Study of Overprotective-Polarization of Steel Subjected to Cathodic Protection in Unsaturated Soil

Autor:	Mandlenkosi G. R. Mahlobo, Peter Olubambi, Phumlani Mjwana, Marc Jeannin, Philippe Refait
Rok vydání:	2021
Předmět:	Technology Materials science Carbon steel 020209 energy polarization level 02 engineering and technology Electrolyte cathodic protection engineering.material Electrochemistry Article Corrosion Cathodic protection 0202 electrical engineering electronic engineering information engineering General Materials Science Polarization (electrochemistry) Voltammetry Microscopy QC120-168.85 voltammetry EIS QH201-278.5 carbon steel Engineering (General). Civil engineering (General) 021001 nanoscience & nanotechnology TK1-9971 Descriptive and experimental mechanics engineering Electrical engineering. Electronics. Nuclear engineering TA1-2040 0210 nano-technology unsaturated soil Layer (electronics) Nuclear chemistry
Zdroj:	Materials Materials, Vol 14, Iss 4123, p 4123 (2021) Volume 14 Issue 15
ISSN:	1996-1944
DOI:	10.3390/ma14154123
Popis:	Various electrochemical methods were used to understand the behavior of steel buried in unsaturated artificial soil in the presence of cathodic protection (CP) applied at polarization levels corresponding to correct CP or overprotection. Carbon steel coupons were buried for 90 days, and the steel/electrolyte interface was studied at various exposure times. The coupons remained at open circuit potential (OCP) for the first seven days before CP was applied at potentials of −1.0 and −1.2 V vs. Cu/CuSO4 for the remaining 83 days. Voltammetry revealed that the corrosion rate decreased from ~330 µm yr−1 at OCP to ~7 µm yr−1 for an applied potential of −1.0 V vs. Cu/CuSO4. CP effectiveness increased with time due to the formation of a protective layer on the steel surface. Raman spectroscopy revealed that this layer mainly consisted of magnetite. EIS confirmed the progressive increase of the protective ability of the magnetite-rich layer. At −1.2 V vs. Cu/CuSO4, the residual corrosion rate of steel fluctuated between 8 and 15 µm yr−1. EIS indicated that the protective ability of the magnetite-rich layer deteriorated after day 63. As water reduction proved significant at this potential, it is proposed that the released H2 bubbles damage the protective layer.
Databáze:	OpenAIRE
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