Which type of corrosion is characterized by an external current flowing through water or soil?

Stray current corrosion occurs when an external electric current, often from nearby electrical systems or ground faults, passes through water or soil, leading to the degradation of metal structures. This type of corrosion typically affects buried pipelines, marine structures, and concrete-reinforced structures, resulting in accelerated corrosion rates due to the influence of the external electrical current. The current can disrupt the natural electrochemical processes on the metal's surface, leading to pits and localized wear.

Understanding stray current corrosion is essential for assessing the integrity and lifespan of infrastructure that may be affected by unintended electrical currents. In contrast, the other types of corrosion listed do not primarily involve external currents as a driving factor. For instance, galvanic corrosion occurs due to the electrochemical reaction between dissimilar metals in an electrolyte. Microbiologically influenced corrosion arises from the activities of microorganisms, while erosion corrosion is a result of mechanical wear from fluid flow. Each of these mechanisms has distinct characteristics and causes that differentiate them from stray current corrosion.