Corrosion Inspection and Maintenance for Your Aircraft
Like anything made of metal, an aircraft is prone to corrosion that often happens when an alloy reacts with other chemical elements or compounds such as oxygen, hydrogen, and battery acids. Other things that can corrode an airplane include cleaning solutions, dirt, grease, water, and dust.
Certain environments can also predispose your aircraft to corrosion. For example, coastal areas can accelerate the corrosion rate of metals because of the high humidity and salt accumulation on the surface. This is why aircraft buyers generally stay away from planes that have spent much time along the Gulf Coast and the Pacific Coast.
Planes operating in corrosive environments require a more aggressive inspection and maintenance program to prolong their lifespan.
Corrosion Inspection: How to Recognize the Problem
When ferrous metals corrode, they usually develop some reddish deposits, while for aluminum, the telltale signs of corrosion are a cottage-like texture and the appearance of grayish-white powder.
During a corrosion inspection, pay close attention to the inside of wheel wells (especially when they are retractable), the trailing edges of control surfaces, the cylinder fins, the propeller surface and hubs, the areas around the fuel tanks, and the battery box.
Frequent inspection is essential to catch any early sign of corrosion, preventing it from becoming a bigger, costlier problem. (Note: Use a strong flashlight, a mechanic’s mirror, and a magnifying glass when doing your inspection.)
While visual inspection is often enough to detect signs of corrosion, your average flashlight may not do the job because it usually has dark spots because of the way it reflects lights off the lens; the problem may also be attributed to the shape of the filament.
When conducting a visual inspection, use light shaping diffusers (e.g., Torrance) attached to a flashlight lens. As their name suggests, they diffuse the light to create an even pattern, which is particularly helpful when viewing at a low angle.
Aircraft Corrosion Removal
In general, light surface corrosion is treated with abrasion followed by the application of a corrosion inhibitor, a primer, then a paint. In contrast, severe corrosion is often best addressed with a complete replacement.
When treating light corrosion, it is important to remove all the corroded areas, neutralize any residual materials in the crevices, and apply protective surface films, which may include temporary or permanent paint or coating.
Light corrosion removal is often performed using chemical and mechanical methods such as abrasive mat or paper, grinding, sanding discs, or metal wool. Meanwhile, the ideal removal technique will depend on the metal and the extent of the problem.
But before the actual removal of the corroded area, it is important to clean it first so that any grease and dirt will not interfere with the stripping chemical compound or the mechanical method. Through deep cleaning, you can also determine the extent of the problem, making sure that you only treat the affected site. (Note: If there is extensive corrosion on a panel, the general recommendation is to treat the entire section.)
Step-by-Step Corrosion Removal
- Brush the entire surface that needs to be chemically stripped. Make sure that any brush that has been exposed to a paint remover should not be used for other purposes.
- Leave the stripper on the surface between 10 minutes and a few hours, depending on the aircraft paint, weather, and humidity. Once the chemical has lifted the paint, you can brush the surface with a bristle brush saturated with paint remover.
- Reapply the stripper where paint remains and repeat the process until you remove all of it. Make sure that you only use non-metallic scrapers when removing stubborn paint finishes.
- Wash and scrub the surface with water and non-woven abrasive pad to remove any residual stripper and loose paint. You may also use low-to-medium water spray or steam-cleaning equipment.
- Apply a corrosion inhibitor, a primer, and lastly, a nice coat of paint.
Corrosion is a natural process, which means you cannot prevent it 100%. However, you can postpone this through treatments that include frequent washing to remove dirt and grimes. To further protect your aircraft from the corrosive elements, you must also treat it with corrosion inhibitors like ACF-50.
Corrosion inhibitors, which are generally applied in a mist form, protect the aircraft by eliminating moisture and creating a protective barrier to prevent moisture build-up.
Another surefire way to protect your aircraft from corrosion is to base it in a dry region. (Note: This is the reason why the Air Force has chosen the Arizona desert as its primary hangar.)
If you don’t have a hangar, a good alternative is to protect it with cabin covers and tightly seal all the windows to prevent moisture from reaching the fuselage from the inside out.
Other Ways to Prevent Aircraft Corrosion
- During the rainy season, seal the aircraft to protect it from water damage. In contrast, ensure that it has good ventilation during hot weather.
- Often drain any fuel cell sumps.
- Frequently wipe exposed areas with a dry fabric.
- Spot treat any surface that has early signs of corrosion with a metal polish.