Influence of AC Stray Current on Corrosion Electrochemistry Behavior

Overhead high voltage AC transmission lines and AC electrified railway can produce AC interference on buried pipelines, resulting in accelerating corrosion of adjacent buried pipelines. This study focuses on the relative direction of AC stray current by means of a self-made analog interference system of AC stray current. The electrochemical polarization curves were measured at various sample rotation angles to analyze and study the effect of vector stray currents on metal corrosion electrochemical behavior. The results showed that the AC stray current can promote the oxygen diffusion process of corrosion reaction depolarization, which could be strengthened with increasing stray current intensity. Additionally, to analyze AC stray current, the electric field can be decomposed into the vertical interference (vertical component), which is vertical to the metal surface, and the horizontal field (horizontal component), which is parallel with the surface. For the anodic process, the horizontal field can produce agitation due to diffusion path change, accelerating corrosion product shift from metal ions or metal surface into the environment, and can promote the anodic dissolution process; however, the vertical field is not significant in promotion of the anodic dissolution process.