Powder coating is a kind of finishing option for surfaces that includes a thin film to protect the surface against chemicals and corrosion. Mostly it’s a dry coating process that is today applied on metals in a variety of different types.
Though parts of it are often given glossy finishes, textures, and colors to enhance its aesthetics, its main job is to protect the surface.
Different Types of Powder Coating
In general, there are two types of powder coating, i.e., thermosets and thermoplastics.
Unlike thermoset powder, thermoplastic coatings are thicker, reversible, and reusable. This is because the finish becomes liquid and very soft when exposed to high heat.
With changing technologies and demand in varieties, there are a number of products used for metals to be powder coated. Each of these resin systems comes with very specific attributes that are better for certain environments. Some of the most common types of powder coating include:
Epoxy is the first of its kind and was one of the original powder coatings to be used widely. Its quite durable and has excellent corrosion and chemical resistance while providing exceptional hardness.
This type of powder coating is also easy to use and comes with a number of curing schedules, so you can find the one that works best with your timeline.
Epoxy sticks to metal quite well due to the different pretreatments of the metal, offering its stellar adhesion. This usually involves sandblasting and phosphate.
The biggest downside of using epoxy powder is that it does not weather well. Exposure to the elements can cause it to chalk and fade in sunlight. It tends to start degrading in only a few months of exposure, making it better suited for indoor applications.
Finally, it’s important to note that many primers are actually epoxies because of their corrosion resistance and adhesion strength.
Because it doesn’t handle exposure to sunlight well, its use as a precoat beneath the paint takes into account its strength while also keeping its weaknesses in mind.
Polyesters are among the most commonly used powder coatings and are quite cost-effective.
The two main types that are used are TGIC and non-TGIC powders. Both of them offer great mechanical resistance, including impact and chemical resistance as well as exceptional flexibility.
One of the perks of this powder is that it offers a lower curing temperature. This low-temperature prerequisite makes it ideal for more sensitive surfaces.
It also offers excellent overbake resistance to issues such as yellowing, which makes it simple to use. This factor also brings with it a long-lasting life, even with exposure to sunlight. You can expect it to perform at its best for up to three years, making it appropriate for use both indoors and outdoors.
The polyester powder comes in a huge variety of colors for you to choose from, as well as a glossy finish and other special effects. This will allow you to pick and choose the result of the product according to your preferences.
TGIC-free polyesters bring with them all of the benefits of TGIC without the chemical itself in it. They also tend to offer better first-pass transfer effectiveness, though they do tend to be more sensitive to any excess film thickness and offer less protection against overbaking than TGICs.
Considered to be among the best options for a coating, it isn’t surprising that there are not very many downsides to using it. If you are coating any pieces that will permanently remain outside and need good durability and wearability, this is one of the best options for you.
3- Epoxy-Polyester Hybrids
Epoxy-Polyester Hybrids are a kind of polyester that is mixed with epoxy to form a hybrid material. They remain quite similar to pure epoxy but provide the kind of weather protection that epoxy alone cannot.
The hybrids can be mixed at various ratios to draw out the characteristics of polyester and epoxy alike.
The polyester works to enhance the resistance to overbaking when you compare it with pure epoxy while also creating a smooth, thin film.
Beyond this, having a combination of these two materials makes them more economical than what you could expect with straight epoxy.
The polyester does a good job of reducing both chemical and corrosion resistance and doesn’t bring in any additional outdoor weather-ability, however.
Hybrids are commonly used on items that need a nice cosmetic appearance along with practical functionality and are used in many of the same areas where you would use epoxy.
They are usually found on household items and indoor appliances such as shelving, power tools, furniture, interior lighting, washers, dryers, and stoves.
4- Super Durable Polyesters
Super Durable Polyesters have quickly become one of the most commonly used types of powder.
Much like the name suggests, they are super tough and durable, especially when compared to typical polyester material. They are made to retain their gloss and color for between five and ten years, especially when compared to a standard polyester option.
Not only do polyesters offer better protection against gloss and color loss, but they are also able to offer better protection against corrosion and humidity.
Because of their many benefits, they have become remarkably popular over the last few years, both for their properties and the fact that they are relatively inexpensive.
They are particularly popular for indoor applications as well as anywhere outside where fade-resistant properties are important.
Fluoropolymers are usually used in architectural settings because of their ability to weather all kinds of elements. They also bring premium gloss and color retention to improve their aesthetics. These are remarkably popular for indoor architectural applications like doors, windows, curtain walls, and beyond.
The two most popular kinds of fluoropolymers in a powder coating include PVDF and FEVE.
Fluoropolymers should always be applied over the top of a powder or liquid primer. Otherwise, they are more difficult to bond when you are generating metallic powders.
FEVE resins tend to be the most popular, on the other hand, because of their amazing exterior performance and the fact that they usually only need one coat, saving plenty of time.
Fluoropolymers that are FEVE-based can also be bonded so that when you apply them, the metal flakes are better distributed throughout the powder. This will offer a more streamlined and consistent appearance. It also provides better resistance against abrasion when compared to the characteristics of fluoropolymers.
IFS 500FP is noticeable on a wide range of projects, from skyscrapers to casinos. However, it must be mentioned that you can usually only find fluoropolymers if you’re a member of a Certified Applicator program.
Urethanes are superior to polyesters, chemically speaking. Their main difference comes in the form of curing agents. They provide a smooth and sleek finish as well as excellent exterior durability and corrosion and chemical resistance. This makes urethanes quite popular for tough jobs like fuel tanks.
Other common uses include air conditioners, agricultural equipment, doorknobs, and car rims. They are also used on oven knobs, doorknobs, and similar applications because they don’t show fingerprints easily.
One of the downsides of urethane paint is that when it gets too thick, it can eventually turn brittle. You may also smell an odor while you’re applying it. When curing it, smoke can also be generated in the oven.
It’s important to keep an eye on the cure parameters and application as you apply it for this reason. Furthermore, they can be more expensive than the other kinds of powders because of the cost of the resin.
What is the Application Process?
Powder coating is usually applied as a dry powder through an electrostatic process, which is then cured with heat.
You’ll first need to prepare the project for application—this is the most important part of the application process. It will determine how well the powder coating will stick to the metal surface you are working with.
There are different options for cleaning and prepping, such as using a phosphate rinse or degreaser.
Pros and Cons of Choosing Powder Coating
Powder coating comes with several advantages, making them a popular choice for metal fabrication. Alongside their strength, there are a few other benefits to consider when trying to decide on a finish:
Powder finishes are an environmentally friendly option that is both recyclable and reusable.
Thermoplastic coatings are easy to reshape, which can’t be said about thermosets. The powder is used in a precise way that minimizes waste, unlike standard paint, which can result in frequent over-spraying.
You may enjoy around five percent or less wastage, saving you money and product. The fact that they do not require solvents is also a big draw.
Powder coating doesn’t release any volatile organic compounds into the world, so it doesn’t harm the environment. Alongside that, it is safe to use, not posing many risks to your health as some other finishes can do.
With a powder coating finish, the initial expenditure will look overwhelming to some. Over time, the cost will be much lower when held in comparison to other kinds of finishes.
You can easily achieve a polished appearance when you powder-coat metal. It also repels moisture, chemicals, and other such elements to keep it simple to clean.
For all of its perks, there are also a few downsides that you should consider when deciding on whether or not to use a powder coating. Below are a few of the drawbacks to keep in mind as you make your decision:
a) Proper Coloring
While reusing and recycling the powder coating is something that is a perk, it might also lead to some cross-contamination. This means that you will notice the colors might not come out as originally intended, which can lower the efficiency of the coating and even generate touch-ups that won’t match.
You can avoid this by cautiously keeping powders tightly packaged when you aren’t using them.
b) Less Control Over the Coating
It can be tricky to get the thickness that you want from the finish. The lack of control may result in uneven thickness levels, which can affect the overall texture of the end result.
If the powder coating runs, then you’ll have to completely redo the entire process. This can be time-consuming and frustrating.
Powder Coating vs. Sacrificial Plating – What’s the Difference?
The sacrificial coating generally offers a layer of protective defense, meaning it will absorb corrosive substances long before they are able to inflict damage on the metal object. Powder coating, on the other hand, provides an additional barrier that safeguards against destructive materials ever reaching and damaging the surface.
But what actually is sacrificial plating, how it works, and what are its benefits? Let’s explore some details.
What is Sacrificial Plating – How Does it Work?
Sacrificial plating (sometimes called sacrificial coating or cathodic protection) is a type of coat comprising metal layers that have a lower electrode potential value compared to the metal that they protect. Also, they may have a higher level in the electrochemical series.
In either case, sacrificial plating (usually zinc) creates a clear coating or barrier that protects the surface underneath. You can think of it as a protective barrier that slowly corrodes over time but is designed to prevent such corrosion or oxidation to the metal it protects.
Just as paint protects the materials that make up your home’s walls, so does sacrificial primer, plating, or coating protect the metals underneath.
Perhaps the most common type of sacrificial plating or primer is the coating used for galvanized steel, sometimes called zinc-coated steel. The anodic reaction will, however, vary depending on how fast the sacrificial coating dissolves.
If a primer is made from noble metals that are more active, such as nickel or tin, then it can provide proper protection for as long as the coating lasts.
But when the coating becomes thin enough in any one area, this will allow the oxidation process to begin on the metal itself. It is especially true with steel that rust or corrosion can become intense.
When adding in tin, the corrosive process intensifies. This is because tin is cathodic, which means it will quicken the pace of the oxidation of steel.
The Benefits of Sacrificial Plating Over Other Coats
The substances used in this type of plating generally include materials that are considerably cheaper compared to the metal they protect. Such materials include Acrylates, Biopolymers, Clear Polymers, and Waxes.
The advantage of polymers is that they create a weak bond with the metal, so they can be removed when needed relatively easily. The other types of plating or protection bond with the metal to a greater degree, meaning it takes more effort to remove it.
There are substantial benefits to using sacrificial coatings, especially on metals that might be vulnerable to corrosion and either not easy to maintain or to save money.
1- Breathable: This may seem counterintuitive at first, but this type of protection allows for some breathability to take place. The advantage is that any moisture that comes from underneath the metal can evaporate away without being trapped. The result is less corrosion, not more, as the coating breathes just enough to allow for proper evaporation to take place.
2- Easy to Apply: If there is one advantage that stands out above the rest, it is that the coating is simple and easy to apply. This means you spend less time applying it, which saves effort and energy.
3- Clear and Environmentally Friendly: Sacrificial coats are usually invisible and clear so that you can add them to the outside, and they will not affect how the surface appears. Also, because the sacrificial primer is mainly water-based, it is better for the environment.
The Bottom Line
Powder coating is available in different types. All of them are considered to be the most durable of the coatings for many surfaces, thanks to the superior chemical bond that it offers, which is resistant to physical impact and weather.
It typically lasts for 20 years. However, the life of the finish on the product will depend on different factors, such as the kind of coating used.
If you are considering the metal surfaces to be powder coated in your residential or commercial space, make sure you go through each of these types before picking the most suitable one.
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Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for more than a decade to serve the customers in areas such as Charleston, Mount Pleasant, Beaufort, Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques that are being implemented in his profession. You may read more about him here or get in touch with him here.
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