What is the Difference Between Sacrificial Anode and Impressed Current?

The main difference between a sacrificial anode and an impressed current lies in the method they use to provide cathodic protection against corrosion. Here are the key differences:

Sacrificial Anode:

• A highly active metal or alloy is placed in the system to act as the anode instead of the metal to be protected.
• The sacrificial anode method uses a metal more active than the base metal to "sacrifice" ions, providing protection until the sacrificial anode is no longer capable of supplying it.
• Examples of materials used for sacrificial anodes include magnesium, aluminum, or zinc.
• This method can provide long protection but has a limited lifespan and is subject to rapid corrosion.
• Does not work well on large metal surfaces without a barrier coating.

Impressed Current:

• Anodes are connected to a power source that provides a perpetual source of electrical flow.
• A DC current is provided to the metal to be protected, making it the cathode.
• Can supply significantly more protective current at a higher driving voltage compared to sacrificial anodes.
• Often used in situations where sacrificial anodes are not effective, such as large steel structures in seawater.

In summary, sacrificial anodes use a highly active material to protect the base metal from corrosion, while impressed current systems use an external power source to provide a continuous electrical flow to the protected metal.

Comparative Table: Sacrificial Anode vs Impressed Current

Here is a table comparing the differences between sacrificial anodes and impressed current cathodic protection methods:

Sacrificial anodes are used in cathodic protection systems that directly utilize the natural voltage differential between the anode and the protected structure. Impressed current cathodic protection systems use an external power source and inert anodes, which are applied with a DC current to make the protected structure function as a cathode. In general, sacrificial anode systems may need less maintenance and have lower initial costs, while impressed current systems can offer greater protection for larger structures and structures with extensive coatings, but require more upkeep and a higher initial investment.