Corrosion of the Titanium and Titanium Alloys for Biomaterials under Fluoride Containing Environment
The corrosion behavior of pure Ti, Ti-6Al-4V, Ti-6Al-7Nb alloys and new Ti-(0.1-2.0)wt%Pt (or Pd) alloys in a fluoride containing environment were examined by anodic polarization and corrosion potential measurements. SEM observation was performed before and after immersion in the test solutions. The artificial saliva containing 0.1% and 0.2% NaF (corresponding to 453 and 905 ppmF) and artificial saliva with a low level of dissolved oxygen were used as the test solutions. In an acidic environment (pH 4.0) including fluoride, surfaces were roughened markedly by corrosion for pure Ti and Ti-6Al-4V and Ti-6Al-7Nb alloys, although the surface of Ti-Pt (or Pd) alloys was not affected for the most part. With a low level of dissolved oxygen, surfaces were damaged microscopically by corrosion for pure Ti, Ti-6Al-4V and Ti-6Al-7Nb alloys even with a fluoride concentration included in commercial dentifrices, although the surface of Ti-Pt (or Pd) alloys did not change. The Ti-0.5wt%Pt (or Pd) alloys were expected to be useful as a new Ti alloy with high corrosion resistance in dental use.