Internal Corrosion by Sulfur Inspection

Process environments that contain sulfur compounds, such as H2S, can be very highly corrosive to carbon steels and low-alloy steels at temperatures above 500°F. This type of corrosion generally occurs as a general wastage of the material, but it can be more severe at locations of high velocity or impingement. Austenitic stainless steel cladding or weld overlays may be required to protect the shell of a pressure vessel from this type of corrosion.

Sulfur compounds can also cause corrosion of carbon steel and low-alloy steel at temperatures below the dew point of water, when they are dissolved in a condensed aqueous phase to form an inorganic acid. This type of corrosion is usually not too severe and can be adequately handled with a corrosion allowance or adjustments to the operating conditions to prevent the condensation of water. Process environments that contain ammonia in addition to H2S can be significantly more corrosive.

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