Anodes are essentially zinc blocks which are tied to the reinforcing steel to prevent corrosion.
The zinc is considered sacrificial because it is more reactive than steel and will corrode before the steel does if the two metals are bonded together.
The sacrificial zinc anodes mitigate oxidation in the steel until the zinc is fully oxidized, thus extending the lifespan of the steel which it is bonded to.
Why Are Anodes Used in Concrete Repairs
Fresh concrete is extremely basic on the pH scale, overtime concrete becomes more acidic due to chlorides & carbonation.
When fresh concrete is placed next to the original concrete in a concrete repair, the steel at the perimeter of the patch is subject an electrical chemical imbalance.
This electrical chemical imbalance creates a different in the electrical potential between the passive steel in the fresh concrete patch, and the active corroding steel in the original concrete nearby. This is referred to as the Ring Anode Effect.
Sacrificial anodes are installed to the reinforcing steel at the perimeter of concrete repair patches, to mitigate the accelerated corrosion due to this Ring Anode Effect.
