Powder Coating is an extremely popular dry metal finishing process widely used in industrial equipment. Since its inception, powder coating has become so effective that it represents more than 15% of the total industrial surface finishing market. Through an electrostatic process, powder coating is applied as dry powder on a wide array of products. Because of its high-quality, durable finish, flexibility, improved efficiencies, and environmental compliance, many organizations specify powder coating as their preferred choice. A wide range of colors and textures gives powder coating an edge over other surface finishes. A German scientist Dr. Erwin Gemmer first developed the powder coating process in the 1940s.
Working and Application of Powder Coating
Powder coatings are based on polymer resin systems. They combine with pigments, curatives, leveling agents, flow modifiers, and various other additives. All these ingredients are melt mixed, cooled, and then ground into a uniform powder. Melting by heating achieves a uniform mix and finish and then cooling makes it hard coating to finally form a powder.
To apply the powder coating on metal or other surfaces, a process called electrostatic spray deposition (ESD) is used.
An electrostatic paint sprayer or spray gun is used to apply the powder coating. It applies an electrostatic charge to the powder particles, which are then attracted to the grounded part. Once the powder coating application is over, the parts are transferred into a curing oven. The heat addition inside the oven helps the coating to chemically react and produce long molecular chains, resulting in high cross-link density, very resistance to breakdown.
There are three steps in the powder coating application process. They are:
- Preparation: Preparing for the powder coating application is the most critical step. The surface must be thoroughly cleaned for a proper level of adhesion of the coating.
- Application: Small objects can be dipped inside the powder coating particles. For large surfaces, the powder coating material is sprayed using a spray gun.
- Curing: Inside an oven, the part is cured to form a thin and strong coating.
Types of Powder Coating
There are two types of powder coating that are widely popular; thermosets and thermoplastics.
When heated, thermoplastic powder coating finishes become very soft that eliminates chemical bonding. Because of the thermoplastic powder coating is reversible and reusable. Also, they are thicker and more durable compared to thermoset coatings and are used on components from metal, auto parts, and even refrigerators.
On the other hand, thermoset powder coating forms a chemical bond once cured. This type of powder coating is not recyclable. As with heat these do not become soft or melt, It is suitable for high heat areas.
Durability of Powder Coating
Powder coating is a high-quality and one of the most durable finishes and because of this thousands of products are provided with powder coatings. It protects the roughest, toughest machinery as well as a variety of surfaces on a daily basis. It provides a more durable finish along with an attractive surface finish suitable for extreme weather and physical impact. Also, Powder-coated products are highly resistant to moisture, ultraviolet light, and chemicals. In turn, this reduces the risk of corrosion, scratches, chipping, fading, abrasions, and other wear issues.
Pre-treated Powder coating finishes can keep their finish for up to 20 years. However, prolonged exposure to UG light and extreme weather conditions can reduce it. Several factors like the type of powder coating, quality of preparation, environmental condition, etc govern the longevity of powder coatings. Usually, fluoropolymers and urethanes last longer.
Advantages of Powder Coatings
Because of several advantages that powder coating offers, it has become an excellent choice for metal fabrication. Apart from longevity, other benefits that powder coating provides are:
- Environment friendly: As powder coatings are free from toxic chemicals and solvents, it’s regarded as safe for usage and disposal.
- Economic or Low Cost: Less overall cost as compared to paints.
- Nice appearance because of smooth surface without drips.
- Efficiency: Highly efficient without any wastage during application.
- Variety: Highly versatile and range of color, texture, and finish options.
- Very easy to maintain without the requirement of special solvents or cleaners.
- Efficient curing and drying process.
- Very good mechanical and physical properties.
Drawbacks of Powder Coating
The main disadvantages of powder coating are:
- higher initial cost.
- difficult to achieve thin coating.
- difficult to apply on very large surfaces.
- the curing capability inside an oven is also limited.
- very difficult to mix powders to get custom colors.
Applications of Powder Coating
Because of so many advantages, powder coating is in huge demand and applied in a range of applications. The automotive and appliance industry is the largest consumer of powder coating. Common applications of Powder coating are:
- Microwaves, refrigerators,
- gates, doors, and windows,
- Dryers and washers
- alloy wheels,
- aluminum, stainless and steel alloys, galvanized steel, and certain cast metals.
- Sports equipment
- Road signs, etc.
Powder Coating vs Paints
The purpose of both powder coating and wet paints is almost similar. But powder coating provides various advantages as compared to paints. The following table lists down the main differences between powder coating and paints.
|Powder Coating does not contain a solvent which is why it is in dry form.||The paint contains solvent and is in liquid form.|
|The initial cost is more but considering its longevity and lower maintenance cost, powder coating provides an optimum solution.||The initial cost is low but the longevity of the paint is less.|
|More corrosion, abrasion, and wear resistance.||Less resistant to wear, abrasion and corrosion.|
|No drips or sags during the application of powder coating.||Highly skilled operators are required during paint application to avoid drips and sags.|
|Exact color matching is usually very difficult for powder coatings.||Liquid paints can be mixed with a high degree of precision to get the exact color.|
|Better performance and efficiency.||Reduced performance and efficiency.|
Is powder coating better than paint?
Yes, Powder coating is better as compared to wet paint. Due to the thermal bonding while curing and much thicker layers as compared to paint, Powder coating provides better performance, more resistant to chipping, scratching, and other wear. At the same time, powder coating has a better color retention capability.
What is the purpose of powder coating?
The main purpose of powder coating is to protect machinery and household items from rough environments. At the same time, it provides a durable and attractive surface finish.
What are powder coating examples?
A vast range of appliances and industrial products are finished with powder coating methods. Some of the examples are tables, laundry machines, stoves, refrigerators, microwaves, alloy wheels, stadiums, sports equipment, lighting, etc.
What materials Cannot be powder coated?
Materials that melt at temperatures are not suitable for powder coating. Some examples of materials that can not be powder coated are plastic, wood, rubber, etc.
How long will powder coating last?
Surface finishing using powder coating methods can last up to 20 years if properly maintained. However, harsh use, UV light exposure, and certain environment can damage the powder coating finish.
Is powder coating rustproof?
In general, powder coating is resistant to rust, abrasion, chipping, etc. However, if the coating breaks, it can corrode or rust.
Can aluminum be powder coated?
Yes, Powder-coated aluminum is widely used in the automotive industry.
Can I powder coat plastic?
No, materials that melt below 400 Degree F temperature can not be powder-coated.