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Cathodic protection of buried steel structures: Processes occurring at the steel/soil interface during wet/dry cycles
Author(s) -
Mahlobo Mandlenkosi G. R.,
Olubambi Peter A.,
Jeannin Marc,
Refait Philippe
Publication year - 2020
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.201911155
Subject(s) - cathodic protection , corrosion , cyclic voltammetry , dielectric spectroscopy , electrolyte , materials science , polarization (electrochemistry) , raman spectroscopy , water content , electrochemistry , metallurgy , analytical chemistry (journal) , composite material , electrode , chemistry , environmental chemistry , geotechnical engineering , geology , physics , optics
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/CuSO 4 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 R s 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.