The effect of Al on the corrosion behavior of Ni-Mo in a H2/H2O/H2S gas mixture |
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| Authors: | Y R He D L Douglass |
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| Affiliation: | (1) Materials Science and Engineering Department, University of California at Los Angeles, 90024-1595 Los Angeles, California |
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| Abstract: | The corrosion behavior of seven Ni-Mo-Al alloys was investigated over the temperature range of 600–950°C in a mixed-gas atmosphere of H
2/H
2O/H
2
S. The parabolic law was followed at low temperatures, while linear kinetics were generally observed at higher temperatures. At a fixed Mo content, the transition from parabolic to linear kinetics shifted to higher temperature with increasing Al concentration. Double-layered scales generally formed on alloys having a low Al content, consisting of an outer layer of nickel sulfide and a complex inner scale. The thickness of the outer scale and the inner scale decreased as the Al content increased. The outer scale became porous and discontinuous with increasing Al content and temperature. Al
2
O
3
was detected in the scales of all alloys corroded at higher temperatures ( 800°C), even though the amount of Al
2
O
3
was very small in some cases. The decrease in corrosion rate with increasing Al content may be attributed to the formation of Al
2
O
3,Al
0.55
Mo
2
S
4,and Al
2
S
3
in the inner scale. |
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| Keywords: | mixed gas Ni-Mo-Al alloys Al2O3 MoS2 Al0 55Mo2S4 Chevrel phase |
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