When metal structural components are exposed to electrolyte environments such as water, soil, concrete, etc., significant corrosion usually occurs within 1-2 years, seriously affecting their durability and safety. To extend the service life of metal structural components to 10-30 years, cathodic protection technology is an efficient and reliable solution. Cathodic protection is essentially an electrochemical corrosion control method. This article will provide a comprehensive introduction to what is cathodic protection, type of cathodic protection, cathodic protection working principle， application scenarios and industry standard etc to help you gain an in-depth understanding of this key corrosion prevention technology and provide a reference for your engineering practice.

What is cathodic protection?

Cathodic protection is a corrosion protection technology based on electrochemical principles, the core of which is to reduce the potential of the protected metal to below the corrosion potential through polarisation, thus inhibiting the oxidation-dissolution reaction of the metal. In this process, the metal surface as a cathode accepts electrons, so that it can not occur anodic corrosion reaction, and thus achieve long-term stable corrosion protection effect.

Type of Cathodic Protection

1. Sacrificial Anode
Principle: Using more negative potential metal (such as magnesium, zinc, aluminium alloy) as the anode, and the protected metal connected to form an electric couple. The anode corrodes preferentially and releases electrons so that the protected metal becomes the cathode and is free from corrosion.
Advantages: No external power supply, easy installation and maintenance, little interference with nearby facilities.
Disadvantages: Limited protection current, not applicable to large structures or high-resistance environment; anode will be gradually consumed, need to be replaced periodically, increasing long-term costs.

2. Impressed Current Cathodic Protection
Principle: Apply current to the protected metal through external DC power supply (e.g. rectifier) and auxiliary anode (e.g. MMO anode) to force it to become cathode and inhibit corrosion.
Advantages: Applicable to large structures or high-resistance environments, adjustable current, adaptable to strong corrosion conditions.
Disadvantages: High initial investment, need to be equipped with power supply, anode and reference electrode system; may produce stray current, interference with nearby metal facilities.

Selection Basis
Sacrificial Anode: Suitable for small structures, low resistance environment or less corrosive medium.
Impressed Current Cathodic Protection: Suitable for large structures, high-resistance environment or complex working conditions (e.g. long-distance pipelines, offshore platforms).

Cathodic Protection System

Sacrificial Anode
Sacrificial anode materials such as magnesium-based, zinc-based and aluminium-based alloys, etc., protected metal structures, electrolyte environments, cable connections, test piles.

Impressed Current Cathodic Protection
Potentiostats/rectifiers, auxiliary anodes (e.g. graphite, high silica cast iron, MMO Anode), reference electrodes, test posts, cables, etc.

How Does Cathodic Protection Work?

The anode and the protected metal are connected by cable to form a complete circuit, in which the anode gives up electrons to protect the metal and the cathode accepts electrons to be protected, inhibiting the oxidative dissolution of the metal, so that the protected metal always maintains a negative potential, effectively preventing it from undergoing corrosion reactions.

Zinc, aluminium, magnesium and other metals have lower electrode potentials (higher chemical activity) than carbon steel, and when they are connected to steel as sacrificial anodes, they will preferentially corrode and release electrons so that the steel becomes the cathode and is protected. This type of protection is widely used in offshore platforms, ships, submarine oil and gas pipelines and other steel structures that are susceptible to corrosion.

For reinforced concrete structures, MMO titanium anodes such as Titanium Mesh Anode, Titanium Strip Anode and MMO Tubular Anode are commonly used. These anodes provide a protective current to the protected reinforcement through ICCP , which maintains it in a cathodic state, thereby effectively inhibiting corrosion.

Cathodic Protection Application

1. Marine engineering and ships
Offshore platforms, port facilities, submarine pipelines, marine structures
Ship hulls and ballast tanks
Sea bridges

2. Oil & Gas Industry
Long-distance pipelines (buried or submarine)
Storage tanks (crude oil, LNG)

3. Municipal and Infrastructure
Reinforced concrete structures
New construction, rehabilitation
Water supply pipes (cast iron, steel pipes)

4. Industrial equipment and chemical facilities
Heat exchangers, condensers
Chemical storage tanks, reactors
Wastewater systems
Plant piping