Correlation between soil electrical resistivity, polarisation resistance and corrosion of steel

ABSTRACT

Soil electrical resistivity, polarisation resistance and similar techniques sometimes are used for predicting both the short and the long-term corrosion of metals such as steels in soils. Herein new field data for pipes after 63 years exposure are presented that show poor correlations to electrical resistivity. One of the reasons is that electrical current flow and hence resistivity cannot be a surrogate for the electrolytic ionic diffusion of metal ions in the corrosion process. Also, corrosion in soils largely is governed by differential aeration, facilitated by air-voids at the soil/metal interface. This phenomenon is not considered in conventional electrochemical experiments. The practical implications are discussed.

KEYWORDS:

• Soil
• steel
• corrosion
• electrical resistivity
• polarisation resistance

Acknowledgements

The authors acknowledge the assistance provided by Sydney Water Corporation in enabling the provision of the electrical resistance, polarisation resistance and historical data used herein. The LPR work was carried out by PCA Echologics, Northmead, Sydney, and the soil testing by SESL Australia, Thornleigh, Sydney.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Robert E. Melchers http://orcid.org/0000-0002-1068-4368

Additional information

Funding

The authors acknowledge the financial support provided for this project by Sydney Water Corporation.