Page 160 - Challenges in Corrosion Costs Causes Consequences and Control(2015)

138 CORROSION CAUSES

Figure 3.8 Internal corrosion of a crude oil pipeline (7).

Figure 3.9 External corrosion on a buried pipeline (7).

often utilize metallic structures such as pipelines in close proximity as a part of the
return path. This “stray” current can be picked up by the pipeline and discharged back
into the soil at some distance down the pipeline close to the current return. Current
pick-up on the pipe is the same process as CP, which tends to mitigate corrosion. The
process of current discharge off the pipe and through the soil of a DC current accel-
erates the corrosion of the pipe wall at the discharge point. This type of corrosion is
known as stray current corrosion and is illustrated in Figure 3.10.