A Novel Corrosion Rate Monitoring Method for Steel in Soil Based on Tafel Extrapolation Method

ABSTRACT It is important to monitor the corrosion rates of steel in electrolyte environments such as aqueous solution as well as soil in order to evaluate the integrity of the members of facilities. As a nondestructive monitoring method, CIPE (Current Interrupted Polarizing Extrapolation) method was developed. By the CIPE method the corrosion rate is calculated by the Tafel equation obtained from the polarization curve of in-situ measurement. It was found that the CIPE method was useful to monitor corrosion rates of steel in concrete as well as in neutral aqueous solution as presented in the conferences of CORROSION 2018 and 2019. In this paper, results of corrosion rates of carbon steel in sand containing sea water, which were measured by the CIPE method were discussed. As a result, it was confirmed that the CIPE method was also useful to monitor corrosion rates of carbon steel in soil. Furthermore, it was considered that when dissolved oxygen decreased the corrosion rate became negligible and the test piece behaved as a reference electrode without corroding.