The Different Types of Powder Coatings
Whether you’re new to powder coatings or an experienced pro, you’re probably well aware that powder coating is a fantastic painting method that creates a tough, durable and beautiful finish. No matter whether you’re using a single gun and small oven or a large fully automated line, the process is basically the same. A powder spray gun is used, which when triggered gives an electrostatic charge to the powder particles passing through it. As the parts to be coated are grounded, the powder is attracted towards the part via the electrostatic process. Once the powder is applied the parts are cured in an oven, which melts and cross-links the powder over the surface of the part and creates a tough, scratch resistant and beautiful finish.
There are literally thousands of different applications for powder coatings. Powder coating is used mainly on metals, so is perfect for industrial parts, medical devices, architectural applications, automotive refinishing, bicycle parts, household appliances, furniture, enclosures, trailers, lighting…the list goes on!
There are many different types of powders used, each with their own characteristics and applications, so making sure you have the right type of powder, and THEN choose the color is very important for a successful application. Check out the different types of powder and the benefits they will bring to the parts.
There are so many advantages to using powder coatings – too many to cover in this blog post – but some of the obvious ones include lack of solvents. This means no volatile organic compounds (VOCs) are released, a great advantage especially when compared to traditional liquid paints. This makes them safer to work with, dispose of and transport and brings unbeatable environmental advantages to you and your customer.
Powder coating allows for much thicker coatings than liquid paint, without running or sagging. With liquid paint, horizontal and vertical painted surfaces often have differences in appearances, but powder coating typically provides a uniform visual appearance regardless of orientation.
Powder coating allows for much thicker coatings than liquid paint without running or sagging. With liquid paint, horizontal and vertical painted surfaces often have differences in appearances, but powder coating typically provides a uniform visual appearance regardless of orientation.
Powder coating also offers a wide range of specialty effects that are hard to achieve through traditional methods. The list goes on, and we could get into better scratch resistance, toughness, and hardness than traditional liquid paints, but let’s take a look at some of the different powders used that help achieve these characteristics.
Epoxies were the first widely used powders. They are very durable, offer excellent hardness and have arguably the best chemical and corrosion resistance of all available powders. Another plus of this type of powder is its ease of use and a wide range of cure schedules. Epoxies adhere to metals extremely well, with various pretreatments of the metal providing excellent adhesion, including phosphate coating and sandblasting.
The drawback of epoxy powders is that they do not weather well. Exterior exposure can cause them to fade and chalk in the sun. They weather poorly and will often start to degrade on the surface after a few months. This makes epoxies better suited to indoor applications.
A final note on epoxies is that many primers are epoxies due to their adhesion strength and corrosion resistance. Since they do not handle the sun well, their use as a pre-coat underneath another paint type utilizes their strengths while covering their weaknesses.
Polyesters are the most commonly used powders and offer great value for money. The two most widely used types of polyester powder: TGIC (tri glycidyl isocyanurate) and non-TGIC, which is also known as TGIC-free or sometimes a ‘Primid’. Both TGIC and TGIC-free polyesters offer good mechanical resistance, including great flexibility and impact resistance, and good chemical resistance. One draw of this powder is its low cure temperature. This low-temperature requirement makes it better for sensitive items. Polyesters will also provide good overbake resistance to yellowing, which makes them really easy to use and Standard Polyesters will offer 1-3 years of good UV resistance, so they work well for all interior and some exterior applications. A huge advantage of standard polyesters is the enormous choice of colors, gloss levels and special effects they’re available in. It’s almost limitless! Polyesters have solid all around properties and are a common first choice for many applications.
It seems kind of obvious, but TGIC-free polyesters offer all the advantages of TGIC polyesters, without the TGIC! They can also give a higher first pass transfer efficiency, but are more sensitive to excess film thickness and provide less overbake resistance than TGICs.
As the workhorse of powder coatings, it’s not surprising that there aren’t that many drawbacks to polyesters. If you’re coating pieces that will be permanently outside and therefore need good wearability and durability, then consider the super durable polyester instead. Limited exterior durability is a standard polyester’s main disadvantage.
Super Durable Polyesters
Super Durable Polyesters have fast become the superhero of polyester powders. As the name suggests these excellent value powders offer superior durability when compared with a standard polyester. They are designed to hold their color and gloss to within set limits for 5 to 10 years more when compared to a standard polyester. Not only is their color and gloss protection better, but they also provide better humidity and corrosion resistance. These Super Durables have become hugely popular over the last few years as their increased capabilities and great value for the money have made them popular for interior applications where improved fade resistance is required and all manner of outdoor applications.
Epoxies and polyesters are often mixed together to form hybrids. These hybrids remain closely related to pure epoxies but offer superior weather degradation properties. These hybrids can be mixed in various ratios to emphasize the characteristics of either the epoxy or polyester. The polyester will enhance the overbake resistance when compared with a straight epoxy and they also create ultra-smooth, thin films. The combination of the resins can also make them more economical than a pure epoxy. The polyester does reduce the corrosion and chemical resistance of the epoxies and doesn’t really add any outdoor weatherability to the product. Hybrids are widely used on items that require good cosmetic appeal along with good functional properties. Hybrids can be used in some of the same areas that epoxies are used, but are typically found on indoor appliances and other household items like furniture, shelving, interior lighting, and power tools. Domestic appliances like stoves, washers, and dryers are a common application for hybrids.
Fluoropolymers are typically used in architectural markets due to their phenomenal weathering properties and world-class color and gloss retention. Their corrosion resistance and excellent weatherability make them extremely popular for exterior architectural applications like curtain wall, windows, doors and more. The two most common types of Fluoropolymers found in powder coatings are FEVE and PVDF. PVDF Fluoropolymers always need a primer beneath them – whether liquid or powder and are much more difficult to bond when creating metallic powders. FEVE resins are the most popular within the powder community for their superior one coat capability and incredible exterior performance. FEVE based Fluoropolymer metallics can also be bonded, so that when applied, the metallic flake is more evenly distributed throughout the powder for a more consistent appearance. Fluoropolymer powders are usually only available to members of a Certified Applicator program, as up to 20 year warranties are available on these products when applied by a certified applicator to architectural aluminum. One popular brand of fluoropolymer is IFS 500FP, which is a high performance, FEVE based Fluoropolymer and adds better abrasion resistance to the standard fluoropolymer characteristics. IFS 500FP can be seen on a huge range of projects from the DSNY building and the beautiful new slender skyscraper at 111 57th in Manhattan, to 9th and Lenora in Seattle and the Winstar Casino in Oklahoma.
Urethanes are chemically similar to polyesters, with a difference in curing agents. Urethanes offer a very smooth finish and very good exterior durability as well as excellent chemical and corrosion resistance which makes them ideal for things like fuel tanks. Other common applications include agricultural equipment, air conditioners, car rims and doorknobs. They are used on door knobs, oven knobs and other such applications because fingerprints are not as visible. One drawback of urethane paint is that at higher mil thicknesses it can begin to outgas and become brittle. You may also notice an odor during application and cure and smoke can also be created in the oven during cure, so keep an eye on your application and cure parameters when applying. Urethanes are also usually more expensive than other types of powders due to the resin cost.
Wrapping it up
Powder coatings are a truly great coating choice with so many product options depending on what you need them to do. And that’s before we even get to the thousands of colors and special effects available! The various powders used in the powder coating industry have different characteristics that make them ideal for different applications. We hope that the above information can give you guidance on the right powder for your needs. The advantages of powder coating over traditional liquid paint are pretty clear. Armed with this detailed product knowledge you can find the right powder to best fit your application.
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