Mixed-Metal Oxide Anodes


Mixed-Metal Oxide (MMO) Anodes - Houston

The mixed metal oxide of Lida or Telpro anodes has a low consumption rate, measured in milligrams per ampere-year. As a result, the dimensions remain nearly constant during the life of the anode, providing a consistently low resistance. Whether operating in soil, freshwater, mud or seawater, mixed metal oxide coatings demonstrate high chemical stability, even in environments with low pH values. Unlike other impressed current anodes, MMO coatings are not affected by the generation of chlorine.

Tubular Anodes

Mixed Metal Oxide (MMO) tubular anodes are titanium tubes with a mixed metal oxide coating. The mixed metal oxide is a crystalline, electrically-conductive coating that activates the titanium and enables it to function as an anode.

Anode Strings

An MMO "anode string" is comprised of electrical cable threaded through one or more tubular anodes. Electrical connection between the anode and cable is via a patented crimping process. The crimp connection seals the anode around the cable at both ends.

The terminal anode, the last anode on a string assembly, has a metal loop for attaching a weight. Since only a single cable lead protrudes from the hole, the junction box is eliminated when using a MMO string - reducing the cost of materials and labor. String assemblies are also available in a looped configuration with two tails, or as multiple, staggered strings for system redundancy and maximum current distribution throughout the ground bed. Like any impressed current anode, proper ground bed design is paramount to optimum, low resistance performance. MMO anode manufacturers recommend quality conductive, carbonaceous back fill, a vent pipe and Centralizers, suitable cable, and good design practices.

Cable Selection

MMO manufacturers recommend dual-insulated cable, such as PVDF/HMWPE cable for use where anodes operate in ground beds high in chlorides. Where chlorides are not anticipated, such as shallow vertical and horizontal surface beds, an economical cable choice is HMWPE. The high current capacity (150 amps) and flexibility of the EPR/CSPE cable makes it ideal for seawater applications. EPR/CSPE is not recommended for ground bed applications where chlorides are present (e.g., deep anode ground beds).

MMO Wire Anodes

MMO wire anodes are copper cored titanium wire with mixed metal oxide coating. The mixed metal oxide is a crystalline, electrically-conductive coating that activates the titanium and allows it to act as an anode.

MMO Disk Anodes

The MMO Disk Anode was developed for cathodic protection of dam and navigation lock gates. Since our disk anodes are designed to operate in fresh, brackish and seawater environments, other suitable applications include: marine structures, water tanks and vessels. With an optional primary seal spacer gasket, it can be used on the inside of pipes, tanks, or other curved surfaces. The active element in the Disk Anode is a 6" diameter x 1/8" thick titanium disk with a mixed metal oxide coating. When applied on titanium, the MMO coating has an extremely low consumption rate, measured in terms of milligrams per year. As a result of this low consumption rate, the dimensions of the anode remain nearly constant throughout the design life.

The mixed metal oxide coated disk is secured into a 12" diameter x 1/8" thick dielectric shield made of a durable, chlorine resistant, molded FRP-vinyl ester. This FRP shield has been designed to resist damage from floating debris and ice, as well as serving to enhance the current throwing capability of the disk. The shield also minimizes excessive current damage to the coating on surrounding steel. The low profile Disk anode fits flush with the surface, so total protrusion from the steel bulkhead is a mere 1/2".

The coated titanium disk and shield assembly is attached to a 1-1/4" diameter FRP stud via an interlocking epoxy joint. This joint enhances torque capability and subsequent sealing. A 100% compressible EPDM elastomeric o-ring molded into the shield assures a watertight seal between the disk and steel bulkhead, while simultaneously allowing the shield to fit flush against the bulkhead. Rod threads are platinum plated to prevent oxidation of the titanium-providing a low and constant contact resistance over the life of the anode. Nickel plated brass nuts further ensure a reliable, low resistance contact. And to prevent crevice corrosion of the titanium disk, a special, mixed metal oxide coating has been applied on the edges and back.

Condenser anodes are available either bare, coated with a plastisol (PVC) coating or with a specially designed molded Polypropylene box used to improve current distribution and increase the effective life of the anode.