Impressed current forces current from the anode to the structure resulting in anode corroding before the structure. Unlike galvanic cathodic protection, impressed current uses inert materials as anodes.

Impressed current is typically used in the following situations:

• Large current requirements
• All soil-resistivities
• Interior of water storage tanks
• bottoms of above ground storage tanks
• large heat exchangers water boxes

Advantages

• Can handle a wide range of voltage and current output
• produce high current
• effective in high-resistivity soils
• less anode consumption

Limitations

• higher inspection and maintenance cost
• external power requirements
• constant power supply cost
• can result in stray current on other structures