How to Conduct a Cathodic Protection Inspection of Water Storage Tanks

An underground storage tank’s galvanic cathodic protection system involves the installation of sacrificial anodes onto the tank during manufacturing, along with wiring for an inspection station positioned near the surface. These systems operate for a finite period, during which the sacrificial anodes deteriorate while safeguarding the tank or piping. As the sacrificial anodes reach the end of their effective lifespan, they diminish in effectiveness and start to corrode.

Impressed Current Cathodic Systems

The impressed current cathodic protection system typically offers electrodes with a significantly extended lifespan compared to a galvanic anode. These setups incorporate a rectifier that transforms the alternating current power source into a direct current, precisely adjusted to deliver the necessary protection. As the power supplied to the electrode isn’t generated by its degradation, the power output to the electrode can be adjusted if necessary, as long as the electrodes remain operational.

Checklist for Impressed Current Cathodic Protection Systems

You should arrange for a periodic inspection conducted by a third-party inspector to ensure that your cathodic protection system effectively safeguards your UST system. This examination should be carried out:

  • At least every 1 year after the previous test.
  • Within 60 days after any repairs to your UST system.
  • Keep the results of at least the last two tests on file.
  • Inspect your rectifier and record the readings at least every 60 days to make sure that it is operating within normal limits. 
  • Keep records of the operating life of the facility.
  • Never turn off your rectifier!

What Cathodic Protection Does

Cathodic protection is an electrical method employed to prevent corrosion. It safeguards underground tanks and pipelines by harnessing the inherent energy present in all metallic substances. Simply put, anodes, which are metallic materials, are buried near the tank and pipelines. These anodes are interconnected by a wire and possess a significant amount of natural energy. This natural energy causes electricity to flow through the soil, wire, and buried metal. Over time, the buried anodes dissolve entirely into the soil, thus preventing corrosion of the steel tank or pipelines. Cathodic protection systems are categorized into two types: impressed current and sacrificial anode. Impressed current systems require an external power source, while sacrificial anode systems do not.

Three Tips for Maintaining Your Cathodic Protection System and Extending its Working Life

1. Are you having regular inspections?

Regular testing and inspection are recommended to verify the effectiveness of your system. Implementing a monitoring and logging system can further assist in preventing corrosion.

Scheduled inspections and maintenance help ensure compliance with current Federal regulations. These regulations mandate 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.

2. Is your cathodic protection system providing the correct amount of protection against corrosion?

In impressed current protection systems, a rectifier control box is typically situated near the tank monitor. The box contains a voltmeter as a standard feature, while an ammeter with a red/green indicator light is optional. It’s important to note that these meters and indicator lights solely signify the presence of power, not its adequacy. If the indicator light on the system is red, corrosion protection is deactivated. In such cases, immediate contact with a cathodic protection specialist is necessary.

3. Is wiring exposed to the system?

Inspect the area around the tanks for any broken or disconnected wires, particularly those likely associated with the cathodic protection system. A damaged wire could lead to malfunctioning of a section of the system, indicating inadequate corrosion protection. If you identify such wires, consult your cathodic protection professional to confirm 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 not exposed.

Always bear in mind that any excavation in the tank field area can potentially disable the cathodic protection system. If you have any concerns, it’s advisable to reach out to your cathodic protection specialist for guidance.

Does Your Underground Tank need a Cathodic Protection Inspection?

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