Ti-Mo系焼結合金に形成される不動態被膜の構造｜Nippon Tungusten Review

Key words	sintered Ti-Mo alloy, corrosion resistance, passivation film, XPS, HCl, NaCl, NaOH
キーワード	Ti-Mo焼結合金，耐食性，不動態被膜，XPS, HCl，NaCl, NaOH

Key words

sintered Ti-Mo alloy, corrosion resistance, passivation film, XPS, HCl, NaCl, NaOH

キーワード

Ti-Mo焼結合金，耐食性，不動態被膜，XPS, HCl，NaCl, NaOH

The structures of passivation films of sintered Ti-(0, 10, 20, 30, 40,100)mass%Mo alloys formed in 35%HCl, 3%NaCl and 103mol/m3(3.8％)NaOH solution were studied by X-ray photoelectron spectroscopy (XPS). X-ray photoelectron spectra of Mo3d, Ti2p and O1s of Ti-Mo alloys immersed in a 35%HCl solution showed that Mo4+/Mo6+ ratio of the passivation film increased with increasing Mo content in the alloy and that Mo in the passivation film was enriched by the preferential dissolution of Ti in this film. This showed that the presence of Mo4+ state in this film was very important for improving its corrosion resistance. From X-ray photoelectron spectra of Ti-Mo alloys immersed in a 3%NaCl solution, it was indicated that the Mo content in the passivation film was equal to that in the alloy and that the passivation film consisted of mixture of Mo6+ and Ti4+ states. On the other hand, X-ray photoelectron spectra of Ti-Mo alloys immersed in a 3.8%NaOH solution showed that Ti in the passivation film was enriched by the active preferential dissolution of Mo. It was thought that the corrosion resistance of this alloy in NaOH solution was improved because of the passivation film consisted of stable Ti oxides

35％塩酸, 3％塩化ナトリウムおよび103mol/m3(3.8％)水酸化ナトリウム溶液中で形成された Ti-(0,10,20,30,40,100)mass%Mo焼結合金の不働態被膜の構造について、Ｘ線光電子分光法(XPS)を用いて研究を行った。 35％塩酸溶液中に浸漬させたTi-Mo合金のMo3d，Ti2p，O1sのＸ線光電子スペクトルでは合金Mo量の増加に伴い，不働態被膜中のMo4+ /Mo6+比が増加し，Tiの活性優先溶出によってMoが濃縮されていることがわかった．このことは被膜中のMo4+が耐食性改善にとって重要であることを示唆した．3％塩化ナトリウム溶液中に浸漬させたTi-Mo合金のＸ線光電子スペクトルから，被膜中の組成は合金組成に等しく，不働態被膜はMo6+およびTi4+で構成されていることがわかった．一方，3.8％水酸化ナトリウム溶液中浸漬させたTi-Mo合金のＸ線光電子スペクトルでは被膜中のMoの優先溶出によってTiが濃縮されていた．水酸化ナトリウム溶液中の耐食性が改善されたのは，不働態被膜が安定なTi酸化物で構成されていたためと思われる．

1999 Volume 31

Abstract

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