Question: How can I test the cathodic protection of an sti-p3® tank?
Answer: STI has a recommended practice, R051, "Cathodic Protection Testing Procedures for sti-P3 UST". It is available on the STI website in our Publications Index (use ctrl + f to find R051).
Question: How do I test an impressed current CP system?
Answer: An impressed current system is tested differently than an sti-P3® tank. This is because the current output of an impressed current system is much greater than that of an sti-P3® tank.
In most cases, instant off readings must be used to account for IR drop. Details of this type of testing are taught in STI's Cathodic Protection Tester Certification class.
Question: What do I do if my cathodic protection on my sti-P3 tank does not meet the -850 mV criteria?
Answer: STI has a recommended practice, R972, for adding supplemental anodes. The first part of this RP covers basic testing and troubleshooting tests. These should give you a fairly good idea of what’s going on at your site. Based on the test results, it may be possible to retrofit the tank with supplemental anodes. The RP covers all the details of how this should be done. Keep in mind that you must follow all state and local regulations when doing this type of work. This RP can be downloaded here. (use ctrl+f to find R972)
Question: My tank did not meet the -850mV criteria for adequate cathodic protection. Does this mean my tank is leaking?
Answer: Cathodic protection testing is not an indication of whether or not the tank is tight. Cathodic protection testing only measures whether or not the cp system meets the required minimum readings. Monthly monitoring, leak detection and tightness tests must be performed to verify that a tank is tight.
Question: What should I do to test the anodes on my sti-P3 tank?
Answer: STI has a Recommended Practice, R051. The RP includes straightforward, step-by-step guidelines for testing the cathodic protection of an sti-P3 tank. It can be downloaded here. (use ctrl + f to find R051).
Question: What does sti-P3 mean?
Answer: P3 stands for three levels of protection. They include:
Level 1: All tanks are coated with a high-quality dielectric coating.
Level 2: The tank is shipped complete with isolation devices to protect it from all other underground structures such as metal piping, hold-down straps, submersible pumps, etc.
Level 3: The final measure of protection is the anodes. The anodes are made from metals that are more electrically active and, therefore, will corrode preferentially to steel. For an sti-p3 tank, this metal anodes will either be zinc or magnesium.