Military coating systems fail for the following reasons: loss of appearance (aesthetics, camouflage, cleanliness); chipping, peeling, or debonding of the coating; and corrosion of the substrate. When they fail, the hardware must be recoated. These paint/depaint/repaint (PDR) operations are a significant source of pollution for the Department of Defense (DoD). This pollution can be greatly reduced by extending the useful life of the coating systems and decreasing the frequency of PDR. To formulate improved coating systems, an understanding of the detailed mechanisms of coating degradation is needed.
The objectives of this project included (1) identifying and quantifying the degradation mechanisms that lead to military coating system failures; (2) quantifying the role of individual coating constituents on resistance of the system to degradation; and (3) recommending new durable coating formulations with greater degradation resistance.
The degradation mechanisms of military coatings used on aircraft, combat ground vehicles, and support equipment were studied in this project. Efforts focused on the new primer/topcoat systems that have been fielded to comply with environmental legislation and regulations. Accelerated tests as well as static and dynamic field conditioning to assess coatings degradation in military systems and environments were investigated. Degradation modes were quantified and modeled to provide a scientific basis for the development of new durable coating formulations that reduce the PDR frequency. A statistical method was developed to accurately predict the performance of coating systems. A thorough and detailed materials characterization of the new coatings provided baseline properties and subsequent changes upon weathering. Results were closely linked to understand synergistic interactions between properties. Accelerated testing methodologies were developed and validated to facilitate more rapid fielding of future environmentally compliant coating systems.
Over 20 coating performance parameters were characterized and modeled, providing insight into coatings degradation through mathematical polymer kinetics, equivalent circuit models, and the establishment of digital pass/fail criteria. Observations, models, and values were incorporated into a statistical matrix system, which will improve formulations, performance, predictability, and survivability of military coating systems. The information discovered, combined with the correlations made, will aid in achieving pollution prevention via extended coating durability. These efforts have provided a scientific base to prioritize the mechanisms for specific military coating system formulations and direct future durable coating formulation efforts. Many research findings have been transitioned to the Army, Navy, Air Force, and Marine Corps for insertion in military protocols. This project was completed in FY 2002.
This project will have a positive impact on both pollution prevention and cost avoidance to the DoD through reduction of pollution via extended coating durability, the establishment of confidence in environmentally friendly military coating systems through understanding of degradation mechanisms, and real-time technology transfer to the military community for maximum mission impact.