Chemical Agent Resistant Coating (CARC) topcoats currently used to paint defense material have an upper volatile organic compound (VOC) content limit set at 3.5 pounds per gallon by the Clean Air Act, but local emission limits at some facilities restrict the VOC content to only 1.8 pounds per gallon. In addition, hazardous air pollutants (HAP) such as methyl isobutyl ketone, toluene and xylene must be eliminated from the current topcoat formulations to comply with the National Emission Standards for Hazardous Air Pollutants (NESHAP) currently being promulgated by the U.S. Environmental Protection Agency. The present approach is to utilize a high-cost emission control system. The objective of this project was to demonstrate and validate, under production conditions, the application of a new low-VOC, water-dispersible (WD) formulation, developed under the Strategic Environmental Research and Development Program project, WP-1056. The new CARC was applied to several vehicles and a variety of equipment at three DoD depots (Tobyhanna Army Depot, Ogden Air Logistics Center, and Barstow Marine Corps Logistics Base) to obtain performance data pertaining to coating application under various climatic conditions. Strippability trials also were conducted.
In developing the new CARC, researchers utilized recent advances in waterborne polyurethane technology and also substituted typical silica-based extender pigments with polymeric beads as the means of gloss reduction. The resulting formulation met the VOC objectives of 1.8 pounds per gallon and, in addition, eliminated all HAP solvents. The new coating also showed significant performance enhancements.
Demonstrations verified that the WD CARC is essentially a “drop-in” substitute for the solvent-based CARC that is currently used because it could be applied and stripped using existing equipment and processes at each depot facility. The exceptional performance of the coating noted in the SERDP effort, especially its flexibility, mar resistance and outdoor weathering durability, was confirmed at the production level. Overall, painters considered the new CARC to be a better coating. Lower amounts were required, and it was easy to use, although mixing and curing took a while longer.
Use of the new WD CARC will eliminate HAPs and reduce VOC emissions by 5 million pounds per year. Furthermore, the new CARC will eliminate the need to install emission control devices to bring facilities into compliance. Total equipment cost avoidance for all depots is estimated at $50 million. Operational costs for using the WD CARC are lower than for the solvent-based CARC that is currently used. Also, due to its enhanced physical properties, the WD CARC coatings will not require stripping and repainting as often and thus will have a longer service life. Even if a conservative 50% extension in life cycle between programmed maintenance is considered, estimated annual cost savings would be between $0.38 and $0.73 million per DoD facility. A new specification (MIL-DTL-64159) was published on January 20, 2002 for ongoing procurement of the new, low-VOC CARC topcoat by the Army and Marine Corps. (Project Completed - 2004)