Surface Chemistry of Passive Films on Ni-Free Stainless Steel: The Effect of Organic Components in Artificial Saliva
化学工程
材料科学
冶金
化学
纳米技术
工程类
作者
Deborah Biggio,Bernhard Elsener,G. L. Usai,Marzia Fantauzzi,Antonella Rossi
出处
期刊:Langmuir [American Chemical Society] 日期:2024-03-18
标识
DOI:10.1021/acs.langmuir.3c03728
摘要
The composition and thickness of the passive film formed on the surface of an austenitic Ni-free DIN 1.4456 stainless steel (18% Cr, 18% Mn, and 2% Mo) used in orthodontics were investigated by X-ray photoelectron spectroscopy following contact with three complex artificial saliva solutions containing different organic components. It was found that the synergistic action of low pH and the presence of sodium citrate and lactic acid in the Darvell formulation resulted in thin passive films strongly enriched in chromium phosphates and oxyhydroxides and depleted in iron oxide. The differences in the surface chemistry of the passive film formed upon contact with the different artificial saliva formulations can be related to the more intense alloy dissolution in the active/passive transition, as shown by the polarization curves. Citrates or lactic acid can complex iron and promote alloy dissolution. The corrosion rates diminish with time, and after 16 h, they are found to be about 0.5 μm/year for all saliva formulations examined.