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