The specimens were mounted into the RCT cells and the NaOH (0.3 mol/L) and NaCl (3 %) chambers were filled. A commercial impedance analyzer was then connected to the RCT cell banana jacks. Using an applied potential of approximately 1 volt (peak-to-peak), with a zero volt DC offset bias, across the RCT cell, the analyzer scanned frequencies from 10 Hz to 1 MHz, completing the test in approximately 1 minute; results using AC potentials ranging from 0.1 to 1.0 volts yielded similar results. The data were stored in the computer for analysis to determine the value of RB .
At the completion of the IS measurement, the analyzer leads were removed from the cell, and the cell was connected to a commercial DC power supply capable of two-way communication to a computer via an IEEE-488 interface. The computer program would initiate the test, query the power supply for the initial current, and subsequently query the power supply for the current every 60 seconds until the completion of the test. The power supply was equipped with remote sensing to compensate for the voltage drop along the power cable. This ensured that 60.0±0.1 volts were delivered to the RCT cell.