Cathodic Protection Testing

System Descriptions
Galvanic Sacrificial:
Most cathodic protection systems installed on underground storage tanks incorporate two or more 17-LB magnesium sacrificial anodes directly attached to the tank shell. These anodes, being more electrically active than the steel UST, allow the corrosive current to exit from them instead of the UST, thus protecting the UST while sacrificing the attached anodes. The anodes are typically welded to the ends of the exterior tank, and test voltages are measured by shorting the inside of the tank and employing a copper/copper sulfate reference electrode cell between a high impedance test meter and the tank. A structure-to-soil measurement of at least minus -0.85 volts must be maintained between the copper-copper sulfate electrode and the structure being tested to ensure compliance with a properly functioning system. Impressed Current: In cases where larger tanks or heated tanks require increased current for complete protection, impressed current cathodic protection systems are commonly used. These systems employ anodes connected to a DC power source, typically a cathodic protection rectifier that converts AC power supply to a DC output. The current is then transmitted through an insulated wire to special metal bars buried near the UST, with the current flowing through the soil to the UST system and returning to the rectifier through another insulated wire attached to the UST.