Corrosion also known as rust can cause tanks and piping to leak. For a more detailed description please refer to the Corrosion Proectcion section on page 299 in the Standardized Inspection Manual.
Cathodic Protection is required on all steel tanks, metallic piping, and metallic fittings.
There are two types of Cathodic Protection:
Galvanic (Sacrificial) Anode Systems
A galvanic (sacrificial) anode system uses anodes that are buried and attached to metal UST components for corrosion Protection. The anode is more electrically active and will sacrifice itself (corrode) to protect the metal component from corrosion. This type of cathodic protection must be tested every 3 years using the following form Galvanic Cathodic Protection Testing Survey (CN-1140).
Impressed Current Systems
An impressed current system uses a rectifier ( a device that converts alternating current to direct current) to provide direct current through anodes to the metal tank, piping, or other underground components to achieve corrosion protection. This type of cathodic protection must be tested every 3 years using the following form Impressed Current Cathodic Protection Testing Survey CN-1309. With this type of system the rectifier must also be checked every 60 days and recorded on the Impressed Current Cathodic Protection Rectifier Reading Form CN-1282.