Elemental Sulfur Corrosion | Materials And Corrosion Control
| Damage Mechanism | Elemental Sulfur Corrosion |
Damage Description |
· Oxygen oxidizes hydrogen sulfide into elemental sulfur, which is kept soluble by combining with H2S to form polysulfide. This inhibits corrosion of steel, but it is not very stable if moisture is present, corrosion is related to the formation of hydrosulfide (HS) and the formation of iron sulfide (FeS). In partially drained process lines, oxygen, coupled with relative humidity, creates rapid corrosion. · With hydrocarbons, it reacts slowly to form H2S which can cause cracking of hardened alloys and cause wet sulfur corrosion especially during downtime. · Oxidation of hot sulfur, by exposure to air, forms SO2 and SO3. · Molten sulfur can be handled by carbon steel up to 275°F. Corrosion is mostly caused by contaminants such as H2S, H2O and Oxygen. Elemental sulfur, in the presence of oxygen, can also oxidize iron and can cause corrosion. |
Affected Materials |
Carbon steel |
Critical Factors |
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Affected Units or Equipment |
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Appearance or Morphology of Damage |
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Prevention/Mitigation |
· Blanket storage tanks and surge vessels with inert gas to prevent oxygen ingress. Ensure that the nitrogen has minimum oxygen (from mothballing manual)
· Wet acidic sulfur requires the use of alloy materials such as stainless steels and Alloy 20. · Ensure complete draining of process lines containing sulfur during downtime to avoid corrosion that may result from O2 contamination |
Inspection and Monitoring |
· Visual and Ultrasonic Thickness measurements for internal equipment inspection
· UT scans or Profile Radiography for external inspection |
Inspection Frequency |
· UT and RT per OSI output.
· Internal inspections |
Key Performance Indicators (KPIs) |
· # Failures due to elemental sulfur corrosion · # TMLs with corrosion rate > 5 MPY · # TMLs with corrosion rate > 10 MPY |
Plant Integrity Windows (PIWs) |
· Dew Point |
Competencies and Training |
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Reference Resources (Standards/GIs/BPs) |
· “Process Industries Corrosion – The Theory and Practice” NACE International, TX, 1986
· Contamination and Purification of Alkaline Gas Treating Solutions by John G McCullough and Richard B. Nielsen, |
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