Application of voltammetry as a technique to monitor cathodic protection performance of steel in simulated soil solution

Abstract

Cathodic protection (CP) in combination with organic coating is applied as a secondary technique to mitigate corrosion of buried steel in an effort to prolong the lifespan of the buried steel pipeline. This study was aimed at developing and applying an adequate technique for monitoring the electrochemical behaviour of buried steel in the presence of CP. A modified voltammetry procedure was applied on carbon steel immersed in simulated soil solution for four days under open circuit potential (OCP) before applying CP for further ten days. Electrochemical impedance spectroscopy (EIS) was also applied at various time intervals to investigate the electrochemistry at the steel/solution interface. The voltammetry experiments revealed that the corrosion rate peaked at 680 µm/yr after three days of being subjected to OCP and then decreased to 411 µm/yr on day four as a result of a passive layer development on the steel surface. The corrosion rate was reduced from 411 µm/yr to 8 µm/yr as result of CP application before fluctuating between 21 and 40 µm/yr. The examination of steel surface via x-ray diffraction revealed the presence of calcareous deposit which resulted due to the application of cathodic protection.

Keywords

• Carbon steel
• Cathodic protection
• NS4 solution
• Voltammetry
• SEM
• XRD