Cathodic Protection Tester Practice Exam

In a voltmeter, which reading indicates structure to electrolyte potential?

1. 200 millivolts

2. 2 volts

3. 20 volts

4. 1000 volts

The correct answer is: 2 volts

The correct reading for indicating structure to electrolyte potential in a voltmeter is generally one that falls within a specific range indicative of cathodic protection effectiveness. In cathodic protection systems, a voltage reading that signifies the potential difference between the metallic structure and the surrounding electrolyte (such as soil or water) helps to assess the efficiency of the cathodic protection system. A reading of 2 volts is considered appropriate as it falls within a range commonly accepted in cathodic protection assessments. This voltage suggests that there is sufficient potential to provide protection against corrosion. Typically, values around -0.850 to -1.100 volts (when measured with respect to a standard reference electrode, such as a copper/copper sulfate electrode) are known to be effective in providing protection, but higher readings like 2 volts can indicate significant cathodic polarization and protection is being actively applied. The other readings do not generally indicate practical or effective structure-to-electrolyte potentials for cathodic protection monitoring. Lower values like 200 millivolts may suggest insufficient protection, while much higher values, such as 20 volts or 1000 volts, are generally indicative of issues such as stray current interference or malfunctioning cathodic protection systems, thus