Powder Coating vs. PaintApril 17, 2018
In the worlds of aircraft, appliance and auto assembly, you’ll find a debate over whether it is better to powder coat or spray paint a metal surface. The truth is, both options have their advantages. Before you can make a choice, however, it is important to first know the answer to the underlying question — what is the difference between powder coating and painting?
What is Powder Coating and How Does It Work?
Powder coating is a color-finishing technique in which powder is used in lieu of paint. The powder is applied with spray tools and heated to a chosen surface to form a color coat. Numerous ingredients can make the powder used for this process, such as acrylic, polyester, epoxy and polyurethane. Powder coating achieves a thicker and more consistent finish than you usually get with spray paint. Note that you can find powder coat spray cans available for light-duty applications.
You see examples of powder coating on a vast range of everyday appliances and household fixtures, such as stoves, refrigerators, laundry machines, tables and lamp vases. Powder coating is also quite common today in the finishing stages of auto assembly.
Powder coating is achievable with either thermoplastics or thermosets. The former is a chemical-free process that relies on heat to bring the powder to its thick, solid-coat state. With thermosets, chemical additives interact with the powder during the application stage. The end result of thermoplastic and thermoset powder coatings are virtually identical. In both processes, you heat the powder to form the color finish on a chosen surface.
Below are the steps involved in powder coating a material:
- In advance of a powder coating, you must prepare the chosen surface to ensure proper adhesion of the finish. For industrial applications, you will clean the surface — usually a metal — of any oil or dirt that would otherwise hinder the usage of powder.
- During the application stage, the powder is transformed and brought to a state of adhesion with the chosen surface through what is known as the electrostatic process, in which the powder granules and the surface are jointly charged with volts of electrostatic energy.
- Once you have applied the powder coating, the finish should cure for at least 10 minutes at heat levels in excess of 400°F. This allows the newly melted powder to settle onto the chosen surface. As the finish sets, the original properties of the polymer, acrylic or epoxy come to bear fruit in the form of a tight, thick and shiny surface coat.
In comparison to spray-paint applications, powder coats are more efficient thanks to the electrostatic process, which reduces waste by 95%. The majority of color granules that go into a powder-coat application arrive at their intended destination, and the amount that doesn’t can be reused in a later application. Conservation of this sort is impossible with applications of spray paint, where stray paint gets lost to the wind.
Another similar process you might see is electrostatic painting. Comparing electrostatic painting vs. powder coating processes, both are based on similar concepts, with electrostatic paint using electrical charges to bond the paint to the metal. The biggest difference is that it does not need to be baked to cure.
Powder Coating Benefits
So how good is powder coating? Powder coats are strong, attractive, long-lasting and applicable to various surfaces. The numerous benefits of powder coating are best outlined as follows:
- Durable. Powder coating creates a thick, adhesive finish that lasts longer than the typical coat of spray paint. In the powder coat vs. paint debate, powder coat durability is superior.
- Fast. You can complete powder coats in a single application, which makes the process quicker and more efficient.
- Diverse. Powder coating allows for a range of colors because you can mix and manipulate the powders beforehand.
- Eco-friendly. The powder-coating process is friendly to the environment thanks to the relative lack of toxins or waste produced during a given application.
- Consistent. Unlike spray paint, which can drip and spread unevenly, powder coats produce consistently smooth and solid surfaces with no trace of application marks. Can you paint over powder coating? Yes, if you sand it.
Granted, powder coating does have a few disadvantages:
- Thick coatings only: For starters, the process limits you to thick coats along the surface of a given metal. In most settings, thin coats of a powdered polymer result in bumpy finishes akin to the skin of citrus fruit.
- Equipment requirements: The second drawback — and the most prohibitive for smaller operations — is the amount of expensive, high-tech equipment required for a powder coat. In order to do powder coats, you need to have an industrial oven and an electrostatic booth in addition to the spray tools, all of which can be cost-prohibitive for the DIY craftsperson or home-garage mechanic.
- Color matching: Liquid paint is easy to mix on-site, but powder coat colors are made with special production runs and determined by the plastics used to create them. Mixing colors together would just give you a speckled pattern. Also, many people reuse excess powder used in the application process, which can lead to further difficulty in matching up colors. This difficulty can reduce efficiency and make touch-ups more difficult, especially when using metallic colors.
- Minor surface limitations: Even though many consider powder coating the more durable and efficient option for finishes on metal surfaces, powder is not an option for rubber, which melts when subjected to the electrostatic process
Nonetheless, you can conquer certain limitations associated with powder coating. For example, the subsequent cuts and touch-ups on an already-coated component can be avoided entirely with today’s advanced product modeling, which is made possible with 3D imaging. The presence of final-assembly engineers on a design team can also help make the process of powder coating more foolproof and hurdle-free.
Things to Consider With Powder Coating Materials
If you’re thinking about choosing powder coat over paint and adding it to your operation, there are a few aspects you’ll want to factor in when buying your supplies:
- Available colors: Liquid paint offers practically endless color options, whereas powder coat colors can be more limited. Some powder manufacturers can create just about any color in powder form, while others are restricted to some basic colors. Some colors may call for special manufacturing runs, which will increase lead time. Consider whether the colors you can get meet your needs and how specific your future color-matching needs might be.
- Volume: Will you be able to meet your volume needs with your powder coating equipment? In addition to the capabilities of the equipment, consider the labor required and your access to materials, such as custom-ordered powder coat colors.
- Compliance: Are your equipment and processes compliant with the 9001:2008 standard from the International Organization for Standardization? This standard helps assure quality and good manufacturing practices.
- Quality of supplies: In addition to compliance, you’ll also want to consider how well your suppliers will support your operation overall. Both your equipment and coating materials need to come through reliable, trustworthy providers with proven track records of success. Look for well-made equipment, strong customer service and individualized solutions.
While powder coating has some special considerations in comparison liquid paint, if you take the right steps, it can provide a unique and advantageous finish to a wide range of metal components.
How Does Spray Painting Work?
Traditionally, industrial color coats have been achieved through the self-explanatory process known as spray painting, where paint is applied in aerosolized form through pump devices at high pressure. In the majority of applications, the paint is delivered via pneumatic-powered tools or machinery to achieve a consistent, even coat along a chosen surface.
Before you can apply a coat of spray paint to a chosen surface, you must clean the metal of oily residue and dirt. You then treat the surface to a wet-blast of roughly 15-20 micrometers. The process continues until you have evenly coated the entire surface with a sufficiently thick layer of paint.
The benefits of spray paint include:
- Self-drying. Wet paint dries on its own — no oven required — and so you can apply it to products that cannot submit to heat treatments.
- Color range. Paint can be rendered in a broader range of colors than powders and is useful for a wider assortment of products and signage.
- Thinness/texture. You can apply wet paint thinly to a surface and still leave a smooth texture. This makes paint the more suitable option for items that require thin coats.
- Affordability. Spray painting — and the tools required for the spray-painting process — is simpler and more affordable than powder coating.
With all the benefits of spray paint considered, the process also has its downsides. First off, paint layers lack the durability of powder-coated finishes. Over time, a coat of spray paint will require touch-ups. In most cases, the painted surface will need an entirely new coat of paint after a number of years.
Generally, it is also more difficult to achieve an even coat with wet paint. Whereas powder coats apply smoothly and evenly, paint can leave trace marks and be under-applied in certain areas, over-applied in other areas, and drippy along points. It usually takes multiple coats to achieve a smooth, even finish with spray paint.
Paint vs. Powder Coating: Which Is Better?
In the powder coating vs. painting debate, numerous questions abound. How durable is powder coating? Is powder coating better than painting? The answer could really boil down to which of the two processes best meet the following criteria.
1. Cost Efficiency of Paint and Powder Coating
When economic factors are taken into consideration, the main benefit of the powder-coating process is its efficiency. With a general transfer efficiency of 60–70%, roughly two-thirds of the powder used for a given application serve the intended purpose. Paint, by contrast, has a transfer efficiency of only 30-35%, and thus wastes two-thirds of the paint used for a given application.
Even when you take the leftover amounts into account, all is not lost with powder applications. Once a powder coat has completed, the percentage of powder that falls aside can be collected and put back to use in the next cycle. No such form of conservation is possible with spray paint, which spreads into thin air if it fails to reach its target the first time.
2. Safety of Painting and Powder Coating
Compared to spray painting, powder coating is a safer process because the active product — polymer powder — is inert and therefore free of toxins. Paint, by contrast, usually has toxic solvents and volatile organic compounds that can be harmful if inhaled.
While you do need to wear protective gear when applying powder coats, the process itself is generally cleaner and free of health-related risks. That said, it is crucial to keep the powder from making contact with your skin, but this is easy to achieve thanks to the low amount of overspray that results from the process.
3. Environmental Friendliness of Powder Coating vs. Painting
The eco-friendly advantages of powder extend well beyond the application process itself. Since there are no toxins or volatile organic compounds found in powder polymers, unused portions do not emit greenhouse gases, whether used or unused. Since the majority of a given powder supply ultimately does get put to use, the option is also easy on landfills. To the contrary, each application of spray paint sends toxins into the atmosphere.
4. Mechanical Convenience of Powder Coats vs. Paints
From a mechanical standpoint, powder coats offer greater degrees of strength and flexibility than spray-painted finishes. For starters, a powder finish has a thickness that is stronger and more difficult to crack or peel. Powder finishes are also more bendable, and this makes powder a better option for items that change shape, as well as for anything with moving parts.
The flexibility of powder coats makes powder the ideal option for transportation equipment, which is subject to constant movements and vibrations. Powder-coat finishes have also shown to be more resilient in the face of pebbles, flying debris and other hazards that get kicked up by the tires of a moving vehicle.
5. Productivity of Powder Coats and Paints
Powder coats also help speed along the production process thanks to the short time it takes for powder polymers to cure on a surface. Unlike paint, which may need days to fully dry, powder will fully cure in 20 minutes or less. A powder-coated part could ultimately be put to work even before it has cooled down from its time in the oven.
Due to the durability and streak-fee quality of powder coats, the process involved with powder applications is now seen as a necessary skill at production plants, where the process is commonly taught to staff.
6. Color Accessibility of Powder Coats and Paints
When it comes to color-matching, wet paints offer the advantage of showing their final, dry-state colors right from the start. This makes it easier to mix and match paints with greater accuracy and achieve hues that are slightly off the basic color scale.
Any place you turn to for wet paint, the supplier can easily mix primary and secondary colors to achieve the exact match of a required hue. Alternately, the supplier could add black or white into the mix and equal the tint, tone or highlight of a specified color.
By contrast, the blending of powder colors involves a specialized production, in which the hue of a given color relies on the polymers that are broken down to form the powder. Consequently, the hue of a mixed color can be difficult to determine in advance. Unlike liquid paints — which blend properties when mixed — different powders will not coalesce into a pure, uniform color. Instead, a speckled combination of colors will form when powders mix into one.
7. Reliability of Painting vs. Powder Coating
When it comes to metal surfaces, the purpose of a paint or powder finish is twofold. On one hand, the coat is meant to offer aesthetic appeal, especially if the surface is part of a commercial product, such as a home appliance or automobile. More importantly, however, are the protective qualities of paint and powder finishes, which safeguard metal surfaces from the corrosive effects of environmental elements.
If left exposed to water or moisture, metal can develop rust in spots. In the most concentrated of rust-afflicted areas, holes can form within the metal surface. A solid coat of paint or powder prevents these corrosive effects from taking root on the surfaces of metal, but only as long as the finish remains intact. Since powder finishes are stronger and more durable than paint coats, powder will generally guarantee superior, longer-lasting protection to the surfaces of metal-bodied products.
The colors of powder coatings also last longer thanks to the retentive properties of polymers, which mostly resist the chalking effects of moisture, heat and UV rays. Paints, by contrast, slowly undergo a breakdown in resins and fade from prolonged exposure to sunlight, moisture and heat. The powders that offer the best resistance to chalking are those made from polyester.
8. Texture Differences Between Powder Coats and Paints
Each approach is better suited to a different type of texture. While both can help you achieve a glossy finish, it’s much easier to do with liquid paint. Thin powder coats are more textured and will feel a bit like the skin of an orange. The thicker the coat, the smoother the texture.
Depending on which type of finish you’re going for, powder coating and painting will affect the difficulty of the process.
Buy Powder Coat or Spray Paint Equipment From Finishing Systems
The choice between painting vs. powder coating should really depend on the needs of your products. Ultimately, both methods can leave smooth, thorough finishes on a vast range of surfaces. At Finishing Systems, we provide a variety of finishing equipment for industrial purposes.