What are the different types of corrosion that affect your aircraft?

Corrosion is a big problem for every mechanic in the world. Like any other vehicle, aircraft are susceptible to corrosion. Its effects may or may not be seen right away, so it is best to always check up on your aircraft for affected areas. Corrosion is responsible for a lot of damages in your plane, and it will cost you a lot if they’re left untreated. 

To deal with this problem, mechanics apply paint on the different parts of the aircraft. The paint will help delay the effects of corrosion on the metal. However, all metals will succumb to corrosion in time. 

Types of Corrosion 

 These are different types of corrosion that affect aircraft: 

Uniform Surface Corrosion 

Uniform surface corrosion is the most common type of corrosion. It is also known as uniform etch or uniform attack corrosion. This type of corrosion appears as a uniform roughening of a metal’s surface, which is often accompanied by powdery deposits. It is caused by direct exposure of the metal to the oxygen in the air, like when the paint peels off. These factors speed up the process of uniform surface corrosion: poor pre-paint preparation, acid, high levels of humidity, and pollutants. 

Filiform Corrosion 

Filiform corrosion is a type of corrosion that occurs on metallic surfaces with a thin coat of organic film. It has a distinctive, worm-like trace of corrosion products beneath the paint. This type of corrosion occurs on metals exposed to high humidity and acidic environments. Steel and aluminum surfaces are affected by filiform corrosion, but its damage is more severe on aluminum. If left untreated, it can lead to other types of corrosion, such as intergranular corrosion, especially the fasteners and seams. 

Intergranular Corrosion 

This type of corrosion is difficult to detect and leads to serious damages that can render metals practically unusable. It attacks along the grain boundaries of an alloy and is commonly caused by the lack of uniformity of an alloy structure. This lack of uniformity results from changes during the heating and cooling process in the manufacturing of the material. High-strength alloys like the 7000-series alloys with significant amounts of zinc are more susceptible to intergranular corrosion if exposed to a corrosive environment or improperly heat-treated. 

Stress Corrosion 

Stress corrosion occurs in highly stressed parts of an aircraft, like the landing gear or engine crankshaft. Failures on the landing gear and crankshafts are often associated with this type of corrosion. Stress may be caused internally or externally. Internal stress comes from the manufacturing process of the material, while external stress is introduced during riveting, welding, clamping, bloating, etc. Stress corrosion effects may be reduced by stress relief heat treatments or applying protective coatings and corrosion inhibitors. 

Crevice Corrosion 

Also known as concentration cell corrosion, this type of corrosion occurs in metal-to-metal joints. It can happen even if the metals joined are identical. Places, where moisture and other pollutants are trapped, are common corrosion spots. 

Pitting Corrosion 

Pitting corrosion is one of the worst types of corrosion. It can affect any metal but is more prevalent on metals that form protective oxide films, like aluminum and magnesium alloys. It appears as white or grayish powdery deposits on the surface like dust. When you remove these deposits, you will see numerous tiny pits that penetrate deep into the metal. Even though they look small, the damage they do beneath the surface is terrible. 

Corrosion Treatment 

As long as it is made of metal, any type of aircraft will be affected by corrosion. Therefore, it is necessary to take several precautions to keep your aircraft’s airworthiness. Just like the old saying, prevention is better than cure. And that goes the same way for dealing with corrosion. Keeping your aircraft in a low-humidity environment will help delay the effects of corrosion. Washing your aircraft frequently to remove dirt and other pollutants will also do the same. If possible, place your aircraft inside a hangar. If not, make use of cabin covers and seal all the windows tightly to prevent moisture from going inside the fuselage. 

When your aircraft already has signs of corrosion, though, the only way to fix it is to remove them. Minor damages can be repaired by using abrasion, application of primers, and repainting. However, severe instances of corrosion need replacement of the affected parts. Under these circumstances, it is best to seek help from professionals. 

Knisley Exhaust specializes in all aircraft repairs you will need. If you find yourself having trouble with corrosion on your aircraft, contact us at Knisley Exhaust, and we will fix it for you.