How is the cathodic protection of reinforcing steel in atmospherically exposed concrete structures primarily achieved?

The primary method for achieving cathodic protection of reinforcing steel in atmospherically exposed concrete structures is through impressed current systems. Impressed current systems are particularly effective because they provide a continuous source of current that can be adjusted and monitored to ensure effective protection of the reinforcing steel.

In an impressed current system, an external power source is used to drive a current through the reinforcing steel, effectively reducing the corrosion potential by making the steel a cathode in the electrochemical cell. This method is well-suited for large structures or conditions where high levels of corrosion are likely due to environmental factors.

While galvanic anodes can provide cathodic protection in some cases, they usually rely on the natural electrochemical potentials of the anodes and are more suited for smaller areas or scenarios where the damage is localized. Passive corrosion control methods and protective coatings serve as preventive measures rather than active cathodic protection systems. They help manage corrosion but do not provide the same direct current-driven protection that impressed current systems are designed to achieve.