CHAPTER 4 CORROSION PREVENTION AND CONTROL As a maintenance crew member, you will work in two main areas when combating corrosion on naval aircraft. These areas include aircraft structures and avionics corrosion control. AIRCRAFT STRUCTURES AND CORROSION LEARNING OBJECTIVES: Describe how metal corrosion can threaten the structural integrity of an aircraft. Identify the personnel required to obtain corrosion control training. Identify the primary reason for selecting materials in aircraft construction. Modern high-speed aircraft depend on the structural soundness of the metals that make up the largest percentage of their thousands of parts. Metal corrosion is the greatest threat to the soundness of metals and to the structural integrity of an aircraft. The materials used to construct an aircraft are designed to carry certain loads, to withstand given stresses, and to provide strength for safety. Corrosion reduces the strength and changes the mechanical characteristics of the materials, thus endangering the aircraft and reducing the margin of safety. The corrosion that occurs on avionics equipment is similar to that which occurs on the basic airframe structure. The main difference is the amount of corrosion that is detrimental. A small amount of corrosion on avionics equipment can cause serious degradation or complete system failure. However, the same amount of corrosion on aircraft exterior surfaces might go unnoticed. You can detect corrosion on the exterior of aircraft or equipment visually. If you follow the scheduled inspection requirements on a day-to-day basis, you will ensure adequate detection of external corrosion. It is harder to detect corrosion on the internal surfaces of an aircraft because such surfaces are not easily accessible. Thus., internal surfaces require special attention. Corrosion often progresses unnoticed by the untrained technician. Therefore, the responsibility for the detection and treatment of corrosion on the aircraft is assigned to all work centers in each activity. This ensures that sufficient knowledge is available to perform all required inspections. Formal training in corrosion control is a requirement for ALL MAINTENANCE PERSONNEL. Through this training, maintenance personnel are qualified to perform inspections, corrosion damage repair, and corrosion prevention. The corrosion control program established by the Naval Aviation Maintenance Program (NAMP) is an ALL HANDS participation concept. Aerodynamic efficiency is the primary consideration of a manufacturer during the design and production of an aircraft. The materials used for construction are chosen for their weight-to-strength ratio-NOT their corrosion-resistant properties. This is one of the reasons your job as a maintenance crew member is so important. When performing maintenance on an aircraft, you must constantly look for surface decay on all internal and external areas of the aircraft. You should learn the corrosion-prone areas of your activity’s aircraft. Then, you can constantly inspect these areas while performing maintenance. When a new aircraft is delivered from the manufacturer, corrosion is already present. Unless this corrosion is detected and treated, it can become a serious problem that can endanger the flight safety of the aircraft. In addition to corrosion inspection of aircraft surfaces, maintenance personnel must be equally aggressive in preventing corrosion damage to aviation support equipment (SE). This equipment keeps the aircraft flying. The reliability and effectiveness of SE also depend largely upon the structural soundness of the metals that make up its parts. SE is used in a variety of climatic and atmospheric conditions, ranging from the hot, arid desert to cold, arctic regions. In addition, the equipment is used in the salt-filled atmosphere of coastal shore bases, islands, and aboard aircraft carriers. In this environment, the sea winds carry 10 to 100 pounds of salt per cubic mile of air. These varying environmental conditions promote corrosion and alter the speed and intensity of its development. Severe corrosion can cause components or systems to fail, perhaps during critical demand times. When this happens, replacements or corrective actions are costly, 4-1