Powder coating is a popular finishing option in the rapid prototyping industry. It's a great way to improve the physical and mechanical properties of custom parts.
This coating process has been used since the early days of powder metallurgy and is becoming increasingly popular. Nowadays it is widely used in industry because it offers numerous advantages, including corrosion resistance, high-quality surface finish and long-term environmental sustainability.
So what types of powder coating are there? How it works? And tips for a perfect powder coating finish. This article will answer all your questions about powder coatings.
What is powder coating?
Powder coating is a type of coating applied to a surface as a dry powder and then cured under heat. The powder may be a thermoplastic or thermosetting polymer. It is typically used to create a hard surface that is more durable than traditional liquid coatings and can be used on plastic, glass or metal surfaces.
Powder coating is generally performed by electrostatic spray deposition (ESD) or fluidized bed application. Both methods offer high levels of gloss, textures, diverse colors and high-quality finishes, allowing them to be used in a variety of products including medical devices, architectural applications, automobiles and even fiberboard avionics.
Types of Powder Coating
Powder coating is generally divided into two main categories. There are thermoplastics and thermosets. There are also three other categories, namely thermoplastics, thermosets and UV curable powder coating. UV curable is the most advanced technology.
This article introduces three types of powder coatings. You can decide which type to choose based on the materials of the pieces, durability, economy and quality.
Thermoplastic powder coating materials
Thermoplastics are those that soften when heated and can then be processed to achieve certain strengths and chemical properties when cooled. Thermoplastic powder coating involves applying dry powder to the desired part/material. When heated, the powder melts and covers the desired part, and when cooled it acquires a certain mechanical resistance.
Thermoplastic coatings are used specifically for industrial purposes for reasons of durability, aesthetics and safety. Some of the thermoplastic powders used in the industry are listed below.
nylon
Nylon is an excellent thermoplastic powder coating material with excellent durability and impact resistance. It is FDA approved and food grade, so it is often used in household and kitchen products such as dishwashers and food storage. It also has a low coefficient of friction, which makes it ideal for surface finishing of gears and mechanical tools.
Polyvinyl chloride (PVC)
PVC coating is launched when powder coating is in the initial stage. These coatings are flexible, smooth, durable and resistant to most solvents. Polyvinyl chloride is manufactured using the polymerization technique in the presence of vinyl chloride and is produced on a large scale in industry. The fundamental benefit of this coating is its chemical and electrical insulation. Additionally, they have excellent splash resistance, FDA-approved food stain resistance, and good dielectric and physical strength.
polyester
Polyester siding is known for its durable finish, weather and temperature resistance, aesthetic appearance, and abrasion resistance. For these reasons, this type is mainly used for exterior parts of automobiles and avionics. Their aesthetic appearance and physical strength also make them ideal for architectural purposes.
Acrylic
Acrylic powder coating has high-quality surface aesthetics and high impact resistance, but this process requires slightly higher curing temperatures, which is why it is generally considered an expensive powder coating.
It has excellent alkali resistance, making it ideal for components such as washing machines and ship structures. Acrylic powder coatings are applied by electrostatic spraying to achieve optimal chemical resistance, weather resistance, excellent smoothness, physical strength and durability.
Thermosetting powder coating materials
During thermoset powder coating, thermosets are ground into powder material, which is applied as a thin film to the desired material. They offer better chemical and physical properties than traditional oil coatings in terms of aesthetics and corrosion resistance.
Much has improved in modern thermostat material technology. The ability to design thermostats is to improve their physical and chemical properties depending on the target object, greatly improving this niche in specialized functions in surface finishing engineering. Below are two common thermosetting materials.
Epoxy
Epoxy is a type of thermosetting powder coating that uses epoxy resin as a binder. Epoxy-coated surfaces are inherently hard and brittle, do not resist the elements well, and tend to become dull over time. For this reason, they are mainly suitable for materials that are not exposed to direct UV light. However, they have excellent durability, chemical resistance and adhesive properties, being widely used in industrial and commercial applications where these properties are required.
Epoxy-polyester hybrid
Epoxy-polyester hybrid powder coatings offer the benefits of both epoxy and polyester. They feature excellent chemical resistance and durability, making them ideal for a variety of applications. These powder coatings are also UV and abrasion resistant, making them an excellent choice for exterior applications.
UV curable powder coating
UV curable powder coatings are coatings that cure under ultraviolet light. Unlike traditional methods that require heat to cure, UV curable powder coatings can be cured at much lower temperatures. This makes them ideal for use on delicate or heat-sensitive materials. They also have a shorter curing time than traditional powder coatings.
UV-curable powder coatings offer a number of advantages over traditional coatings, including faster cure times, greater durability and greater flexibility in color selection. They are typically more expensive than traditional methods, but the improved performance may justify the additional cost.
How does the powder coating process work?
The powder coating process is divided into different steps essential for smooth, high-quality work. The entire work process can be divided into three stages.
- Pretreatment
- Application of powder coating method (fluid sintering and electrostatic spray deposition)
- Healing process
Pretreatment
If you want a smooth, high-quality surface finish on your piece, you need to apply some pre-treatment techniques. The presence of dust, oil and fatty pigments negatively affects the coating of the material, therefore the part must be treated appropriately.
If your workpiece is covered with debris such as existing paint or rust, you will need to have it processed in a sandblasting room. The space mechanism uses compressed air to remove any unwanted debris from the workpiece. Pressure and conditions are selected according to the required conditions. For example, if the workpiece is covered with excess paint, iron blasting may be necessary.
On the other hand, if your piece contains traces of oil, grease or other chemical solvents, it is essential to wash it with a chemical product such as iron phosphate for steel, zinc phosphate for galvanized steel and chromium phosphate for chrome-free treatments. In addition to these common pretreatment processes, many other new groups of technology are in use today that utilize transition metals and other organometallics in conjunction with the zinc sulfate formulation. These processes are ideal for reducing costs and achieving a consistent surface finish.
Application of powder coating method
Powder coating is also applied in different ways and depends on production requirements, price range and material selection. The two most common methods are electrostatic spray deposition and powder coating using the fluid sintering process.
Electrostatic deposition
During electrostatic deposition, charged powder particles are deposited on the part through the electrostatic process. The application process consists of an electrostatically charged spray gun, a powder conveyor and a powder spray unit. The electronic gun is manually operated or computer controlled and charges powder via the HIT generator. When the application process begins, the electrostatic gun begins spraying negatively charged powder.
These charged particles are dropped onto the grounded, positively charged workpiece and remain attached to the surface of the workpiece due to electrostatic attraction. After the powder has been deposited, the part is heated for some time to obtain a smooth surface. To create thicker coatings, the spraying process must be repeated or adjusted accordingly.
Electrostatic powder coated parts are used in a variety of industries, including automotive, architectural, furniture and appliances. It offers a number of advantages over traditional liquid coatings, including better durability, greater resistance to chips and scratches, and an overall smoother appearance.
Fluidized Bed Powder Coating
In contrast to ESD powder coating, fluidized bed powder coating is a type of powder coating in which the powder coating is applied to the workpiece using a fluidized bed. The workpiece is placed in the fluidized bed and the powder is applied to the workpiece using a spray gun. The powder is then hardened using heat or ultraviolet light. The fluidized bed helps distribute the powder evenly across the workpiece and the spray gun ensures the powder is applied evenly.
Fluid bed powder coating is a durable finish that is resistant to chips, scratches and fading. It is also easy to care for and does not need to be polished or waxed.
Healing process
Finally, the part, which has been powder coated electrostatically or using a fluidized bed process, is hardened in the hardening oven for several minutes. The curing schedule depends on the parts, materials and finishing requirements. Thick film parts require more time than thin film parts. Typically, the ideal curing time is 10 to 20 minutes at a temperature of 350-400 degrees. Under these conditions the powder melts and produces a smooth, high-quality surface.
Advantages and Disadvantages of Powder Coating
Powder coating is a much better alternative to traditional wet painting for both protective and decorative purposes. It offers a wide range of colors with a high-quality surface finish, but it also has some disadvantages. Read on to learn more.
Advantages of powder coatings
durability
The main advantage of powder-coated parts is their durability. Powder-coated materials generally do not fade, do not chip, do not scratch, and are resistant to wear. They are more resistant to mechanical stress, have a more durable surface and are more resistant to environmental influences than spray painting.
Thanks to the materials and other additives used, they are perfectly protected from UV light and, unlike conventional liquid coatings, they do not fade outdoors. For this reason, this technique is most often used in the automotive and aviation industries.
Furthermore, rust is very common on metal parts. Powder coatings provide amazing results on metals. They not only protect the surface of metal parts, but also prevent them from rusting for a long time. Rust protection is the most well-known feature of powder coating compared to traditional paint.
Cost effectiveness
It is a more economical option than liquid paint. Although the initial cost is higher, less energy is required for healing. Additionally, powder coating provides a more durable finish than liquid paint, which means powder coated products last longer.
Good quality
Powder coating creates high-quality pieces with a clean surface and a modern aesthetic. The physical strength, wear resistance and other properties of the product have been improved.
Environmentally friendly
Powder coating is an ideal and eco-friendly method as it is free from all forms of harmful chemicals and solvents due to the presence of volatile organic compounds. Furthermore, this powder is applied to the surface and then cured under heat. The excess powder is then recycled, so this process generates very little waste.
Disadvantages of powder coatings
Higher acquisition costs
The initial setup cost of the powder coating industry is a little high due to the high cost of raw materials. However, it is much more cost-effective when compared to traditional paint over time, as traditional paint degrades after 1 or 2 years, while powder coating lasts for decades.
Powders cannot be mixed
With wet paint, you can mix multiple colors to create a new color that achieves the result you want. However, this is not possible with powder coating. Powders cannot be mixed, they must be used separately. However, there is a wide variety of colors to choose from.
Thin layers
Powder coating is not ideal for thin coats; can be applied in a minimum layer thickness of 40 to 60 microns. If you want a much thinner layer, it is recommended to use wet paint for best results.
Difficult to repair
Touch-ups are easy to do with wet paints, but not with powder paints. Because if a repair is necessary, the entire process must be carried out. Therefore, you need to be well versed in this mechanism.
Powder coating applications in various industries
Due to their high industrial utility, these powder coating products have a wide range of applications in a wide variety of industries and their usage is increasing day by day.
automobile : Powder coatings are mainly used in all areas of the automotive industry, especially in the production of wheels, door handles, motorcycle frames, brake components, radiators, metal surfaces, shock absorbers, oil filters, battery compartments and coils.
Architecture and steel industry : Due to their physical strength, corrosion resistance, high gloss and aesthetic appearance, powder-coated products are used in the architectural industry for stadiums, aluminum windows and doors, fences, sheet metal, electrical appliances and building facades .
Outdoor applications : Due to their robustness, UV protection and durability, powder coated materials are predominantly used in the sports industry, agricultural machinery, outdoor products and signage.
electronics : Powder coating is widely used in the electronics industry. Powder coated household cables, electrical appliances and power tools for daily use are safer and more beneficial than wet coating. This is due to their altered electrical conductivity and electrical dissipation properties.
Medical Industry : In the medical industry, sterilized tools and a smooth surface finish are essential; Powder coatings are used in medical devices, disinfection devices, etc.
5 Tips for a Perfect Powder Coating Finish
Powder coating is a robust and long-lasting technology. There are several things you can do to ensure your painting looks perfect. Here are some tips:
1. Prepare the surface
This is probably the most important step to getting a good powder coat finish. If the surface is not properly prepared, the powder will not adhere well and will not produce the desired results. Be sure to sand the surface smooth and free of contaminants before beginning the powder coating process.
2. Choose the right powder materials
There are different types of powder for different applications. Make sure you select the correct powder coating materials for your project. If you are unsure, contact a professional powder coating company.
3. Avoid picture frames
Image edges are a common problem with powder coatings and can have a variety of causes. It most commonly occurs when too much powder is applied to the component, resulting in a thicker film around the edges. Other causes may include the spray gun pointed directly at the edges of the component or gun settings set too high.
To avoid image edges, pay attention to the distribution of the spray and the gun when applying the powder. Try not to aim directly at the edges and watch the flow carefully to adjust your weapon settings accordingly.
4. Use the coating gun correctly
If you use a powder paint gun, make sure the nozzle is the right size for the job. A nozzle that is too small will cause the powder to not flow properly and result in uneven coverage. Too large a nozzle will result in overspray.
You must also set the correct voltage on your powder coating gun. If the voltage is too high, the powder will form beads and will not adhere properly to the surface. If the voltage is too low, coverage will be insufficient.
5. Make sure to harden the powder
Curing actually sets the powder and gives it its final surface. Be sure to cure the powder according to the manufacturer's instructions. This step is usually performed in an oven at a specific temperature for a specific time. Once the powder has cured, you will need to inspect the powder coating for imperfections.
University Degree
Powder coating is a dry finishing process that uses finely ground pigments and resin particles to achieve a surface shine and uniform finish. It provides a more durable finish than traditional paint and is available in a variety of colors and finishes. When considering powder coating for your projects, you may need to invest a lot of time to gain the right knowledge and experience to get the best results.
Common questions
What is the difference between powder coating and wet paint?
Both processes contain pigments, additives and chemicals. However, the main difference is the presence of solvents. Wet paint contains a solvent that keeps it liquid. Wet paints tend to lack contraction and expansion, while powder coatings adhere well to surfaces and exhibit contraction and expansion depending on conditions, making them more durable and long-lasting.
How much does powder coating cost?
The cost of powder coating depends on several factors, including the type of powder used, the size of the surface to be coated, and the complexity of the coating process. In general, powder coating is cheaper than traditional liquid coatings. The average cost of powder coating services is $75 to $150 per square foot.
Why is powder coating better than traditional paint?
Powder coating is typically used to create a hard coating that is more durable than traditional paint. It is more durable than regular paint and resists corrosion, chipping and fading. It is also easier to apply evenly than regular paint and can be applied to a variety of surfaces.
Why is industrial powder coating environmentally friendly?
Powder coating does not use volatile organic compounds containing methylene chloride, benzene and formaldehyde. This is safer for painters and anyone who comes into direct contact with the product. Furthermore, the powder itself does not contain carcinogens or heavy metals. You can recycle powder coating materials and recover up to 92% of the original powder.
