Passivation by Metal

In “The Blueprint of Water”, passivation is described as a ceasefire, not immunity: corrosion by-products form a thin surface film that raises resistance to electron transfer, ion migration, and oxidant access. Each common metal forms a different film with its own stability window and its own way of failing.

Metal	Passive film	Stability window	What breaks it
Mild (carbon) steel	Loose, porous iron oxide layer, patchy and easily disturbed	Survives only where operating conditions stay stable enough to avoid stripping the film	Once breached, corrosion resumes immediately at the exposed site; easily disturbed by upset conditions
Copper	Dense, adherent patina from copper ions reacting with oxygen and carbonate species	Often protective, limiting electron transfer and shielding the metal beneath	Conditions that destabilize the patina chemically, mechanically, or biologically
Stainless steel	Exceptionally thin chromium oxide film, only atoms thick but tenacious and self-healing	Reforms almost instantly when damaged, provided oxygen is present	Low oxygen (anaerobic) environments interfere with repassivation; chloride-rich environments drive localized attack
Galvanized steel	Zinc coating (a less noble metal) that sacrifices itself, supplying electrons and satisfying cathodic demand	Protects the steel beneath as long as zinc remains	The truce ends when the zinc is consumed

Related concepts

Passivation · Corrosion Cell · Film Saboteurs · Galvanic Corrosion · Anodic Protection · Cathodic Control · Larson-Skold Index · Under-Deposit Corrosion · Oxygen Differential Corrosion

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Part of The Blueprint of Water