High Temperature H2-H2S Corrosion

High-temperature H2-H2S corrosion is typically categorized as a sulfidation process assisted by hydrogen, as opposed to sulfidation occurring without the presence of H2. This form of corrosion is predominantly associated with hydroprocessing operations, where temperatures rise above approximately 230°C (450°F), and both H2S and hydrogen are present. The forthcoming chapter will delve into the primary characteristics of H2-H2S corrosion, highlighting essential parameters and offering a tools for estimating corrosion rates

General Information

High-temperature H2-H2S corrosion represents a more aggressive form of traditional sulfidation. In this process, various sulfur species directly interact with the metal surface, forming corresponding sulfide scales. While H2-H2S corrosion also results in the formation of metal sulfide scales, the presence of hydrogen distorts this process, ultimately leading to higher corrosion rates compared to sulfidation without H2. For details on sulfidation, please refer to the Sulfidation Chapter.

It is worth noting that H2-H2S corrosion has not been the subject of as extensive research as sulfidation without H2. The primary investigations into H2-H2S corrosion were conducted over 50 years ago, leading to the formulation of what is known as the Couper-Gorman curves.1 2 3 These curves, following subsequent adjustments, establish correlations among H2S concentration, temperature, and the corrosion rate of diverse materials. While the Couper-Gorman curves reasonably predict corrosion rates in specific scenarios, in others, particularly at very low H2 concentrations, the predicted rates are lower than those observed in practical settings.6 7

Table 1 lists typical process areas susceptible to H2-H2S corrosion.

Table 1 Potential locations for H2-H2S corrosion in Hydroprocessing Units.3 5

Affected AreaComments
Feed stream after H2 injectionOperating T: >230°C (>446°F)
Before injection: use McConomy curves
After injection: use Couper-Gorman curves
Reactor outlet to hot HP separatorOperating T: >230°C (>446°F)
Couper-Gorman curves are in good correlation with industry data
From hot HP separator to REAC (before water wash)Operating T: >230°C (>446°F)
Couper-Gorman curves are in good correlation with industry data
Separator to Stabilizer columnOperating T: >230°C (>446°F)
Select either the McConomy or the Couper-Gorman curves based on the presence or absence of H2
McConomy/Couper-Gorman curves are in good correlation with industry data
Stabilizer/ReboilerOperating T: >230°C (>446°F)
Couper-Gorman curves are in good correlation with industry data
McConomy curves are in good correlation with field data at low H2S and lack of H2

High Temperature H2-H2S Corrosion is governed by a combination of several factors like chemical species and concentration, temperature, materials and/or flow regimes.

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References

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