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MMO Anode

Item: MMO Anode

Product Introduction

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.

Originally developed to produce chlorine from seawater electrolysis, MMO anodes have been used in cathodic protection (CP) applications since the 1980s. They have continued to gain acceptance in a wide range of applications due to significant advantages.

MMO Anode Advantages

Demonstrated reliability

Exceptionally long life

Available in numerous anode configurations

Lightweight

Low cost

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 cathodic protection applications two primary electrocatalysts are used:

Ruthenium Oxide (RuO2)

Ruthenium oxide, which is the cheaper of the two electrocatalysts, should only be used in chlorinated environments (seawater). The catalytic life is significantly reduced when the primary reaction is the evolution of oxygen (freshwater, soil, coke backfill, and concrete environments).

Iridium Oxide (IrO2)

Most CP manufacturers use Iridium Oxide mixed metal oxide for their cathodic protection anodes because it is suitable for both chlorinating and oxygenating environments. The bulk oxides are typically a mixture of Titanium Dioxide (TiO2) and Tantalum Oxide (TaO5). Their primary purpose is to provide an oxide film over the substrate material to prevent corrosion of the substrate.

MMO Coated Titanium Anodes

Mixed metal oxide anodes are applied over a commercially pure titanium substrate. Titanium offers several key advantages as a substrate: