Underground storage tanks can be protected from corrosion using a galvanic cathodic protection system. This system involves attaching special metals called sacrificial anodes to the tank during manufacturing. These anodes are connected by wires to an inspection point near the surface. The anodes act like a shield, corroding themselves slowly to protect the tank from rust. However, these anodes don’t last forever. After a certain period, they wear out and become less effective.
Impressed Current Cathodic Systems
The impressed current cathodic protection system usually includes electrodes that have a much longer lifespan compared to galvanic anodes. These systems involve a rectifier that converts alternating current from the power source into direct current, carefully adjusted to provide the required protection. Because the power supplied to the electrode is not dependent on its degradation, adjustments can be made to the power output if needed, as long as the electrodes continue to function.
Checklist for Impressed Current Cathodic Protection Systems
It’s important to schedule regular inspections by a third-party inspector to ensure your cathodic protection system effectively protects your UST (Underground Storage Tank) system.
These inspections should occur:
- At least annually following the previous test.
- Within 60 days after any repairs to your UST system.
Maintain records of at least the last two tests.
Regularly inspect your rectifier and record readings at least every 60 days to ensure it operates within normal limits.
Keep records of the facility’s operational lifespan.
Never deactivate your rectifier.
What Cathodic Protection Does
Cathodic protection (CP) is a clever way to use electricity to stop underground tanks and pipes from rusting. It takes advantage of the natural energy metals have. Here’s how it works: special metals called anodes are buried near the tank or pipe. These anodes are connected by a wire and act like a battery with their own natural energy. This energy creates a flow of electricity through the soil, the wire, and the buried metal.
Over time, the anodes slowly dissolve, sacrificing themselves to protect the steel tank or pipes from corrosion. There are two main types of CP systems: impressed current and sacrificial anode. Impressed current systems need an outside power source to keep things going, while sacrificial anodes don’t.
Three Tips for Maintaining Your Cathodic Protection System and Extending its Working Life
- Are you conducting regular inspections?
Regular testing and inspection are recommended to validate the effectiveness of your system. Implementing a monitoring and logging system can further aid in preventing corrosion.
Scheduled inspections and maintenance help ensure compliance with current federal regulations. These regulations require that your system undergo testing by a qualified cathodic protection tester within six months of installation and every three years thereafter.
However, delaying testing for three years poses a significant risk of substantial damage to steel tanks and lines if the cathodic protection system has not been functioning properly.
- Is your cathodic protection system providing adequate corrosion protection?
In impressed current protection systems, a rectifier control box is typically located near the tank monitor. The box includes a voltmeter as a standard feature, and an ammeter with a red/green indicator light is optional. It’s important to note that these meters and indicator lights indicate only the presence of power, not its sufficiency. If the indicator light on the system is red, corrosion protection is inactive. In such cases, immediate contact with a cathodic protection specialist is necessary.
- Are there exposed wires in the system?
Inspect the vicinity of the tanks for any wires that are broken or disconnected, especially those likely associated with the cathodic protection system. A damaged wire could cause a section of the system to malfunction, indicating inadequate corrosion protection. If you discover such wires, consult with your cathodic protection professional to verify if they are part of the cathodic protection system. If these wires are indeed part of the system, repairs will be necessary to ensure they are properly insulated.
Always remember that any excavation in the tank field area has the potential to disable the cathodic protection system. If you have any concerns, it’s advisable to contact your cathodic protection specialist for guidance.
Do You Require a Cathodic Protection Inspection for Your Underground Tank?
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