Aqueous Anodes

Typical Applications: Featuring: Design Considerations:

Sizing - To determine proper anode size it is necessary to know both the required current distribution and service life. Current distribution will dictate the length of the rod (probe anode) or strip (low profile anode). Once that has been decided and the intended service life is known, the proper amount of active surface coating can be selected. Although the coating material is the most expensive part of the anode, it is most efficient to design with as thick an active surface as possible. Doubling the coating thickness does not double the cost!

Style - EDI manufactures aqueous anodes in a variety of styles to meet the requirements of the intended application. The two most common anode designs are probe and low profile. Probe anodes are typically 3/8" or 1/2" diameter with 2-9" active and 1-9" standoffs. They are best where throwing power to a remote location is required. Low profile anodes consist of strips that are typically 2-3" wide and 6-16" long. They are mounted on the surface and are less likely to cause personnel hazards during maintenance. Platinum or mixed metal oxide coatings can be applied that provide 20 or more years' service life. EDI also designs and builds custom anodes for special applications.
Design Parameters Probe Anode Low Profile Anode
Max. Flow Rate 15 ft/sec 40 ft/sec
Pressure Rating 150 psi 50 psi
Max. Operating Temp. 160 F 140 F
Max. Excursion Temp. 200 F for 1 hr 200 F for 1 hr

Substrate Selection - Titanium should be chosen when the anode surface voltage will be less than 10V such as in high conductivity waters like seawater. A niobium substrate should be used where the anode surface voltage may exceed 10V.

Surface Coating Selection - EDI's aqueous anodes are available with either platinum or mixed metal oxide active surfaces. Platinum is usually the best choice when current densities are below 10 A/ft2 in brackish or fresh water environments. It is also the preferred coating in all seawater applications where chlorine is generated at the anode surface. Mixed metal oxide coatings are the best option where oxygen evolution is expected at the anode surface such as in fresh water locations. However, the cost for this coating is somewhat higher than for platinum.

Platinum Consumption Rates

Coating thickness, operating current density and anode design life are interrelated as shown here. Please note that while there is no published data for anode life with mixed metal oxide coatings, they have been used at the same current densities as platinum.

Recycling

EDI will Refurbish Aqueous Anodes whose active surfaces have been consumed and/or standoffs or mounting nipples have been damaged. In most cases an anode can be restored for less than half the cost of a new one.