Naphthenic
acid corrosion characteristic and corrosion product
film resistance of carbon steel and Cr5Mo low alloy steel in secondary vacuum
gas oil
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Type
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Journal
Article
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Author
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G.
Q. Liu
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Author
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X.
L. Zhang
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URL
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Volume
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51
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Issue
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6
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Pages
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445-454
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Publication
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Corrosion
Engineering, Science and Technology
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Date
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August
17, 2016
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Abstract
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While
naphthenic acid corrosion (NAC) has been studied extensively, the mechanism
of NAC is not fully understood. Researchers examined high-temperature NAC in
secondary vacuum gas oil of an industrial crude oil vacuum distillation
tower. They applied a high-temperature autoclave to conduct high-temperature
corrosion test to investigate NAC behavior of carbon steel and Cr5Mo low
alloy steel at different sulfur contents and total acid numbers (TAN).
Results revealed that the corrosion rate of carbon steel and low alloy steel
is high at low TAN and high TAN while it keeps at a low value at medium TAN.
Corrosion product film on Cr5Mo low alloy steel surface is denser and more compact than that of carbon steel at high TAN. The chromium present in Cr5Mo low alloy steel plays an important role in NAC resistance by the formation of Cr7S8 film in the inner layer of the scale. Corrosion rates of the two steels in secondary vacuum gas oil are high at low TAN and high TAN, but low at medium TAN. This differs from previous experimental results conducted in non-industrial oil solution. A tentative explanation for this new phenomenon is also put forward. |
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