Hosted by the e, this event will bring together professionals from across the automotive sector, including OEMs, material and paint suppliers, and Tier 1 suppliers. The goal is to enhance dialogue within the automotive community and tackle widespread corrosion issues. Attendees can expect a detailed program featuring insights from leading industry experts, ahead of the event.

Corrosion remains a critical concern in the automotive field, affecting both vehicle aesthetics and their functional, reliable, and safe operation. The push for stricter emission standards has led the industry towards adopting high-strength, lightweight materials that exhibit distinct corrosion behaviors and the potential for mixed-metal interactions, making this an area of heightened concern.

The symposium is curated by industry professionals from diverse technical backgrounds dedicated to addressing automotive corrosion. The organizing committee includes Niamh Hosking, Ph.D., from Ford Motor Company; Ullrich Haus of General Motors; Wenping Zhang, Ph.D., from Arconic; Sean Fowler of Q-Lab; Brian Okerberg, Ph.D., with PPG; and James Dante from the Southwest Research Institute.

For further details, including how to register or find accommodations, please visit .

Introduction

Aluminum-based effect pigments are widely used in automotive coatings, but it has been found that such coatings frequently disturb the transmission of radar signals, if the radar source is hidden behind the coating. To measure this reduction in transmission, the permittivity dielectric constant (e) and the loss tangent, tan (d) (dissipation factor) of radio waves in the desired frequency band are used. Many published results show that the e increases with rising pigment mass concentration,² while d changes are negligible. Figure 1 shows frequently cited data where the relative permittivity of automotive effect coating (including metal-based effect pigments) is analyzed with respect to the metal mass content.^1,3 According to Pfeiffer, the exemplary limits of radar transmission in terms of relative permittivity of automotive coatings are assumed to be < 10 as uncritical, < 30 as little critical, < 50 as medium critical, and > 50 as highly critical.³

Figure 1. Permittivity vs. metal content of automotive coatings together
with typical limits of applicability for radar sensors.³

With a lack of information on the various properties of effect pigments used in the experiments (e.g., particle size distributions, thickness distributions, densities), no other conclusions were drawn other than to avoid or minimize the metal-containing effect pigments.^4-7 The requirements would imply a lot of effort to reformulate coatings components, and many of the appearance targets such as hiding, flop, lightness, and chromaticity, as well as suitable LIDAR visibility,8 would not be fully reached.¹ Therefore, the present article deals with the radar transmission behavior of well-defined, metal-based effect pigments in combination with the expected coloristic requirements. There is a special focus on Metal Interference Pigments (MIP), introduced to the market under product names as Paliocrom, Meoxal, and Zenexo.

Experimental

Base coatings containing well-characterized, metal-based effect pigments were prepared with different pigment mass concentrations (PMCs) by a pneumatic spray application, at a layer thickness (T ) of 14 μm on an optical transparent, 2-mm thick sheet of polycarbonate. No filler and no clear coat were used. The transmission of those samples is measured with a Radome Measurement System2 at a frequency of 76.5 GHz for a perpendicular incidence. The substrate (the polycarbonate sheet), without the base coat, exhibits an e of 2.736 and tan (d) of 0.007.

The LIDAR reflection measurement was performed at a wavelength of 905 nm, utilizing an Ulbricht Sphere with a measurement geometry that excluded the specular component. This configuration ensured that only the integrated, diffusely scattered IR-radiation was detected. It was hypothesized that a high level of diffuse LIDAR reflection could serve as a relative measure for ensuring good LIDAR visibility.

Applying the same coating, as used for the radar measurement, on black and white steel substrates and adding a 40 μm clear coat on top, the coloristic data were evaluated using a goniophotospectrometer BYK-mac i. Thus, the color values for geometries of aspecular angles of -15°, 15°, 25°, 45°, 75°, and 110° for a light incidence of 45° were measured.

The effect pigments are characterized by measuring the densities using an Ultrapyc 1200e instrument, the equivalent diameter distributions by a Sympatec Helios/Quixel instrument, and the thickness distribution by Scanning Electron Microscopy.

By Michael J. Dvorchak, Dvorchak Enterprises LLC

INTRODUCTION

Over the past decade, the automotive-refinish industry has been forced to look at innovative technologies to reduce volatile organic compound (VOC) content and hazardous air pollutants (HAPs) while providing a rapid return to service of the consumer’s vehicle.

UV-A-cured one-component (1K) auto-refinish primers were first introduced in the mid-1990s. UV-A clearcoats were subsequently introduced in the late 1990s.

Materials have continued to be developed and pushed to mimic the classic two-component (2K) solvent-based polyurethanes (PURs); however, slow acceptance by the auto-refinish market over the past two decades is indicative of a market that is difficult to change.

The automotive-refinish coatings market is forecast to surpass U.S. $6.3 billion globally in 2021.¹ This market is expected to increase by 5.4% CAGR between 2021 and 2031. The main technology types are solventborne, waterborne, and UV cure. The classic coating layers are primers, basecoats, topcoats, and clearcoats.¹ A specific parameter in the refinish area that must be addressed is the bottleneck of a 2-hour cure for the primer before it can be sanded. Current UV-cure primers can be sanded within 2 minutes. The need to lower VOCs and volatile HAPs (VHAPs) is among the current constraints for all technologies. A hurdle that was recently cleared in the UV-cure sector is the price barrier for UV light equipment. Reports for the market have UV LED units priced under $1,000.² This market continues to consolidate and will be required to decrease refinishing speeds to remain competitive.

This article will review the history of the UV-cured 1K and 2K auto-refinish market and formulations for primers and clearcoats. It will also attempt to look at current UV-cured 1K and 2K auto-refinish primers and clearcoats in the global market, new formulations, and new developments in UV equipment.

CHANGES IN THE AUTOMOTIVE OEM AND REFINISH MARKETS

The automotive OEM and refinish markets have undergone incredible changes in both polymer technologies and substrates over the past several years. The original markets used nitrocellulose lacquers when the only color you could specify was black. Today, the number of 2K reactive primers and clearcoats, as well as basecoats, has pushed the limits of polymer chemistries. With the pressures to lower VOCs and VHAPS, solvent-based systems have shifted to water-based chemistries. The OEM’s substrates have evolved from the traditional steel metals to composites and aluminum.

INTRODUCTION OF UV-A-CURABLE AUTO REFINISH

Early attempts to develop a UV refinish clearcoat

The earliest paper that reviews the use of UV-cure clearcoats for auto refinish was focused on the use of a UV Flash lamp (Xe lamp).³ The idea was that after application, the fully formulated UV clearcoat would be flashed several times (by the Xe lamp) to activate the photoinitiator (PI) for this dual-cure system. The dual-cure crosslinking of this system was done with a polyol that had acrylate and hydroxyl functionality in combination with a dual-cure crosslinker that possessed acrylate and polyisocyanate functionality. This system was a 2K system. Due to the Xe lamp wavelength occurring around 480 nm, the use of a bis-acylphosphine oxide photoinitiator was specified for this use. Cure was done by using 10 to 20 flashes at 20 °C.

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My recent keynote presentation on megatrends given at the Paintistanbul Turkcoat Congress generated significant interest in electric vehicles (EV) as a driver for coating innovations. Given that every major automobile manufacturer has announced plans for conversion to electric vehicles in the next decade and global sales of new EVs are rising significantly, it is no surprise this market represents new opportunities for growth.

While the net number of cars being sold may stay relatively constant, the coating types per vehicle will grow based on the increased number of EV components per unit that require coatings. For example, there are at least 100 more electronic control units per EV than found in gas-powered cars.

While each model may look different, the overall design of an EV has three basic areas where coatings are useful:

• Battery packs
• Power conversion components
• Electric drive systems

Each manufacturer has its own battery pack design, with a unique set of needs and challenges. Regardless of the construction of the pack, they all need fire protection, corrosion and impact protection, temperature management and electrical shielding.

Temperature control is essential to maintaining battery efficiency and durability over time. Innovative thermal management coatings can provide a partial solution by helping to control temperatures, whether they are too hot or too cold.

Battery packs also require protection from electromagnetic interference. Coatings with dielectric properties can help prevent arcing between metal parts. Intumescent coatings may protect from fire damage if batteries fail, overload and start a fire. The battery pack environment contains polyelectolytes that requires coatings that resist corrosion. EVs are also designed with hundreds of sensors, all of which need protection from wear. Clear protective coatings can be used but they cannot diminish signal tranfer.

In addition to the EV itself, developments in autonomous-
vehicle technology have demonstrated the need for road improvements, particularly in the requirement for consistent, easily visible pavement markings. If not properly marked, it is harder for an autonomous vehicle to know exactly where they are on the road. Here, coating manufacturers can play a role in providing traffic paints that can potentially communicate with the EV. Photonic pigments can be added to coatings to help provide guidance on road postion. Thus, smart traffic coatings can be formulated to help talk to the EV.

Autonomous vehicles are also programmed to read road signs. Similarly, coatings that contain NIR transparent or reflective functional pigments can deliver a signal response back to the EV and improve object recognition. Several pigment manufacturers already have products available for this purpose.

Obviously, the coatings industry has been serving the automotive market since the introduction of the Ford Model-T. Many traditional coatings used today can be used on electric vehicles. But EVs represent a major engineering pivot from mechanically driven to chemically driven vehicles. As climate change pushes further regulatory changes to reduce fossil fuels, electric vehicles will eventually dominate the market. This requires the coatings industry to respond quickly with new products and innovations to address the needs of electric vehicles and their vastly different architecture.

Car buyers around the world prefer neutral colors by a large margin and have done so many years. That trend is expected to persist for the next several years as well, although colors should make a small comeback.

Of all possible color choices, white predominates in the global vehicle market and holds a 38% share. The four neutral shades—white, black (19%), gray (15%), and silver (9%)—made their way onto 81% of vehicles produced in 2020, according to Axalta’s 68^th Global Automotive Color Popularity Report. Meanwhile, colored shades such as blue, red, brown/beige, yellow/gold, and green each accounted for less than 10%: 7%, 5%, 3%, 2%, and 1%, respectively. These statistics are based on Axalta’s analysis of 2020 automotive build data and are an indicator of current market trends, notes Nancy Lockhart, global product manager of color at Axalta.

Within the neutral shades, one shift of note identified by the Axalta report is the increase in popularity of gray, which is now perceived as being more modern and luxurious, at the expense of silver. PPG, in fact, forecasts that gray will remain a popular core color for automotive stylists moving forward, driven by the resurgence of concrete and stone materials and the on-going appeal of ceramic and metal tones, according to Misty Yeomans, PPG color styling manager, Americas. The gray palette will shift toward warmer hues with brown influences, while blue-inflected grays will retain their fashionability. The influence from nature will be apparent in silver stylings moving forward as well.

“Warmer and more organic tones will further reflect current consumer tastes while also aligning with the highly compatible nature of very light tones, including whites, and with new radar and LiDAR technologies,” she says.

White remains the top color for not only due to consumer preferences, but also the move toward autonomous driving technologies. Within the white space, demand was up in Asia-Pacific market but slightly down in South America, according to PPG’s 2020 automotive color popularity report.

In North America, there was particularly strong growth in white metallics within the luxury car segment (21% to 38%). In addition to being highly compatible with emerging radar and LiDAR technologies that enable self-driving vehicles, white colors reflect consumers’ desire for refined simplicity and versatility in turbulent times, according to Yeomans.

“In addition to the pearl and metallic whites that are already widely popular, we anticipate a new dimension of white stylings in the automotive market that create a warm, sophisticated feel, such as creamy shades of ivory or bone-colored tints and ceramic effects,” she observes.

Potenial solutions for keeping cars cool and making them visible to LIDAR technology are based on combining organic pigments with NIR reflectors, such as inorganic pigments or aluminum, and avoiding carbon black, adds Bernhard Stengel-Rutkowski, senior global technical marketing manager at Clariant.

Demand for black vehicles remained steady in 2020 compared with 2019, as the color remained a common choice due to its versatility and dramatic design potential, according to Yeomans.

“Effects and finishes that incorporate black tones allow for artistic reveals in the way color shifts, highlighting hidden undertones and adding a dramatic flair to the possibilities provided by the new pigments and finishes being developed within this color family,” she says.

Increasing interest in shades of blue was a key influence in developing Axalta’s 2019 Global Automotive Color of the Year, Sea Glass, which is a turquoise blue color. In PPG’s 2020 automotive color popularity report, blue accounted for a slightly higher percentage of vehicles than identified by Axalta—9%, which was up 1% from the previous year and reinforced the company’s 2019 automotive color forecast, which anticipated that sales of blue automobiles would increase over the next four years. Most of this growth occurred in Asia-Pacific markets; 10% of North American vehicles are already blue.

Yeomans says she believes the COVID-19 pandemic will further fuel global preference for the color.

“COVID-19 has consumers focusing on their desires and priorities,” she says. “Blue is an optimistic, comforting color that conveys trust, dependability, confidence, healing and hope. It’s also associated with nature, cleanliness and future-forward technology.”

She adds that more vivid or desaturated shades, deep-sea luxury tones and hues with a slight turquoise influence are expected to emerge, including digital-inspired aqua-blues that combine versatility with a sense of youthfulness and a fresh spirit. The emergence of the electric vehicle (EV) market will also drive growth in vibrant tones and interesting effects, such as color-shifting colors.

After two decades of focus on achromatic colors, Clariant has also observed a global color megatrend towards chromatic shades that stand out and add more color, according to Stengel-Rutkowski.

“Just like the auto industry that is currently reinventing itself and developing a more optimistic and sustainable image, these shades exhibit vibrant freshness and surprising color changes. These types of shades serve as an additional motivation for drivers to experiment with new forms of mobility themselves,” he notes.

Even so, there are some challenges to overcome, such as formulating bright yellow or red solid shades that hide well. Clariant offers “pseudosolids” formulations that contain aluminum flakes to afford solid-looking shades. Colored aluminum flakes and their combinations with bright mineral flakes supplemented by organic pigments, meanwhile, can be used to create formulations with attractive “color travel” properties, Stengel-Rutkowski says.

He adds that tinted clears can be used to produce very bright shades possessing “false-fluorescence” and are also being applied as highly transparent second layers to increase the depth of sparkle of the base layer or create a pearl effect, providing unique colors that support innovation in the automotive industry.

These trends are also reflected in the new 2020-2021 Automotive Color Trends collection from BASF. Called CODE-X, the collection includes new, reimagined whites, the darkest of jet blacks, and a variety of vibrant color spaces in-between and serves as inspiration to automotive designers for vehicles that will be on the road in three to five years, according to the company. Many have effects or textures, providing tactile as well as visual and emotional experiences.

The three key global colors are Social Camouflage, a grayish-green; Pundits Solution, a warmer beige; and Dark Seltzer, a medium-dark gray. As new thinking drives big transitions in the values around society, identity and progress, this collection represents the blend of the physical and digital worlds to stay hopeful and positive while coping with change, the company says.

For the European region, BASF’s automotive color collection includes soothing, calming colors with bold, new, distinct positions that bring the familiar together with the new and different, according to Mark Gutjahr, head of Automotive Color Design, EMEA at BASF. The warm and emotional colors in the Asia Pacific collection reflect a positive, flexible attitude for change, action and the future.

“Individuality is the trend in play here. We live for today and want to make the future better,” said Chiharu Matsuhara, head of design, Asia Pacific or BASF. In North America, the color collection leverages new colorant technologies that exhibit a greater sensitivity to the environment combined with grace and simplicity.

“It’s not unusual to presuppose technological stewardship dominates research, but it’s refreshing to see just how much the consumer is willing to forego traditional norms of beauty in order to satisfy the hunger for smart and responsible color designs,” says Paul Czornij, BASF’s head of design in the Americas.

The future landscape of automotive color continues to change as vehicle and consumer preferences evolve, Lockhart stresses. “Some key drivers for that evolution are more obvious than others, such as ecommerce, generational preferences, fashion styles and social currents. The mobility sector is very dynamic, and the evolution of technology and mobility platforms will change how people live,” she says. “Coatings technology has been challenged to not only be durable and aesthetically on trend, but also functional in the role it plays with autonomous vehicle driving sensors.”

There are also, however, environmental and economic requirements, as well as technical developments, that have considerable influence on the color palettes which will appear in the model years 2021 to 2023, according to Rutkowski.

“The car industry is currently going through a phase of transition, exploring alternatives to the traditional combustion engine, and trying out new ways of improving the safety and efficiency of transportation. These innovations can enhance both the creativity and feasibility of automotive color designs,” he concludes.

By D.H. Campbell, BASF Corporation; G. Singh, Magna International; Prasanna Kondapalli, BASF Corporation; Cindy Peters, Ford Motor Company; and Jacob Dumbleton, Nissan North America

Achieving Class A appearance over fiber-reinforced substrates can be challenging. We discuss the evolving measurements used to characterize topcoated surface appearance. The influence of carbon fiber on the surface appearance of a thermoplastic resin-transfer-molding (RTM) substrate is related to differences in thermal expansion within the substrate.

The mechanism identified here is then extended to several chopped-fiber-filled thermoplastic substrates where the fiber-mapping effect is manifested in a different manner. We then investigate the influence of thick-film applications to the Class A surface on appearance. Our analysis finds that both the depth and the width or wavelength of the substrate affect the ability of the thick films to cover fiber mapping.

INTRODUCTION

Fiber-reinforced exterior automotive body panels are receiving increased interest due to light-weighting activities in the automotive industry. In addition to meeting their requirements for stiffness, weight, and cost, exterior automotive body panels must also be capable of providing excellent appearance as a painted part. This is often referred to as “Class A appearance” within the industry, and it is a requirement that proves to be a challenge.

CLASS A APPEARANCE DEFINED AND MEASURED

Class A appearance is a visible test that requires that the surface of the panel after painting be smooth and free from defects. The smoothness is now measured instrumentally to define the smoothness more precisely. The requirement to be free of defects is still evaluated visually.

A good example where the fiber-reinforced substrate has influenced paint defects is sheet-molding compound (SMC). Fiber protrusion and porosity in SMC panels have long been known to cause solvent and air release during the baking of the topcoat, which results in small boiling defects. Such parts could not be sold, and SMC coating processes frequently had rejection rates of 20-40% due to this defect alone.¹ Another common defect is de-wetting or cratering due to mold-release agents². These defects and their solutions are better understood, so this article will not address these further.

The smoothness requirement is always assessed via the light reflected from the surface after the topcoating. Visually, the observer will judge the quality of the images reflected from the surface. These reflected images are distorted by any waviness or diffuse reflection from the surface. Many factors can influence surface waviness, including both the quality of the substrate and the coating itself. Due to this complexity, the waviness itself is usually composed of many wavelengths superimposed upon one another. Fortunately, we now have instruments such as the BYK Wavescan® that can measure the complex reflected-wave pattern and deconvolute this into its constituent wave packets of varying amplitudes.

Although the Wavescan uses visible light reflection from the surface, the wavelengths reported refer to those of the coating surface structure and not to those of the electromagnetic radiation that is reflected. This concept is represented in Figure 1 where the individual wave packets Wa-We are shown along with their corresponding wavelengths.

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��References

1. Kia, Hamid G.; Shah, Bhavesh; Wathen, Terrence J.; Mitchell, Harry A.; Berger, Christina R. Powder Priming of SMC,��Journal of Composite Materials.��2006, vol. 40, no. 16, 1413-1429.
2. Florio, John; Miller, Daniel.��Handbook of Coating Additives; Marcel Dekker: New York, 2004; p 328.
3. Neitzel, M.; Blinzler, M.; Edelmann, K.; Hoecker, F.��Polymer Composites.��2000, vol. 21, no. 4, 630-635.
4. Noordegraaf, D. A.; Nuss, R. Lightweight High Stiffness Composites Having a Class A Surface Finish, WO2009 147633 A1.
5. Beyl, N. Carbon fiber-polyurethane composites produces class A finish,��Plastics Today, Oct 16, 2013.
6. Warta, H.; Faerber, P. Fiber-Reinforced Shaped Articles with Painted Surfaces and Process for their Production, EP2643394 B1.

COATINGSTECH JUNE 2021 | Vol. 18, no. 6

The Spanish car maker SEAT has taken this concept to the next level with its wellness center for cars. Located at SEAT’s production site in Martorell, near Barcelona, Spain, the wellness center includes nine “immersion pools” for preparation and corrosion pretreatment of car bodies and spray booths with pressure jets for paint application. “Every car body undergoes a beauty ritual in the paint area to ensure the best color outcome before taking to the road,” says Javier Pérez, the head of Paints at SEAT.

The first part of the beauty treatment involves repeated washing and rinsing in the immersion area to clean the metal of the car body. Sealants are then applied that prevent corrosion by reducing the risk of water infiltration and contribute to noise reduction in the vehicle cabin via sound dampening. Each car is then painted using pressurized jets that apply approximately 2.5 kg of coating/car. Some models offered by SEAT have nearly 70 possible color combinations, allowing for sophisticated customization. A combination of robots and skilled technicians make sure the right paint formulations are applied in the right areas of the vehicle at the right time. After each treatment in the immersion baths and the other areas of SEAT’s “spa,” drying and setting processes (curing) are performed in one of six ovens at temperatures varying from 45–180 °C for 30–35 min.

The last step is “chromotherapy” in which the vehicle slides through a scanner and no fewer than 50,568 photos are taken in 43 seconds by 28 cameras that capture 42 images/sec. The collected data is used to evaluate the bodywork to within one millimeter and make for any flaws or imperfections. Overall, each car is pampered by 1,100 workers and 200 robots for six hours, according to Pérez. After their visit to the wellness center, vehicles head off to the showroom.

The automotive industry is undergoing a significant transformation. Conventional internal combustion engines (ICEs) are being replaced by batteries in electric vehicles (EVs), and drivers will ultimately become passengers in autonomous vehicles (AVs). Coatings have an important role to play in making these new technologies possible. Beyond their traditional jobs of protecting automobile components from corrosion, abrasion, and ultraviolet (UV) degradation and providing a unique and striking appearance, automotive coatings are already providing additional functionality. This includes soft-touch and sound-dampening interior surfaces and self-healing and easy-to-clean exterior surfaces. Additional performance capabilities are being achieved on a continual basis, with some technologies adopted from other industrial applications and others developed specifically to meet the needs of the evolving automotive sector.

The future of the automotive industry will be heavily dependent on electric and hybrid vehicles, as well as autonomous vehicles, according to Christopher M. Seubert, research engineer in the Paint and Coatings Research group at the Ford Research and Innovation Center. “As we look at the current industry transformation, the focus is on CASE solutions—connected, autonomous, shared, and electrified,” adds Peter Votruba-Drzal, global technical director for PPG. As companies explore connected and autonomous vehicles and new, alternative powertrains, coatings need to be adapted to meet these needs, asserts David Cranfill, BASF technical director for OEMs.

Energy Conservation Crucial for Electric/Hybrid Vehicles

Electric and hybrid vehicles are already here today and are expected to represent an increasingly large proportion of the global fleet going forward. Hybrid and EVs, however, carry a higher price tag than ICE vehicles. To make the case for EVs and hybrids more compelling to consumers, car makers are focused on maximizing range and fuel efficiency. As such, Seubert notes that energy conservation is very important, and the cooling of a hot vehicle using air conditioning is a very energy-intensive process. In addition to contributing personality and style, coatings, when applied to EVs and hybrids, will help handle the heat management requirements around batteries and electric motors, according to Cranfill. “External coatings with infrared-reflective pigments will keep the cabin cooler to reduce the need for extra energy to power air conditioning. That lets the electric car go farther on a single charge,” he says. Of particular interest are darker pigments that can increase the total solar reflectivity (TSR) of the exterior paint system, such as those that can provide black jetness similar to that achieved from standard carbon black pigments, adds Seubert.

We expect automakers to ask for more deeply saturated colors to help them claim their place in the market.

Development of advanced reflective coatings must, in fact, be achieved while meeting consumer expectations for color and overall appearance. Carmakers follow color trends very closely, looking to industries such as fashion and interior design to determine the options that should be developed, explains Paul Czornij, BASF design manager in charge of colors and trends. “Each year, BASF creates 65 novel and innovative designs to capture color trends that may be seen on the road three to five model years in the future. We expect automakers to ask for more deeply saturated colors—like rich blues—to help them claim their place in the market. Developments in pigments and dispersions are making those new chromatic colors possible. In addition, BASF sees the flip-flop color travel in metallic shades to be more eye-catching, playful, and evocative. A car’s character lines and body style become even more expressive with these colors,” he says.

There are somewhere on the order of two to four times the coating opportunities in EVs compared to conventional combustion engine vehicles.

Under the hood of these electric and hybrid vehicles are other opportunities for the coatings industry, according to Michael T. Venturini, marketing director for Coatings at Sun Chemical. Three examples include thermally conductive coatings, fluids for battery pack control, and coatings that insulate the yards of wires and cables required in these cars. “We believe that there are somewhere on the order of two to four times the coating opportunities in EVs compared to conventional combustion engine vehicles,” agrees Votruba-Drzal. New coatings, adhesives, and sealants will be needed to provide functional performance in the powertrain, such as dielectric coatings that provide electrical resistance and thermal conductivity, and to ensure long-term battery cycle performance. Thermal control systems that help moderate the temperature at the interfaces between the battery systems and battery management system rely on coating and adhesive technologies as well. The need to seal and protect battery packs provides opportunities for fire protection materials, too. For this solution, PPG is leveraging expertise developed in its protective and marine coatings business, including passive fire protection (intumescent) coating technology.

Several sustainability trends continue to drive market innovation, including low-temperature cure and integrated processes to compress the paint shop footprint and reduce energy usage.

Coatings that protect against electromagnetic interference are needed to shield electronics used in vehicle communication systems from the large magnetic field generated by vehicle battery packs, according to Votruba-Drzal. Positive temperature coefficient coatings, meanwhile, offer creative solutions when there is no large heat source available from an internal combustion engine. These coatings can be deposited in a pattern on surfaces, such as seats, door panels, and floors, enabling localized heat when a current is applied. Thermoelectric coatings, meanwhile, take advantage of temperature differences generated all over electric cars, from the sun on the vehicle panels, inside the cabin, to motor parts and electrical batteries—and can generate electric current. “While flexible thermoelectric materials and coatings are at their early stages, if these coatings are low-cost, there could be an opportunity to use them to generate an electrical current for the vehicle,” Venturini explains.��

Coating manufacturers are also challenged by the use of thick metal sections in EVs and hybrids to not only support the heavy battery systems but also to protect them from collision. These sections have significant thermal mass, and it takes a lot of energy and time in the oven to heat these sections to traditional cure temperatures (140°C). Formulators are actively developing coatings that cure at lower temperatures, allowing the use of existing oven configurations while reducing energy consumption and CO₂��emissions, and increasing efficiency and productivity, according to Votruba-Drzal. “With these new coating systems, it is possible to use existing wet-on-wet and other compact approaches,” he comments.

Mixed Substrates Are Becoming the Norm

Lightweighting of EV and hybrid structural components is another approach to energy conservation. Many new and dissimilar materials are being used to assemble these vehicles to allow for the incorporation of heavy battery packs. All newer vehicles, regardless of the powertrain, are, in fact, being constructed of lighter-weight materials to achieve better fuel economy. The goal, according to Todd Coggins, technical manager Surface Treatment Processes—Metal Pretreatment with Henkel Corporation, is to reduce car weights by 10% and to drive efficiency improvements of five to eight percent. The use of lighter-weight metals and various types of composites is increasing dramatically. “Dissimilar metals and composites cannot be joined using traditional spot welding; however, structural bonding and reinforcement, as well as noise vibration reduction, must be achieved using novel adhesives and sealants,” Votruba-Drzal observes.

Coating systems must also now be formulated with the ability to adhere to these very different substrates—as well as provide solar reflectivity, corrosion protection, and the desired appearance—at the same time as these systems are becoming thinner and designed with fewer layers. “As automakers change their products, coatings will have to adapt,” asserts Sean McKeon, BASF vice president of Global Key Account Management. “New coatings will need to resist corrosion more than ever, while reducing overall waste and cost,” he adds. There is also a desire to reduce the temperature required to cure exterior coating systems used on these vehicles, because many of the new substrates cannot survive the current cure temperatures. BASF, for instance, has developed coating systems with reduced cure requirements that allow the OEMs to utilize one paint system to paint the entire mixed-substrate vehicle,” McKeon says.

Surface treatment coatings are also very important for newer vehicles manufactured using more lightweight metals. Three types of lightweight coating pretreatments are available, according to Coggins: electro-ceramic coatings, zirconium coatings, and titanium bases. “Battery-heavy and electric vehicle coatings require the lightweighting that aluminum and magnesium offer while still benefiting from corrosion protection and the excellent base they establish for adhesives and paints,” he says. He notes that the biggest challenge that these coatings must overcome is the inconsistent surface cleaning and de-oxidizing observed for the different lightweight metals used today. “A key focus at Henkel, therefore, is the development of coating technologies that keep pushing the boundaries of providing uniform surfaces prior to coating,” Coggins notes. He also says that Henkel is consistently investigating new additives for performance and durability leveraging various sustainable sources.

One example of a new offering is the company’s electro-ceramic coatings, which are produced using a patented plasma deposition process. To date, zirconium coatings and titanium bases have experienced the widest adoption because they have been around the longest, are the least expensive to use, and the production part approval process is available online, according to Therese Niemi, technical manager Surface Treatment Processes—Light Metal Pretreatment with Henkel Corporation. Electro-ceramic coating, she says, offers outstanding features of corrosion protection, friction reduction, heat resistance, and it provides an excellent base for paint, adhesives, and coatings. It is designed specifically to be applied to aluminum, magnesium, and titanium.

Sensor Challenges for Autonomous Vehicles

It is expected that AVs will be used 24 hours a day, 7 days a week, unless repairs or maintenance are needed, to haul both people and products/goods, according to Seubert. “At this usage rate, the realistic lifetime of these vehicles is three to five years,” he notes.

While AVs are further out on the development timeline, they have their own set of coatings challenges, most notably related to supporting the uninterrupted transfer of data between the computer driver, sensors, and the communication system. Three main types of sensors are employed on AVs: cameras, light detection and ranging (LIDAR), and radio detection and ranging (RADAR) systems. “Coatings will have to reflect LIDAR, not interfere with RADAR, and interact seamlessly with various autonomous sensors, adding to the reliability of the entire transportation ecosystem,” says Cranfill. When selecting a pigment for AVs, therefore, the reflective signature of the pigment in relationship to the wavelengths being used by the detectors is important. “It is necessary to understand these parameters. Finding the right balance of coating reflectivity, transparency, and absorption, and how they each affect signal strength will be an area of ongoing material research,” states Venturini. This need is driving innovation within the industry to formulate coatings that are compatible with the sensors, but stay within the desired color space, according to Cranfill.

The use of lighter-weight metals and
various types of composites is increasing dramatically. . . . the biggest challenge that these coatings must overcome is the inconsistent surface cleaning and de-oxidizing observed for the different lightweight metals used today.

The lenses themselves for cameras and LIDAR units must be kept sufficiently clean and transparent to collect needed data. While these lenses are often glass, they can be made of polycarbonate or other optically suitable substrates. “Coatings are required for camera and LIDAR lenses that not only resist the deposition of dirt, but also facilitate the easy removal of that dirt via air or cleaning fluid spray,” Seubert observes. “While easy-clean coatings exist, most are used in applications with minimal outdoor exposure, and many of the coatings that have been examined at this time do not have the ability to retain their hydrophobic and transmissive properties (anti-reflectivity and optical clarity) for even just three years in service,” he adds. Coatings for LIDAR lenses must also have a very uniform thickness to prevent any scattering or refraction of the sensor beams, according to Seubert. PPG is leveraging technologies developed for its other business units, most notably industrial and aerospace applications. “We are developing anti-glare, anti-scratch, and easy-to-clean systems that enable optical sensors on AVs to remain operating with high visibility, even in challenging environments, including snow, sleet, rain, and bug buildup,” Votruba-Drzal says.

Laser-based LIDAR units are also affected by the reflectivity of the substrates they are intended to detect. Darker colors absorb the wavelength (905 nm) commonly used for these systems, making these objects difficult for the LIDAR to “see,” while silver coatings have a high reflective signal. To increase visibility, therefore, coating manufacturers are turning to near-infrared reflective (NIR) technology initially developed for the aerospace and building industries. These coatings keep airplanes cool when parked at the gate to reduce fuel demand. “In LIDAR applications, incorporation of NIR pigments into coatings can dramatically increase the reflectivity of dark colors, even to the point where black reflects similarly to white,” observes Votruba-Drzal. He also comments that the enhanced reflectivity of the vehicle improves the reliability of LIDAR sensors in inclement weather and challenging light conditions.

BASF, for instance, has developed Centripetal Blue, a blue-black color with a medium-coarse sparkle that addresses NIR reflectivity challenges, according to Czornij. The pigment technology is used in the company’s LIDAR-detectable coatings, which include a LIDAR-reflective layer that reflects NIR radiation back to its point of origin for calculation of distance and mapping of the environment

RADAR sensors do not present the same cleanliness/clarity issues that LIDAR units and cameras do. There is, however, a push to locate them behind solid parts, such as bumper fascia, to hide them from view. These locations, however,�� require the radio waves to pass through the fascia substrate, as well as the front paint system. Even so, it is imperative that the single intensity of the emitted and returned signal does not attenuate so much that detection distance or fidelity is compromised, according to Seubert. “Bumper fascia and coatings must, therefore, be formulated and applied such that the RADAR signal does not significantly diminish during operation,” he explains. Metallic pigments in the basecoat are the greatest concern, because they can cause significant attenuation, and thus currently OEMs are limiting the quantities of aluminum and other metallic flakes contained within paint systems used on AVs, Seubert notes.

Coating systems must also now be formulated with the ability to adhere to these very different substrates—as well as provide solar reflectivity, corrosion protection, and the desired appearance.

Ultimately, the biggest challenge to developing coating technologies for autonomous vehicles is the fact that the performance targets are still unknown for both the sensors themselves and the coatings used on them, according to Seubert. “Both technology and design continue to change, and the coatings used on these sensors must also adapt to those changes. In addition, the government has yet to decide what, if any, requirements and restrictions to implement on AVs and the sensors/materials used. Without industry-wide or governmental requirements, each AV manufacturer will continue to develop their AV platforms to the best of their abilities,” he explains.

Connected and Shared Opportunities

In the connected vehicle space, PPG has observed an exponential increase in the number of antennas and communication inputs to vehicles. There is growing interest, notes Votruba-Drzal, in the use of conductive coatings to form patterns that serve as RFID antennas. “Using conductive inks and coatings makes it possible to print an antenna into the configuration of the car,” he notes. Venturini stresses, again, that for antennas and sensors placed behind body panels, the coatings cannot have obstructive properties that could interfere with the antenna/sensor technology. “For instance,” he notes, “metallic effect pigments may interfere with certain wavelengths, while pearlescent pigments are less obstructive. The former may, therefore, find higher usage in vehicle coloration as vehicle-to-vehicle communication becomes more widespread.”

Shared riding—and semiautonomous and autonomous vehicles as well—will affect coatings used in vehicle interiors. The focus in these cases will be less about the driver experience and more about the passenger experience, according to Votruba-Drzal. A host of coating opportunities are emerging as a result. “Much larger touch screens for vehicle displays and the coatings used on personal consumer electronic products—anti-glare, anti-scratch, anti-fingerprint—will need to be translated to vehicles. There will also be more functional surfaces within car interiors that will require tactile coatings that impart tactile functionalities, such as soft-touch or low-friction slippery-feel surfaces. Many surfaces—think shiny dark dashboards—could also benefit from self-cleaning and/or anti-fingerprint coating technologies. Electronics embedded into the interior structure of the vehicle that are touch-enabled will also play a big role in future vehicles,” he explains.

In LIDAR applications, incorporation of NIR pigments into coatings can dramatically increase the reflectivity of dark colors,
even to the point where black reflects similarly to white. . . . The enhanced reflectivity of the vehicle improves the reliability of LIDAR sensors in inclement weather and challenging light conditions.

Liquid-applied sound damping (LASD) and liquid-applied sound barrier (LASB) technologies are also emerging as major trends in the automotive industry as alternatives to traditional methods used to both protect components from damage and premature wear and to lessen unwanted noise experienced by drivers and passengers inside the cabin, according to Akbar Hussaini, technical specialist for LASD and NVH Coatings at BASF. “Traditional methods are often unwieldy and time-consuming to install, requiring the use of heavy pads or foams, and LASD/LASB methods have proven to help automakers dramatically reduce weight, labor, and material costs,” he observes. While the two technologies are applied by a similar spray technique and provide similar benefits, they have distinct properties that make them ideal for use in different parts of the vehicle. LASD is used primarily in vibration damping, which isolates structural noise (low frequency, usually 0–1000 Hz), and occasionally in barrier treatment. LASB is used primarily in barrier treatment, to block the transmission of airborne noise (higher frequency, 1000+ Hz), and occasionally in sound absorption. “Therefore,” Hussaini says, “LASD technology is applied to metal parts as an alternative to traditional asphaltic or butyl die cut pads on the bottom of the vehicle, while LASB technology is designed for nonmetal surfaces like PET or shoddy fiber found behind the instrument panel.” LASD and LASB technologies can also provide some benefits in lightweighting, as traditional methods have limitations in film thickness.

LASD and LASB technologies are examples of the BASF strategy to move beyond paint to the entire spectrum of surface solutions. “We treat various types of surfaces that require specific properties: we color them, we protect them, and we make them functional,” says McKeon. “Functional coatings will be an important enabler as the industry adopts driver assist and autonomous driving technologies,” he predicts. There is, in fact, adds Seubert, always a desire for coatings to do more than just “look good.” Ultimately, however, “when it comes to any new coating technology, durability and cost are the biggest challenges to implementation. The coatings used on standard vehicles must last 10 years in service, which is not a trivial performance target to meet,” he adds.

Growing Popularity of Contrast-Color Canopies

Two-tone styling has become increasingly popular and has moved from side panels and striping to vehicle rooftops. The latest trend in car styling is contrast-color canopies in which the roof of the car is a different color than the body. “This design trend has taken off quickly. There is always a push to differentiate the look of vehicles, and contrast-color canopies is one of the latest ways to achieve that goal,” Seubert says. It poses application problems, however. Painting the roof or canopy a different color is not easy. It typically requires the vehicle to be sent through the topcoat process twice, with significant masking labor needed to paint just the roof. The result, notes Votruba-Drzal, is reduction of production capacity.

Much larger touch screens for vehicle displays and the coatings used on personal consumer electronic products—
anti-glare, anti-scratch, anti-fingerprint—will need to be translated to vehicles.

“One potential solution is to use paint replacement films on the roof, but this process is very time-intensive and cannot be used for high-volume applications. Ultimately, I don’t think material changes to the coatings alone can help. New automation to either allow precise color and paint application or to accelerate the masking process is what is really needed to help implement this design at high volumes,” Seubert says. Indeed, Votruba-Drzal notes that a number of OEMs are working to increase the transfer efficiency process for application of the contrast color on a horizontal surface. Toyota, for instance, presented a new bell atomization technology at an industry conference in 2019 that is reported to allow for much more locally controlled delivery of the paint and an increase in the transfer efficiency to greater than 95%.¹ “There is a recognition by paint shops that the use of robotics that can apply paint with high precision, [which] should make it possible to perform two-tone applications inline, and dramatically increase throughput,” Votruba-Drzal says. He adds that there is an environmental benefit as well, because more efficient delivery of paint dramatically reduces the amount of energy required, not only for atomization, but also for overspray collection.

Sustainability Continues to Be at the Forefront

Several sustainability trends continue to drive market innovation, including low-temperature cure and integrated processes to compress the paint shop footprint and reduce energy usage, according to Cranfill. Governments around the world also continue to establish new standards for lower VOCs. “There is always a push to make the paint process more environmentally friendly, be it through new materials (low-temperature cure), different curing technologies (UV/EB), new automation, or new sources of resins and solvents,” adds Seubert. Any new technology, though, must meet durability requirements and have an acceptable cost of implementation.

In fact, the need to satisfy longer ownerships will increase the length of warranties, according to Venturini. “We are already seeing warranties significantly increase from even just a few years ago. This is simply because engines are lasting longer, and part design has gotten better. Electric vehicles are going to continue to push that with extreme longevity as electric motors don’t wear out as quickly as internal combustion engines and transmissions,” he says. Coating technologies will continue to advance as well, he adds. “Anti-corrosion and protective technologies that are both lightweight and environmentally friendly, such as waterborne, powder technologies, and heavy-metal-free alternatives, are the strongest areas for future development. Interior coatings for seating and touch points are also being influenced by longer ownerships and even the shared vehicle economy. “With coatings being applied in more complicated painting processes and layers, while meeting the criteria of the autonomous vehicles, connected vehicles, and longer-life vehicles, the worlds of pigments and resins are now overlapping more than ever. The combination of the two is what will drive development and innovation through the next decade,” Venturini asserts.

Many Design Concepts

That overlap is reflected in BASF’s most recent trend predictions, which Czornij says aim to visually relate to the new technology focus in the automotive market and reflect responsibility for the environment. “New coatings containing materials from renewable resources while minimizing environmental impact and carbon footprint will help automakers connect with this part of their consumer base,” he says. PPG is energized by the opportunity to leverage specialized coating technologies developed for other businesses in the automotive market. “What is most exciting is that concepts are evolving very rapidly, with new groups within the OEM trying to understand what they need to create brand recognition and value in the future as the industry moves away from the size and power of the engine as the defining factor to autonomous, connected, electrified vehicles,” Votruba-Drzal says.

In fact, the greatest difficulty may be the large number of possible design concepts. “With so many opportunities, it is essential to understand the risks associated with each in order to determine which ones to focus on,” he concludes. Clearly, it is a challenge the coatings industry welcomes.

Reference

1.  SURCAR, June 2019, Cannes, France.

CoatingsTech | Vol. 17, No. 4 | April 2020

Positively Trending Market

Estimates for the size of the heavy-duty transportation coating market vary depending on the definition of the market and the classes of vehicles included in the category. They generally fall in the range of 5–15% of the overall transportation market. In 2019, the value of the North American heavy-duty transportation coatings market, including coatings for heavy and medium trucks, specialty trailers, truck trailers, specialty truck bodies, buses, recreational vehicles (RVs), and emergency vehicles, was estimated by market research firm Kusumgar, Nerlfi, & Growney to be $594 million, according to principle consultant Steven Nerlfi (see Table 1).

The ChemQuest Group pegs the value of the North American market for heavy-duty transportation coatings, including heavy-duty trucks, buses, and RVs but excluding agricultural and construction machinery and equipment (ACE) at $291 million in 2018 and expanding at a compound annual growth rate of 2.2% on a volume basis and 2.5% on a value basis, according to senior consultant Daniel R. Daley. The average selling prices, he notes, is $34.60 (five-year growth on price forecasted: 0.3%).

“In the United States, the current state of the market for heavy-duty vehicles is trending positive,” asserts Dan Weinmann, market development manager, Epoxy Specialties, Hexion. “There is growth in the United States due to improving economic conditions driven by the tax incentives and increased demand for heavy-duty vehicles that meet the lower emission standards implemented in 2017,” he adds. Strong demand in the trucking industry and spending in public transportation linked to urbanization have driven recent growth, according to Eric Dumain, global marketing director for Coating Resins with Arkema. The forecast for new vehicle builds remains strong, adds Eric Casebolt, market development manager, Eastman, due to increased infrastructure and construction projects and the continued proliferation of the e-commerce industry. “We expect to see growth slightly above GDP (3–4%) on a global basis for the next few years,” he notes. Dumain does note, however, that the ACE market has been flat, and the global heavy-duty vehicle coatings market has been growing more slowly in recent years due to uneven growth in the agricultural, oil, and gas segments.

The overall outlook for the state of the market continues to be healthy, however. “In most developed countries right now, demand for hauling freight is high, drivers are earning record wages, and in general the industry is undersupplied, so overall demand in the sector is high and expected to remain that way for the coming years,” says Hans Schellekens, allnex’s marketing manager Automotive. Transportation coatings are also a growing segment because manufacturers are looking for cost-effective methods for protecting their equipment during shipping and storage, according to Markus Bieber, VP of Integrated Solutions at Cortec. Evolving technology will provide economical coatings that can easily adhere to multiple substrates and offer enhanced corrosion protection against aggressive environments, agrees Avinash Bhaskar, transportation coatings segment manager at BASF.

Sustainability, Durability, and Efficiency Are Key Drivers

Three key trends have developed in heavy-duty transportation coatings over the last several years: the need for more sustainability to meet both regulatory requirements and customer expectations, demand for higher performance in the form of greater durability across many performance properties, and the desire for coatings that serve multiple purposes.

From a regulatory perspective, no major changes in federal requirements are expected in the United States in the near future, but waterborne coatings will be mandated in China by 2020, according to Daley. As a result, for commercial vehicles in China, the trend is to use a single waterborne topcoat over an electrocoat, leading to reductions in VOCs from 48 to 17 g/m², according to Johnson Zeng, APAC marketing leader for DSM Resins and Functional Materials.

There are other drivers in the United States for moving away from solvent-based systems, Daley observes. “Waterborne systems are easier to spray with superior flow, provide better worker safety while producing less waste and enabling easier cleanup. They also offer the opportunity for brighter, more vibrant custom color options.” Daley adds that while smaller users continue to prefer solvent-based coatings, larger OEMs tend to be more sophisticated and are proactive in adopting more sustainable technologies. Separately, in Europe and possibly China, tin-free e-coat formulations may be required in the future.

As VOC regulations do tighten around the world, coating manufacturers are working very closely with OEMs to develop coating systems that will allow plants to remain compliant without sacrificing productivity, according to Geoff Webster, technical associate, Eastman. “The most common approach is to move to higher solids coatings and/or use less coating on each vehicle by improving application efficiency, but these new coating systems must maintain a high level of durability, weathering, and corrosion protection in the field,” he says. “While the heavy-duty vehicle segment is not seeing explosive growth, it is benefiting from economic drivers—using less coating material and energy per unit. This has driven coating innovations to allow for lower viscosity, faster curing products,” adds Dumain.

Weight reduction in vehicles via the introduction of lighter substrates like aluminum, magnesium, plastics, fiber reinforced composites, etc. combined with the move to water-based and high-solids coatings is also driving the need for new performance capabilities with respect to both coatings and the coating process, according to Schellekens. “Developing coatings that can adhere to multiple substrates and protect the outside surfaces of trailers and cabins against corrosion caused by road-salt and deicing agents for longer periods of time continues to be a key area of focus for formulators,” Bhaskar says. He adds that reduction of coating layers, such as a mono-coat technology, is on the wish list of fleet companies, which have to apply a coat approximately every 250,000 miles to protect the bodies of heavy-duty trucks from corrosion. Daley notes that the design life for long-haul trucks is typically 1.5 million miles, with testing out to 2.5 million miles. Powertrains are generally rebuilt at 1.0–1.5 million miles, while bodies and frames run much longer. Electrocoat and powder applications are increasing to address internal and external environmental mandates that OEMs are aiming to comply with, adds Thomas McAfee, PPG global segment manager for Transportation. “As a result,” he remarks, “e-coat��and powder are supplanting the use of liquid spray coatings, which are regarded as being less environmentally advanced.”

Toughening regulatory standards and changing environmental trends could also be coming from states such as California, where there is a push for zero-emission vehicle (ZEV) deployments. There is also significant worldwide development of next-generation powertrains and body designs to ensure vehicles meet new greenhouse gas emission standards, according to Daley. Government incentives and subsidies are driving interest in the use of alternative fuels (biodiesel, liquid natural gas, hydrogen fuel cells, etc.) and electric vehicles as well. “The electric truck market is led by Europe, with North America in a crucial growth role, while the bus market is currently dominated by Asia-Pacific. Heavy-duty trucks have a long way to go to electrify despite the splash made by certain startups (Tesla, Faraday Future, etc.).

Germany’s dynamic highway charging approach certainly shows promise, but hybrids seem to be the only viable near-term long-haul solutions. Buses and medium-duty (commercial) vehicles are better suited for conversion to hybrid and fully electric vehicles,” Daley says. He does add, however, that autonomous vehicles will be a significant market segment soon in long-haul trucking if the regulatory situation gets worked out, because it provides a more efficient driving model in any platform. Electrification is important because it would lead to significant body and chassis redesigns and major process changes. It will also impact coatings by increasing the need for extended service life, improved vehicle aesthetics, and cost-effective application solutions, Weinmann notes.

“Overall, customers expect sustainable solutions that save them time, labor, energy, and material consumption,” asserts Ewout Bosman, AkzoNobel segment manager, Commercial Vehicles & Transport. In this respect, growth of automation is an important trend, according to McAfee. “OEMs are always looking to their suppliers to help them drive down production costs or increase efficiencies. That’s why it is important to deliver technical solutions that increase throughput, extend service life, promote light-weighting and fuel efficiency, or make it less expensive to meet environmental mandates,” he states. As in the past few years, globalization remains the best path to success in these markets, according to Dumain. “With larger OEMs and transportation companies broadening their global footprint, the suppliers that can meet their local needs across multiple continents are seeing the greatest potential for growth,” he asserts.

Varying Expectations

The properties required for heavy-duty coatings depend on their specific application. Two questions must be answered first, according to Schellekens: How is the vehicle being used and where is the coating being applied? “There are many diverse needs and it is unlikely a single coating will match them all, even on the same vehicle. Parts exposed to corrosive chemicals or fertilizer require one coating, while continually moving parts may require a mix of flexibility and durability. “It is our job to work with formulators to determine what works best where,” Schellekens explains. The desire for multiple performance is driving new product development where a mix of benefits might be possible, Schellekens adds—a flexible superdurable powder resin, for example, or a corrosion-resistant coating that offers better durability. “There is no magic coating that covers them all, but we can work with formulators to produce products that meet specific needs,” he states. Adds Dumain: “When we work with a coatings developer or formulator serving these segments, we always start with their pain points—what is the primary need. While we develop binders and additives that can address multiple needs, it is always best to start with what is needed most.”

At a minimum, coatings need to be low in VOCs, environmentally friendly, and easy to apply, but also easy to remove with minimal effort, adds Bieber. Durable coatings with improved color retention and resistance to corrosion, scratches, dents, and chipping that are easy to apply and offer extended service life meet significant market needs, agrees Weinmann. As one example, he points to linings for dump trucks, which should offer decreased friction to prevent material hold-up and areas of high wear and impact combined with improved toughness and durability. There also remains strong demand for UV durability in addition to color retention and chemical and corrosion resistance. Most of the investment in R&D and technical improvements at PPG continue to be focused on corrosion resistance, according to McAfee. “If our coatings make equipment or equipment parts last longer, OEMs see that as a big win for themselves and their customers,” he says.

Coatings that can provide high gloss, reflectivity, and have strong resistance against acid-rain, de-icing agents, and bird debris are some of the technologies currently being pursued, notes Bhaskar. In addition, he says that strong adhesion with minimum surface preparation is required for coatings to adhere to substrates such as cold rolled steel, hot rolled steel, Galvanneal, and plastic substrates to help increase longevity. The coatings, which are often applied with high dry film thickness, should also not crack upon application. AkzoNobel customers today demand high aesthetic longevity and long-term asset protection, agrees Bosman. Due to the increasing demand for high-quality aesthetic finishes, there is growing expectations for greater color variety as well. “The need for fast and accurate color development is crucial, especially as customers work with a large number of suppliers, and consistency in color is essential. It is important to offer resources and tools that are easy to operate, measure accurately, and find the right color formulation

from a large color database,” he explains. AkzoNobel relies on customer-specific color references to secure traceability for each customer and related subcontractors and provide the reliability the market expects, Bosman adds.

Many Formulation Solutions

The main type of coatings used on heavy-duty vehicles include solvent-based urethanes, epoxies and acrylics, as well as water-based epoxies and electrocoats. The exact chemistry is application-specific and depends on the purpose of the vehicle and, just as importantly, where on the vehicle the coating is to be applied. A listing of different coatings used for specific applications as tracked by KNG is provided in Table 2.

By value, ChemQuest estimates that for heavy-duty trucks in North America, buses, and RVs, 61% of coatings are liquid, 12% powder, and 27% coil coatings. The research firm has different breakdowns for specific end uses compared to those identified by KNG. Based on his 30+ years at Navistar International (a truck and engine OEM), Daley estimates that most heavy- and medium-duty trucks use a 30% volume/40% value basecoat/clearcoat topcoat system and 20% volume/10% value miscellaneous epoxies and acrylics. Urethane monocoats are standard as chassis paints and in a few other applications (chassis paint is either acrylic or urethane). E-coats are predominant for truck bodies, frame rails, and many chassis and body components, Daley adds. Waterborne epoxy e-coats account for 30% volume/20% value of use, while solvent-based urethane monocoats are estimated at 20% volume/30% value. Buses use around 80% solventborne urethanes by value, including urethane monocoats, barring limited use of TSA on small applications (e.g., non-glare bus hoods). Otherwise, Daley notes that bus body primers are exclusively coil-coated epoxy or polyester, while bus frames and chassis are treated similarly to trucks.

McAfee adds that while liquid spray is still more prevalent in the United States and Canada, electrocoat or different combinations of e-coat and powder are the most commonly used coating technologies in the HDE market in China, Europe, and the Middle East.

Higher-volume truck cabs will typically start with an e-coat primer applied in an electrodeposition tank, while low-volume trucks, RVs, and buses are coil-coated, according to Daley. Some (cement mixers and other specialized applications) use stainless steel with a spray primer, he adds. Traditional processes use sequentially sprayed surfacer, basecoat/color coat, and clearcoat layers with corresponding baking steps. In particular, a primer/surfacer is common for coil-coated bodies as a filler or repair for body work damage, except on e-coat products, because UV protection is addressed with topcoats in these cases. Most, if not all, frames are now powder-coated, with some applied over e-coats for improved corrosion resistance. Powder coatings are also widely used for chassis and some interior components. Tier 1 suppliers occasionally use polyurethane dispersions (PUDs), acrylic-PUD hybrids, and other hybrid technologies. Solvent-based two-component (2K) polyurethanes dominate all topcoat applications due to their robust application properties and superior weathering characteristics. Dispersants aid in pigment dispersion, while UV absorbers help maintain the gloss and provide protection against UV damage.

There is growing use of direct-to-metal (DTM) coatings on chassis applications, eliminating the need for a primer. Wet-on-wet processes are also being incorporated into new compact and renovated process lines. Many applicators desire to use low-bake temperatures for reduced energy consumption and to accommodate lower bake tolerant plastics—predominantly TPOs, Daley notes. “We are seeing increased use of waterborne products in the applications where they can meet performance requirements. The same is true for low-temperature cure powder products,” Dumain observes. Although solventborne coatings are still the most common due to their lower cost and robust applications, Bosman notes that waterborne coatings are growing in popularity. The challenge, he notes, is that waterborne coatings typically have a much narrower application window and are sensitive to annual variations in humidity and temperature. Even so, Bieber asserts that newer technologies using waterborne thin-film coatings with corrosion inhibitor packages are replacing the older products because they are more effective, easier to use, and easier to remove without all the hazardous waste associated with solvents. “Given the continued drive towards lower VOC emissions, waterborne coatings are forecast to be the fastest growing coating type since this is preferred by stakeholders that are concerned with long-term sustainability,” Weinmann concludes.

Challenges to Overcome

The most difficult task for ingredient suppliers and coating formulators is to deliver all of the desired properties in one coating system. It is, for instance, necessary to achieve the same appearance and performance using less coating layers/processing time to��save energy and increasing efficiency, according to Zeng. “OEMs want to increase productivity by using higher solids coatings and fewer layers, but clearly would not want to sacrifice appearance or performance and risk tarnishing their brand,” adds Casebolt. Proving that new technologies can deliver productivity gains in the short-term while maintaining best-in-class performance over the long-term can take many years.

It is particularly challenging to deliver the superior corrosion resistance of a traditional epoxy coating in a waterborne system, adds Weinmann. “Solventborne coatings are typically based on solid epoxy resin solutions that are cured with a high-molecular-weight polyamide curing agent. A solventborne epoxy/polyamide binder provides fast-dry, superior corrosion resistance and superior flexibility/impact resistance.��Moving to a waterborne system may result in a coating with reduced corrosion resistance or flexibility or both, so selecting a higher-performance waterborne binder system becomes very important,” he explains.

Achieving greater durability can be difficult in cases where it is necessary for the coating to also be removable, because these two properties generally contradict one another, notes Bieber. The size of some heavy-duty vehicles poses other challenges, according to Schellekens. “The components often cannot be dipped into a cathodic electrodeposition (CED) bath or dried in an oven. The challenge is then to obtain the required corrosion resistance and chemical resistance with an air-dried coating system,” he says.

Making Progress

Both ingredient suppliers and coating formulators are working hard to meet the growing expectations of customers in the heavy-duty transportation market while simultaneously overcoming these various challenges and meeting increasing regulatory requirements. “There have been a lot of steady but incremental improvements in coatings applications that are enabling coatings to last longer and protect substrates more effectively,” asserts McAfee.

For instance, many formulators are looking for alternatives to the traditionally used inhibitor systems that contain heavy metals or other undesirable components.��“New technologies such as vapor-phase corrosion inhibitors (VpCIs) have been shown to perform just as well as historically used inhibitors,” notes Bieber. Advances have also been made in waterborne systems. Hexion is actively developing new waterborne epoxy systems (resin dispersions and specialty curing agents) that offer coating formulators the opportunity to increase performance, to reduce cost, or reduce VOC content (e.g., less than 50 g/L VOC), according to Weinmann.

Arkema has introduced a waterborne, APEO- and ammonia-free short oil alkyd used in a wide range of applications where the feel and performance of conventional alkyds is desired in a low-VOC and solvent-free formulation, including excellent gloss, good hardness, and other properties, according to Dumain. Arkema has also developed high-solids alkyds with lower VOC content that offer the performance of conventional alkyds. DSM, meanwhile, recently developed a high-solids, low-VOC baked coating for trucks that has a 60% solids content at ready-to-spray viscosity, as well as high-solids and waterborne 2K polyurethanes for use on buses, according to Zeng. Separately, resins for nonisocyanate coating systems from Arkema have been designed to improve health and hygiene needs at the manufacturing level, Dumain says.

Many new developments have been designed to increase efficiency and productivity. AkzoNobel launched a new range of primers to meet the growing demand for production efficiency, including a multi-substrate primer. “This coating provides excellent performance on almost all substrates used within the transportation industry and thereby eliminates the needs for substrate-specific primers, ultimately saving customers time and money,” Bosman asserts. The BASF Resins and Additives business is in the final stages of developing a resin system for heavy-duty trucks and buses that has excellent adhesion to multiple metal substrates and very good corrosion resistance and weathering properties. The technology is ideal for primers, topcoats, or monocoat applications and is expected to be commercially launched in the second quarter of 2020, notes Bhaskar. Eastman has developed a new resin technology that offers excellent appearance and durability combined with best-in-class weatherability for 2K topcoat and DTM applications, according to Webster. “The ability to combine DTM corrosion resistance with long-term weathering enables OEMs to increase productivity through layer reduction without sacrificing coating lifecycle,” he observes. Allnex has a new technology that makes it possible to formulate 2K coating systems that dry exceptionally fast even at room temperature, allowing truck producers to reduce the coating process cycle time for all vehicle parts that are too big to be dried in an oven without sacrificing coating performance with a worker friendly, isocyanate-free coating, according to Schellekens.

Driving Toward More Sustainable Solutions

Going forward, it is generally anticipated that coatings for heavy-duty vehicles will need to meet ever greater expectations for sustainability. These solutions will include the extension of coating lifetimes, according to Bosman. Customers will also continue looking for coating solutions that offer better performance for longer periods of time so that they can minimize their risk during shipment or storage, Bieber adds. “The ultimate long-term goal would be to use 100% solids single-layer coating systems, but there is still quite a bit of technology development needed before the market can realize that ideal combination,” observes Casebolt. Cost reduction of the entire coating process will also remain an important topic, says Schellekens. Weinmann expects some of the coating technology advances being commercialized for OEM automotive coatings to eventually move over to the adjacent market of heavy-duty vehicles.��Specific examples might include all-waterborne coating systems (primer/color coat/clearcoat), wet-on-wet coatings systems that eliminate one coating layer, and coatings with improved stone-chip resistance.

Two long-term trends will impact the market, according to Dumain: the trend towards vehicle sharing and away from vehicle ownership; and the increasing adoption of automated or driverless vehicles. “These trends will drive demand for materials that are receptive to rapid changes in the local environment—innovations that allow coatings to detect small changes in heat, light, and sound energies,” he comments. Ultimately, coating formulators and end users will continue to look for multipurpose coatings that meet a variety of needs in the heavy-duty transportation market related to increasing sustainability, durability, performance in extreme conditions, and overall value, Dumain concludes.

CoatingsTech | Vol. 16, No. 10 | October 2019

I have been involved with automotive coatings for more than 40 years. When I started, car bodies were made of cold-rolled steel with little galvanized steel or plastic, primers mainly were spray-applied and many were alkyds, topcoats were low solids monocoats and some still were lacquers. Quality and appearance requirements were lower and surface defect and dirt levels were higher than they are today.

I began my coatings career in the Physical Chemistry Group at PPG under industry stalwarts Charles Hansen and Percy Pierce. We did research and problem solving and could extend the latter into research projects. We did work related to all the company’s coating products. Automotive was just one part of our effort, but over time it became more and more important and we did paint plant and customer support as well as research. I soon became involved in trying to solve and prevent customer problems, particularly craters and dirt.

One of the first problems that I encountered was delamination of acrylic topcoats over alkyd primers. This occurred after minor damage down to metal that led to what appeared to be relatively small amounts of corrosion, but was followed by loss of sheets of coating. We found that the corrosion products caused saponification of the alkyd primer and attacked the zinc phosphate pretreatment and continued to undermine the coating until there was nothing holding the topcoat in place. The solution to the problem was to change to cationic ED primers, which virtually all automakers eventually did. I became more involved in electrodeposition coatings, especially studying why and how surface defects and other problems occurred and how they could be prevented. I learned how critical the proper cleaning and pretreatment steps prior to electrocoat are to the performance of the entire coating system.

Many people really liked lacquers. They looked great, polished beautifully and because they were thermoplastics, many defects could be removed by careful use of a heat gun. However, coatings with only 18-20% solids no longer were acceptable and we entered the high solids and waterborne eras (and later produced automotive powder coatings). High solids solventborne coatings gave us a lot of problems as they required low molecular weight resins, even oligomers, to provide paints with low enough viscosity under shear to allow spraying. However, the low molecular weights meant that the coatings kept on flowing after application, especially in the oven, and were more sensitive to contaminants. Much work was needed to balance sprayability with sufficient viscosity recovery for resistance to hot sag and defect formation, yet not so fast or so much as to cause orange peel. Appearance was improved by the movement to color plus clear, although that development was not done without difficulties. Early wet on wet applications of the clear over the color basecoat often lead to mixing or waviness in one or both layers. Later, we concluded that one cause was convective flows like those that produce Bénard cells and flooding/floating in pigmented coatings.

We also looked closely at waterborne coatings for all industrial coatings, including automotive topcoats. I recall that some of first trials of waterborne basecoats took place in a plant where mornings were cool and relatively humid and afternoons were hot and dry. The paints stayed too wet and sagged in the morning and spray was too dry for acceptable appearance in the afternoon. It was obvious that humidity and temperature control were necessary in plants that wished to use such basecoats. Basecoat dehydration had to be carefully controlled. If completely dry, a basecoat absorbed solvents from the clear as it was applied and there was popping during the final bake; if too much moisture was present, water vapor blew through the clear as it was baked, resulting in pops.

Powder primers and clearcoats brought their own problems, including dirt (some of it clumps of powder), craters and pops. Powder had to be applied under true clean room conditions and crater antidotes could not be added to the mix just before application. Instead, that batch had to be removed, the hopper carefully cleaned and loaded with new powder.

I like to visit auto plants to observe the painting processes, work on problems and try to understand why and how defects occur. You can learn things from closely observing paint application at a plant that you never would notice in the lab. You also can identify bad customer practices that contribute to serious paint problems. I have learned a lot about how to reduce dirt levels and push customers to do a better job of filtering air, reducing dirt generation and protecting the paint and car bodies. I did my first dirt and crater audit as a favor in 1995 at a plant in Mexico and have done many since. ��An audit that includes a check list can be useful as a teaching tool as well as for identifying problem areas in a plant.

I worked on some crazy problems and situations over the years, including white pickup cabs and boxes coming out pink, black spots in silver basecoats, basecoats that clogged paint lines, and clearcoat craters caused by basecoat contamination traced to an attempt to clean conductive grease from inside the electrostatic spray electrodes.