Bridge Utilities Infrastructure News


4 Cathodic Protection Testing Methods: Preventing Rust Through Vigilance

Posted by Edward Dill on Jul 20, 2018 9:02:00 AM



Why Test Your Cathodic Protection System? 

Ensuring your cathodic protection systems are in good working order comes with the job description of installing them. In our last primer on cathodic protection, we covered the basic principles of cathodic protection systems, offered a discussion on the strengths and weaknesses of sacrificial and impressed current systems, and addressed stray currents. Today we’re here to give you a general overview of testing your cathodic protection systems to keep them in prime running condition. 

Like anything performing a job at all hours of the day, different components start to burn out. It’s your job to ensure all elements of your cathodic protection systems remain operational for the life cycle of the underground structure you’re working to prevent from corroding. Underground piping systems and propane tanks can suffer severe corrosion without proper maintenance. Without routine testing and maintenance checks, your underground systems can potentially become volatile. Remember, your underground systems are constantly giving off an electrical charge.

In some instances your systems may have an external power source. That’s right. That’ll need maintenance too. You’ve got your work cut out for you, but we’re here to help! If at any point you want to speak directly to a cathodic protection engineer to answer specific questions unique to your current project, feel free to reach out to us.

How Often Should I Check My Cathodic Protection System?

You should perform maintenance testing and servicing every two to four years. Ensuring optimum anode health is absolutely crucial in safeguarding the longevity of your underground cathodic protection system. The anodes in your system are working overtime to protect the main structure of your CP system. Every hour of every day those anodes are taking the brunt of corrosion damage, diverting oxidation from underground piping systems. As a direct result, those sacrificial anodes need replacing, as they are in a constant state of decay.

And that’s exactly what we want.

However, failing to maintain the integrity of the anodes within your CP underground system will cause complications and may foment irrevocable damage to the internal structure in need of protection.

Watch Out! Remember to Check for:

Before launching into your work, remember you may be entering an unintentionally hostile environment. Proceed with caution while keeping the following in mind:

● Wild animals may have found their way into your system. Be careful not to disturb them. Be ever wary of snakes, unfamiliar bugs, aggressive wasps, and potentially poisonous spiders.

● Remain mindful the earth surrounding your cathodic protection structure may have eroded, encountered unexpected flooding, or may be effected by surrounding environmental conditions. Proceed with caution.

● Test stations and rectifiers with care, and be mindful of open junction boxes.

● Avoid performing maintenance during rainfall.

● Before initiating testing, first check for shorts and address them if necessary.

● Remember to turn the power off before handling anything!

● While working do not create a circuit with your body! Work with one hand where applicable.

Cathodic Protection Testing Equipment & Specifications
You’ll have to gather a few materials before you’re ready to conduct cathodic protection maintenance testing. The following is a list of common equipment used during testing.

Portable Voltmeter
Ensure your voltmeter is of good quality, and that there are no points of corrosion on its surface. Try avoiding low grade voltmeters, as they have a penchant for providing inaccurate readings. Higher end models are preferred specifically because they’re able to detect low voltage anode levels. Remember to calibrate your voltmeter on an annual basis.

High Impedance Digital Multimeter
Recommended by the US Department of the Interior Bureau of Reclamation: Fluke Model 27
Minimum input impedance: 10 megohms
Ensure your device will measure DC voltages between .1mV to 1,000 volts

Selectable Input Resistance Digital Multimeter
Recommended Model: MCM LC-4, M.C. Miller Co.
Input resistance 0-200 ohms (.1 -ohm resolution)
Selectable input resistance 0-200 ohms (.1-ohm resolution)
Selectable DC voltage 0-200 volts (.01 -mV resolution)

Portable Copper Sulfate Reference Electrode
Also called a half cell or reference cell– place in soil vertically when executing maintenance testing. Ensure the testing solution within the electrode is clear and free of cloudiness. Replace the solution every two to three months. Keep the tip of the electrode moist for accurate readings. Follow all operating maintenance instructions carefully, or risk the integrity of your testing.

Resistivity Soil Meter
For use around anode.

4 Common Cathodic Protection Testing Methodologies

1) Pipe-to-Soil Voltage Potential

Connect a copper sulfate half-cell to your volt meter and make contact with the ground, while connecting your meter to underground metal. Afterwards, measure the pipe to soil voltage potential. Your readings should be 0.85 or higher. Measurements lower than 0.80 is indicative of corrosion.

2) Testing Pipe Continuity

Test piping continuity with an ohmmeter and small internal battery, which is used to provide a small voltage current. Ensure your voltage meter is set to OHMS. Connect both ends of your meter to separate anodes. The circuit created will test the entirety of your underground piping system, and will (1) confirm if your pipe is outputting a successful continual current and (2) indicate if wires between testing boxes are broken or offer poor piping connection.

3) Testing Anode Voltage Output

Utilizing a copper sulfate half-cell, measure the potential anode voltage. Normal measurements range between 1.4-1.6 volts. Ranges from 0-.3 indicates a broken wire or connection between the origin test box and anode.

4) Measuring Anode-to-Pipe Flow

Set your voltmeter to milliamp readings and connect to the anode wire and pipe wire. Readings may range from 5ma (.005 amp) to 300ma (.3 amp). Beware of current flows larger than the design current; if left unaddressed, your anode’s life will be shortened. If measurements exceed 1.3 times the design current, resistances should be put in place to increase the longevity of your anodes.

Know When to Call the Professionals

Sometimes you need expert help. And that’s okay. Aptus prides itself on a venerable legacy of superior bridge utility infrastructure services– take a look at some of our work.

We’re here to answer your questions. Day or night.

Drop us a line.

Topics: Cathodic Protection Testing