Cathodic protection of buried steel structures: Processes occurring at the steel/soil interface during wet/dry cycles

Mandlenkosi G.R. Mahlobo, Peter A. Olubambi, Marc Jeannin, Philippe Refait

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The behavior of steel coupons buried in soil under cathodic protection (CP) was studied during wet/dry cycles using electrochemical impedance spectroscopy and voltammetry. The coupons were left at open circuit potential for 7 days before applying CP for 51 days at potentials of −0.8 and −1.0 V versus Cu/CuSO4 on coupons 1 and 2, respectively. Wet/dry cycling was achieved by first saturating the soil with an electrolyte inside a sealed electrochemical cell and by allowing the soil to dry by opening the top lid of the cell for various periods in the experiment. Surface analysis was performed after the experiments by X-ray diffraction and Raman spectroscopy. The soil electrolyte resistance Rs depended mainly on the variations of soil moisture for coupon 1 but was strongly affected by the effects induced by CP for coupon 2. Residual corrosion rates of 17–18 and 7–10 µm/year for coupons 1 and 2, respectively, were estimated via voltammetry. The kinetic parameters vary with the polarization level so that the data obtained with a coupon polarized at a given potential cannot be used to predict the residual corrosion rate of a coupon polarized at another potential.

Original languageEnglish
Pages (from-to)451-463
Number of pages13
JournalMaterials and Corrosion - Werkstoffe und Korrosion
Volume71
Issue number3
DOIs
Publication statusPublished - 1 Mar 2020

Keywords

  • EIS
  • carbon steel
  • cathodic protection
  • unsaturated soil
  • voltammetry
  • wet/dry cycles

ASJC Scopus subject areas

  • Environmental Chemistry
  • Mechanics of Materials
  • Mechanical Engineering
  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Materials Chemistry

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