Understanding Cathodic Protection: Galvanic vs. Impressed Current Systems

Adelphi Enivronmental
Apr 30
2 min read

If you're operating a fuel site with underground storage tanks (USTs), corrosion isn’t just a maintenance issue—it’s a compliance and safety concern. Left unchecked, corrosion can lead to leaks, contamination, and costly repairs. That’s where cathodic protection systems come in.

These systems are designed to prevent metal degradation by redirecting corrosion away from your fuel tanks. But not all systems are the same. The two primary methods—galvanic protection and impressed current systems (ICCP)—serve the same purpose, but work in very different ways.

Let’s break down the differences, when each is appropriate, and how Adelphi Environmental ensures your system stays compliant and effective.

Illustration comparing galvanic cathodic protection (sacrificial anode system) and impressed current system for underground storage tanks, showing components like anodes and power source with labeled corrosion flow.

Illustration comparing galvanic cathodic protection (sacrificial anode system) and impressed current system for underground storage tanks, showing components like anodes and power source with labeled corrosion flow.

What Is Cathodic Protection?

Cathodic protection (CP) is a method used to prevent corrosion of metal surfaces in underground tanks and piping by making them the "cathode" of an electrochemical cell. It’s required for most metallic USTs under EPA regulations and must be tested regularly to ensure performance.

There are two primary types:

Galvanic (Sacrificial Anode) Systems
Impressed Current Cathodic Protection (ICCP) Systems

1. Galvanic Cathodic Protection (Sacrificial Anodes)

How It Works:Galvanic systems use sacrificial metal anodes (usually magnesium or zinc) that are more reactive than steel. These anodes corrode in place of your tank, offering protection without external power.

Pros:

Low maintenance
No power source needed
Cost-effective for small or newer tanks
Simpler installation

Cons:

Limited current output (not ideal for larger or older tanks)
Must be replaced periodically
Less effective in high-resistivity soils

Best For:

Smaller fuel sites
Areas with naturally moist or conductive soil
Sites with minimal electrical infrastructure

2. Impressed Current Cathodic Protection (ICCP)

How It Works:ICCP systems use a power source to drive current from inert anodes (like graphite or titanium) into the tank system. The current prevents oxidation of the steel tank.

Pros:

Highly effective over large areas
Adjustable current levels
Ideal for older, larger, or complex systems

Cons:

Requires regular monitoring and testing
Needs external power and rectifier maintenance
Higher upfront cost

Best For:

Large-scale or older tank systems
High-resistivity environments
Facilities with reliable electrical infrastructure

How Often Should Cathodic Protection Be Tested?

The EPA mandates that all cathodic protection systems be tested at least every 3 years by a certified technician. Adelphi Environmental provides full CP testing and reporting, including: