Cathodic Protection (CP) is an electrochemical process that applies DC current to a metal to slow or stop corrosion currents. When applied properly, CP stops the corrosion reaction from occurring.
Cathodic protection works by placing an anode or anodes (external devices) in an electrolyte to create a circuit. Current flows from the anode through the electrolyte to the surface of the structure. Corrosion moves to the anode to stop further corrosion of the structure.
Pipeline Cathodic Protection Example
On an unprotected pipeline, potential variations occur naturally. Wherever you go from a minor positive to a minor negative, current flows and galvanic pipeline corrosion will occur. If you apply CP to that pipeline—for example MATCOR’s linear anode that runs parallel to the pipeline—current discharges off of the anode and onto the pipeline, preventing corrosion.
Pipeline without CP applied
CP applied to pipeline
Cathodic Protection Systems
Corrosion is a leading cause of premature failure in metallic structures. Operators can extend the service life of their facilities and equipment by installing CP systems and testing them regularly. CP engineers can design systems for maximum life and ease of replacement.
A wide range of civil and industrial applications use these systems to prevent corrosion for many years. They are typically installed during original construction, major expansions or upgrades. MATCO typically designs systems to operate for 30 years or longer.
CP Systems protect infrastructure assets from corrosion. These structures include:
- Above ground storage tanks
- Buried pipelines
- Reinforcing steel in concrete structures
- Heat exchangers
- Marine piles
- Sheet pile walls
- Other metallic structures
What are the Two Types of CP Systems?
Cathodic protection is a means of preventing metal structures—such as pipelines and storage tanks—from reacting with the environment and corroding. When exposed to the environment, carbon steel and other metals break down electrochemically and ultimately fail. CP systems prevent the oxidation process from occurring by creating a current flow from the system to the structure.CP 101 Video »
There are two basic types of cathodic protection systems: galvanic and impressed current.
Galvanic Cathodic Protection
Galvanic corrosion is an electrical-chemical process where one metal is more susceptible to corrosion than another when both metals are linked electrically. Galvanic (also called sacrificial) anodes utilized to protect steel structures are an example of galvanic corrosion, where the galvanic anode corrodes to protect the structure.
A sacrificial anode is a metal anode electrically linked to the structure to be protected that is more reactive to the surrounding corrosive environment. The sacrificial anode corrodes, protecting the metal of the structure being protected.
In a galvanic system, the anodes connected to the protected structure have a natural potential that is more negative than the structure’s. When connected current flows from the anode (more negative potential) to the structure (less negative potential) in a DC circuit.
Galvanic anodes (also referred to as sacrificial anodes), when properly applied, can protect underground steel, marine, internal and industrial structures from corrosion. They do not require an outside power source to operate, and are therefore limited in their use. Where properly applied they can be designed to provide long life with ease of operation.
Galvanic anodes are available in a variety of configurations, including:
- Bare metal anodes including magnesium, zinc, aluminum and other alloys
- Packaged in backfill for underground use
- Made with external steel straps for mounting to structures
- Ribbon types
- Rod and special shapes
In many applications, the potential difference between the galvanic/sacrificial anode and the steel structure is not enough to generate sufficient current for protection to occur. In these cases, a power supply (rectifier) can generate larger potential differences, enabling more current to flow to the structure being protected. This is referred to as an impressed current cathodic protection (ICCP) system.
To be the most effective and economical, CP systems must be designed properly. CP design is the scientific discipline involving:
- An understanding of the environmental conditions and the structure to be protected from corrosion
- Review of options for the structure or application
- Selection of the appropriate system
- Complete design including comprehensive specifications and drawings utilizing the latest engineering software
Design engineers possessing the right expertise and knowledge of the structure to be protected from corrosion should perform all phases of CP design.
MATCOR Products & Services
MATCOR offers a range of solutions that protect infrastructure assets including:
- Gas pipelines
- Above ground storage tanks
- Marine structures such as docks and piers
- Plant piping
- And more…
MATCOR cathodic protection systems include:
- Impressed current linear anodes
- Deep anode systems
- Tank anode systems
- Marine and water anode systems
- Ground bed anodes
- Internal probe anodes
Additional CP Systems Components
- Cathodic protection rectifiers
- Cathodic protection reference electrodes
- Junction boxes
- Splice kits
- Cathodic protection test stations
Browse all MATCOR CP Solutions
To get in touch with our team of cathodic protection experts for more information, to ask a question or get a quote, please click below. We will respond by phone or email within 24 hours. For immediate assistance, please call +1-215-348-2974.Contact a Corrosion Expert