Electrochemical study of calcareous deposit formation in simulated soil solution under cathodic protection

Mjwana Phumlani, Refait Philippe, Obadele Babatunde, Jeannin Marc, Olubambi Peter

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

Cathodic protection induces the formation of a calcareous layer has been shown to improve metal protection against corrosion by reducing the oxygen diffusion on the metal surface. The present study focuses on the electrochemical scaling induced by the application of cathodic polarisation. A combination of non-invasive in-situ electrochemical techniques and electrochemical impedance spectroscopy was used. Metal/electrolyte interface behaviour was studied using voltammetry to determine the controlling anodic and cathodic reactions. One-week long experiments were conducted. Applied potential –1.2 VSCE was shown to enable the formation of CaCO3 allotropes calcite and aragonite, and brucite due to increased interfacial pH which resulted in the formation of hydrogen at the electrode surface. Time constants from bode plots for applied potential –1.2 VSCE also illustrated the inhomogeneity of the calcareous layer. Modelling of polarisation curves illustrated a “passivation” phenomenon which resulted from formation of hydroxyl cations. This was further validated by bode plots with the added information on the diffusion reaction process. High frequency behaviour showed a steady increase in the electrolyte resistance which may be attributed to the formation of the calcareous layer. Evidence of the initial Mg-gel porous layer, which precedes the formation of brucite, was found.
Original languageEnglish
Title of host publicationKey Engineering Materials
PublisherTrans Tech Publications Ltd
Pages307-312
Number of pages6
ISBN (Print)9783035714807
DOIs
Publication statusPublished - 2019
Externally publishedYes

Publication series

NameKey Engineering Materials
Volume821 KEM

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  • Cite this

    Phumlani, M., Philippe, R., Babatunde, O., Marc, J., & Peter, O. (2019). Electrochemical study of calcareous deposit formation in simulated soil solution under cathodic protection. In Key Engineering Materials (pp. 307-312). (Key Engineering Materials; Vol. 821 KEM). Trans Tech Publications Ltd. https://doi.org/10.4028/www.scientific.net/KEM.821.307