Sur le mecanisme de la passivite secondaire

✍ Scribed by A. Desestret; I. Epelboin; M. Froment; M. Keddam; Ph. Morel

• Book ID: 103065245
• Publisher: Elsevier Science
• Year: 1963
• Tongue: English
• Weight: 566 KB
• Volume: 8
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(63)85001-x

✦ Synopsis

Une 6rude potentiocin6tique de la courbe de polarisation avait d~j~t r6v616 l'influence pr~ pond6rante du carhone sur la passivit~ secondaire du fer, du nickel et des aciers inoxydables.

On examine d'abord le comportement d'aciers inoxydables aust6nitiques de diff6rentes teneurs en carhone. U apparaIt que la passivit6 secondaire ne peut ~tre expliqub~.comme fl a 6t6 propos6 darts la litt6rature, par la formation d'un oxyde a structure de spineUe mais par la presence clans la couche anodique de carbone ou de silicium favorisant la formation de combinaisons qni limitent la diffusion des substances r6agissantes.

Cette explication du mb:anisme de la passivit6 secondaire a 6t6 confil"m~e par une 6tude potenticstatique et potentiocin6tique de la transpassivit6 du nickel en fonction de la temp&ature et du pH de solutions aqueuses d'acide sulfurique.

Abstraet--A potentiokinetic study of polarization curves had already revealed the preponderant influence of carbon on the secondary passivity of iron, nickel and stainless steels.

We have now examined the behaviour of austenitic stainless steels of different carbon contents. It seems that secondary passivity cannot be explained, as proposed in the literature, by the formation of an oxide of spinel structure, but by the presence in the anode layer of carbon or silicon favouring the formation of material that limits the diffusion of the reacting substances.

This explanation of the mechanism of secondary passivity has been confirmed by a potentiostatic and potentiokinetic study of the transpassivity of nickel as a function of temperature and pH in aqueous sulphuric acid solutions. * prc~sent6 h la 13me r6union du CITCE, Rome, Septembre 1962.