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Cathodic Protection of Reinforced Concrete Structures
In reinforced concrete, a passive oxide film is created around the reinforcing steel by the alkaline Portland cement, which protects the steel from corrosion. This oxide film is weakened or destroyed when aggressive ions, like chlorides, attack the concrete around the reinforcing steel causing corrosion of the reinforcing steel. Corrosion is an electrochemical process having anodic and cathodic areas formed on the steel. When the circuit of the corrosion cell is completed by the presence of continuous steel bars connecting anodic and cathodic areas and by immersion in the same electrolyte, corrosion occurs at the anodic regions. The corrosion continues until failure occurs at the anodic area.
- Cathodic protection does not replace corroded steel
- Impressed current cathodic protection systems are not recommended for general usage on prestressed concrete structures because hydrogen produced can make the high-strength steels brittle in nature
- Passive sacrificial systems can be used for post- tensioned structures after detailed corrosion analysis
- Electrical continuity of the reinforcing steel and ionic conductivity of concrete must be confirmed during system installation.