What primarily causes stray current corrosion?

Stray current corrosion arises from the presence of electrical currents that flow through unintended paths, typically in the ground or through water. This can occur when an external power source, such as a nearby electrical system or ungrounded equipment, introduces voltage into the environment. The resultant currents can then interact with metal structures, such as pipelines or rebar in concrete, leading to electrochemical reactions that cause corrosion.

When stray currents pass through the metal, they can accelerate the natural corrosion process by shifting the electrochemical balance, which normally would require only minimal interaction with the environment. Unlike the other factors mentioned, which can contribute to corrosion processes under certain conditions, the primary driver of stray current corrosion is the unwanted flow of electricity from an external source. This electricity alters the protective equilibrium that typically exists on the metal surfaces, leading to localized corrosion and potential long-term structural damage if not properly managed.