The Defense Department’s environmental research arm has tapped Sherwin-Williams to lead the development of a novel Chemical Agent Resistant Coating (CARC) powder topcoat for military vehicles and support equipment.
The goal of the $1.4 million project is to develop a zero-VOC, zero-HAP exterior topcoat to replace the military’s current generation of liquid-applied CARC topcoats.
Images: Department of Defense
|CARC safety has long been a concern for the Department of Defense. The Army’s PS Magazine: The Preventive Maintenance Monthly addressed the topic in 2000.|
Those coatings emit about 5.2 million pounds of organic solvents each year, according to DOD’s Strategic Environmental Research and Development Program (SERDP), which is sponsoring the powder coating project.
“To date, no vendors, raw material suppliers or independent formulators have been able to successfully meet the requirements for a chemical agent resistant powder topcoat that can be used as an alternative to current Army CARC topcoats,” SERDP wrote in 2010, in an FY 2012 Statement of Need for the coating.
First developed by the Army in 1974, chemical agent resistant coatings—CARC—make up the largest category of paints applied to the U.S. military’s inventory of equipment.
In 1983, the Army began to require that all combat, combat support, tactical wheeled vehicles, aircraft, and essential ground support equipment be painted with CARC, according to a DOD Environmental Exposure Report that examined CARC use during the Gulf War of 1990-91.
Although lead and hexavalent chromium have been removed from CARC and the levels of solvents and volatile organic compounds have been reduced, concerns about painter and environmental health and safety have persisted, said the report, written in 2000.
CARCs are “essentially a low-gloss version of automotive-grade polyurethane paint,” the report notes.
“While it is well known that the isocyanates found in polyurethane paints pose the most significant health risks, solvents in the paints, thinners, and cleaning products are also known to pose a secondary health risk, if absorbed in sufficient quantity.”
‘Tremendous Environmental Benefits’
A CARC powder topcoat would deliver “tremendous environmental benefits for the Department of Defense,” according to SERDP, which is charged with improving DOD’s environmental performance, reducing costs, and enhancing and sustaining mission capabilities.
The use of solventless powder top coatings in depots, OEMs and other high-production environments “has the potential to eliminate hundreds, If not thousands, of tons of VOCs, HAPs, and other organic solvent emissions per year,” according to SERDP’s Statement of Need.
“Another significant advantage to this technology is providing superior preparation of surfaces and pretreatments prior to the primer application to support a powder topcoat. This will support DOD initiatives to reduce and/or eliminate corrosion.”
|The 325th Maintenance Company applies Chemical Agent Resistant Coating at the Al Jubayl Paint Facility in Saudi Arabia.|
Powder coating would also improve worker safety and reduce the logistical burdens associated with hazardous waste handling and disposal, SERDP said.
Finally, SERDP says, powder coatings “require stringent methods for surface pretreatment” that “should provide an improved corrosion protective surface, thereby supporting the DOD Corrosion Prevention and Mitigation Plan, while maintaining focus on warfighter survivability.”
Specs and Requirements
Naturally, the new coating must meet the highest performance demands and exacting specifications. In addition to meeting the conventional roster of physical testing typically conducted to validate an exterior topcoat, it must:
• Resist chemical warfare agents;
• Meet color and IR requirements;
• Impart low gloss and low sheen specularly;
• Withstand UV degradation in both outdoor and accelerated chamber evaluations; and
• Resist decontamination solutions.
The topcoat will have to meet Army and Marine Corps coating requirements and must be available in 383 Green, 686 Tan, Aircraft Green, Black and Brown.
Other major variables include surface preparation requirements, end-user considerations, cure process and cure time.
Equally critical will be the new coating’s compatibility and interaction with the current generation of CARC system pretreatments, primers and water- and solvent-based topcoats.
The Army and Marine Corps currently use about two million gallons of CARC topcoats for their camouflage coating systems each year, according to SERDP.
The powder coating must be able to be used over a conventional non-powder primer and must be able to be cleaned and top-coated with a non-powder CARC.
The topcoat will be based on polymer blends formulated with fillers and pigments, according to SERDP.
“This approach involves the design, synthesis, and optimization of functionalized polymers,” SERDP reports. “These new polymer technologies will be coupled with a formulation strategy that will maximize light scattering efficiency and crosslink density so as to produce ultra-low gloss, highly durable, chemical agent resistant coatings.”
Sherwin-Williams’ Product Finishes Division will lead the project team, which will also include academic and military personnel. The project will be based at the company’s facilities and labs in Chicago and in Grove City, OH.
“We are excited that Sherwin-Williams has been selected to leverage its experience as a global developer, manufacturer and supplier of CARC coatings as we lead a dynamic team of highly-qualified academic, military and industry personnel,” said Beth Ann Pearson, Sherwin-Williams Global Product Line Manager- Military Coatings.
“Sherwin-Williams is an industry leader in lowering VOC emissions and was the first company to commercialize water-based CARC topcoats. We believe that our experience and overall capabilities were positive factors in being chosen from a strong field of applicants to lead the development of this new technology.”
SERDP has high expectations for the coatings project, which is expected to run through 2015.
“As a result of new regulations, increased costs of hazardous waste disposal, and an increased awareness of the costs associated with employees’ health and safety,” the agency says, “it has become imperative to develop viable, robust coatings to minimize repainting and provide an exceptional first line of defense to DOD assets through use of protective coatings.”