As the Aerospace (AS) industry pushes for next-generation air and space coating technologies to protect materials exposed to harsh air and space environments, coating manufacturers dive deep to provide higher-performing coatings. The global aerospace coatings market in 2021 was valued at USD 2.15 billion. It is estimated to grow with a CAGR of 5.2% through 2030. Some investment is earmarked for research and development to replace chemicals of high concern and innovation to support the protection of advanced aerospace materials. This article discusses current and future aerospace coating technologies to protect modern air and spacecraft.
How do air and space coating technologies protect and improve aerospace material survivability?
The potential for mechanical functions to be affected by corrosion in aerospace is not a matter of if, but rather when corrosion will impact those functions. To counter the high stakes that aerospace corrosion presents, mission-critical applications require the most innovative, comprehensive, and reliable coating technologies available. Additionally, it is vital to continually invest in developing more high-performing chemical technology as they become available.
When aerospace coatings are applied correctly, they are a first line of defense from the elements. These coatings are designed to create a continuous void-free barrier keeping substrate materials protected from corrosive media.
Certain aerospace coatings have specific critical jobs, for example,
- A conductive lightning strike coating allows the energy from the lightning’s electrical charge to pass through the coating without harming the aircraft. The anti-static coating provides electronic component protection from static electricity caused by rapid airflow across the surface.
- Primers provide a functional base layer that serves as the anchor point for all subsequent layers of paint and topcoats.
- Specialty coatings provide customized protection that resists the corrosive effects of service chemicals like hydraulic fluids, jet fuel, and aircraft deicers.
Aircraft are made up of over 50% carbon fiber composite. While incredibly lightweight and strong, such aircraft composites are not always sufficiently conductive, thus requiring additional protection to mitigate lightning strike damage. This is resolved by building a metallic mesh into the composite or by using specially designed coatings that are conductive and strong enough to withstand the energy involved in a lightning strike.
Conductive coatings provide protection from aircraft lightning strikes. Anti-static coatings protect electronics from electrical surges.
Providing a safe path for lightning strikes on various materials: https://weatherguardaero.com/composite-aircraft-lightning-protection-solutions/.
Grounding and bonding electrical components / protecting components from static charge build-up: https://nycote.com/case_studies/coatings-for-electrical-bonding-points/.
When looking at an aircraft or spacecraft, be assured that dozens of coatings are applied to keep it safe. From top to bottom to inside and out, the AS industry coats to keep corrosion and wear from degrading mission-critical assets. It’s the job of coating manufacturers to formulate the highest performing, longest lasting, and lightest weight coatings possible.
Coating manufacturers formulate to the unique needs of Aerospace materials and rigorous service conditions. What types of coatings provide ‘The Right-Stuff’?
Hybrid Cross-Linked Coatings
What coatings are used in the aerospace industry? Cross-linking known polymers, monomers, and branches can improve coating capabilities and this process yields several advantages. 1.) A customized coating via cross-linking combines the performance benefits of two or more polymers and is a good strategy for meeting critical demands. This formulation strategy creates more durable coating systems that offer lightweight, efficient, and improved protective properties. 2.) Well-known polymers come with performance testing data that aerospace and coating engineers rely on. Strategic polymer coating formulations are essentially strong and flexible liquid composites. These coatings successfully replace heavier materials such as metal additives or rubberized thicker coatings.
Self-healing Coatings
A self-healing coating possesses the ability to repair physical damage to the coating and protect the underlying substrate from corrosive media with minimal intervention. The autonomous healing particles are suspended in the liquid coating system and are cured. With particles embedded in the coating layer(s), it ensures that if the coating layer is disrupted, the healing agent releases and the CI is activated to fill the void repairing the rupture.
Self-healing systems can be accomplished by adding a corrosion inhibitor (CI) to other monomer chains or by suspending an enclosed CI-filled microcapsule into the base formula. Both can be efficient ways to formulate, however, the latter could produce a longer more stable coating shelf life.
Thermal management coatings provide AS materials extra protection in extreme temperature environments. They protect the underlying coating or substrate from damage. For instance, air and space coatings require protection from electrical conductivity, atomic oxygen, UV, or solar radiation. These enhanced aerospace coatings require high wear and abrasion capabilities.
Urethane Coatings
The urethane topcoat is the topline defense between the aircraft’s outer shell and the environment. Every aircraft needs several paint refreshes or new liveries in its service life and that can cost between 150K and 200K per job, a well-made and applied topcoat is critical. https://simpleflying.com/aircraft-paint-cost/?newsletter_popup=1
Electronics / Avionics coatings
Conformal coatings protect printed circuit boards, wired systems, and electronic components from unfavorable factors such as corrosion, salt spray, moisture, shock, dust, fungus, and more by applying a non-conductive film coating over the terminal or circuit board. The coating helps prevent electronic failure and can extend the service life of protected components. There are many types of electronic conformal coatings such as acrylic, epoxy, silicone, parylenes, polyurethane, and ultra-thins.
Choosing the correct conformal coating for an aerospace component requires extensive research and testing to ensure the part and the coating are compatible and no unintended consequences occur. For instance, some Printed Circuit Board coatings can be difficult to remove, some are longer lasting or more durable than others, and some have a thick appearance while some are ultra-thin. When considering color or tinting options, ease of application and other factors are important to take into account.
Another important consideration when choosing conformal coatings is testing to standards that ensure the product will perform correctly. Standards such as IPCC830, or Mil-I-46058C are common standards for a conformal coating. Recycling a printed circuit board is a major benefit to reducing the replacement costs of high-value electronics. Not all coatings are removable and therefore require patching or sourcing a new board. Removing coatings from PCBs can be tedious due to the amount of sensitive areas and may require a more gentle coating remover. Nygone by Nycote offers one such solution. In this situation, there may not be an abundance of options, but Nyform (https://nycote.com/products/) fills a service gap. It is a durable, long-lasting, thin-film coating that can be safely and efficiently removed without difficult or time-consuming processes. Nygone coating remover – https://nycote.com/case_studies/coating-remover/
Paints/pigments
The most noticeable coating on an aircraft is the paint, but paints are not only for design or identification purposes. The main reason for painting the aircraft is to prevent material failure and keep the underlying materials safe from corrosive media. The pigments disperse into a paint base and remain solid in the base coating and impart the bright color we see. Pigments can be classified as functional or decorative, and organic or inorganic. The pigment selection is determined by the required performance for a specific application.
Interior and exterior paints are formulated to the exact conditions they will encounter in service. Paint chemistries are strategically chosen to provide benefit to the underlying coatings and/or the substrate they’re applied to. From factoring in substrate surface tension for optimal adhesion or ensuring low observation with covert paint there are many considerations when it comes to aircraft paint.
Space Coatings
Space materials require coatings that can provide optimal survivability and longevity over critical parts. This environment is very different from that of Earth. Because of this, coatings chosen for space applications must slow erosion rates, material stresses, and oxidation. The most corrosive elements to space materials are ATOX-Atomic Oxygen. This is a type of corrosion not found on Earth and is considered the most serious and hazardous to spacecraft materials. ATOX exists at altitudes between 200 and 700 km according to ESA (European Space Agency) http://esmat.esa.int/Publications/Published_papers/Corrosion_in_Space.pdf
Coating types provide benefits that reduce corrosion and wear in space environments. They are lightweight thin-film coatings that have mission-specific functions, exotic metal coatings, and high-performance pigment coatings designed to provide high-level UV and radiation protection.
What do modern air and space coating technologies look like and how are they helping?
Modern aircraft builds incorporate more composite materials to lighten the overall weight and improve fuel efficiency. The idea is that all materials on the aircraft become lighter and as efficient as possible. High-tech additives combined with the protective properties of conventional coating systems offer new and enhanced capabilities and an opportunity to strengthen the coating performance without adding weight. From improving mechanical properties to preventing the spread of contagious viruses, high-tech multi-functional coatings are interesting for the aerospace industry. Here are some next-generation coatings that meet today’s challenges head-on with new ways to protect air and space materials.
Multipolymer Electronic Conformal Coating with Additives:
Conformal coatings are high-performance materials that meet the complex demands of aerospace electronics such as Printed Circuit Boards (PCBs), circuit assemblies, and electronic components. Conformal coating enhancements are achievable by cross-linking polymers and adding functional particles to provide customized performance features. There can be service gaps in conformal coatings, for example, pinholes or bubbles, low adhesion, or the coating is not removable. A new conformal coating on the market, Nyform, is a cross-linked polymer ultra-thin conformal coating matrix with tints or fluorescent additives. This coating’s clear or tinted lightweight protection is highly durable, capable of withstanding extreme environments, and it’s fully and safely removable.
Read more about Nyform (https://nycote.com/products/nyform/) and Nygone remover (https://nycote.com/products/nygone/).
Anti-counterfeit Covert Coatings
With supply-chain changes and challenges now more than ever, counterfeiting of aerospace parts is substantially increasing every year. The problem has been ongoing for decades. The FAA estimates that counterfeit or unapproved parts contributed to 174 U.S. aircraft crashes and accidents between 1973 and 1996. They also estimate that 2% of the 26 million aircraft parts installed each year are counterfeit. Even with new OEM and FAA standards for defending AS against counterfeit parts, the problem remains without a solution. Mitigation is largely focused on ensuring counterfeit parts do not become installed on an aircraft. While important, the mitigation in place doesn’t address the overall loss of revenue.
Intelligent new anti-counterfeit coating innovations could help. Machine-readable coatings are good strategies for alleviating counterfeit parts. The suspension of a unique technologically advanced additive into a high-performance surface coating serves as a covert chemical QR code. This provides a scannable signature that follows the part throughout its service life. A new coating, Surface Trace, is a way to mitigate these concerns. Surface Trace coatings provide a scannable read of the particles embedded in the coating and record this unique signature safeguarding critical parts. The base coating is already approved by aerospace OEMs which is shortcutting the product’s long approval process.
Here are additional resources about this anti-counterfeit technology: (https://youtu.be/ZrENTzOUpu8) (https://nycote.com/solutions/)
What does counterfeiting look like: (https://www.lockheedmartin.com/content/dam/lockheed-martin/eo/documents/suppliers/training-2020-counterfeit-parts.pdf)
Microbial and Viral surface contamination solutions
Airline cleaning and disinfecting costs post-COVID are exceptionally high and unsustainable. The chart below shows estimates of past, current, and future spending on cleaning chemicals alone. These figures do not consider the cabin-cleaning crew spend.
What was missing in the AS industry was a permanent solution to pathogen contamination. Mass transit, medical, and hospitality industries must incorporate new more permanent technologies to prevent the spread of viruses and bacteria if they want to decrease their costs. During the pandemic there was a mad dash to find a coating that would eliminate contamination and decrease the spread risks in public spaces—remember the “super spreader-events”? The main problem was finding an easy-to-apply product that could provide durable long-lasting protection.
Airline cleaning and disinfecting costs (post-COVID)
Nysafe 700 & 900 Anti-viral are long-lasting durable high-performance air and space coatings formulated from popular well-known technologies. These coatings are approved by Boeing, Airbus, Embraer, and others to protect high-value parts from damage. Nysafe contains two elements that collectively and significantly reduce viral and bacterial contamination load on all high-touch surfaces. The first is a known polymer that microbes cannot penetrate or grow on. The second is an antiviral additive known to reduce the viral load on surfaces. Nysafe is safe for humans and is a long-term solution proven and tested against viruses and bacteria. Learn more here (https://youtu.be/l76DSq__qlE) and (https://nycote.com/products/nysafe-av-700) (products meet flammability, fungus, microbial, and viral AS testing requirements)
What challenges exist when reformulating or innovating new air and space coating technologies?
Today there is a significant industry drive to innovate next-generation air and space coating products. These innovations have the potential to outperform chrome, PFAS, or other obsolete or phased-out harmful chemicals. This is a big task since these coatings effectively prevent corrosion.
Collaborating with aerospace OEMs is crucial to modernize current coating tech and to innovate future coatings. As air and space companies innovate and materials evolve so must coatings. The addition of additives to existing technologies and emerging technologies provides coating manufacturers with a path to innovate for these modern and changing times.
In the last 10 years, the push to phase out harmful chemicals like Chrome, PFAS, Benzene, and others on the chemical watch list is an invitation to create next-generation products that are safer and better for the environment.
The aerospace community and U.S. government agencies provide a coating innovation path through partnerships and grants available to solve, disrupt, and improve current technologies.
