A Guide to Aircraft Corrosion Types and Prevention Methods

Aircraft corrosion is a critical issue that can affect the longevity and safety of aircraft components, as it can compromise their structural integrity and performance. Understanding the various types of corrosion, their causes, and the methods for treatment and prevention is essential for maintaining the reliability of aircraft structures, and we will discuss it all in this blog.

1.Filiform corrosion

Firstly, filiform corrosion is a variation characterized by thread-like filaments that form beneath paint or other coatings on metal surfaces. This type of corrosion is particularly insidious because it is often not immediately visible, making early detection challenging. Filiform corrosion typically occurs in humid environments where moisture can penetrate beneath the protective coating, leading to the formation of corrosion cells that produce acidic environments and progressively eat away at the metal. The primary causes of filiform corrosion, aside from humidity, include improper surface preparation before painting and inadequate application of protective coatings. To treat filiform corrosion, it is necessary to remove the affected coating and clean the underlying metal thoroughly before applying new protective layers. Methods of prevention involve ensuring meticulous surface preparation and the subsequent application of high-quality, impermeable coatings.

2.Pitting corrosion

Pitting corrosion is another prevalent form of degradation characterized by small, localized pits or holes that penetrate a metal surface. This type of corrosion is particularly dangerous because it can lead to significant structural weakening with minimal surface evidence. Pitting corrosion typically occurs in environments where chloride ions, such as those found in saltwater, are present. The primary factors contributing to pitting corrosion include the presence of aggressive ions, such as chlorides, and the inherent susceptibility of the metal. The treatment of such corrosion involves mechanically or chemically cleaning the pits and applying protective coatings to prevent further attack. Meanwhile, preventative measures include using corrosion-resistant materials, applying protective coatings, and controlling the environmental exposure of susceptible components.

3.Intergranular corrosion

Intergranular corrosion is a type of corrosion that occurs along the grain boundaries of metal alloys like aluminum and stainless steel, leading to the weakening of the material. It is often caused by improper heat treatment or welding processes that create zones of differing chemical composition and microstructure along the grain boundaries, which then become anodic or cathodic relative to the rest of the metal and lead to localized corrosion. To treat intergranular corrosion, the affected areas must be removed, and the component should be heat-treated once again to restore its integrity. Prevention methods include using proper heat treatment procedures, selecting corrosion-resistant alloys, and avoiding processes that can introduce stress or contamination to the grain boundaries.

In addition to these specific types of corrosion, aircraft components are also susceptible to general surface corrosion, stress corrosion cracking, and exfoliation corrosion, each with unique characteristics and challenges. Stress corrosion cracking involves the growth of cracks due to the combined effect of tensile stress and a corrosive environment, while exfoliation corrosion occurs when layers of the metal peel away due to severe intergranular attack, similarly being exacerbated by stress and environmental factors.

Ways to Prevent Corrosion

Effective corrosion prevention and control in the aviation industry rely on several strategies. First and foremost, regular inspection and maintenance are critical for early detection and remediation of corrosion. Moreover, employing corrosion-resistant materials, applying high-quality protective coatings, and ensuring proper sealing and drainage of aircraft structures can significantly reduce the risk of corrosion. Additionally, it is a worthwhile practice to control the environmental conditions in which aircraft are stored and operated, such as using dehumidification systems and avoiding exposure to harsh chemicals. With a comprehensive approach to mitigating corrosion risks, those in the aviation industry can ensure the longevity and reliability of aircraft components and their fleet as a whole.

Conclusion

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