Ti-Mo焼結合金の腐食挙動について｜Nippon Tungusten Review

Key words	Sintered Ti-Mo alloy, corrosion resistance, polarization curve, HCl, NaCl
キーワード	Ti-Mo焼結合金，耐食性，分極曲線，HCl，NaCl

Key words

Sintered Ti-Mo alloy, corrosion resistance, polarization curve, HCl, NaCl

キーワード

Ti-Mo焼結合金，耐食性，分極曲線，HCl，NaCl

The corrosion behavior of Ti-(0 to 40)mass%Mo alloys prepared through powder metallurgy (PM) technology was studied by immersion test and electrochemical measurement. The corrosion rate of sintered Ti-Mo alloys in a 35%HCl solution decreased remarkably as molybdenum content increased. The corrosion rate of Ti-40mass%Mo alloy, for example, was found to be 5×10^-3 mm/year , which was 104 times lower than that of pure titanium. In a 3%NaCl solution, on the other hand, the corrosion rate was not affected by the molybdenum content of the alloy, and was less than 10^-3 mm/year.
Potentiodynamic polarization curves in a 35%HCl solution showed that with increasing molybdenum content the open circuit potential (corrosion potential) shifted toward noble potential, while the anodic current density decreased. It is thought that the presence of spontaneously-passivated film in which molybdenum is enriched by preferential dissolution of titanium suppresses the anodic reaction and improves corrosion resistance. On the other hand, increased molybdenum content in a 3%NaCl solution shifts the corrosion potential toward increased base potential, and increased anodic current density, because of the active molybdenum dissolution.

粉末冶金法を適用したTi-(0～40)mass%Mo合金の腐食挙動について、腐食試験および電気化学的測定法を使って研究を行った。35%塩酸溶液中のTi-Mo合金の腐食速度はMo量の増加とともに著しく小さくなった。例えば、Ti-40%Mo合金の場合は5*10^-3 [mm/year]の腐食速度であり、純Tiと比較して4桁低い値となった。一方、3%塩化ナトリウム溶液中の腐食速度はMo量に関わらず、10^-3 [mm/year]以下であった。
35%塩酸溶液中の動電位分極曲線によると、Mo量の増加とともに腐食電位は貴に移行し、アノード電流密度も低くなった。これは、合金上にTiの優先溶出によりMoが濃縮された自己不働態化被膜が存在するため、アノード反応が抑制され，耐食性が良くなったと考えられる。一方、3%塩化ナトリウム溶液中の動電位分極曲線ではMoが活性溶解するため、Mo量の増加とともに腐食電位は卑に移行し，アノード電流密度が高くなった。

1997 Volume 29

Abstract

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