Internal Corrosion Mechanisms and Mitigation

Pitting corrosion along the bottom of the pipeline is the primary corrosion mechanism leading to failures in sweet gas pipelines. The common features of this mechanism are:

• The presence of water containing any of the following; CO₂, bacteria, O₂, or solids;
• Pipelines carrying higher levels of free-water production with no means of water removal, i.e. well site separation or dehydration;
• The presence of fluid traps where water and solids can accumulate;
• Vapor phase corrosion is a less common mechanism that has also led to failures. Although not specifically addressed in this recommended practice, many of the preventative measures described in this document will also mitigate this mechanism.

See also:

• Rupture and Fire Near Carlsbad New Mexico August 19, 2000