BEST DEFENSE: Military approves CARC powder coats

The race is on amongst powder coating manufacturers to turn out a new product that will meet military CARC specifications and hopefully grab a share of the $2 billion defense coating market.

The U.S. Department of Defense issued specifications in late 2010 to allow powder coaters to finish military vehicles and equipment which ‑ until now—could only be done using liquid paint.

CARC requirements

Chemical Agent Resistant Coatings are surfaces that resist the absorption of chemical warfare agents, making decontamination much easier to accomplish with vehicles, artillery pieces and missile launchers, rotary and fixed-wing aircraft, and support equipment such as communications vans, water purification units, generators and forklifts.

The U.S. Army Research Laboratory (Aberdeen, MD) released the specs—MIL-PRF-32348—to allow powder coating as a finish because of increased pressure from the U.S. Environmental Protection Agency, which wants the military to use coatings that are free of volatile organic compounds (VOCs), volatile organic hazardous air pollutants (VOHAPs) and inorganic hazardous air pollutants (HAPs).

“There are many advantages to allowing powder coating to a part of the program,” says John Escarsega, DOD CARC Commodity Manager for the coatings team at Aberdeen. “Environmental is a big reason, but there is also some reduced costs we should be seeing. It’s a good step forward.”

New specs outlined

The specification for primer and topcoat contains four types of coatings:

• Type I Coating—epoxy-based primer, chemical agent resistant coating.
• Type II Coating—epoxy-based primer for interior components, chemical agent resistant coating,
• Type III Coating—camouflage top coatings, chemical agent resistant coating. The primary colors required by the ARL are 383Green, 686 Tan, Aircraft Green, Black and Brown.
• Type IV Coating—coatings for ammunition containers.

Getting a seal of approval from the DoD on meeting the new specs will be a challenging—and lengthy—process.

For a topcoat to be approved, it must be highly chemical resistant, lusterless (below 1.5 units of gloss), absent of infrared detection and provide exterior durability properties. And before approving the topcoat formulation, each color match has to be approved by the ARL separately.

To achieve the camouflage requirements, the powder coating industry is facing a challenge as the readings go above and beyond what the typical in-house color measurement equipment used today in the industry can provide.

While normal powder topcoats are often very good in UV and conventional chemical  resistance, Escarsega says these elements suffer significantly when their gloss is reduced to levels required for camouflage CARC: no greater than one unit of gloss at 60˚, no greater than 3.5 units of gloss for Green, and 4.0 units for Tan at 85˚.

Chemical and UV resistant

“It is imperative to establish a sufficiently high degree of cross-linking to impart chemical and UV resistance,” says Escarsega. “However, introducing matting agents or cure characteristics to impart low gloss often degrades the agent resistance below acceptable levels.”

But Escarsega says it will take up to three years to get the first topcoat approved because of the strenuous specs. 

To help the vendors with their research, his group has sought funding from the “Strategic Environmental Research and Development Program,” funded by the DoD, the EPA and the Department of Energy to help private companies develop products to be used by the military.

Escarsega and his staff submitted a “Statement Of Need” to the SERDP agency to help fund the powder coating research. It is expected up to three manufacturers will join the group and seek funding for the research dollars.

One of the key arguments for the federal funding, says Escarsega, is the amount of VOCs to be reduced by using powder coating instead of liquid paint. At about two million gallons per year and an average of 2.6 pounds of total organic solvent per gallon, he says the DoD and its industrial base currently emit upwards of 5.2 million pounds (2,600 tons) of organic solvents per year from CARC topcoat application. 

“The use of solventless powder topcoats in high production environments such as depots and OEMs has the potential to eliminate hundreds—if not thousands—of tons of VOCs, HAPs, and other organic solvent emissions per year,” says Escarsega.

SERDP will make a decision on who to fund based on  the research proposals submitted and this will be announced later this year.

Escarsega says he believes that in less than a year after the SERDP funding is approved some significant research will have been done to get a topcoat ready for testing and final approval.

“I think the chemistry will be ready for lab and outdoor  testing in about a year,” he says. n

For information on the CARC powder coating process, please visit the U.S. Army Research Laboratory at www.arl.army.mil.