What type of corrosion occurs under painted or plated surfaces, appearing as worm-like filaments?

Filiform corrosion is a specific type of corrosion that can occur beneath painted or plated surfaces, characterized by the appearance of worm-like filaments. This type of corrosion typically arises when moisture or moisture-laden environments penetrate through the coating, leading to localized corrosion underneath. The moisture forms an electrolyte that facilitates the corrosion process, while the protective layer remains intact at the surface level, making the corrosion less noticeable.

The filiform structure, resembling small, thread-like formations, is created as the corrosion progresses, often along the edges and seams of the coated area. This can be particularly problematic in aerospace applications, where maintaining the integrity of surface treatments is critical to the durability and safety of aerospace components. Understanding the nature of filiform corrosion is essential for prevention and maintenance in engineering contexts.