Evaluation of Corrosion Progress Using Multichannel Iron Wire Electrodes Embedded in a Cement Test Block

Abstract

Eight thin iron wires were embedded in a cement test block to evaluate corrosion behavior during cement carbonization by CO 2 absorption. The gases supplied sequentially to the chamber containing the cement test block were air, CO 2 , and then air. Electrical resistance measurement of the thin wires revealed that the iron wires remained passivated during the supply of air and uncorroded during the supply of CO 2 to promote carbonization. The iron wires started corroding from the surface when the air was resupplied after carbonization due to the presence of O 2 in the air as an oxidizing agent. A set of two-electrode impedances between two selected iron wires was measured as a function of depth from the surface. The impedance of all electrodes dropped considerably several hours after the CO 2 supply due to the difference in the immersion potential of the iron wires as a function of depth, that is, the pH transition from alkaline to neutral. Consequently, the iron wires were polarized when electrically connected to each other during carbonization. After carbonization, each iron wire showed an impedance response corresponding to its corrosion condition, which depended on its depth.