Powder coating revolutionized architecture, furniture manufacturing, and outdoor metal maintenance. This versatile coating protects metals and other materials from corrosion, dents, and scratches while elevating the surface finish. How does it work, though?
- What is Powder Coating?
- Why Use Powder Coating?
- How Does Powder Coating Work?
- Types of Powder Coating
- Powder Coating Process
- Powder Coating Gun
- Benefits of Powder Coating
- Rust Prevention
- Tougher Than Paint
- High-Quality Surface Finish
- Wide Aesthetic Range
- No Volatile Compounds
- Recycling the Overspray
- Fast Curing Time
What is Powder Coating?
Powder coating is a surface treatment used to protect metals and other materials against potentially harmful environmental factors. This coating is applied electrostatically as a free-flowing powder and cured under heat or UV light. It can be applied to any material, but it is commonly used on steel, aluminum, and plastic.
Powder coating differs from traditional liquid paint, which is generally applied using an evaporating solvent. Though it is not as durable as PVD coating due to its thickness, it provides excellent rust prevention, color uniformity and scratch protection.
Why Use Powder Coating?
Metals tend to corrode under normal usage conditions. Even stainless steel can rust under specific conditions. Here, it is helpful to apply a protective surface layer that is corrosion resistant and tough enough to withstand expected wear that the part in question may undergo.
Powder coating is a commonly used surface coating since it is tough, can vary in thickness, and comes in various colors and surface finishes. Areas where powder coating is advantageous include marine applications and roadways where de-icing salts are commonly applied.
Non-metallic materials sometimes require a protective surface layer too. These include plastics, carbon fiber, composites, and MDF (medium-density fiberboard). Here, the surface coating will usually protect the part in question from the sun or other harmful environmental factors.
How Does Powder Coating Work?
Powder coating is divided into three categories: thermoset, thermoplastic, and UV curable. While these categories differ in application and execution, they all have this in common: a powder is applied to a surface, which hardens under specific conditions. This creates an even, corrosion-resistant surface coat.
Types of Powder Coating
The three main types are,
- Thermoplastic and
- UV Curable Coatings
Thermoset powder coating is most commonly used since it is generally the least expensive option and easy to apply. Thermoplastic powder coating is usually more expensive, although recent technological advancements enabled enormous cost reduction in the process.
Thermoplastic coating offers higher performance than thermoset. It is also less dense than thermoset powders. Thus you can use far less powder to achieve the same finish. Thermoplastic powders are also thicker and more flexible than thermoset powders. Here, thermoset powders, which are harder than their thermoplastic counterpart, offer greater scratch resistance. Conversely, thermoplastic powders offer greater impact resistance due to their superior flexibility, although these are less resistant to scratches.
Thermoplastic powders can be recycled since they become liquid again when reheated. Unfortunately, thermoset powders cannot be recycled since their set is final after the initial curing process.
UV curable powder coating is similar to thermoplastic coating, except it cures under UV light instead of at high temperatures. The advantages here are legion. Since this process doesn’t require high temperatures, heat-sensitive materials such as wood and organic fibers can also be powder coated. The decreased heat requirements also translate into economic savings since you no longer require an oven on-site, reducing space and energy costs. UV powder coating also cures faster than the heat-sensitive thermoset and thermoplastic powders, decreasing turnaround times.
Each powder coating category has specific strengths and weaknesses. Thus the requirements of each application will determine the one best suited to that situation.
Powder Coating Process
The powder coating process requires three basic steps, regardless of the type of powder used: preparation, or pre-treatment, application, and curing. Here is an overview of each step.
Preparation is essential for successful powder coating. All dirt, oil, and debris get cleaned off the part in question since these could hinder powder adhesion in later steps. This preparation step could consist of several steps in itself, depending on the material in question and the initial state of the part. The first step is generally physical cleaning, where the part is scrubbed, sand-blasted, or washed using a high-pressure spray. This reliably removes most of the physical dirt that could be present on the part.
Often, metallic parts are chemically treated in processes called phosphating and chromating. Here, the metals are dipped in corrosive acids for a predetermined, concise time, after which they’re rinsed and dipped in phosphate or chromate solutions. This improves the subsequent bond between the metal and powder, improving the surface finish and product performance. The phosphate and chromate solutions used aren’t environmentally friendly. For this reason, many coating services have replaced them with titanium zirconium silanes, which offer similar corrosion resistance and powder adhesion properties.
Heat-sensitive plastics and composite materials are often hydrophobic, have a low degree of wettability, and have low-energy surfaces. These aspects all negatively affect powder adhesion during the powder coating process. These materials undergo plasma treatment to overcome this challenge, which creates chemically active binding sites on the material’s surface. Now, this surface is wettable and hydrophilic, providing ideal conditions for powder adhesion.
Powder application varies slightly depending on the material being coated. Generally, one of three application methods is used: electrostatic gun, electrostatic fluidized bed, or electrostatic, magnetic brush.
When powder coating metal objects, the powder is usually sprayed onto the object using an electrostatic gun, also called a corona gun, after the most common nozzle configuration. Here, the metal part is electrically grounded, while the spray nozzle imparts a negative electrostatic charge to the powder particles. The particles are shot towards the metal, either mechanically or through compressed air. Once airborne, they’re accelerated by the electrostatic attraction between the negatively charged particles and grounded metallic surface.
Various spray nozzle configurations are available, each suited to coating specific object shapes. This variety enables precise coating practices, minimizing waste and optimizing surface finish.
After coating, curing takes place – this is most commonly achieved through high heat. In some cases, the metallic part is heated before powder application. Here, the powder melts onto the surface, achieving a more uniform surface finish. When too much powder is applied in this manner, the powder could run down the surface, ironically creating a poor surface finish.
Electrostatic Fluidized Bed
A fluidized bed is essentially a tub of powder with air flowing through it. Aerated powder behaves like a fluid, which allows parts to be dipped into it. In a conventional fluidized bed, this part would be metallic and heated. When dipped into the bed, the powder melts and sticks to the part, after which conventional curing would take place.
An electrostatic fluidized bed is similar to a conventional fluidized bed, but it has more powder depth and an electrostatic charging medium added to the bed. This creates a cloud of electrostatically charged particles floating above the bed. The metallic part to be coated is grounded and passed through this cloud, causing the negatively charged particles to stick to its surface. This is followed by curing.
Electrostatic Magnetic Brush
Electrostatic magnetic brush, or EBM, coating is relatively new and works on similar principles as a copier machine. Here, the powder is applied to a flat surface using a roller. This application is highly accurate, allowing layer thicknesses between 5 and 100 micrometers, applied efficiently at great speed.
Curing differs depending on the type of powder used. Thermoplastic and thermoset powders both require heat to cure. Here, each powder requires exposure to a specific temperature for a set amount of time to attain the desired properties. Traditionally, thermoplastic powders were cured at 200֯C (390֯F) for ten minutes. Recently, a low-bake approach enabled adequate curing at 160֯C (320֯F) for ten minutes, decreasing production costs and rendering the process more environmentally friendly.
Since the low-bake approach necessitates the use of catalysts to ensure proper curing, they’re not as color-stable as their high-temperature cured counterparts.
UV, or ultraviolet, curing still requires heat for proper curing, but at far lower temperatures than thermoplastics and thermosets. UV powder coating curing times are far shorter than their traditional counterparts, requiring only one or two minutes at 110-130֯C (230-266֯F). UV powder coating applications use UV LED curing systems, which are more environmentally friendly than conventional curing ovens. Their high energy efficiency, paired with the low-temperature requirements and fast curing times of UV-cured powders, decrease production costs considerably compared to thermoplastic and thermoset applications.
Powder Coating Gun
Typically, powder coating applications use one of two powder coating guns: the tribo gun or the electrostatic gun, also known as the corona gun. The corona gun is most commonly used and works on imparting a negative electrostatic charge to the powder particles. After receiving the charge, these particles are shot at the part to be coated through compressed air or mechanical action.
The corona gun has various nozzle configurations, enabling the user to easily coat surfaces in multiple configurations in any orientation. A downside of using the corona gun is its affinity for back ionization and the Faraday cage effect. Here, the charged powder particle fails to find a ground point on the surface to be coated and thus builds onto particles already stuck to the surface. This causes uneven coverage in what’s called the “orange peel effect.”
The tribo gun imparts a positive electrostatic charge to the powder particles through triboelectric friction. Here, the powder particles move through a Teflon tube inside the gun. Friction with this surface imparts the charge, which then causes the particles to be attracted to the grounded metal object to be coated. While the tribo gun requires a different powder type to the corona gun, it doesn’t suffer from the same weaknesses (back ionization and the Faraday cage effect).
Benefits of Powder Coating
Powder coating provides better corrosion resistance, longer life, and better appearance than the traditional liquid-coating method. Here are some of the benefits of powder coating.
Powder coating is an excellent method to protect the steel pieces from rust. The coated layer prevents the atmosphere from coming into contact with the steel and eliminates the possibility of oxidization. You can also coat metals such as brass, copper, bronze etc. to prevent them from oxidation. You can even powder coat stainless steel to enhance the rust resistance of the metal alloy.
Tougher Than Paint
Powder coating offers a tougher layer than conventional paint, rendering it more hard-wearing and thus suitable for a greater range of applications. This hard-wearing aspect also prolongs the surface coating’s useful lifespan compared to conventional paint. Powder coating layers can be thicker than paint since they won’t sag or run, adding to their toughness.
High-Quality Surface Finish
Paint is liable to the formation of pinholes. These tiny air bubbles burst as the paint dries, leaving tiny holes in the surface finish. Here, corrosive substances gain access to the material underneath, causing long-term damage and negating the protection offered by the paint. Since powder coating isn’t applied using a brush, there are no pinholes or other surface blemishes. This enhanced quality in the surface finish offers greater protection to the finished product.
Additionally, parts can be powder coated in any orientation since there is no difference between parts coated horizontally or vertically. This is opposed to traditional paint, where the orientation plays a vital role in the subsequent surface finish.
Wide Aesthetic Range
Powder coating comes in various colors and surface finishes. It is thus suitable for a wide range of architectural and aesthetic applications. This allows for designs that incorporate the structural strength of metals, paired with the aesthetic finish of any color and texture.
Various powder colors can be applied in a single layer and cured together, allowing for color blending and bleeding. These special effects are often hard to achieve using traditional paints.
No Volatile Compounds
Powder coating is just that – powder. There are no carrier liquids and thus no volatile organic compounds (VOC) that will evaporate during curing. This renders powder coating safer than traditional paint.
Recycling the Overspray
When applying powder coating or traditional paint using a spray gun, a large amount of material is likely wasted as “overspray.” This refers to the portion of material dispensed from the spray gun that never reaches the intended surface. In the case of traditional paint, this is wasted. However, in powder coating applications, this overspray can be collected and recycled, saving material and minimizing waste.
Note that when various colors are mixed and applied to the same surface, the overspray may not be viable for recycling since the color balance will be incorrect.
Fast Curing Time
The curing time for powder coating is far shorter than that required for traditional paint. This is especially true in applications using UV curing or advanced low-bake thermosetting powders.
Limited by Heat Curing
Powder coating applications that require heat curing can only be used on certain materials, mainly metals. The high temperatures required in this process rule out most polymers, composites, and MDF (medium-density fiberboard), since these materials aren’t heat resistant.
Thin Layers Don’t Always Cure Well.
While thick layers of powder coating cure smoothly and are easily applied, thin layers can be challenging. Since the powder’s particle size is quite large, thin layers often show the orange peel effect. Many applications call for a smooth surface finish, although the orange peel effect is desirable in some applications. This effect hides metal defects and renders the finished surface less prone to showing fingerprints, both of which are desirable in specific applications.
Powder Coating Has A Large Capital Outlay
Purchasing and maintaining the equipment needed for powder coating is expensive and often prohibitive. This is far more expensive than traditional paint, for which you only need a paintbrush and cleaning products.
What are the different types of powder coatings? ›
There are two types of powder coating, thermosets and thermoplastics. Thermoplastic powder coating finishes become liquid and very soft when heated. This eliminates chemical bonding. This process makes the powder coating both reversible and reusable.What is the benefits of powder coating? ›
If your part has been powder-coated, it will be highly resistant to wear and tear no matter what it's used for. The coating is resistant to chipping, fading, scratching and wearing. This durability makes it well-suited for metal parts that come into contact with sunlight and other environmental factors.What is the process of powder coating? ›
Powder coating is a dry powder applied to a charged surface, creating a thicker coating in one application more than a single coat of paint. An electrostatic charge holds the coating onto the surface, which remains in place after curing the object.What is powder coating advantages and disadvantages? ›
Powder coatings are also comparatively durable, cost-effective, and environmentally-friendly. However, they may not be suitable for all manufacturing applications, such as for low budget, thin film, or large part coating applications.What are the three types of coating? ›
Coatings are varied, but primarily fall into three categories: Architectural, Industrial, and Special Purpose.What are the benefits of powder coating steel? ›
Powder coating adds to the steel's durability, helping the frame to withstand damages better and last longer. Corrosion Resistant. Moisture and humidity can cause metal frames to rust. When applied to steel, powder coating provides a protective barrier that helps prevent corrosion.What are the advantages of powder coating vs paint? ›
Powder coating provides better performance than wet paint—it is more resistant to chipping, scratching, and other wear because of the thermal bonding it undergoes during curing, and because it can be applied in much thicker layers.Which chemical is used in powder coating? ›
It contains epoxy and polyester resin. It is a powder type developed to provide physical and chemical resistance properties together. It is used indoors.
Benefits of Powder Coating
Corrosion resistance: The powder coating creates a barrier to protect against many different types of corrosion, including rust. Many natural metals like steel rust over time with exposure to moisture and oxygen. Powder-coating creates a protective barrier so the metal remains rust-free.
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.
Is powder coating waterproof? ›
Polyester powder coating (PPC) is an increasingly popular alternative to wet paint finishes, and one of its basic qualities is that it is waterproof. However, this is far from the only advantage powder coating enjoys over traditional paint materials.What's better than powder coating? ›
STEEL-IT® stainless steel based industrial coating – a top alternative to powder coating – is tougher, lasts longer, and offers superior protection against corrosion and abrasion.What are the 2 types of coatings? ›
Coatings are specified as organic or inorganic according to the nature of their binder. Organic coatings are those that have an organic binder. Inorganic coatings are those that have an inorganic binder such as a silicate.What is 3 layer coating? ›
Three-layer coating consists of an epoxy or FBE, a thermoplastic adhesive coating and a polypropylene top coat. The polyethylene (PE) and polypropylene (PP) coatings are extruded coatings.Which type of coating is best? ›
The ceramic coating is very durable and can last 5-7 years depending on the kind of coat applied. Scratch-resistant and helps prevent swirl marks: The hard nature of ceramic coating does a good job of protecting the car's surface against scratches and swirls keeping the surface smooth and shiny.What are the different methods of coating? ›
- Dip coating.
- Roll coating.
- Spin coating.
- Flow coating.
Fusion-bonded epoxy coating offers the strongest shield against corrosion on pilings, sheeting and steel reinforcement layers. Nonetheless, the use of a powder coating to prevent corrosion is just one of the steps to ensure the long life of a steel component.Which are the coating processes? ›
- Vapor deposition.
- Chemical and electrochemical techniques.
- Roll-to-roll coating processes.
The primary difference between powder coatings and paint is that powder coatings have no solvent. A solvent is used to hold the paint in its liquid form. As the paint dries, it transforms into a solid. However, powder coatings are applied in their solid, powdered form.How long does powder coating last? ›
Powder coating can last up to 40 years depending on the preparation, type of coating used, materials and treatment process. While most powder coatings are highly durable, weather-resistant and provide years of high-traffic use, certain factors can significantly accelerate fading and performance.
Can you paint over powder coating? ›
Powder coated steel can be painted if the surface has been prepared properly. After cleaning the surface, you will need to apply a primer. This will ensure the topcoat will adhere to the surface.Is Powdercoat stronger than paint? ›
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.How can you tell if powder coating is good quality? ›
- Crosshatch. The crosshatch test is designed to test the adhesion of the powder coating to the metal substrate. ...
- Mandrel Bend. This test checks the elasticity and the adhesion of the powder coating to the substrate. ...
- Impact Test. ...
- Salt Spray Test. ...
- MEK Rub Test. ...
- Color Match. ...
- Gloss Measurement.
Cleaning and priming surfaces are crucial to the successful outcome of the powder coating process. Powder coating will bond better when the material it's applied to is clean.What metals Cannot be powder coated? ›
Metals that are not electrically conductive, like those that use certain fillers, cannot be powder coated.Does powder coating crack? ›
Sometimes powder coating will chip or crack, and continue peeling just like an egg shell. Not only does chipped powder coating look bad, it can it allows the elements to wear away the precious parts you tried so hard to protect.Is powder coating better than epoxy? ›
Epoxy coatings are more durable than powder coatings. Powder coatings are more resistant to chemicals than epoxy coatings. Epoxy coatings are more difficult to apply than powder coatings. Powder coatings are more environmentally friendly than epoxy coatings.What is the most common powder coating? ›
The two most widely used types of powder coating are TGIC Polyester and Urethane Polyester. Both types of powder coating provide excellent wear resistance and outdoor durability. Polyester Urethane powder systems provide excellent chemical resistance.What temperature does powder coat? ›
Unlike conventional liquid paints, which require an evaporating solvent for application, powder coating uses electrostatic application methods before being cured under high heat. Most powders require baking at around 350-400 degrees Fahrenheit for 10-20 minutes to fully cure.What is the standard for powder coating? ›
Architectural powder coating must meet AAMA 2604 or 2605 standards because, for items like metal railing, fencing, window frames, doors, grills and facades, durability and weather-resistance are critical to both durability and safety.
How do you maintain powder coating? ›
The best method of cleaning is by regular washing of the coating using a solution of warm water and mild detergent. All surfaces should be cleaned using a soft cloth or sponge, using nothing harsher than natural bristle brushes.Does powder coating last in the sun? ›
Sun exposure or direct sunlight breaks down the particles within the paint which then makes the coating fade.Can you powder coat over rusted metal? ›
Answer: Powder coating over rust is a bad thing. The rust will eventually bleed through the coating when your part is exposed to moisture. Eventually the coating will delaminate and fall-off your part.What is the maximum thickness of powder coating? ›
Coating thickness can range from 20 to 100 microns (1 to 4 mils). The most significant challenges of UV-curing are the current cost of the powders required, as well as a need to position the UV light to ensure 100% coverage.What is EP & PP powder coating? ›
Epoxy Polyester (Ep) Or Hybrid Powders. Pure Polyester (Pp) Powder Coating Process. Powder Coatings.What is Class A powder coating? ›
We deliver a quality highly protective and versatile metal finishing solution. 'A' Class Powder coating refers to the aesthetic standard requirement, meeting the highest quality of coating possible. It is otherwise known as 'eye level' powder coating.Are there different grades of powder coating? ›
Choosing the Right Color
Before you settle on a color, choose the right powder coating type because they come in different grades with some fit for exteriors and others fit for interiors.
Powder coating is an organic powder applied onto metal using an electrostatic process. Upon heating the coating, it creates a smooth, robust, chemical-resistant, and hard layer over the metal surface. The result is a subtly glossy finish.Does powder coating hide cracks? ›
However, if the surface is scratched, dented, or has other imperfections the powder coat will not hide these. Powder Coat can end up drawing attention to such flaws. Myth #4. Powder coat has a quicker dry and cure time than wet paint.Is powder coating an epoxy? ›
Epoxy powder coatings provide tough, durable and resilient coatings for metal. They are well-suited to applications where there is a requirement for a hard, electrical insulating coating, or where there surfaces will be subject to a wide range of temperatures.
Is it cheaper to paint or powder coat? ›
POWDER COATING COST VS PAINT COST
The average cost of powder coating is about $2,000 vs the average cost of painting which is about $1,900. Powder coating is a great alternative to painting. Powder coating is mostly used when you need a durable protective finish added to a metal product.
Powder will likely have more texture than liquid and be more rounded at the edges than liquid paint. Measure the film thickness if you can. There are gauges made for that purpose. If you do not have a thickness gauge you may be able to take your part to a coating shop and have them do it for you.Which type of powder coating is the best? ›
The two most widely used types of powder coating are TGIC Polyester and Urethane Polyester. Both types of powder coating provide excellent wear resistance and outdoor durability. Polyester Urethane powder systems provide excellent chemical resistance.What are the major groups of coatings? ›
- #1. Polyurethane coatings. These coatings produce a high-gloss, abrasion-resistant finish. ...
- #2. Epoxy coatings. These coatings are composed of an epoxy base topped with a curing agent. ...
- #3. Alkyd coatings. ...
- #4. Zinc-rich coatings. ...
- #5. Acrylic coatings.
If your customer repaints, recommend using thermosetting acrylic, epoxy, polyester or polyurethane enamels. Although they may not provide the same quality, air drying enamels including aerosol spray can paints will adhere as well.What materials Cannot be powder coated? ›
- Wood. Wood is tricky to powder coat for two reasons — the first that it doesn't always withstand the extreme temperature, and second that it isn't always electrically conductive. ...
- Glass. ...
- Plastics. ...
- Fabric. ...
- Items Without a Charge.
Corrosion resistance: The powder coating creates a barrier to protect against many different types of corrosion, including rust. Many natural metals like steel rust over time with exposure to moisture and oxygen. Powder-coating creates a protective barrier so the metal remains rust-free.What does PPC stand for in powder coating? ›
Polyester Powder Coating, or PPC, is one of the options from our range of rainscreen cladding finishes. PPC is a type of dry coating, rather than a conventional liquid paint, and is applied to metal rainscreen as a free flowing, dry powder.What is FEP coating? ›
FEP (Fluorinated Ethylene Propylene) is a fluorocarbon-based polymer. FEP coatings can provide a low co-efficient of friction or slipperiness (0.08 kinetic), are non-porous, non-stick, remain chemically inert, with good dielectric strength (1300v/mil) and are often used as bonding agents.What is PE powder coating? ›
Polyethylene is a multi-purpose, thermoplastic powder coating designed to meet a wide range of qualifications. As a general purpose coating, it rivals Vinyl in variety of uses but has a higher impact rating than Vinyl. Common applications for Polyethylene are: Outdoor Furniture. Playground equipment.
What are the two types of coating? ›
Coatings are specified as organic or inorganic according to the nature of their binder. Organic coatings are those that have an organic binder. Inorganic coatings are those that have an inorganic binder such as a silicate.