Film growth and proton sorption-desorption on passive iron in neutral solution

✍ Scribed by Norio Sato

• Publisher: Elsevier Science
• Year: 1967
• Tongue: English
• Weight: 845 KB
• Volume: 12
• Category: Article
• ISSN: 0013-4686
• DOI: 10.1016/0013-4686(67)80109-9

✦ Synopsis

Abrtraet-Iron in the passive state in neutral boric-acid-borate solution was anodically oxidixed or cathodicagy reduced in the potential regions of passivity and oxygen evolution. It is shown that the potential of passivated iron is not a single-valued function of the surface tilm thickness but is controlled by only a small amount of charge, equivalent to less than 1 r cent of the Slm thickness, which can be associated with protons sorbed in the outermost layer oft e oxide. llY The rate of proton sorption at constant potential decreases with increasing the amount of proton sorbed, according to is = A. exp (-AQ43.1, which is of the same form as the equation for the steady growth of the surface oxide on iron. Constant B. depends on the tilm thickness Qr, and a kinetic parameter ba = d&/dQr is a function of the potential at which proton is sorbed. The parameter b. decreases with potential, extrapolating to zero at the oxygenevolution potential, suggesting a correlation between the sorption-desorption kinetics of proton in the outermost layer of the surface oxide and the onset of oxygen evolmion.

R&mrn&L'on a proc&ie a l'oxydation anodique et B la reduction catbodique du fer a p&at passif dans une solution neutre d'acide bori ue-borate, d'evolution d'oxyglne. On montre