Corrosion

WHAT ARE THE TYPES OF AIRCRAFT CORROSION?

Aircraft corrosion can be broken down into several different categories depending on what causes the corrosion, where it’s located and what it looks like. Distinct types of corrosion in aircraft to be aware of include:

Surface corrosion: The most common type of aircraft corrosion, surface corrosion occurs when metal on the surface of an aircraft oxidizes, such as when paint wears away. Typically, you can recognize surface corrosion by the roughening, pitting or etching of surface metal and the presence of grey-white powdery deposits on aluminum. However, another type of surface corrosion called filiform corrosion may resemble small worms underneath the paint surface, eventually leading to bubbling and cracking.

Dissimilar metal corrosion: Dissimilar metal corrosion appears when dissimilar metal parts come into contact with each other in the presence of a conductor. This type of electrochemical corrosion can cause extensive pitting damage. It often takes place out of sight, making it particularly dangerous.

Intergranular corrosion: This type of corrosion affects the grain boundaries of an alloy, so it’s often related to a lack of uniformity in alloy structure. Although intergranular corrosion often exists without surface evidence, it can lead to the lifting and flaking of surface metal over time. Extruded components may be particularly susceptible.

Stress corrosion: As the name suggests, stress corrosion develops when parts such as landing gear and engine crankshafts are put under sustained tensile stress in corrosive environments, sometimes leading to cracking and failure.

Fretting corrosion: Fretting corrosion is caused by the slight relative motion of two mating surfaces on an aircraft. Characterized by significant pitting and fine debris, this type of aircraft corrosion is greatly accelerated when water vapor is present.