Sacrificial anodes for storage tanks
Sacrificial anodes may be used for both external and internal cathodic protection of storage tanks.
Due to limited lifespan, external cathodic protection with sacrificial anodes are normally arranged for smaller tanks and as temporary protection.
Cathodic protection of underground storage tanks may be arranged by installation of magnesium anodes. The high grade magnesium alloy is recommended as it has a higher driving voltage, which is required for buried applications. The anodes are prepackaged in a cotton bag, surrounded by a special chemical backfill with high carbon content, for low anode-to-soil resistance.
The anodes are installed in a certain distance from the tank to ensure sufficient protective current distribution. Each anode is connected to the tank, preferably inside the tank dome, or in separate connection box, to enable control of the anode current output. The number of anodes required for protection depends on the size of the tank.
In order to measure the cathodic protection level, monitoring equipment should be installed aside the tank. Due to very dense coating systems
used, the measurement equipment should include both a suitable reference electrode and a steel monitoring coupon for accurate cathodic protection potential measurements.
Internal cathodic protection may be required due to condense water accumulated in the tank bottom. Arrangement of cathodic protection is made by installation of sacrificial anode chain, consisting of several anodes. The anode wire is connected to the tank by either bolting or welding.