What does Impressed Current Cathodic Protection (ICCP) mean?
Impressed current cathodic protection (ICCP) is a corrosion control method that sends current from an external source through anodes and concrete to the reinforcing steel.
How it works
A rectifier supplies the current. The current flows from an auxiliary anode, through the concrete, to the surface of the steel. A zinc anode in contact with the steel forms a galvanic couple, which is how a galvanic system works.
Use on bridge decks
FHWA describes ICCP with titanium mesh anodes as a durable repair for chloride-contaminated bridge decks. The protection lasts only while crews maintain the rectifiers and wiring. For prestressed beams, FHWA names arc-sprayed zinc or titanium anodes. It also warns that overprotection can cause hydrogen embrittlement of the prestressing strands.
Anode life and monitoring
FHWA monitored 20 highway structures for 5 years. Its estimated anode lives range from more than 25 years for titanium mesh to 5 to 10 years for conductive paint. The study judged protection with a 100 mV depolarization requirement, measured with embedded reference cells. Systems run at too low an output current performed poorly.
Airfield use
The airfield sources in the TarmacView library do not mention cathodic protection. FAA Item P-501 requires epoxy-coated dowel bars in concrete pavement joints, which is corrosion protection by coating. TarmacView does not inspect cathodic protection systems.
Frequently Asked Questions
- How is ICCP different from galvanic cathodic protection?
- ICCP uses an external source of current, supplied through a rectifier and wiring. A galvanic system relies on a zinc anode that forms a galvanic couple with the steel. In an ICCP system with zinc anodes, the zinc can still form this couple when the power is off.
- How long does an ICCP anode last?
- It depends on the anode material and the environment. FHWA estimated more than 25 years for titanium mesh and 15 to 25 years for titanium ribbon. It estimated 10 to 15 years for arc-sprayed zinc in deicing conditions and 5 to 10 years for conductive paint.
- Can ICCP damage prestressed concrete?
- Yes, if it overprotects the steel. FHWA warns that overprotection can cause hydrogen embrittlement of the high-strength prestressing strands. It recommends electronic remote monitoring of any installed system.
References
- fhwa-rd-98-088
- Corrosion Protection: Concrete Bridges (FHWA-RD-98-088), Chapter 6, Summary FHWA
- fhwa-rd-01-096
- Long-Term Effectiveness of Cathodic Protection Systems on Highway Structures (FHWA-RD-01-096) FHWA
- faa-ac-150-5370-10h
- AC 150/5370-10H, Standard Specifications for Construction of Airports FAA
This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.