Polyester Powder Coating Explained: Is it Good?

Polyester powder coating is the process of applying an electrostatically charged powder over the surface of the workpiece, followed by heating to cure the powder and produce a protective coating. This coating offers good resistance to fading, chipping, and impact, making it suitable for a wide range of applications.

Polyester powder coating is the way to go if you're looking for an efficient and cost-effective way of adding a protective layer over your workpiece.

This article discusses polyester powder coating in detail by going through its process, types, advantages, and applications.

In the end, the article also differentiates polyester powder coating from epoxy powder coating and provides information about hybrid powder coating.

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What is Polyester Powder Coating?

Polyester powder coating is the process of applying a polyester-based powder over the workpiece, by using a spray gun.

The powder is electrostatically charged while the workpiece is connected to the ground circuit, enabling the powder to adhere to the workpiece's surface.

Therefore, this process is only suitable for conductive materials, such as metals.

After spraying the powder, the workpiece is heated, allowing the powder to cure and bond to the surface of the workpiece.

The resulting external protective surface is highly resistant to wear and tear and has a visually aesthetic appearance.

This finish is much more uniform and smooth than a simple paint finish.

Moreover, performing pre-processes, such as sandblasting the workpiece before powder coating, further improves the quality of the coating.

Generally, this non-toxic and high-speed process can be used on different complex surfaces.

Although the polyester powder coating process is relatively safe from an environmental health and safety point of view, a few hazards still need to be catered to while performing this process.

The dust cloud that results from the excessive powder can lead to a dust explosion or fire if ignited. As a result, it is advised to implement a good exhaust system to dispose of the excessive powder safely.

Apart from that, always wear face masks, goggles, gloves, safety shoes, and a protective coat to ensure personal safety and health.

Types of Polyester Powder

There are mainly three categories of polyester powders.

Polyester powder coating is available in different textures, finishes, and colors or clear powder coats.

Apart from these, polyester powder coating can also be classified based on the type of powder being used for the application.

Polyester TGIC-Free Powder Coating

Polyester TGIC (triglycidyl isocyanurate) free or pure polyester powders are purely made up of polyester resins and are highly durable and corrosion-resistant.

This type of powder coating is also known as HAA polyester powder, as they contain the HAA curing agent.

It has good chemical and solvent resistance, making it ideal for applications such as automobile and food utensils.

Polyester TGIC Powder Coating

Polyester TGIC powders contain TGIC as the chemical curing agent.

This coating has good mechanical and chemical resistance properties and relatively the best color stability.

These coatings cure at lower temperatures compared to pure polyester-type powder coatings.

They are commonly utilized in the furniture and industrial machinery industry.

This polyester type is most likely to release volatile organic compounds (VOCs) into the environment if exposed to extreme heat.

Hybrid Polyester Coating

There are mainly two hybrid polyester coatings: polyester polyurethane coating and polyester epoxy coating.

The polyester epoxy coating comprises both polyester and epoxy resins and results in a heat-, chemical-, and impact-resistant powder coating ideal for extreme environments. 

Moreover, its shiny and vibrant appearance makes it popular for applications demanding visual aesthetics, such as architectural applications.

On the other hand, polyester polyurethane coating consists of polyester and polyurethane resins.

Besides its high durability and flexibility, its corrosion resistance and glossy texture make it ideal for applications where extreme durability with enhanced aesthetics is desirable, such as automobile parts.

Other hybrid coatings include acrylic polyester and silicon polyester powder coatings but are less prevalent in the industry due to relatively lower durability and less attractive visual appearance.

Advantages of Polyester Powder Coating

Polyester Powder Coating is Environment-Friendly

The process of polyester powder coating does not result in toxic emissions or waste.

Although TGIC-type polyester powder coating can release VOCs into the atmosphere upon excessive heat exposure, other polyester powders do not emit such harmful substances.

This aspect is favorable, especially from a DIY perspective, as no intensive waste disposal process would be needed.

Polyester Powder Coating Enhances Physical Durability

All types of polyester powder coatings are highly resistant to heat and ultraviolet radiation (i.e., sunlight).

Moreover, these coatings provide excellent impact resistance, flexibility, hardness, and abrasion resistance to the workpiece.

These aspects render workpieces with such coatings suitable for use in harsh outdoor conditions.

Polyester Powder Coating Improves Chemical/Corrosion Resistance

Polyester powder coatings exhibit high chemical/corrosion resistance, especially to acids and alkalis.

This feature enables workpieces with polyester powder coating suitable for use in liquid mediums with varying chemical concentrations that can otherwise corrode away material.

The Process of Polyester Powder Coating is Efficient

The process of polyester powder coating is much quicker compared to conventional painting, thus making this process suitable for bulk production. 

This method ensures minimal wastage of material during painting as the oppositely charged workpiece surface and coating particles provide maximum adhesion.

Any extra or unused coating suspended in air can be extracted in a chamber and reused.

The polyester powder coating tightly bonds and adheres to complex-shaped surfaces and all cavities and crevices, resulting in a smoother and more uniform texture than conventional painting methods.

These coatings have low curing temperatures, so this process does not require a stringently controlled environment. 

The high color stability ensures that a uniform colored texture is formed on the workpiece surface without any faded portions.

Polyester Powder Coating is Economical

Although this process is more capital-intensive for small-scale applications, it is more favorable in terms of running costs and bulk production.

As these coatings tend to last longer and the coating process is much quicker, the operational costs and bulk coating of materials are more economically feasible.

Cost of Polyester Powder Coating

Workpiece	Approximate Price Range
Automobiles parts like door handles or rims	$100 to $500
Furniture like tables and chairs	$50 to $250
Architectural parts like window frames and door handle	$50 to $150
Sports equipment like hockey sticks and tennis rackets	$50 to $200

The most common polyester powder-coated workpieces include automobile parts, furniture, architectural parts, and sports equipment.

Generally, the average cost of powder coating automobile parts is the highest as these components have a vast surface area and require a thicker coating due to their intended application.

Architectural parts like window frames and door handles have a much smaller area, thus lowering the cost of coating.

Suppliers usually charge for polyester powder coating on a weight-consumption basis.

The larger the part, the greater the amount and weight of the polyester powder required, thus higher the cost. 

Moreover, the cost also depends on the polyester powder type used for the coating.

Polyester TGIC-type powder coating costs about $8 to $35 per pound, and Polyester Epoxy costs between $10 to $25 per pound of usage.

On the other hand, polyester polyurethane ranges between $10 to $35 per pound of use on average.

The minimum order weight is usually about 1 pound of powder usage for small-scale businesses to several hundred pounds of powder usage for large-scale companies. 

Applications of Polyester Powder Coating

Polyester powder coating is a widely used coating method commonly applied to metal surfaces such as steel and aluminum. 

As a result, it finds its applications in various industries such as the automotive industry, construction industry, furniture industry, etc.

Polyester Powder Coating in Automotive Industry

The automotive industry commonly uses this coating for essential components like the intermediate finish of external door surfaces, under-the-hood finishing, wheel finishing, etc.

Many famous automobile manufacturers, like Volvo, BMW, Audi, etc., use this coating on their car components.

Brake parts, engine blocks, shock absorbers, and external battery surfaces have significant potential to be coated with polyester powders.

Apart from these, polyester powder coating is also used for other automobiles, such as trains, bikes, and trucks.

Polyester Powder Coating in Home Appliances

The appliance industry uses this coating for several appliances like refrigerators, washing machines, freezer cabinets, air-conditioner cabinets, food utensils, microwave ovens, and water heater surfaces.

These applications require heat, chemical, and abrasion-resistant surfaces, which is where polyester powder coatings perfectly fit in.

The overall cost of these appliances rises due to these coatings, but the durability is also significantly increased.

Polyester Powder Coating in Furniture Industry

Excellent UV stability, hardness, abrasion, and corrosion resistance make these coatings ideal for furniture like tables, chairs, slabs, cabinets, cages, patio furniture, etc.

These features mean you can use your furniture in indoor and outdoor settings without any concern about getting worn out.

You can apply a thicker coat on your furniture for better protection and durability.

Polyester Powder Coating in Architectural Industry

Polyester powder coating's excellent resistance to fading and availability in a wide variety of color textures render this coating ideal for stadium seating, window frames, fencing, posts, guard rails, light poles, and hinges.

For visual aesthetics, some applications can use chrome and brass plating instead of polyester powder coating, but it is more costly, and the difference in durability is insignificant.

Polyester Powder Coating in Electronics Industry

These coatings are also used in electronic appliance wires, transformers, and motor windings.

Moreover, external frames and surfaces of electronic appliances like blenders or pumps can also undergo polyester powder coatings for additional protection.

Polyester Powder Coating for Non-Metal products

Although polyester powder coating requires a conductive workpiece, it can be applied to non-conducting materials like wood and plastics.

Generally, a wooden workpiece with uniform density, such as MDF, provides better adhesion for the powder coating.

Acrylics and ABS plastics are common types that can undergo this coating process.

This process involves passing the wood or plastic workpiece through a moist or humid chamber so that water molecules sit on its surface and get electrostatically charged, which then attracts the powder.

After that, the workpiece is subject to UV rays and concentrated heat to cure the powder coating.

Another method is using a preparation coat before the powder coating step to induce separate charges.

Polyester Powder Coating vs Epoxy Powder Coating

Parameters	Polyester Powder Coating	Epoxy Powder Coating
Bond Strength	Relatively lower bonding strength	Higher bonding strength
Durability	Relatively lower	Relatively higher
Cost	Cheaper	More expensive
Moisture resistance	Lower	Higher
Curing Time	Faster curing time	Longer curing time
Odor	Stronger foul odor	Relatively weaker foul odor
Life-span	Shorter life	Longer life

Epoxy has a higher bonding strength of up to 2,000 pounds per square inch, contrary to polyester resin, which has a lower bonding strength of about 500 pounds per square inch.

Polyester resin is more suited for applications with low-magnitude localized stresses and mechanical wear, whereas epoxy can be used for more extreme applications due to higher durability.

Generally, epoxy resin is comparatively more costly than polyester resin. As a result, epoxy powder coating is more costly and is suitable for industrial applications.

Furthermore, epoxy coatings are more resistant to humidity and moisture than polyester coatings, making them more suitable for outdoor applications.

On the other hand, polyester powder coating cures much faster than epoxy, leading to a shorter processing time.

From a user standpoint, polyester resins smell bad and can cause nasal irritation, whereas this is not the case with epoxy.

Epoxy has a longer shelf life of up to several years compared to polyesters, which usually have a life of around a few years.

Final Thoughts

Polyester powder coating is more visually aesthetic, durable, and long-lasting than standard powder coating.

It is relatively more expensive from a DIY perspective but results in a more uniform and smooth external coating.

However, it may not be suitable for materials having low melting points. 

If your application demands a smooth external protective layer with a high surface finish, irrespective of the cost, then polyester powder coating is the way to go.

Frequently Asked Questions (FAQ)

How long does the polyester powder coating process take?

The polyester powder coating process takes about 10 to 20 minutes, while the surface preparation and curing take about 15 to 30 minutes. In total, it can take up to 4 hours if cleaning and post-processing are included.

Can polyester powder coating be applied to all types of materials?

No, polyester powder coating can not be applied to all types of materials. Some materials like foam, rubber, thin gauge plastics, and aluminum have low melting points and can deform upon heat exposure, making the coating useless.

What is defined by additives, resins, and fillers in polyester powder coating?

In polyester powder coating, resins are the major components in a coating, forming the bulk of the complete composition. Additives are substances added in small amounts to the coating composition to improve specific properties, such as UV stabilizers are added to enhance the UV resistance of the coating. Fillers are substances added to improve mechanical properties while also substituting some of the resin to lower the coating cost, such as calcium carbonate.