United States Department of Agriculture
Natural Resources Conservation Service
200 Fourth Street SW
Huron, SD 57350-2475
(605) 352-1288 (FAX)
ENGINEERING - DESIGN SD-2003-3
September 24, 2003
Dwight Hale, Engineer, Northern Plains Region
This Technical Note replaces Design SD-2003-2, dated July 7, 2003. Voltage Polarity was added under the
Maintenance section of this Technical Note.
The purpose of this Technical Note is to provide design and maintenance information for sacrificial anode cathodic
protection systems. Biological corrosion, stray current corrosion, and the use of impressed electrical current are
beyond the scope of this Technical Note. The purpose of cathodic protection is to protect metal (pipes, etc.,) from
rapid deterioration by galvanic corrosion (rusting, etc.,) due to contact with low electrical resistance soil and water.
For additional information, refer to Peabody’s Control of Pipeline Corrosion, A. W. Peabody, 2nd Edition, 2001.
Corrosion of metals at near-ambient (normal) temperatures occurs in water containing environments and is an
electrochemical process involving a complete electrical circuit. Within the circuit, one metal (or location on the metal)
corrodes (anode) and protects the other (cathode) metal (or location on the metal). This process involves four essential
elements to create the corrosion cell or battery:
1. There must be corroding metal (anode). The anode produces the electrical negative (-) pole of the battery.
2. There must be protected metal (cathode). The cathode produces the electrical positive (+) pole of the battery.
3. There must be a metallic path electrically connecting the anode and cathode. This could be through the object
itself, or (as in a cathodic protection system) an electrical wire may be installed to connect the