What is critical about the visibility of corrosion in aircraft materials?

Corrosion in aircraft materials is a significant concern because it can compromise structural integrity and safety. The correct choice highlights that corrosion can be both visible and not visible, which is critical for maintenance and safety assessments.

Certain types of corrosion, such as subsurface corrosion, can occur beneath protective coatings or in areas that are not easily seen. This means that there may be serious degradation of the materials, impacting the aircraft's performance and safety, even though no external signs are present.

Understanding that corrosion may not always be apparent stresses the importance of regular inspections, including methods like non-destructive testing, so that underlying issues can be identified and addressed proactively. Recognizing this helps technicians to remain vigilant and thorough in their maintenance practices, ensuring the reliability and safety of the aircraft.