Sweet and Sour Service

Sweet gas service mean the gas which has no more than the maximum sulfur content defined by:

- the specifications for the sales gas from a plant;

- the definition by a legal body.

Hope this helps

'Sweet' corrosion is due to CO₂ in combination with water.

If you want to know more about corrosion, there are loads of excellent websites, including http://www.corrosion-doctors.org/CorrDocs/CDs.htm and http://corrosion.ksc.nasa.gov/PAforms.htm.

Have you ever heard of Google? A simple Google search on 'sweet' corrosion would have led you to dozens of useful sites. Why post your question here when a simple Google search would have yielded an answer much more quickly and completely?

When you talk about "Sweet" and "Sour Service" in selecting materials you refer to:

"Sweet" a service with no H2S and corrosion is mainly due to CO2

"Sour" a service with H2S content above the threshold defined by ISO 15156 / NACE MR 1075. The limit for carbon steel is 3 millibar of H2S (partial pressure of H2S) in the gas phase. When selecting material for a sour service you've to consider the requirements of NACE / ISO in terms of material supply, and material fabrications.

S

One addendum I would add, NACE MR 0175 also makes a distinction in the specific application of the material. Material that is acceptable for use in sour service for say packer slips (generally carbourized 8620) is not acceptable for a different application, such as say a coupling. MR 0175 also does not take CO2 or chloride cracking into account, so if that is an issue, you need to address that separately. 316 stainless in the annealed state for instance is acceptable per MR0175, but is very susceptible to Chloride attack.