How Cathodic Protection Works in Concrete

The main causes of corrosion of steel in concrete are chloride attack and carbonation. These two mechanisms are unusual in that they do not attack the integrity of the concrete. Instead, aggressive chemical species pass through the pores in the concrete and attack the steel. This is unlike normal deterioration processes due to chemical attack on concrete. 

A number of fundamental measures can be taken to address the problem of reinforcing steel corrosion. However, an important 

The following sections describe how CP can be used to protect reinforced concrete structures against corrosion by using either an ICCP system or sacrificial anodes. 

ICCP consists in polarizing the rebar with a DC current source (rectifier) to a cathodic potential where anodic dissolution of the rebar is minimized (Fig. 13.20). Three basic methods are available for controlling the output of a rectifier  

Unfortunately, the current requirement cannot be measured directly and various indirect criteria have been proposed (Table 13.1). The ICCP current requirements are often expressed in terms of the potential of the reinforcing steel relative to a reference electrode, or alternatively as a shift in this potential when the ICCP system is activated or deactivated. Reference electrodes can be located externally by being placed in contact with the outside concrete surface, or they can be embedded directly in the concrete with the rebar. 

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