MMO-Coated Titanium Anode

Mixed Metal Oxide Anodes (MMO Anodes), also called dimensionally stable anodes (DSA), are a type of Impressed Current Protection Anode, consisting of rare earth oxides coated onto a titanium substrate.

MMO anodes have imperceptibly low wear rates and are often referred to as DSA as they do not change geometry over time. MMO anodes are quickly becoming the most popular impressed current anode gaining market share over conventional anodes such as graphite and high silicon cast iron.

What is mixed metal oxide?

There is no precise industry definition for mixed metal oxide. Each supplier has a unique recipe for their mixed metal oxide coating. The coating recipe consists of an electrocatalytic conductive component that catalyzes the reaction to generate current flow, and bulk oxides (cheaper fill materials) that prevent corrosion of the substrate material. For MMO Anode for Cathodic Protection applications two primary electrocatalysts are used:

For MMO wire anodes, some suppliers utilize a bimetallic substrate with a thin layer of titanium extruded over a copper core. The use of copper-cored titanium wire is primarily a cost consideration as much of the titanium content found in solid titanium wire is replaced with a lower-cost copper material. Additionally, there is a modest improvement in the conductivity of the wire as copper is a better conductor. However, the use of a copper-cored wire increases the anode substrate's susceptibility to corrosion and chemical attack in a highly acidic environment since copper does not have the same high resistance as titanium.

The typical manufacturing process for MMO anodes starts with surface preparation of the substrate by thoroughly cleaning the commercially pure titanium. This is followed by a chemical etching and in some cases mechanical abrasion of the surface. Once the substrate surface preparation is complete, the coating is applied as a mixture of metal salts and then thermally decomposed at temperatures ranging from 400 to 600 °C. This forms an adherent layer of mixed metal oxides. The MMO coatings can be applied in many layers and heat treated after each coat to achieve the desired coating loading to meet the current capacity requirements for the application.

MMO anodes are typically rated for a given output and life. Within the normal range of current discharge for MMO anodes, this relationship is linear. The same 5 amp anode rated for 20 years of service would provide 40 years if only operated at 2.5 amps.

Mixed metal oxide-based electrocatalytic anodes are a different type of anodes when compared to conventional anodes. These anodes are dimensionally stable, long-life anodes that are not consumed during the process of generating an MMO Anode for Cathodic Protection current. The use of iridium oxide (IrO2) is preferred for all cathodic protection applications. Ruthenium-based MMO should be avoided for MMO Anode for MMO Anode for Cathodic Protection applications except those in highly chlorinated environments (seawater). The concern over substrate failures resulting from titanium polarization exceeding the substrate break down voltage has been proven to be unfounded.

MMO anodes continue to gain market acceptance and are quickly replacing conventional anodes in a wide range of applications.

The benefits of MMO anodes are built into all of our core cathodic protection anode products, we can supply the MMO anode material available in rod, wire, tubular, ribbon, or mesh form.

MMO-coated titanium anodes are lightweight and geometrically flexible, thereby assuring ease of installation, quick replacement, and capability for multiple refurbishing in a cost-effective way.

Titanium offers several key advantages as a substrate:

Mixed Metal Oxide Anodes have proven to operate effectively in all types of environments. Including areas with extremely low pH levels and high levels of chloride concentration. While these anodes can be used singularly, their unique configuration makes them ideal for use in strings on offshore platforms or deep-ground beds. In addition, the string anodes can be installed parallel to transmission pipelines, or used for other special applications.

With over 10 years of experience in manufacturing MMO-coated Titanium Anode, we believe that our technical expertise is matched by our production capability, providing our customers with the highest quality products and first-rate service.

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