The electrochemical performance of aluminum makes it an attractive galvanic anode material, especially in low resistivity applications such as seawater and produced brines. Compared to the performance of magnesium, aluminum’s lower driving potential and high current capacity per pound are key aspects for its use in long life saline systems.
For years, the low current efficiency of commercially available aluminum hindered its use in cathodic protection systems. The high efficiency alloy series were developed to correct this problem and have become the industry standard.
Modern aluminum anodes stand out with respect to:
- High Current Capacity Under Variable Conditions
- Desirable Operating Potential
- Current Capacity Maintenance Over Time
- Constant Potential Over Time
Indium activated anodes are recommended for use in seawater, saline mud, at both ambient and high temperatures, and in hot brines including most oil field brines. Indium activated tank anodes are recommended for use in hot brine and oil field brine applications. This alloy provides a longer life, reducing costs for protecting tanks containing oil field brine. Aluminum anodes can be installed by suspending anodes from the deck of the tank from a deck mount. Or the anodes can be placed on concrete or tile blocks placed in the bottom of the tank. Many of the anodes can also be installed by welding or bolting the anode core to the structure. In most cases it is recommended that the lead wire from the anodes be attached to the outside of the vessel. A shunt should be placed in series with the lead wire to measure the current output in order to determine the life expectancy of the anodes.
Aluminum platform anodes are supplied in a variety of shapes and sizes for seawater applications; for example, offshore pipelines, bay platforms, etc., where the anodes are placed in the mud zone or where high resistivity conditions exist. In many cases, as a result of the higher driving potential of the Indium activated alloy, fewer anodes may be required resulting in savings in installation costs. However, the life of the anodes is reduced by 20% due to the higher current output.
Indium activated alloy hull anodes are also used in ballast tanks and small oil field brine containing vessels.
Background: Galvanic Anode Cathodic Protection System
The galvanic system uses the natural difference in potential between metals to cause a direct electrical current from an anode through the soil or water to the structure being protected. BK Corrosion has provided industry with quality cathodic protection equipment for over 65 years.