The effects of cyclic bidirectional transients on buried steel corrosion

Cathodic protection (CP) may lose its effectiveness for protecting buried steel pipeline from soil corrosion due to the effects of potential excursions caused by stray currents. Although the effects of anodic excursions on CP are well-known, the effects of cathodic excursions have been rarely studied. In this work, the effects of cyclic anodic and cathodic transients on cathodically protected steel in aqueous and soil corrosion conditions have been studied. Corrosion in soil was visualised using an lectrochemically integrated multi-electrode array, often referred to as the wire beam electrode (WBE). The results showed that the amplitude of cathodic transient, as well as the ratio of anodic to cathodic cycles, can significantly affect the corrosion rates and patterns. For instance, if the cathodic transient leads to a very negative potential, e.g. −1350 mVvs.CSE, rapid corrosion would occur on buried steel.