JANUARY 31 2003
naturally forms on the surface of bare titanium. When the mixed metal oxide film has
been consumed, the insulating titanium dioxide film will cover the anode and not allow
current to discharge unless the applied voltage is greater than 10 volts in seawater, or
50 to 70 volts in fresh water.
The U.S. Army Construction Engineering Research Laboratory (USACERL)
has developed a ceramic anode as a Facility Engineering Application Program (FEAP).
Good performance of the ceramic anode has been demonstrated in a wide variety of
applications. Procurement, material specifications, performance parameters, and
application designs are detailed in Engineering Technical Letter (ETC) 1110-9-10 (ER).
The following data details the maximum recommended current densities for various
Soil, mud, fresh water: 100 amps per square meter (9.3 amps per square
foot (20 years).
Seawater: 600 amps per square meter (55.7 amps per square foot (15
Anodes in soil or mud must be backfilled with fine, low resistance, calcined
petroleum coke breeze for maximum life and performance. Even when the anode is
pre-packaged with petroleum coke, conservative engineering judgment would dictate
that the anode package be surrounded with metallurgical coke, prior to finishing the
backfilling with native soil. Consumption rates at these densities range from 0.5
milligrams per amp-year in seawater to 5 milligrams per amp-year in coke breeze, fresh
water, and sea mud. As with any anode, the connection must be constructed so as to
be moisture proof, water tight and have no more than 0.001 ohms of resistance.
Advantages of mixed metal oxide anodes:
Lightweight and unbreakable
Negligible consumption rate
Inert to acid generation
High current density output
Polymer Conductive Anodes. In 1982, a new anode material was test-
marketed. The material provides a small amount of current in restricted spaces, such
as internal pipe surfaces, heat exchangers, utility ducts, and areas shielded from