder coatings, most industries nowadays have replaced liquid paints with powder coatings. With increasing technologies in the powder coating industry, many more industries are turning to them.
Prepared by: Mojtaba Zeinal
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