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Cathode Block

cathode blocks

Cathode Block

Cathode blocks are used for the masonry lining of aluminum electrolytic cells. As a positive electrode conductive material, it has the characteristics of high-temperature resistance, molten salt corrosion resistance, and good conductivity. There are many types, including ordinary carbon cathode block, semi-graphite carbon block, high-graphitic carbon block, and graphitized cathode block. The current specifications are 550mm×900mm×3600mm and 650mm×700mm×3600mm and above.

What is it use of?

Cathode block is essential as negative electrodes in the electrolysis process of aluminum from alumina. It help improve the efficiency of aluminum smelting, which consumes a lot of electricity. So it is the central part of the cathode structure of the aluminum electrolytic cell.

So it acts as a cathode conductor in the aluminum electrolysis production process. It exists as the lining material of the electrolysis cell container. With the rapidly increasing demand for aluminum globally, cathode blocks play an essential role in the industry.


The primary function of the cathode carbon block is as the lining material of the electrolysis cell and for the conduction of electric current.

At the same time, it must withstand the erosion of high-temperature cryolite melt during the aluminum electrolysis process.

There is also the electrochemical action of high-temperature slag in the electrolysis process.

Therefore, its quality plays a vital role in the operation of aluminum electrolytic cells.

The grade directly affects the service life of the electrolytic cell, especially in terms of sodium corrosion resistance, thermal expansion rate, and resistivity.

Improving its quality reduces the power consumption in production and is of great significance to prolonging the service life of the electrolyzer.

The main cause of damage to it of an aluminum electrolytic cell is that the infiltration of sodium causes the expansion of the carbon block, and the infiltration of the molten electrolyte increases its thermal expansion coefficient.


Cathode blocks Cathode carbon block-graphitized cathode block



It has low resistance and good conductivity, so its voltage drop is small, which can reduce the power consumption of electrolytic production.

It has specific mechanical strength. During aluminum electrolysis, the volume of the cathode block expands, resulting in considerable expansion

stress and high mechanical strength, which will reduce the damage rate.

The low porosity of it does not break down quickly when the electrolyte content permeating into it increases.

The ash content is small, so it will not increase the specific resistance and affect the conductivity.

The damage coefficient of it is small, which can prolong its service life.


 Properties of cathode block

PROPERTIES UNIT amorphous carbon semi-graphite semi-graphitized graphitization
Real density g/cm3 1.85~1.95 2.05~2.15 2.05~2.18 2.20
Apparent density g/cm3 1.50~1.55 1.60~1.70 1.55~1.65 1.6~1.8
Total porosity % 18~25 20~25 15~30 25
Open porosity % 15~18 15~20 15~20 20~24
Electrical Resistance μΩ·m 30~50 15~30 12~18 8~14
Thermal conductivety W/mk 8~15 30~45 32 80~120
Compressive strength MPa 25~30 25~30 20~25 15
Bending strength GPa 6~10 10~15 6~10 10~15
Rapport test % 0.6~1.5 0.3~0.5 0.3~0.5 0.05~0.15
Ash content % 3~10 0.1~1.0 <1.5 <0.5


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