Cathodic Protection Tester Practice Exam

Which backfill composition is appropriate for magnesium anodes?

1. 75% bentonite, 25% sodium sulfate

2. 75% Gypsum, 20% bentonite, 5% sodium sulfate

3. 50% clay, 50% sand

4. 100% gypsum

The correct answer is: 75% Gypsum, 20% bentonite, 5% sodium sulfate

The appropriate backfill composition for magnesium anodes is 75% Gypsum, 20% bentonite, and 5% sodium sulfate because this mixture creates an optimal environment for the performance of magnesium anodes in cathodic protection systems. Magnesium anodes operate effectively in a high electrical conductivity environment, which is enhanced by gypsum. Gypsum provides the necessary ionic conductivity, helping to facilitate current flow between the anode and the cathode, while bentonite acts as a binder and helps retain moisture in the backfill mixture. The addition of sodium sulfate supplements the ionic content and supports effective corrosion control. This particular combination of materials ensures that the magnesium anodes can maintain their effectiveness over time, providing adequate protection against corrosion by enhancing the overall electrochemical performance of the system.