Prior to March 2020, you may not have thought twice about grabbing a door handle at the store or touching a railing in the park. Now that our daily habits are being shaped by the novel coronavirus, though, we’re all thinking more about what germs might be on any given surface. As you might expect, demand for antimicrobial coatings has risen dramatically.

Lux Research (Boston, Mass.), a technology scouting and strategic advisory firm, has had its eye on the antimicrobial sector for about five years. Senior analyst Anthony Schiavo, who has a background in material science engineering, reports that antimicrobials may add as much as a half a billion dollars of new demand into the coatings market.

Jessica Elges, marketing manager at antimicrobial additive supplier BioCote (Coventry, U.K.), notes that their business has seen a considerable increase in inquiries since March this year. The company is not alone.

Steve Houston, director of sales and marketing at powder coating supplier Vitracoat (Elkhart, Ind.), says, “The interest has grown immensely. We’ve got so much more lab work, and we’re selling more antimicrobial product than ever before.” Quint Towle, director of sales and marketing for PTI (Schofield, Wisc.), echoes that sentiment. “I don’t want to say demand has been nonstop, but there’s been tremendous interest. It’s a differentiator for our customers.”

As much as the market is growing, it can be difficult to assess. Antimicrobials have been around for centuries, but new technologies are emerging. Refined testing methods have been developed. With regulations, it’s tricky to know what claims to make and it can be difficult to determine what antimicrobials can and can’t do. 

Do antimicrobial coatings kill COVID?

There’s still a lot we don’t know about COVID, which is part of what’s driving innovation. The simple answer is that some antimicrobial agents may kill SARS-Cov-2, the virus that causes COVID, but finishers and coaters are not likely to be able to make those claims definitively anytime soon.

It’s also worth considering what “antimicrobial” means. If something has antimicrobial properties, it destroys or inhibits the growth of microbes. “Microbes” can refer to all manner of microorganisms — bacteria, viruses, even fungus.

If you don’t remember much from biology, Schiavo clarifies, “A virus and a bacterium are very different — a virus is about an order of magnitude smaller.” While we are seeing a rise in antimicrobial coating technology, it’s essential to note that a material can be antimicrobial without being effective at killing SARS-CoV-2.

Jennifer Collier, partner development manager at BioCote, explains, “SARS-Cov-2 as a strain of coronavirus isn’t currently available for commercial testing. There are some universities that have a strain, but the disinfectant market is very much driving that industry. Because of the fast-acting nature of disinfectants, they’ll have first access and they’ll have the inroads into that that sort of testing because testing disinfectants is much more well established.”

According to Schiavo, “There are a number of groups who are testing against other types of similar enveloped viruses, as you can imagine, but there’s a lot of different factors: the extent to which the activity is reduced, the time it takes, the conditions, all these things are very different.”

Tiffany Hua, research associate at Lux, elaborates, “A lot of companies are doing these tests through third party laboratories organizations. So everyone might have somewhat similar, but different ways of measuring.”

Whether a given technology kills SARS-CoV-2 or not, it’s essential to look at these solutions as what they are — just one piece of the puzzle. Schiavo points out, “No amount of coatings are going to prevent COVID-19 on their own. A lot of the spread is from person-to-person contact. It’s worth recognizing that this plays an important role, but a limited one.”

Antimicrobial coating options

There’s a variety of options when it comes to antimicrobial coatings. Because copper and silver have been around the longest, they are the most common additives, but most antimicrobial technology works the same way. Schiavo explains, “Silver or copper nanoparticle coating works by basically disrupting the cell wall. The same thing is true for photocatalytic splitting.”

Although the mechanisms may be similar, each type of technology has different advantages and drawbacks.

Copper

Copper has broad spectrum antimicrobial efficacy, with alloys of 60% or more copper generally found to be effective. There is a long list of harmful microbes that copper will inactivate, including strains of coronavirus. Early research shows that a 99.9% copper alloy can inactivate SARS-CoV-2, the virus that causes COVID-19, in four hours, but the testing is still preliminary.

In plating and coating, copper can be susceptible to surface damage which can interfere with its antimicrobial properties. Durability and efficacy over time are key factors, so testing is essential. Thermal spray company TST Coatings (Sun Prairie, Wisc.) has been coating parts with copper for prototypes and testing.

TST has seen a rise in requests for antimicrobial coating on high-touch surfaces like doorknobs, and even hospital beds, with some effectiveness even coating plastic. According to John Koppes, R&D manager at TST, there is a balancing act between cosmetics and effectiveness.

“The surface doesn’t only need to be functional as far as being able to kill the virus or bacteria, but it also has to look good. Different finishing techniques are being investigated to determine how to get the cosmetics to be appealing to the marketplace.”

Another consideration, of course, is cost. “It comes down to finding the right applications that our customers feel they can commercialize within the right economics of what they can afford and what the market wants to pay,” Koppes says.

Silver

Like copper, silver and silver nanoparticles are used widely in antimicrobial coatings. BioCote uses a silver-based formulation in most of their antimicrobial additive offerings, including the formulation their partner, PTI, uses. According to Towle, their antimicrobial product was tested according to ISO 22196 and shown to have an over 99% efficacy rate against MRSA and E. Coli. Because SARS-CoV-2 isn’t widely available for testing yet, it will take time to determine how silver may affect the spread of COVID-19.

While copper formulations require a careful balance between efficacy and aesthetics, antimicrobial coatings made with silver often have no visual difference from their conventional counterparts. Vitracoat also uses silver ions in its antimicrobial products. Houston explains, “In terms of application characteristics, it really doesn’t impact the coating itself.”

Silver has the same consideration as copper when it comes to cost, though. “It’s hard to pay for something and not see what you’re getting. It’s like using high-end synthetic oil in your car — the oil change is twice as much, and you have to decide whether it’s worth it. It’s a premium price for a premium product,” explains Towle.

Houston also sees cost as a major deciding factor when coaters are considering antimicrobial additives like silver. “At the end of the day, it depends on what our customers are willing to spend. What antimicrobial technology can give you is a small amount of cost per gallon or per pound that really enhances the value of your finished product.

Structural, photocatalytic and other new technologies

According to Schiavo, “One of the interesting things that people have done in the past is make nanostructured or nanotextured surfaces. There’s been a number of groups doing this with various electroplating or electrochemical means on metal surfaces that turn the bare surface itself into an antimicrobial surface.” He cautions that the difference in size between a bacterium and a virus can make this ineffective against viruses, though. “For metal finishing companies, in particular, it’s going to be very challenging. The set of technology options are limited.”

Hua brought up the buzz emerging around photocatalytic technology, which was originally designed to combat air pollution. Hua explains, “It is a light-activated coating that really destroys pollutants on the surface of the coating. So people have pivoted there with COVID in hopes it could act as an antimicrobial or antiviral. The thing with photocatalytic coatings is, because they weren’t originally meant to address microbes and viruses, there really isn’t much regulation or testing. That efficacy testing is being done now.” Although it’s still being tested, Schiavo explains that photocatalytic solutions are an appealing option because they create a high density of active agents on the surface.

Another emerging technology is LeKem’s (Batesville, Ind.) MicroKoat antimicrobial electroless nickel (EN) formulation. Paul Feagins, second-generation owner of LeKem, has been focusing on providing quality baths, plating and advice since he took over in 2006. When one of his customers asked for an antimicrobial formulation of his EN, he did two years of R&D to get it right. The resulting solution, MicroKoat, was on the market for about a year before COVID hit.

MicroKoat was designed to be used for everyday production, passing current EN specs as well as providing antimicrobial properties. It contains an antimicrobial preservative to inhibit the growth of odor-causing and spoilage organisms including bacteria, fungi and mildew on the treated article. It has been tested according to the Japanese Industrial Standard Z 2801 and was shown to reduce Staphylococcus aureus, MRSA and E. Coli microorganisms by 99.9% in 6 hours. With the same test against human coronavirus strain 229E, MicroKoat was shown to reduce the virus by 90% in 6 hours. It also showed no corrosion or fungi growth after the 28 day ASTM G21 test, which assesses coating resistance to fungi.

Feagins points out that silver and copper may beat out MicroKoat’s reduction times, but MicroKoat has all the durability and versatility of electroless nickel, along with antimicrobial efficacy that reportedly lasts for the life of the product.

Advice for adding antimicrobial technology

If you’re considering adding antimicrobial technology to your coatings, Towle of PTI suggested a list of questions to ask your provider:

• Are the additives EPA registered? (They should be.)
• Is there additional PPE required?
• Can it be disposed of without extra precautions?
• Up to what temperature is it effective?

You’ll also want to review efficacy testing documentation from the supplier.

Claims are another important topic to consider. “The biggest thing we caution people on is, make sure you market this correctly,” Towle says.

Houston has similar advice. “Don’t oversell. Don’t tell the market something that really isn’t true. Do your due diligence. Work with your coating supplier. Use the terminology that they use, and make sure that’s how you go to market. We don’t want to say that it’s going to protect you from getting sick. It’s not. It’s going to be a layer of protection, but it’s not going to protect you from getting sick.” He also advises to keep in mind that antimicrobial coatings still need to be cleaned routinely, and they don’t absolve folks from having to wash their hands.

Collier agrees. “What products can offer is an improved, long lasting hygiene measure that will work alongside cleaning and hand hygiene and just generally keep chipping away at the contamination on surfaces that are easy to keep hygienically clean, working around the clock.” Making the appropriate claims is essential for integrity in the marketplace, but it’s also necessary to stay out of regulatory trouble.

Treated article or pesticide?

One of the most complex areas of the antimicrobial sector has nothing to do with biology. In the U.S., there are strict regulations about what claims a company can make when it comes to microbes. These regulations are rigorously enforced by the EPA.

Jennifer Collier of BioCote has a thorough understanding of how to work within the regulatory framework. Her job includes providing support to BioCote’s partners, making recommendations to small job shops and multinational companies alike.

Collier explains how the treated article exemption works for many of her clients. “Companies will buy the raw material chemical from us, which is a registered pesticide with the EPA, apply that powder coating, then that powder coating becomes a certain category of product called a treated article. And because it’s a treated article according to the EPA, it has to follow certain rules in order to avoid registration as a pesticide.”

The fact that supply companies like BioCote offer this type of consultatory service hints at the complexity of the issue. “It’s a bit obscure, but this is our specialty,” Collier says.

In general, antimicrobial agents may be considered pesticides when they are intended to protect public health. In this case, a pesticide refers to a substance that is intended to destroy or suppress the growth of harmful microorganisms. Under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), all pesticides must be registered with the EPA. The benefit of registering a coating as a pesticide with the EPA is that you can make claims about the coating’s antimicrobial properties, which is attractive to many companies, especially during COVID.

The drawback is that registering as a pesticide can take years and hundreds of thousands of dollars. Any change in formulation for a registered coating requires re-registration, so this may not be a one-time cost. According to Collier, this presents significant barriers for many smaller operations, but larger companies may opt for this choice.

The alternative is to use what is commonly known as “the treated article exemption.” Pesticide Registration Notice #2000-1 from the EPA defined exemptions from FIFRA in certain cases where a product is treated with antimicrobial chemicals. If the antimicrobial agent is registered with the EPA and the product claims describe protection of the product, not people, the product does not need to be registered as a pesticide with the EPA.

The benefit of using the treated article exemption is that products need not be registered with the EPA, but companies must be careful not to make any claims regarding public health. Under these regulations, finishers would not be able to make any claims against viruses at all. To comply with the treated article exemption, a company’s claims can be about performance (such as “reduces microbes by 99%) or product protection from microbe-related problems like odors and material degradation, but those claims must be narrow and specific.

The future of antimicrobial coatings

When asked whether these coatings were just a fad in response to the pandemic, Hua predicts that some industries will have a longer-lasting impact than others. High-touch surfaces like school lockers, outdoor play equipment and handrails are likely targets. So are HVAC systems and surfaces on public transportation.

When asked about what the future holds for antimicrobial technology, Towle sums it up. “Boy, my only guess is you’ll see a lot more of it. A lot of our customers are saying, once we do this, we’re just going to do it on everything. It’ll likely cost a little more. But from a manufacturing standpoint, if you have a certain number of products and you offer them all with an antimicrobial option, you’ll double your offerings.”

“What COVID did,” Houston muses, “is revitalize the idea of antimicrobial coatings. It’s going to drive innovation and testing. I think we all have become a lot more cautious and hygiene aware. If there’s one thing this pandemic has taught us, it’s taught us that we really need to be more cognizant about how we protect ourselves, our families and our community.”