Filiform Corrosion
Filiform corrosion is a type of undercutting corrosion where thread-like cracks spread over the metal surface. It mainly occurs on aluminum and steel when they are in humid environments.
Physico-Chemical Mechanism
Filiform corrosion arises from the action of hydrogen ions on the metal surface. These react with the aluminum or steel and form thread-like corrosion products that slowly penetrate the material structure.
Metallurgical Relevance & Risks in Welding
Filiform corrosion can occur due to poor surface preparation or lack of coating on aluminum and steel sheets. It leads to undercutting cracks that progressively destroy the material and impair its mechanical properties.
Workshop Practice & Instructions
To avoid filiform corrosion, it is crucial to prepare the metal surface thoroughly. This includes removing dirt, paint, and rust. For aluminum, an appropriate coating should be applied. The environment should be kept dry, and for steel sheets, a proper pretreatment with a suitable corrosion protector is necessary.