Tetsu-to-Hagane
Online ISSN : 1883-2954
Print ISSN : 0021-1575
ISSN-L : 0021-1575
Effects of Ni and Mo on Critical Conditions for Crevice Corrosion of Low Alloy Titanium
Takanori KIDOHShigeo TSUJIKAWA
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JOURNAL FREE ACCESS

1989 Volume 75 Issue 8 Pages 1332-1337

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Abstract

Critical conditions to repassivate growing crevice corrosion in terms of electrode potential, ER, temperature, TR, and NaCl concentration, CNacl, R, were determined for metal/metal-crevice of ASTM Grade 12 (G 12 Ti) and Ti-x (=0?2%)Ni-y(=0?0.4%) Mo alloys.
G 12 Ti with 0.8%Ni and 0.3% Mo has more noble ER values than commercially pure Titanium (C.P. Ti)and this tendency is more enhanced in lower concentrations of NaCl solutions. G 12 Ti is predicted to be resistant to crevice corrosion in solutions containing as high as 9% NaCl at 100°C, which is markedly high-er than 1% NaCl or less as the highest concentration for C. P. Ti to be resistant at the temperature.
ER value for Ti-x Ni-y Mo alloy depends almost on Ni content. Sufficiently noble value of ER is attained for the alloys with Ni contents over 0.2%. The beneficial effect of Ni could be explained from formation of Ti2Ni which works as Pd does in Ti-0.15 Pd alloy.
CNaCl, R depends not only on Ni content but also on Mo content. It decreases with increasing Mo content in the range from 0 to 0.1?0.2%, above which CNaCl, R increases with increasing Mo content. This shows beneficial effect of Mo combined with Ni. Based on the results of Ti-x Ni-y Mo alloy, characteristics of G 12 Ti are found to be accounted for approximately through its contents of Ni and Mo.

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© The Iron and Steel Institute of Japan
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