Conventional and pulse cathodic protection of reinforced concrete: Electrochemical behavior of the steel reinforcement after corrosion and protection

Abstract

The applicability and efficiency of an alternative for impressed current cathodic protection (CP) for reinforced concrete, based on pulse technology, was investigated. The technique, denoted as pulse CP (pCP), was evaluated on the basis of a comparative analysis to reference (non-corroding), corroding, and conventional CP conditions, in terms of long-term monitoring of electrochemical parameters for the embedded steel with time of corrosion and protection. The hereby reported results are for the total duration of the experiment, i.e., 460 days of conditioning, also presented in comparison with earlier stages. Protection was applied after corrosion was initiated (using corrosion medium of 5% NaCl), at different time intervals (here reported are starting points 60 and 150 days of age). Both CP regimes used current density of 5 or 20 mA/m 2 steel surface. The pulse CP was applied as a pulse-shaped block current (square wave) with the current itself being the feedback control signal, using 12.5-50% duty cycle at 500 Hz to 1 kHz frequency. Under equal environmental conditions and for a comparatively long period of application, the pulse CP was found to perform as effectively as the conventional CP with regard to electrochemical behavior of the steel reinforcement. Furthermore, the pulse CP technique was found to achieve more rapidly the so called ''open circuit potential (OCP) passivity'' as a result of an enhanced ion transport (chloride withdrawal) and more favorable cement chemistry (increased alkalinity around the steel reinforcement).

Corrosion Performance of Carbon Steel in Simulated Pore Solution in the Presence of Micelles

“…44 These preliminary investigations did not fully reveal whether the nanoaggregates were indeed present at the steel/cement paste interface and/or on the steel surface ͑considering the nanosize of the formations and the variety of cement hydration/corrosion products on the steel surface͒. Although steel corrosion in cement-based materials was substantially studied and results were reported ͑including some of the present authors͒, [45][46][47] the remaining fact is that the system reinforced mortar ͑and concrete, respectively͒ is highly heterogeneous and complicated by itself. Therefore, the presence of nanoaggregates ͑as hereby discussed͒ leads to even more complexity in deriving electrochemical response for the steel reinforcement or within the steel surface analysis.…”

Assessing the long term benefits of Impressed Current Cathodic Protection

“…ICCP of atmospherically exposed steel reinforced concrete structures has been used since 1970s and it is a proven technique which is able to arrest ongoing corrosion and induce and sustain steel passivity [1]. The main principle of cathodic protection is applying an impressed current such as to induce negative steel polarisation [2], in other words to drive the steel potentials more cathodically than -850 mV (SCE), where corrosion process is thermodynamically impossible to occur [3].…”

Electrochemical and Microstructural Studies in Reinforced Mortar, Modified with Core-Shell Micelles

“…2, 3). Moreover, the higher chloride concentration, is not a result of higher porosity, since both OPCcorr and PoOPCcorr present approximately 12% porosity at 320 days of age (6). Obviously hydration mechanisms were altered as a result of the presence of the micelles, leading to increased chloride threshold in the specimens and thus impeded corrosion products formation.…”