Corrosion mechanism of Ti-Cr alloys in solution containing fluoride.
OBJECTIVE
The objective of this study was to clarify the influence of chromium content on surface reaction of Ti-Cr alloys in an acidic fluoride-containing saline solution.


METHODS
Four Ti-Cr alloys containing 5, 10, 15 or 20 mass% chromium were characterized in terms of dissolution of metals in an acidic fluoride-containing saline solution and surface structure by X-ray photoelectron spectroscopy and Auger electron spectroscopy.


RESULTS
Total amount of metals dissolved from each alloy decreased with increase in chromium content. The surface oxide films of Ti-Cr alloys before and after immersion in an acidic fluoride-containing saline solution consisted of titanic and chromic species, such as oxide, hydroxide, and hydrate. The [Cr]/([Ti]+[Cr]) ratio in the surface oxide film on as-polished Ti-Cr alloys was closely correlated with chromium content. However, the ratio in any alloy approximately doubled after immersion. Although thick oxide films were observed after immersion, all alloys showed a thinner oxide film than commercially pure titanium.


CONCLUSIONS
In all alloys, concentration of chromic species such as oxide and hydroxide in the surface oxide film was associated with chromium content, and chromic species improved corrosion resistance to fluoride.
Takemoto
Shinji
S
Department of Dental Materials Science, Tokyo Dental College, Japan. takemoto@tdc.ac.jp
Hattori
Masayuki
M
Yoshinari
Masao
M
Kawada
Eiji
E
Asami
Katsuhiko
K
Oda
Yutaka
Y
D002858:Chromium Alloys / Q000737:chemistry*; D017608:Chromium Compounds / Q000737:chemistry; D003343:Corrosion; D005459:Fluorides; D008422:Materials Testing; D012995:Solubility; D012996:Solutions; D013057:Spectrum Analysis / Q000379:methods; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
D002858:Chromium Alloys; D017608:Chromium Compounds; D012996:Solutions; D014025:Titanium; D005459:Fluorides; C023600:chromic oxide