Nondestructive flaw detection
2017-02-28 Rongda test 277 times
Detection Purpose: Make the metal surface produce dense structural film, increase the corrosion resistance of the metal
Detection range: All kinds of metal
Passivation, the metal due to the action of the medium generated by the corrosion products if there is a dense structure, formed a layer of film (often invisible), closely covered in the surface of the metal, the change of the surface state of the metal, the metal electrode potential greatly in the positive direction jump, and become a blunt corrosion resistance. Such as Fe→ When Fe2+, the standard potential is -0.44V, and after passivation, it jumps to +0.5 ~ 1V, which shows corrosion resistance of noble metals. This film is called passivation film.
Principle of passivation
The mechanism of its passivation can be explained by the thin film theory, that is, the passivation is considered to be due to the action of metal and oxidizing substances, which generates a very thin, dense, good covering performance and firmly adsorbed on the metal surface. This film exists in a separate phase, usually a compound of metal oxide. It plays a role of completely separating the metal from the corrosive medium, preventing the metal from contacting with the corrosive medium, so that the metal basically stops dissolving and forms a dull state to achieve the role of anti-corrosion.