Maintenance of Cathodic Protection
State and federal UST regulations require that the metallic components that routinely contain petroleum be protected from corrosion. This can include the tank, piping, flex connectors, or any other tank or pipe fitting constructed of metal. These metal components are cathodically protected through cathodic isolation, a galvanic (sacrificial) anode system, or an impressed current system. All types of cathodic protection require routine inspection and maintenance, but some require more than others.
Cathodic isolation requires relatively low maintenance, at least compared to the other methods of protection. Essentially, you must keep the components free from contact with soil, backfill, liquid, and debris. This can be done by removing the corrosive elements or by using an isolation sleeve/boot. In most cases, this issue can be addressed by the owner or operator and is as simple as removing the liquid of soil/backfill so that the metal component is completely clear. These areas must be inspected regularly to ensure that the issue does not reoccur. If the situation persists, a call to your service company may be in order to find a more permanent solution.
Galvanic (Sacrificial) Anode System
Galvanic (sacrificial) anode protection is a self-contained cathodic protection system. The anodes are attached directly to the tank or piping, and nearly everything is kept below the ground surface. In this type of installation, the metal has to be in contact with the soil/backfill or water to work properly. The anodes are engineered to protect the metallic structure they are attached to by corroding instead of that structure. The anode is placed in the backfill or water and then attached to the metal fitting with a lead wire and clamp.
The lead wires and clamps must be inspected regularly to verify that it has a good connection to the metal component. It’s also important to routinely check the anode to make sure it hasn’t depleted to the point that it is no longer functional. In most cases with this type of corrosion protection, there is little for the owner/operator to do aside from maintaining the systems certification with the service provider.
The photos above are of the same containment area under a dispenser. The photo on the left was taken in 2015, while the photo on the right was taken in 2018. Can you see the difference? The white, chalk-like substance is what's left behind as the anodes deplete over time.
Impressed Current System
This type of protection is similar to the sacrificial method, in that the components and anodes are below the ground surface. Impressed current differs from sacrificial protection by utilizing a rectifier and wiring to move energy between the components being protected and back out to the anodes. Of the three methods, the impressed current system requires the most attention. Operators must check the rectifier output values (amps, volts, & hours) every month, in addition to visually inspecting the anode wiring to make sure that none of the wires are exposed to potential damage. If the wires get damaged, the system will not work properly and the metal components will not be protected. The rectifier must remain on and operational at all times.