Kyuya Nagasaki1, Shiro Haruyama1, Teruo Miyashita2 and Satoru Asawa3
1Department of Metallurgical Engineering, Faculty of Engineering, Tokyo Institute of Technology, Tokyo
The anodic behavior of Fe-Ti alloys (0.2 ∼ 7.5Ti wt%) was investigated in acidic (pH 3.50) and alkaline (pH 8.40) solutions by using an electronic potentiostat. The results are summarized as follows: (1) The potentiostatic transient current of the alloys decreased in reverse proportion to time in the passive region. (2) In α single phase alloys the Flade potential observed in the acidic solution shifted to the noble direction with increasing Ti content. As to α + TiFe2 alloys, however, they remained constant regardless of Ti content. Therefore it was concluded that the Flade potential of Fe-Ti alloys was controlled by the α matrix. (3) The anodic current in the passive range decreased with increasing Ti content in the acidic solution, while it increased in borate-boric acid solution. (4) Transpassive dissolution was observed at about 1100 mV (vs. S.C.E.). Especially in α + TiFe2 alloys, a sharp current increase was observed, due to a combined effect of the transpassive dissolution of the α matrix and the fall-off of TiFe2.
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