Which corrosion prevention strategy involves forming a thin, adhering oxide layer that slows corrosion?

• A. Passivation
• B. Applying physical barriers
• C. Using metals that are relatively unreactive
• D. Slowing oxidation/reduction reactions by removing reactants

Answer: (A)

Passivation is the formation of a protective, adherent oxide layer on a metal surface that slows corrosion by acting as a barrier to water, oxygen, and ions. This oxide film forms in situ for metals like aluminum and stainless steel, creating a thin, stable shield that reduces the rate of active metal dissolution. If the film is scratched, it can quickly reform, restoring protection—this self-healing aspect is a hallmark of passivation. Because the protection comes from a surface film produced by the metal itself under the right environment, this strategy is distinct from applying an external barrier, from simply using inherently unreactive metals, or from trying to slow reactions by removing reactants from the environment. Therefore, forming a thin, adhering oxide layer that slows corrosion is passivation.