What parameter is checked to test the cathodic protection system?

• A. Tank-to-soil potential
• B. System voltage
• C. Tank pressure
• D. Soil resistivity

Answer: (A)

The key idea is that whether a cathodic protection system is doing its job shows up in the actual potential of the tank relative to the surrounding soil. In practice, you test by measuring the tank-to-soil potential with a reference electrode placed in the soil near the tank and a high-impedance voltmeter. If the reading is sufficiently negative (for steel, a common criterion is around -0.85 V with respect to a copper/copper sulfate reference), the tank is adequately polarized and protected from corrosion. If the potential isn’t negative enough, the CP system isn’t providing full protection and adjustments may be needed, such as increasing current or adding anodes.

System voltage is about the supply level, not the protection status itself. Soil resistivity affects how much current the system can deliver but doesn’t by itself indicate whether protection is achieved. Tank pressure is unrelated to galvanic or impressed-current protection.