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.
Since powder coating is quickly becoming the go-to finishing method for many people with metal projects there are several different types of powder coating finishes available, and understanding each type can help you choose the best option for your project.
In this blog, we’ll explore the process along with all the types of powder coating out there so that you can decide which one is right for you and your project to get the job done smoothly — let’s dive in.
How is Powder Coating Done?
Powder coating is a multi-step process that starts with the preparation of the surface, usually through cleaning and sandblasting to ensure that it’s free from any debris or corrosion.
The next step is the application of the powder, which is typically done using a spray gun that gives the powder a positive charge. The charged powder particles adhere to the negatively charged surface creating an even layer.
Once the surface is evenly coated, it is then heated in a curing oven. The heat causes the powder to melt and form a hard, durable finish.
This process ensures a high-quality, long-lasting, and resistant coating that enhances the lifespan and aesthetics of the surface.
Different Types of Powder Coating
Powder coating can be broadly categorized into two types: thermoplastic and thermoset coatings. While thermoset powder creates a durable finish, thermoplastic coatings offer the advantage of being thicker, reversible, and reusable because when exposed to high heat these become liquid and malleable.
Additionally, there are various types of specialized powder coatings within these categories that are formulated specifically for metallic surfaces. Some of these include:
Epoxy is the first of its kind and was one of the original powder coatings to be used widely. It’s quite durable and has excellent corrosion and chemical resistance while providing exceptional hardness.
Epoxy sticks to metal quite well due to the different pretreatments of the metal, offering its stellar adhesion. This usually involves sandblasting and phosphate. 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.
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 widely used as powder coatings due to their cost-effectiveness. One of the advantages of this type of powder is its ability to cure at lower temperatures, making it suitable for delicate surfaces. Additionally, it exhibits excellent resistance to issues like yellowing, ensuring ease of use. Furthermore, it boasts a long-lasting lifespan, even when exposed to sunlight, with optimal performance expected for up to three years. This versatility makes it suitable for both indoor and outdoor applications.
The polyester powder also comes in a huge variety of colors and finishes allowing you to pick the product according to your preferences. 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
This type of coating is a kind of polyester that is mixed with epoxy to form a hybrid material that remains quite similar to pure epoxy but provides 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. These coatings 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
Just like the name suggests, super durable polyester coatings are tough and durable and are designed to keep their glossy finish and vibrant color for anywhere between five and ten years. This is pretty impressive compared to a standard polyester option.
Not only do polyesters offer better protection against losing gloss and color, but they also do a great job of shielding against corrosion and humidity. They’re relatively affordable too. People love using them indoors and outdoors, especially when they need fade-resistant properties.
Fluoropolymers find extensive use in architectural settings due to their exceptional ability to withstand various environmental elements. These are highly favored for indoor applications such as doors, windows, curtain walls, and more because they enhance aesthetics by providing superior gloss and color retention.
Fluoropolymers should always be applied over the top of a powder or liquid primer otherwise, they are more difficult to bond. When done correctly, their non-stick properties make them incredibly easy to clean and maintain, giving them an edge over other coatings on the market.
The two most popular kinds of fluoropolymers in a powder coating include PVDF and FEVE. FEVE resins tend to be the most popular because of their amazing exterior performance and the fact that they usually only need one coat, saving plenty of time.
It’s important to note, however, that fluoropolymers tend to be a bit more expensive than other coatings. So if you’re looking for something affordable and long-lasting, this may not be your best option. But if price isn’t an issue and you want an incredibly durable coating that can handle pretty much anything, fluoropolymers are definitely worth considering.
Urethanes offer superior chemical properties compared to polyesters. The key distinction lies in the utilization of curing agents, which yield a smooth and polished finish, coupled with exceptional exterior durability, corrosion resistance, and chemical resistance.
These attributes render urethanes highly sought-after for demanding applications such as fuel tanks, air conditioners, and agricultural equipment. Moreover, they prove invaluable for everyday items like doorknobs, car rims, and oven knobs, as they effectively resist visible fingerprints.
Nevertheless, one potential drawback of urethane paint is its tendency to become brittle when applied in excessive thickness. Additionally, a discernible odor may be present during application, and curing it in an oven can generate smoke. These coatings also tend to be pricier compared to other types of powders due to the resin’s higher cost.
Pros and Cons of Choosing Powder Coating
Alongside powder coating’s strength, there are a few other benefits to consider when trying to decide on a finish for metal fabrication:
Powder finishes are an environmentally friendly option that is both recyclable and reusable. Alongside that, it is safe to use, not posing many risks to your health (as some other finishes can do) as it doesn’t release any volatile organic compounds into the world.
That said, 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 also enjoy around five percent or less wastage, saving you money and products and the fact that they do not require solvents is also a big draw.
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 thereby extending its life.
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.
Moreover, if the powder coating runs, then you’ll have to completely redo the entire process which can be time-consuming and frustrating.
c) Temperature Dependence
To apply a powder coat to metal, the metal needs to be heated up first. This means that it is not appropriate for certain kinds of items or materials. For example, plastics may not fare as well in the process due to their low melting point. If done incorrectly, it might also cause warping or deformation, depending on the material.
d) Lack of Flexibility and Color Options
Once a powder-coated metal is formed into an item, it does not have much flexibility. It can’t be reshaped without some difficulties which means that if you need to make drastic changes in the future, you may have to start your project over from scratch.
Also, for the most part, powder coating is available in a limited range of colors and hues. While it’s possible you might find a shade that suits your needs, there may be times when you just cannot get the exact color you are looking for. This can be especially frustrating if you have a very specific design in mind.
Powder Coating vs. Sacrificial Plating – What’s the Difference?
The primary difference between powder coating and sacrificial plating lies in their approaches to protecting metal surfaces. While both techniques aim to protect and prolong the life of metal products, they do so in fundamentally different ways.
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 does it work, 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 sacrificial 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.
a) 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.
b) Easy to Apply, Clear, and Environmentally Friendly:
One advantage that clearly stands out is the simplicity and ease of applying the sacrificial coating. This not only saves time and effort but also conserves energy.
Moreover, since the sacrificial primer is primarily water-based, it is environmentally friendly. The coats are also typically transparent and invisible when applied to the surface, ensuring that they do not alter their appearance.
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 they offer, which is resistant to physical impact and weather.
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. The longevity of the coating may vary based on factors such as the type of coating applied but on average, the finish of the product has a lifespan of 20 years which is significantly higher than that of other coatings.
Jack Luis is a semi-retired painter who loved painting his clients’ ideas on their walls.
He had worked as a painter for over a decade serving customers in areas such as Charleston, Mount Pleasant, Beaufort, and Georgetown, SC (South Carolina). Today in his free time, he likes to read and write about the newer techniques implemented in his profession. You may read more about him here or get in touch with him here.