An impressed current anode is a durable, largely non-consumable anode that discharges cathodic protection current into soil or water when powered by an external DC source. Unlike a sacrificial anode, which is consumed to generate its own current, an impressed current anode is driven by a transformer rectifier and is designed to last for many years while delivering high current output. Impressed current anodes are used to protect large or high-demand structures such as cross-country pipelines, storage tank bases, offshore platforms and reinforced structures.
Choosing the right impressed current anode depends on the current output required, the environment and how the anode will be installed. This guide explains the main anode types, where each is used, and how they are selected and supplied.
Impressed current and sacrificial anodes: the difference
The distinction matters because it determines which anode type is appropriate. A sacrificial, or galvanic, anode is made of a reactive metal that corrodes to generate its own protective current, needs no power, and suits smaller structures and low-resistivity environments. An impressed current anode is made of an inert or slowly consumed material, is powered by a transformer rectifier, and delivers far higher current, suiting large structures, high current demand and high-resistivity environments where a sacrificial system could not drive enough current.
Because the current is supplied externally, impressed current systems can protect very large surface areas and can have their output adjusted over the life of the asset. The anode itself is selected to withstand years of continuous current discharge.
The main types of impressed current anode
Mixed metal oxide (MMO) anodes
Mixed metal oxide anodes consist of a titanium substrate coated with a catalytic oxide layer. They have a very low consumption rate, a high current capacity for their size, and are lightweight and dimensionally stable, which makes them versatile across a wide range of applications. MMO anodes are available in several forms, including tubular, wire, ribbon and mesh, allowing them to be used in groundbeds, inside tanks and within reinforced concrete. Their combination of long life and design flexibility has made them one of the most widely used impressed current anode types.
Silicon iron anodes
High silicon cast iron anodes are a long-established impressed current anode, valued for robustness and a proven service record. They are well suited to conventional groundbeds, both shallow and deep, where their durability and current output make them a dependable choice for pipeline and buried-structure protection. They are heavier and consumed more quickly than MMO anodes, but remain a cost-effective and reliable option in many soil applications.
Other impressed current anode materials
Depending on the application, other anode types are used, including graphite, platinised titanium or niobium for specific high-performance requirements, and linear or continuous anodes for particular installation geometries. The right choice is determined by the current demand, the environment and the installation method.
Matching the anode to the application
Impressed current anode selection balances current output, design life, environment and installation method. As a general guide:
| Anode type | Key characteristics | Typical applications |
| Mixed metal oxide (MMO) | Very low consumption, high output, lightweight, many forms | Groundbeds, tank internals, concrete, versatile use |
| High silicon iron | Robust, proven, higher consumption, heavier | Shallow and deep groundbeds, pipeline protection |
| Graphite / platinised | Specific high-performance or specialist duties | Selected groundbed and specialist applications |
| Linear / continuous | Distributed current along their length | Particular installation geometries and close-interval needs |
The anode is only one part of the impressed current system. It works alongside the transformer rectifier that powers it, the backfill that surrounds a groundbed anode to lower resistance and extend life, and the cables and connections that carry the current. All are selected together as part of the cathodic protection design.
The role of backfill and installation
Impressed current anodes installed in soil are normally surrounded by carbonaceous backfill, such as coke breeze. The backfill lowers the anode-to-soil resistance, spreads current discharge across a larger effective surface, and extends the working life of the anode. Correct installation, with the backfill properly placed and compacted, is essential to achieving the designed output and life, since voids reduce the effective anode surface and shorten its life. Anodes may be installed in shallow horizontal groundbeds or in deep boreholes, depending on land availability and soil resistivity.
UK-manufactured impressed current anodes from Corrpro Europe
Corrpro Europe designs, manufactures and supplies a full range of impressed current anodes, including MMO, high‑silicon iron, graphite, platinised titanium, titanium mesh and linear types, in a wide range of weights, dimensions and configurations. These anodes are assembled at our Stockton‑on‑Tees foundry, supported by dedicated MMO encapsulation and cabling facilities. We maintain stock levels to ensure low lead times, and we can provide any cable length specified so anode arrangements can be optimised to suit the installation. Anodes can be supplied with individual cables or as complete deepwell anode strings where required. All products are manufactured under an ISO 9001‑registered quality management system and can be produced to bespoke project requirements.
Supplying anodes alongside the transformer rectifiers, cables, backfill and monitoring products that complete an impressed current system means the components are matched to one another and to the cathodic protection design, backed by in-house engineering support.
Frequently asked questions
What is an impressed current anode?
An impressed current anode is a durable, largely non-consumable anode that discharges cathodic protection current into soil or water when powered by an external DC source such as a transformer rectifier. It delivers high current output over a long life and is used to protect large or high-demand structures.
What is the difference between MMO and silicon iron anodes?
Mixed metal oxide anodes have a very low consumption rate, high output for their size and are lightweight and available in many forms, making them highly versatile. High silicon iron anodes are more robust and long-proven but heavier and consumed faster. MMO suits a wide range of applications including tanks and concrete, while silicon iron is a dependable, cost-effective choice for groundbeds.
When is an impressed current anode used instead of a sacrificial anode?
Impressed current anodes are used for large structures, high current demand and high-resistivity environments where a sacrificial system cannot deliver enough current. Because the current is supplied externally by a transformer rectifier, impressed current systems can protect very large surface areas and allow output to be adjusted over the asset’s life.
Why is backfill used with impressed current anodes?
Carbonaceous backfill such as coke breeze surrounds a groundbed anode to lower the anode-to-soil resistance, spread current discharge across a larger effective area and extend the anode’s working life. Correct placement and compaction are essential, as voids reduce the effective surface and shorten anode life.
To specify impressed current anodes or a complete ICCP materials package, contact our team or explore our Cathodic Protection Materials range.
