pitting

Pitting corrosion, or pitting, is a form of extremely localized corrosion that leads to the random creation of small holes in metal. The driving power for pitting corrosion is the depassivation of a small area, which becomes anodic (oxidation reaction) while an unknown but potentially vast area becomes cathodic (reduction reaction), leading to very localized galvanic corrosion. The corrosion penetrates the mass of the metal, with a limited diffusion of ions.
Another term arises, pitting factor, which is defined as the ratio of the depth of the deepest pit (from localized corrosion) to the average penetration depth (mean thickness of the corrosion layer produced by the general uniform corrosion), which can be calculated based on the weight loss and corrosion products density.

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