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Comparison of Several Cathodic Protection Systems for Oil Storage Tank

Jan 20, 2017

Sacrificial Anode cathodic protection system

 

It is easy to install and will not produce corrosion interference by using sacrificial anode protection for the storage tank. However, usually the tank will not be adequately protected when the tank is not well insulated from piping and other systems. Those systems include pipe networks, instrument cables, cable bushings, concrete rebars, and tank group grounding systems. Insulation for so many parts is not only costly, but also expensive to maintain. Sacrificial anode system driving voltage is generally lower than 0.7V, which limits the current output of the cathodic protection system. Once the tank is shorted to any of the above part, it is difficult to protect the tank, and the sacrificial anode system would quickly depleted and the protection life become shorter.

 

Deep Well Cathodic Protection System

 

This system is mainly used in the storage tanks which have already been built, especially for the narrow space. The disadvantage is that the cathodic protection current is not uniform, its prone to produce corrosion interference. While the anode is in very poor working conditions, very easy to cause premature damage.

 

Flexible Anode Systems

 

The flexible anode is made of conductive rubber which is coated on the outside of the cable, and the rubber is wrapped with a layer of carbon powder backfill. The flexible anode system can be installed under the tank bottom plate, the current distribution is uniform and it is not easy to cause corrosion interference. While there are still some disadvantages:

 

a. The system is much more expensive to transport and install than the mesh anode system.  Difficulty and cost of handling will increase due to the weight of every anode roll.

b. Packing belt could be easily damaged, resulting in filler leakage.

c. The anode can not be over bent.

flexiable anode

 

Mesh Anode Cathodic Protection

 

The mesh anode is an impressed current cathodic protection auxiliary anode composed of a precious metal oxide ribbon anode and a titanium base metal connecting piece. To embedded the anode mesh  in the storage tank base to provide a protection current to the tank bottom. Comparing to the above cathodic protection methods,this system has the following advantages:

 

a. The current distribution is very uniform, the output is adjustable to ensure adequate protection of the tank; stray current generated very little, and it will not cause corrosion interference to other structures.

b. No need for backfill, easy installation, long service life.

c. The mesh anode can be placed in the bottom of the tank and the impermeable membrane or between the concrete base, no need to filler.

mmo mesh anode

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