PSI - Issue 64

Hideki Oshita et al. / Procedia Structural Integrity 64 (2024) 48–55 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

49

2

Metals with a high ionization tendency Sacrificial anode

Auxiliary electrode

Corrosion protection current

supression

Corrosion current Corrosion protection current

supression

Direct Current

rebar

Corrosion current

rebar

Anode reaction

Cathodic reaction

Cathodic reaction

Anode reaction

concrete

concrete

Fig. 1. (a) External Power Supply Method; (b) Impressed Current Cathodic Protection

durability. Research on methods to prevent rebar corrosion is actively underway, and various corrosion protection techniques have been proposed. These approaches aim to prevent rebar corrosion and enhance the durability of RC structures. The primary corrosion prevention method currently in practical use for reinforcing bars is electrochemical corrosion protection. This method aims to prevent corrosion reactions on the corroded surface of rebars (anodic region) by eliminating the potential difference between the corroded region and the healthy region (cathodic region) and then External Power Supply Method (Galvanic Anode Method) by Kanbara (1969) and Impressed Current Cathodic Protection (ICCP) by Shigeno (1957) as shown in Fig.1 are proposed. The former method involves using an external direct current power supply to electrically connect auxiliary electrodes and reinforcing bars, forming an electrical circuit. By supplying a protective current to the reinforcing bars, it suppresses corrosion current and eliminates the potential difference on the surface of the bars. The latter method follows the same principle as the external power supply method, but with a key difference: it connects the reinforcing bars electrically to a sacrificial anode made of a metal with greater ionization tendency than iron. This ensures a continuous supply of protective current from the anode to the reinforcing bars. However, both methods have drawbacks. The external power supply method requires complex electrode placement, while the impressed current anode method involves relatively short lifespans for the anode material used in corrosion prevention, leading to significant replacement costs. Additionally, both methods share the major drawback of requiring protruding concrete cover for electrode installation. From the above all, considering the drawbacks of existing practical methods, urgent development of a novel electrochemical corrosion protection method that is non-destructive, non-contact, cost-effective, and easy to implement is essential. In this study, we aim to develop a new corrosion protection technique based on the principles of electrochemical corrosion prevention. Specifically, our approach relies on the electromagnetic induction method, which prevents the formation of localized galvanic cells that induce corrosion or rapidly collapses them if already formed. Experimental investigations were conducted on microcell corrosion of reinforcing bars exposed to salt damage in an atmospheric environment. Additionally, we examined macrocell corrosion in cracked RC members containing reinforcing bars. 2. Principle of Electromagnetic Induction-Based Cathodic Protection Method The principle of cathodic protection, as mentioned in the previous chapter, involves forcibly applying an external current to suppress the release of iron ions from the reinforcing bar into the pore solution within the concrete. The essence of this study lies in leveraging this perspective, but with a significant departure from conventional methods. Instead, we employ electromagnetic induction to achieve a more effective and non-destructive approach, all while maintaining a non-contact process. 2.1. Principle of cathodic protection The overview applying the electromagnetic induction corrosion prevention method to a single reinforcing bar, is illustrated in Fig 2. In this technique, a coil connected to an alternating current (AC) power source is installed on the concrete surface where the reinforcing bar is embedded. Under a specified frequency, AC current is