Abstract: Accordingly, a tank, preferably on a wheeled vehicle such as a railcar or trailer, is provided with a protective liner. Two electrodes are preferably permanently mounted within the tank and respectively connected to a monitor. Another two ground connections are made from the monitor to the tank. At least one of the two probes in the tank are utilized with the monitor to measure the voltage between the tank and the selected probe. When the tank is filled with an ionic solution, a breach of integrity of the liner results in a voltage corresponding to the difference in potentials of the metals forming the probe and tank is read by the monitor. This triggers an alarm. Furthermore, the monitor provides a voltage or current from probe to probe, probe to shell, and shell to shell on a periodic basis to measure and then record the performance of the liner.