What are visible signs of filliform corrosion?

Filliform corrosion is a type of corrosion that typically occurs under a painted surface, particularly when water or moisture is trapped beneath the paint layer. One of the most recognizable signs of filliform corrosion is the appearance of worm-like tracks, which are often accompanied by blistered paint surfaces. This phenomenon arises as the corrosion process creates gas and results in the lifting of the paint, forming blisters and those characteristic tracks that resemble worms meandering across the surface.

The presence of these tracks indicates that the corrosion is progressing under the paint, often leading to further deterioration if not addressed. This particular pattern of corrosion is distinct and serves as a warning sign that moisture and contaminants have infiltrated the protective layer, prompting the need for inspection and potential remediation to prevent further damage to the underlying metal.

Other manifestations of corrosion, such as rusted metal edges or cracked surfaces, indicate different types of corrosion and do not specifically represent filliform corrosion. The identification of blistered paint surfaces and worm-like tracks is crucial in recognizing and addressing filliform corrosion effectively.