Which arrangement is considered more desirable for cathodic protection?

In cathodic protection systems, the effectiveness of the arrangement largely depends on the current distribution and the potential developed across the surfaces. A small cathode paired with a large anode is desirable because it allows for efficient current flow and minimizes the current density on the anode. This configuration reduces the risk of anode dissolution or damage while ensuring that the cathode (the structure being protected) receives sufficient protection from corrosion.

Having a large anode relative to the small cathode helps to spread the protective current over a wider area. Since the anode is larger, it has the capacity to release the requisite electrons to protect the small cathode effectively, which is actively corroding. This arrangement leads to lower corrosion rates at the cathode, making it a more efficient use of resources and energy.

Overall, this configuration significantly enhances the protection of the structure in need and results in a more balanced and effective cathodic protection system.