Steel structures at Army installations must be protected from atmospheric corrosion. Many commercially available coatings that have been used are subject to combined effect of exposure to sunlight, changing humidity, and hot and cold cycles experienced during weathering. In many cases, due to lack of maintenance, the paint has deteriorated, and has begun to peel. Also, in the past, lead-based paint was used as a primer for the coating systems applied to these steel structures. Peeling lead-based paint will eventually fall into and contaminate the soil, and require extensive environmental cleanup.
Surface tolerant coatings, which can be applied over existing coatings with minimal surface preparation, provide a solution to these problems. Steel structures at an Army installation were chosen for application of these candidate coating systems. Two aircraft hangars and two deluge tanks (water tanks for fire suppression at the airfield) were overcoated with polyurethanes, which actually cure by reacting with moisture from the air. Critical areas of the deluge tanks were coated with self-healing coatings that contain microcapsules with film formers and corrosion inhibitors, which are released to repair the overcoating if it is damaged. Fluoropolymer coatings were applied over the existing paint on a flight control tower. The benefits of surface tolerant coatings are extension of service life, reduction in maintenance cost, elimination of the expense of removing hazardous lead coatings and preservation of appearance.
An Army installation in the Southeastern part of the Unites States has encountered problems with atmospheric corrosion and peeling paint on steel aircraft hangars, steel flight control tower, and steel deluge tanks (for fire suppression), all located near their airfields, where training and deployment of helicopter flights are conducted. These structures are shown in Figures 1, 2 and 3, respectively. The commonly used protective coatings on these steel structures are susceptible to peeling and spalling, or other deterioration, due to the combined effect of exposure to sunlight, changing humidity, and hot and cold cycles experienced during weathering. Furthermore, in the past, lead-based paint was used as a primer for the coating systems applied to these steel structures. Peeling lead-based paint (LBP) will eventually fall into and contaminate the soil, and require extensive environmental cleanup. Other military installations have deluge tanks, flight control towers and hangars that suffer these same problems.
If this problem persists, coatings on mission critical structures such as aircraft hangars, flight control towers, and deluge tanks will continue to deteriorate, resulting in corrosion of the structures, eventual decreased service life, and degradation in performance of mission. Corroding hangars can be dangerous for personnel working inside of them. Furthermore, the peeling LBP on these structures will create a lead dust hazard, which will eventually fall to the ground, resulting in a costly environmental cleanup. Moreover, helicopter flight training is cancelled if the deluge tanks are leaking. This happened at the Army installation in question in 2002, when leaks on a deluge fire suppression system impacted all flight operations, including proficiency training, and potential deployment. It will cost more to rectify these problems at some later date than to fix them now by overcoating with surface tolerant coatings, which can be applied over the existing coatings with minimal surface preparation. In addition, some critical items, such as the lower ring on deluge tanks that need recoating can be made to be self healing so that they self repair wh
