Acrylic powder coating is an environmentally friendly powder coating that uses acrylic resin as the main film-forming material and forms a film through electrostatic spraying and high-temperature curing. It is known for its excellent weather resistance, color and gloss retention, and decorative properties.
This article systematically introduces the concept, types, characteristics, functions, application fields, selection considerations, and solutions to common problems of acrylic powder coating, with a focus on the applications of acrylic powder coating, to help everyone better understand what acrylic powder coating is and what functions it provides.
What Is Acrylic Powder Coating
Acrylic powder coating is a thermosetting powder coating that uses acrylic resin as the main film-forming material and forms a film through electrostatic spraying and high-temperature curing. It is one of the powder coating types with the most outstanding weather resistance and decorative properties.
It consists of acrylic resin, curing agents, pigments and fillers, and additives. Acrylic resin is formed by copolymerizing hard monomers, soft monomers, and crosslinking monomers. The hardness and flexibility of the coating film can be adjusted by changing the monomer ratio. According to the functional groups contained in the resin, it is mainly divided into three systems: those containing glycidyl ether functional groups (GMA type), those containing carboxyl groups, and those containing hydroxyl groups.
Types of Acrylic Powder Coating
According to chemical functional groups, it can be divided into the following types:
- GMA Acrylic (Containing Glycidyl Ether Functional Groups)
This is currently the mainstream type used in high-weatherability outdoor applications. GMA acrylic resin usually uses dodecanedioic acid (DDDA) as the curing agent and can form an extremely smooth coating film with excellent weather resistance. It can withstand more than 10 years of Florida outdoor exposure testing.
- Hydroxy Acrylic (Acrylic Polyurethane Type)
It is crosslinked and cured by hydroxy acrylic resin and blocked polyisocyanate. This system usually requires a relatively high curing temperature (>375°F), but it can provide the highest chemical resistance and hardness among all outdoor-durable powder coatings. It was widely used on home appliance panels in the 1980s, such as stove side panels and refrigerator doors, and was known for its excellent stain resistance. It is also used for outdoor vending machines.
- Carboxyl Acrylic (Acrylic Hybrid Type)
It is crosslinked and cured by carboxyl acrylic resin and epoxy resin and is usually referred to as an “acrylic hybrid.” Because it contains an epoxy component, this type of coating does not have outdoor weather resistance. The epoxy component will fade and yellow when exposed to UV radiation, so it is only suitable for indoor applications. Its performance advantages are high hardness and good chemical resistance, which is better than polyester hybrids. It was once used for coating home appliances such as washing machines and dryers.
- Acrylic Polyester (GMA Acrylic and Carboxyl Polyester Reactive Type)
GMA acrylic resin is combined with carboxyl polyester through a reaction, providing some characteristics of both systems. However, this usually produces low-gloss coatings, with relatively poor flexibility and impact resistance.
Characteristics of Acrylic Powder Coating
Acrylic powder coating has the following characteristics:
Excellent Weather Resistance: GMA acrylic is representative of this category and can withstand more than 10 years of Florida outdoor exposure, with excellent gloss and color retention. It is one of the powder coating types with the strongest outdoor durability.
Excellent Decorative Properties: It provides good flow and leveling, high distinctness of image, and high gloss. It can be made into a transparent clear coat with a mirror-like smooth surface, making it suitable for high-end appearance requirements.
High Hardness and Scratch Resistance: Pencil hardness is typically ≥2H. The coating film is hard and provides excellent scratch and wear resistance.
Good Chemical Resistance: It can resist the attack of chemicals such as acids, alkalis, detergents, and gasoline. Hydroxy acrylic systems have particularly strong chemical resistance.
Excellent Adhesion: It provides strong adhesion to metal substrates, and the cross-cut test can reach Grade 0.
Functions of Acrylic Powder Coating
The functions of acrylic powder coating are as follows.
- Protective Function
(1) Weather Protection: Resists outdoor climatic effects such as UV radiation, acid rain, and temperature differences, preventing coating chalking, fading, and cracking, and maintaining the appearance and structural integrity of facilities over the long term.
(2) Corrosion Protection: Forms a dense coating on the surface of metal substrates, isolating moisture and oxygen and slowing the corrosion process.
(3) Chemical Protection: Resists the attack of chemicals such as detergents, solvents, acids, and alkalis, protecting the substrate from chemical damage.
(4) Mechanical Protection: With its high hardness and scratch resistance, it resists daily impacts, scratches, and wear.
- Decorative Function
(1) Improving Appearance and Texture: Provides a smooth surface with high gloss and high distinctness of image, or a transparent clear-coat effect, significantly enhancing product quality and appearance.
(2) Color and Gloss Retention: Maintains color and gloss after long-term outdoor use, preventing facilities from appearing aged due to coating deterioration.
(3) Providing Diverse Appearance Options: Can achieve various effects such as high gloss, low gloss, metallic appearance, and transparency to meet different design requirements.
- Functional Applications
(1) Clear-Coat Protection: Used as a transparent topcoat over colored paint layers or metal wheel surfaces to provide additional weather and scratch protection.
(2) Insulation Protection: Some acrylic systems can be used for insulating coatings on electronic components.
(3) Environmentally Friendly Alternative: Contains no VOCs, can be recycled and reused, and can replace traditional solvent-based coatings to reduce environmental pollution.
Application Fields of Acrylic Powder Coating
Which household appliances may use powder coating? The specific application fields of acrylic powder coating are as follows.
- Automotive Industry (The Most Important Outdoor Application)
This is the most mature and demanding field for acrylic powder coating technology.
(1) Automotive Aluminum Wheel Clear Coating: GMA acrylic transparent powder coating is the preferred system for aluminum wheel clear coats. Due to its excellent flow and leveling, transparency, and weather resistance, it can maintain the wheels’ bright appearance like new for a long time.
(2) Automotive Bodies and Components: Historically, it was used as a topcoat for truck color coatings. It is also used for exterior components such as rearview mirror housings, grilles, roof racks, and wheel covers.
- Architectural and Outdoor Metal Decoration
(1) Architectural Aluminum Profiles and Curtain Walls: Used for door and window frames, curtain walls, etc., where it provides weather resistance and decorative advantages. In the aluminum building materials field, acrylic powder coating is often used together with polyester powder coating or in applications with higher decorative requirements.
(2) Outdoor Metal Decorative Components: Includes metal railings, metal frames of outdoor furniture, bicycle components, door handles, etc., where it is used as a high-performance clear coat.
- Home Appliances and Indoor Applications (Systems Must Be Distinguished)
(1) Special Attention Is Required Here: Carboxyl acrylic hybrid (epoxy type) systems are limited to indoor use because the epoxy component will fade and yellow when exposed to UV radiation.
(2) Home Appliance Panels: Used for washing machine drums and panels, dryer panels, microwave oven interiors, vacuum cleaner housings, etc., taking advantage of its high hardness, chemical resistance, and scratch resistance.
(3) Indoor Metal Furniture and Office Facilities: Such as filing cabinets, metal tables and chairs, shelving, storage cabinets, etc.
(4) Lighting Fixtures: Indoor lighting housings and decorative metal components.
(5) Retail Displays and Interior Decoration: Store shelves, display racks, curtain rods, picture frames, etc.
- Other Industrial and General Applications
Acrylic powder coating is also used for coating agricultural machinery, high-end household appliances, consumer electronic housings, bicycles, and other hardware facilities.
Key Selection Point: For outdoor applications, GMA acrylic (top-level weather resistance) or hydroxy acrylic (high hardness and chemical resistance) must be selected. For indoor applications, acrylic hybrid systems can be considered (higher cost-effectiveness, but strictly prohibited for outdoor use).
Differences Between Acrylic Powder Coating and Polyester Powder Coating
The main differences between acrylic powder coating and polyester powder coating are reflected in the following aspects.
| Comparison Dimension | Acrylic Powder Coating | Polyester Powder Coating |
| Core Positioning | Top-level weather resistance, high-end appearance | Comprehensive balance, mainstream outdoor choice |
| Weather Resistance | Stronger (up to 60 months of exposure) | Conventional outdoor (approximately 12 months of exposure) |
| Mechanical Properties | High rigidity, poor toughness | Good flexibility, strong impact resistance |
| Hardness | Higher, suitable for thin coatings | Slightly lower |
| Flow and Application | Poor flow and leveling, sensitive application | Good flow and leveling, stable application |
| Transparent Clear Coat | Significant advantage (wheel clear coat) | Relatively weak |
| Cost | High | Low, cost-effective |
| Applicable Scenarios | Automotive wheels, ultra-high weather resistance | Fences, furniture, architectural profiles |
How to Choose Acrylic Powder Coating
When choosing garden facility powder coating, we may face the problem of not knowing how to make the right selection. Based on our industry experience, our company recommends focusing on the following aspects when selecting garden facility powder coating.
- Distinguish Between Indoor and Outdoor Applications — This Is the Dividing Line
There are several types of acrylic powder coating, and their weather resistance varies greatly. Choosing the wrong type for outdoor use will cause rapid chalking and discoloration.
(1) Outdoor Applications (Gardens, Automotive, Architecture): GMA acrylic (containing glycidyl ether functional groups) or hydroxy acrylic must be selected. GMA acrylic has top-level weather resistance and can withstand more than 10 years of Florida outdoor exposure.
(2) Indoor Applications (Home Appliances, Office Furniture): Carboxyl acrylic hybrid (epoxy type) can be considered for better cost-effectiveness. However, it is absolutely prohibited for outdoor use because the epoxy component will rapidly fade and yellow when exposed to UV radiation.
- Determine the Performance Grade According to Environmental Severity
Even for outdoor acrylic powder coating, the requirements for an ordinary courtyard and a coastal high-salt-spray environment are completely different.
For conventional outdoor applications (garden furniture, fences, courtyard lighting), basic GMA acrylic or an acrylic/polyester blended system is sufficient, with a salt spray resistance requirement of more than 500 hours and humidity and heat resistance of approximately 800 hours.
For harsh outdoor applications (coastal areas, strong UV exposure, industrial zones), more stringent performance indicators need to be considered:
(1) Artificial Weathering Resistance: It is recommended to select products with QUV or xenon lamp testing ≥1.000 hours, with an outdoor service life of more than 10 years.
(2) Salt Spray Resistance: Coastal or salt-spray-prone areas require ≥3.000 hours.
(3) Gloss and Color Retention: After 5 years of outdoor exposure, the gloss retention rate should be >90%, with a color difference ΔE≤2.
If the environment is extreme (deserts, plateaus, photovoltaic mounting systems), a fluorosilicone-acrylic hybrid system can be considered. After 3.000 hours of QUV aging, the gloss retention rate can still reach more than 90%.
- Verify Key Additives and Application Parameters
(1) Additive Configuration: Prioritize products containing a combination of hindered amine light stabilizers (HALS) and UV absorbers. The synergistic effect of the two can extend the outdoor service life of the coating by 2–3 times. In coastal environments, attention should also be paid to whether hydrolysis-resistant additives are included.
(2) Curing Conditions: The typical curing temperature of acrylic powder coating is 180–200°C. Be sure to measure the substrate temperature according to the data sheet requirements. Insufficient curing will seriously weaken weather resistance.
(3) Safety Reminder: Acrylic powder coating has an explosion hazard classification of St2. which is higher than the St1 classification of polyester. The spraying workshop must implement explosion protection and dust control measures.
Common Problems and Solutions for Acrylic Powder Coating
The most common problems encountered during the use of acrylic powder coating are mainly reflected in the following aspects. Based on our industry experience, our company proposes corresponding solutions to help effectively resolve the powder coating problems you encounter.
- Poor Resistance to Indentation (Permanent Indentations After High-Temperature Stacking Pressure)
Problem Description: Coated workpieces, especially aluminum wheels and architectural profiles coated with transparent acrylic powder coating, may develop irreversible indentations on the coating surface when transported or stacked under relatively high temperatures. This can seriously affect the product qualification rate.
Possible Causes:
(1) Insufficient Crosslinking Density: If the curing system of acrylic powder coating has insufficient crosslinking density, the coating film’s ability to resist plastic deformation at high temperatures decreases, making it prone to permanent indentation under pressure.
(2) Improper Matching of Resin Acid Value and Curing Agent: Different acid values of acrylic resins combined with different curing agents and hardening additives directly affect the indentation resistance of the coating.
(3) Low Glass Transition Temperature (Tg) of the Coating Film: The coating film softens at high temperatures and loses its ability to resist external forces.
Solutions:
(1) Optimize the Resin and Curing Agent Combination: Based on the curing mechanism of powder coating, study different combinations of acrylic resins with different acid values, curing agents, and hardening additives to obtain an optimal formulation that balances conventional performance and indentation resistance.
(2) Increase Crosslinking Density: Appropriately increase the amount of curing agent or select a system with higher reactivity so that a denser three-dimensional network is formed after curing.
(3) Add Hardening Additives: Introduce additives that can improve the surface hardness and thermal stability of the coating film to enhance resistance to deformation at high temperatures.
- Poor Scratch Resistance of Acrylic Matte Coating
Problem Description: Acrylic matte powder coating, used to achieve an extremely matte finish of <10°, has poor scratch and wear resistance. Clear scratches appear on the coating surface after scratch testing, and gloss increases at the scratched areas (commonly referred to as “bright spots”), damaging the matte effect.
Possible Causes:
(1) Migration of Hard Monomers to the Surface: Hard monomers such as styrene introduced into epoxy acrylic matte resin have poor compatibility with polyester. They precipitate and disperse on the coating surface during film formation. When scratched, the hard monomers on the surface are damaged, exposing the internal low-gloss structure and causing increased gloss at the scratched areas.
(2) Insufficient Crosslinking Density: The matte system sacrifices part of its crosslinking density to achieve low gloss, resulting in insufficient overall coating hardness and weak scratch resistance.
(3) Differences in Resin Compatibility: The surface tension of epoxy acrylic resin differs significantly from that of polyester resin. If the matching is improper, the surface structure of the coating film will be uneven, making certain areas more susceptible to damage.
Solutions:
(1) Introduce a High-Crosslinking-Density Hydroxyl System: Improve the overall crosslinking density of the coating film through formulation adjustments to enhance the scratch resistance of acrylic powder.
(2) Match the Acid Value of Polyester Resin: Tests have shown that the higher the acid value of the polyester resin, the greater the crosslinking density and the better the scratch resistance. A polyester resin with surface tension compatible with the epoxy acrylic resin should be selected.
(3) Select and Optimize Fillers: Flake-like fillers such as sericite and talc have different effects on hardness. Scratch resistance can be improved by optimizing the type and amount of filler.
- Flow and Leveling and Surface Defects (Orange Peel, Cratering, Particles)
Problem Description: Orange peel (uneven surface), cratering (circular depressions), or particles may appear on the coating surface, affecting appearance and protective performance. These problems may occur in both thick-coating and thin-coating applications of acrylic powder.
Possible Causes:
(1) Improper Powder Particle Size Distribution: Larger particles require more time to melt and are more likely to produce orange peel, while excessively small particles may affect the uniformity of electrostatic spraying.
(2) Improper Coating Thickness: Coatings that are too thick or too thin can result in an uneven surface.
(3) Workpiece Temperature or Humidity Issues: Excessively wet or cold workpieces can affect powder adhesion and flow and leveling.
(4) Improper Curing Parameters: The melting and curing temperature ranges of acrylic powder overlap. If the temperature rises too quickly, the curing reaction may occur before flow and leveling are complete, “locking” the surface texture and preventing self-repair.
(5) Equipment Contamination: Deposits on nozzles and cross-contamination caused by insufficient cleaning when changing powders can cause particles or cratering.
Solutions:
(1) Optimize Powder Particle Size: Communicate with the powder supplier to ensure that the particle size distribution is suitable for the application, which helps improve flow and leveling and appearance.
(2) Adjust Spraying Parameters: Control the powder output to avoid excessively thick or thin coatings. For highly visible flat components, appropriately reducing gun voltage and optimizing overlap consistency can help improve flow and leveling.
(3) Verify the Curing Curve: Use the workpiece metal temperature curve rather than simply looking at the oven temperature to confirm that the workpiece heats up at the correct rate and ensure sufficient flow and leveling time before the curing reaction becomes dominant.
(4) Strengthen Equipment Maintenance: Regularly clean the nozzles and spray booth, and thoroughly clean the equipment when changing powders to prevent cross-contamination.
- Poor Storage Stability
Problem Description: Acrylic powder coating has a relatively short storage period (commercial products generally specify 8 months) and is prone to caking during storage, affecting its use.
Possible Causes:
(1) Low Glass Transition Temperature (Tg) of the Resin: If the resin Tg is not sufficiently high, powder particles will gradually adhere to each other and form lumps at room temperature or slightly higher temperatures.
(2) Conflict Between Low-Temperature Curing and Storage Stability: Pursuing low-temperature curing often requires a low-melting-point resin, which can aggravate the caking problem.
(3) By-Product Issues in Polyester Systems: In some acrylic powder systems, condensation products generated during thick coating can cause cratering, and caking during storage can also be relatively severe.
Solutions:
(1) Strictly Control Resin Tg: Ensure that the Tg of the acrylic resin used for powder coating is within an appropriate range (typically 40–70°C), balancing storage stability and flow and leveling performance.
(2) Optimize Storage Conditions: Powder coating should be stored in a cool, dry place, avoiding high-temperature and high-humidity environments. Seal the packaging promptly after opening.
(3) Select an Appropriate Curing System: Find a balance between low-temperature curing requirements and storage stability, avoiding excessive pursuit of low-temperature curing at the expense of storage performance.
If you need acrylic powder coating or encounter problems in the powder coating field, please feel free to contact us at any time to obtain professional technical support, discuss solutions together, and promote the development of the powder coating industry.
We hope this article can provide you with a professional and reliable reference regarding the powder coating industry. We sincerely welcome you to consult us actively regarding powder coating product performance, industry standards, application methods, precautions, or any related questions. We look forward to hearing from you at any time through messages or direct contact, so that we can provide you with more detailed product information, demonstration videos, or customized solutions to help you fully understand all the functions and advantages of our products.
