The reaction starts at the surface and proceeds uniformly.

The basis metal is eaten away and perforated in places in the manner of holes, the rest of the surface being affected only slightly or not at all.

The corrosion causes localized scarring.

Imperceptible or barely perceptible from outside, since the corrosion proceeds at the grain boundaries.

The grain boundary material is retained, since the corrosion proceeds preferentially within the grain.

Increased corrosion in crevices or cracks or at contact surfaces between two metal articles.

Corrosive attack on structural constituents

Occurs in deformed articles. Corrosion follows „fiber orientation“.

Frequently observed at water-air interfaces.