Aging of Passive Oxide on SUS304 Stainless Steel in a Sulfuric Acid Solution. Issue 8 (2nd June 2016)

• Record Type: Journal Article
• Authors: Ohtsuka, Toshiaki; Ueda, Mikito; Abe, Masatoshi
• Is Part Of: Journal of the Electrochemical Society. Volume 163:Issue 8(2016)
• Page Start: C459
• Page End: C469
• Publication Date: 2016-06-02
• Subjects: n-type semiconducting -- oxide -- passive -- stainless steel -- SUS304; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0721608jes
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : The passive oxide film on SUS 304 stainless steel (SS) was studied in a 0.1 mol dm −3 sulfuric acid solution as a function of passivation time. The passive oxide films were measured by ellipsometry and X-ray photoelectron spectroscopy (XPS). A Mott-Schottky plot of the film capacitance was employed to determine the donor density in the n-type semiconducting oxide film, and current measurements of the Fe 3+ /Fe 2+ redox couple were employed to investigate the electronic transfer process on the passive oxide film. The passive oxide consists of Cr-Fe-Ni oxides in which enrichment of Cr to 57 mol% occurs as the potential increases. During the aging of the passive oxide at 0.6 V vs. Ag/AgCl/saturated KCl (SSC) for 43 ks, the current decreased from 30 μA cm −2 at 10 s to 0.025 μA cm −2 at 43 ks, and the Cr ratio in the oxide increased from 49 to 57 mol% with an increase in the O 2– ratio. Notably, the film thickness remained nearly constant at 1.3 nm during the aging process. Enrichment of the Cr content resulted in a decrease in the donor density of the n-type semiconducting passive oxide and the inhibition of electronic charge transfer from/to the Fe 3+ /Fe 2+ redox couple in the electrolyte.