MMO Linear Anode for Cathodic Protection

Introduction

In a cathodic protection system, the MMO Linear Anode for Cathodic Protection acts as the anode, supplying cathodic protection current to the protected metal structure via an impressed current. When the anode is energized, the MMO coating undergoes an oxidation reaction, effectively releasing electrons into the surrounding electrolyte environment. These electrons are transferred through the electrolyte to the protected metal structure, forming a negatively charged layer on its surface, thereby inhibiting corrosion.

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Technical Specifications

The working principle of MMO Linear Anode for Cathodic Protection is based on impressed current cathodic protection technology, inhibiting corrosion of metal structures through electrochemical action. Its core mechanism can be broken down into the following steps:

Basic Principle: Impressed Current Cathodic Protection

The essence of metal corrosion is the process of metal atoms losing electrons (oxidation reaction). For example, the corrosion reaction of iron is: Fe → Fe²⁺ + 2e⁻. In a humid environment, oxygen or water acts as an oxidant, accepting electrons (reduction reaction), forming a corrosion cell and accelerating metal degradation. The principle of cathodic protection is to apply an external direct current to the protected metal structure (cathode), shifting the metal surface potential negative to the protection potential range (typically -0.85V to -1.2V vs. Cu/CuSO₄ reference electrode). At this point, oxidants in the corrosive medium (such as O₂ and H⁺) undergo reduction reactions on the metal surface, rather than metal corrosion.

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The Core Role of MMO Flexible Anodes: Current Output and Distribution

MMO flexible anodes, as auxiliary anodes, together with the protected metal structure, DC power supply (rectifier), and reference electrode, constitute the cathodic protection system. Its working process is as follows:

Current Output Mechanism

Anode Material Characteristics: MMO flexible anodes typically use a titanium (Ti) substrate coated with a mixed metal oxide (MMO, such as IrO₂−Ta₂O₅ or RuO₂−TiO₂). The titanium substrate provides mechanical strength and corrosion resistance, while the MMO coating acts as an electrocatalytic active layer, reducing the oxygen evolution reaction overpotential and improving current efficiency.

Electrochemical Reaction: Under DC power, an oxygen evolution reaction (OER) occurs on the anode surface, releasing electrons. These electrons flow through an external circuit to the protected metal structure, inhibiting its corrosion.

Key Design for Uniform Current Distribution:

Flexible Adaptive Structure: The anode is flexible and foldable, tightly laid along the surface of the protected structure (e.g., pipes, tanks), reducing current shielding effects and ensuring uniform current diffusion from the center outwards.

Low Resistivity Conductive Core: Internal copper core wire or conductive polymer is used to reduce the anode's own resistance, minimizing voltage drop and ensuring uniform current output along its length.

Optimized Filler Layer: The outer layer of the anode is wrapped with coke powder or conductive concrete, increasing the contact area with the soil, reducing interfacial resistance, and further improving current distribution.

System Collaborative Operation: Closed-Loop Control and Protection Effectiveness
Reference Electrode Monitoring: A reference electrode (e.g., Cu/CuSO₄ electrode) is embedded in the system to monitor the potential of the protected metal structure in real time, feeding back the data to the DC power controller. The controller adjusts the output current based on the potential feedback, ensuring the protected structure's potential remains within the protection range. For example, when the anti-corrosion coating is damaged, causing a decrease in local resistance, the system automatically increases the current output; when environmental changes (such as increased soil moisture) cause a decrease in resistance, the system reduces the current to avoid over-protection.

Performance Evaluation: The system's effectiveness is evaluated by periodically testing parameters such as protection potential distribution and current decay rate. The discharge density of the MMO flexible anode can reach 900 mA/m, far exceeding that of traditional anodes, ensuring sufficient protective current even in complex environments (such as high-resistivity soils and dense pipe networks).

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Application Scenarios and Advantages

Tank Bottom Plate Protection: The tank bottom plate is in contact with the foundation, and the coating is easily damaged. Traditional distributed anodes suffer from current shielding due to their irregular shape. Flexible anodes are laid in a ring along the edge of the bottom plate, allowing the current to diffuse evenly from the center outwards, covering all coating damage points, achieving a protection potential compliance rate of over 98%.

Marine Engineering Corrosion Protection: Seawater has high salinity and strong corrosiveness, making traditional anodes susceptible to seawater erosion. The MMO coating is resistant to seawater corrosion, the titanium substrate is resistant to mechanical damage, and the flexible anode can be laid along pipeline bends, ensuring long-term stable output current.

Corrosion Protection in Dense Pipe Networks: In dense pipe networks, traditional anodes are prone to mutual interference. Flexible anodes are laid along individual pipes, avoiding current diversion and improving cathodic protection efficiency.

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Product Features (Key Features)

• Long-Lasting Durability: Designed for up to 20 years of continuous service, MMO Linear Anodes are made from high-performance materials to resist corrosion in harsh environments.
• Cost-Effective: Provides an efficient solution for large-scale cathodic protection projects, reducing maintenance and replacement costs.
• Customizable: Available in various sizes and configurations to meet specific project requirements.
• Superior Corrosion Resistance: Effectively protects pipelines, tanks, and offshore structures in industries like oil and gas, marine, and chemical processing.
• Ease of Installation: Simple and fast to install, reducing labor costs and downtime during setup.

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Manufacturing Process

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Problems Solved by MMO Linear Anode for Cathodic Protection

Oil and Gas Pipelines
Pipelines are often exposed to uneven corrosion, especially over long distances and in difficult soil conditions. Traditional solutions wear out quickly and require frequent replacement. MMO linear anodes provide a steady and evenly distributed protective current, helping pipelines last longer while reducing maintenance efforts and costs.

Storage Tank Bottom Protection
Tank bottoms are one of the most vulnerable areas due to constant exposure to moisture and corrosive substances. Conventional anodes are hard to install and may leave unprotected zones. MMO linear anodes can be arranged to cover the entire bottom area, offering reliable and consistent protection that helps prevent costly leaks.

Underground Structures and Infrastructure
Buried structures such as cables, tunnels, and foundations are difficult to inspect and maintain. Corrosion caused by stray currents and complex environments can go unnoticed until serious damage occurs. MMO linear anodes provide continuous protection along the structure, reducing risks and minimizing the need for disruptive excavation.

Marine and Offshore Structures
In seawater environments, corrosion happens much faster and maintenance is both difficult and expensive. Traditional anodes require frequent replacement. MMO linear anodes are designed to perform reliably in harsh marine conditions, delivering long lasting protection and reducing the need for underwater maintenance.

Municipal Pipeline Networks
City pipeline systems often run through different soil conditions, making corrosion control challenging. Inconsistent protection can lead to failures over time. MMO linear anodes deliver stable and adjustable current, ensuring reliable protection across the entire network and helping utilities operate more efficiently.

Reinforced Concrete Structures
Structures like bridges and parking garages can suffer from hidden corrosion inside the concrete, mainly due to chloride exposure. Repairs are costly once damage appears. MMO linear anodes allow for proactive protection by controlling corrosion before it starts, helping extend the life of the structure.

High Resistivity Environments
In dry or sandy soils, it is difficult for electrical current to flow, which reduces the effectiveness of many protection systems. MMO linear anodes, when used with conductive backfill, create a more efficient current path and maintain reliable performance even in challenging environments.

System Retrofit and Upgrade Projects
Many existing systems become less effective over time but replacing them entirely can be expensive and disruptive. MMO linear anodes offer a flexible solution that can be integrated into current systems, improving performance and extending service life without major reconstruction.

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For more information or to get a quote, feel free to contact us at:

• Email: Jolina@bjhyti.com
• Phone: +86-18691787097