Ti-Mo系焼結合金のNaOH溶液中の腐食挙動 Corrosion Behavior of Sintered Ti-Mo Alloy in NaOH Solution
The corrosion behavior of sintered Ti-(0, 10, 20, 30, 40)mass%Mo alloys in (10, 10<SUP>2</SUP>, 10<SUP>3</SUP>, 10<SUP>4</SUP>)mol/m<SUP>3</SUP> NaOH solution was studied by immersion test and electrochemical measurements. The corrosion rate of sintered Ti-Mo alloys in NaOH solution increased with increasing NaOH concentration and Mo content. The corrosion rate of Ti-40mass%Mo alloy in 10<SUP>3</SUP>mol/m<SUP>3</SUP> NaOH solution, for example, exhibited 5×10<SUP>-3</SUP> mm/year, which was 10 times higher than that of pure Ti. But any corrosion rate of Ti-(10, 20, 30, 40)mass%Mo alloy in 10<SUP>3</SUP>mol/m<SUP>3</SUP> NaOH solution was less than 1×10<SUP>-2</SUP> mm/year. This fact showed that these alloys had a high corrosion resistance in 10<SUP>3</SUP> mol/m<SUP>3</SUP> NaOH solution. Immersion test showed that dissolved Mo content was higher than Mo content in the alloy, in spite of Mo content or NaOH concentration. An intergranular corrosion was observed in SEM microstructure of Ti-(20, 30, 40)mass%Mo alloys after immersion test. Potentiodynamic polarization curves in 10<SUP>3</SUP>mol/m<SUP>3</SUP> NaOH solution showed that the open circuit potential (corrosion potential) shifted toward more noble potential and corrosion current density increased slightly as the alloy Mo content increased. This might be caused by the unstable spontaneously passivated film formed by the active preferential dissolution of Mo in the alloys.
粉体および粉末冶金 45(8), 769-774, 1998-08-15
Japan Society of Powder and Powder Metallurgy