The Role of Powder Coatings in the Evolving Automotive Industry

By Sarah Mueller and Jacob Collison

Powder coatings play an integral part of the total coating solutions used in the automotive industry. Their function varies greatly depending on component environment and automotive original equipment manufacturer (OEM) requirements. Performance ranges from automotive exterior decorative coatings, which provide protection toward harsh environmental conditions, to internal components where the coating plays a functional and/or protective role.

Today, powder coatings are contributing to the electric vehicle (EV) evolution by delivering functional benefits to the battery pack providing improved scalability, safety, lifetime, and performance.

Movement to Electric Vehicles
The past 20 years have ushered in a new era in the automotive industry focused on the electrification of the traditional internal combustion engine (ICE) powertrain. These changes have become increasingly feverish during the late 2010s and early 2020s due to the increasing environmentally focused legislation limiting ICE vehicle sales, the subsidization of EVs, and challenges caused by post- COVID-19 supply chain challenges.

Coating systems help to mitigate many challenges of a quickly scaling industry by broadening the engineering design space in EV batteries. Coatings provide the required functionality (or multifunctionality) for a given environment, while relying on application methodologies and chemistries that are known to the automotive industry.

Three key material performance properties must be considered in the battery pack. Dielectric isolation, thermal management, and fire mitigation and protection are safety- critical properties that build the foundation for what can be described as a pyramid of safety.

Dielectric isolation is the cornerstone of these material performance properties as it is a physical barrier that protects the battery pack from electrical damage due to shorting and adds to the system’s safety by isolating high-voltage systems from vehicle occupants. Dielectric isolation provides battery pack longevity, performance, and safety. Dielectric isolating materials based on powder coatings are at the forefront of this space. Specially designed powder products for dielectric isolation are commercially available.

The second material performance property for safety in EV battery packs is thermal management. Battery packs are becoming more energy dense and are being subjected to faster charging demands by customers, which lead to an increase in system heating and a greater requirement for thermal mitigation. A lack of appropriate thermal mitigation and operation within safe temperature operating tolerance is a risk factor that may lead to an enhanced propensity for a thermal runaway event. Engineering solutions such as cooling snakes or tubes, commonly found in cylindrical battery pack designs, or cooling plates, used in both prismatic and cylindrical battery pack form factors, pull heat from the cells of the battery. These engineering solutions require protection from the environment, while still transferring heat from the cell to a cooling medium. Coating companies have developed powder solutions that provide dielectric isolation protection, but also provide increased thermal conductivity properties that help pull heat away from critical components.

Finally, if the battery pack has the appropriate dielectric isolation and adequate thermal conductivity, the risk of fire and thermal runaway is greatly reduced. As a last line of defense, fire mitigation and protection can play an essential role for safety of vehicle occupants and first responders in the event of a vehicle collision or unforeseen event. Powder coatings provide flame retardancy to limit the propagation of a fire within the pack.

The three material performance properties of dielectric, thermal mitigation, and fire protection and mitigation may be served by powder applications but are not the only beneficial properties powder coatings provide. Powder coatings may also yield benefits in corrosion protection, weatherability, and reduced corrosion at edges. For these reasons, powder coatings remain a popular solution in battery design and protection compared to other solutions that offer only a subset of functional properties.

In addition to these performance benefits, powder may improve productivity and has a potential for increased sustainability through the application process. Powder coatings have near 100% solid content and can be applied with high transfer efficiencies, thereby reducing waste.

Powder coatings also provide excellent mechanical properties helping to enhance durability of coated components and have the potential to extend overall battery life. They are applicable to many different part types and shapes within the battery pack, including lids, trays, frame plates, module racking and housing, cooling plates and tubes, busbars, and unfilled cell cans. Powder coatings are a powerful option in terms of application flexibility and material property performance.

Powder for the Automotive Industry
In addition to coatings specifically formulated for dielectric performance, powder can be used on many components on an ICE, hybrid, or full-electric vehicle. Both functional and decorative powders are used to enhance the lifetime of the vehicle and make the car aesthetically pleasing.

Functional powders can be used on the car body and wheels as a primer layer. These coatings provide corrosion resistance and impact resistance to gravel chips. Primers for this end use also must have excellent adhesion to the substrate, electrocoat layers below, and topcoat layering systems above.

A substantial number of automotive accessory parts can be painted with powder coatings. Powders used for parts need to be both decorative and functional in nature. Parts like wiper arms, running boards, tow hitches, roof racks, bumpers, mirror housings, handles, and other trim pieces can be coated with powder. These parts require superior weathering, corrosion, and resistance to a variety of chemicals to mimic exposure of acid rain, animal droppings, and car wash solutions. On the interior of the vehicles, powder coatings can be used on instrument panels, consoles, and displays. These powders are similar to those used on the exterior of the vehicle.

Under the hood, powder coatings are functional in nature. Suspension systems rely on superior corrosion protection, flexibility, and gravel- chip resistance on coil springs. Wheel wells and chassis require the powder toughness for impact and corrosion resistance. Lastly, brake systems require corrosion performance, but also appropriate surface properties to ensure brake system functioning.

Redefining Edge Protection
One recent addition to the powder coatings market is high-edge powders, which provide enhanced edge protection leading to improved longevity and aesthetics. The coatings provide enhanced performance for sharp edges, louvers, blades, mesh, and other parts that contain hard-to-cover features. High-edge powders may be used to improve the corrosion performance of traditional monocoat powders as a subsequent layer. The exceptional edge protection goes beyond the convenience and savings that come with a one- coat application. These products also have higher first-pass transfer efficiency versus traditional powders, leading to less powder use, thereby delivering potential savings in the long run.

High-edge powder formulations provide up to four times more dry film thickness on the edge in a single powder booth pass and can be run on a standard line, reclaimed, and used in automatic and manual powder systems. These features allow for ease of line changeover if enhanced edge performance is needed. Additional edge corrosion may be needed for any parts with sharp edges and exterior exposure. Some additional examples are heavy duty equipment such as tractors or boom lifts, electrical generators, and outdoor tank systems.

High-edge powder has advantages versus conventional direct-to-metal powder in some circumstances such as:

• Enhanced part appearance by allowing uniform coverage, color, and gloss across the part.
• Reduced touch up and associated labor.
• Reduced part edge rounding or grit/sand blasting.
• Fewer sharp edges for improved handling.
• Reduced part cost due to lower powder usage.

High-edge powders can also replace the primer layer in many applications. Potential cost savings can be captured by eliminating the primer and associated labor to run the powder coating booth. Removing a powder layer also has sustainability advantages such as energy savings gained by running one less powder booth and waste reduction due to fewer powder painting operations.

Today, powder coatings technologies provide several performance, cost, and sustainability benefits to the automotive parts industry and beyond. Enhanced powder coatings are contributing to the electric vehicle (EV) evolution by delivering functional benefits to the battery pack providing improved scalability, safety, lifetime, and performance.

Sarah Mueller is powder technical manager, U.S./Canada and Jacob Collison is global strategic product manager for PPG.