Repassivation

Definition

Repassivation is the reformation of a protective passive film after it has been damaged. Its speed and ability determine whether localized attack can take hold.

Stainless steel repassivates almost instantly under good conditions, but the process is hindered by low oxygen and by chloride, which forms soluble metal complexes that prevent film recovery. When anodic sites are exposed faster than they can repassivate, such as at high-shear fittings, corrosion localizes. Inside an established pit, diverging local chemistry makes repassivation unlikely, which sustains the attack.

Related concepts

Pitting Corrosion · Passivation · Chloride Attack

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Part of The Blueprint of Water · ⚡ electrochemistry