A method for passivating a metal surface including, generating an atmospheric plasma beam by electrical discharge in a working gas, introducing an acid-containing passivating agent into the plasma beam, applying the plasma beam containing the passivating agent to the metal surface, and depositing a passivating salt on the metal surface by a reaction between the acid-containing passivating agent and the metal surface. This method simplifies the process for passivating a metal surface and renders it more effective.