SEAL Aviation

Aircraft corrosion: Find it. Identify it. Prevent it. Fix it.

Every aircraft eventually becomes vulnerable to the omnipresent threat of metal corrosion. If corrosion is not detected and treated in a timely manner, it can lead to costly repairs and downtime.

Types of aircraft corrosion and where to find it:

1. Stress corrosion - Typically this type of corrosion appears in highly stressed metal parts like landing gear or engine crankshafts detected by non destructive testing.

2. Filiform corrosion - This type of corrosion develops on aluminum surfaces and will show up as tiny, worm-like lines underneath paint work causing it to bubble up and flake off detected by visual inspection and NDT.

3. Surface corrosion - Visual inspection

4. Dissimilar metal corrosion - Visual inspection

5. Exfoliation corrosion - Visual inspection

6. Chemical induced corrosion - Visual and NDT inspections areas like battery storage, laboratory including bacterial growth

7. Intergranular corrosion - This kind of corrosion attacks 7000-series alloys like stringers or wing spars. This form of corrosion is the most difficult to find and once found visually, typically it is too late to save that particular piece of metal. Early detection can be found by Non Destructive Testing.

As aircraft age corrosion will increasingly become a problem. Any aircraft that spend a substantial amount of time in a humid environment like Florida are very susceptible to the effects of corrosion. Regardless of where an aircraft is based, it is imperative that all aircraft be regularly inspected by technical personnel who have been specifically trained to recognize corrosion in its earliest stages to reduce repair cost and down time. Ferrous metals will exhibit a reddish discoloration while aluminum parts will sometimes have a grayish-white color on them. Key areas on a aircraft to inspect are fuel tanks, laboratory area, control hinges, battery boxes and anywhere on the aircraft that is devoid of paint.

Prevention is critical as is the fix.

Having personnel that are trained to inspect for early signs of corrosion will help reduce down time and repair cost. Keeping an aircraft constantly washed is imperative to prevent the accumulation of pollutants and dirt and can deter the progression of corrosion. Utilizing a corrosion inhibitor product can also play a role in preventing corrosion. Once found, fixing corrosion damage is a job best left in the hands of highly trained and certified technicians who are familiar with all aircraft types. A quick read of FAA Advisory Circular 43-4B will give one an idea of the complexities involved with the control of corrosion on aircraft.

Citation fuselage skin corrosion
Citation fuselage skin corrosion
Microbiologically Influenced Corrosion (MIC)