Anode beds are typically filled with which substance?

Anode beds are primarily filled with coke breeze due to its properties that enhance the efficiency of cathodic protection systems. Coke breeze is a byproduct of the carbonization of coal, and it possesses several characteristics that make it ideal for use in anode beds. It has good conductivity, which allows for effective electron transfer, crucial for the functioning of the anodes. Additionally, coke breeze is porous, facilitating the flow of electrolyte around the anodes, thus improving their performance and longevity.

The other materials listed do not possess the same properties that make them suitable for anode beds. Sawdust, for example, lacks the necessary conductivity and could decompose over time, affecting the anode's effectiveness. Sand, while it may support the anodes, does not provide the electrical conductivity required to foster effective cathodic protection. Steel, being a more reactive material, would not only fail to provide the necessary protection but could also corrode, negating the benefits that an anode bed is supposed to provide.