The sacrificial anode packing material is mainly composed of gypsum, bentonite, diatomite and sodium sulfate. Its function is to prevent the deposition layer of high resistance corrosion products formed on the surface of the anode material to make the anode material dissolve evenly. Absorbent bentonite and similar diatomite, by their special material structure and properties, can maintain the moisture of the soil around the anode and equalize the fluctuation of soil moisture. Bentonite is a special silicate soil, with strong water absorption, and can form a semi-permeable film and prevent the loss of soil anions in the packing material, so it is not possible to use clay to replace bentonite. Sodium sulfate can reduce the resistivity of the filler, which is beneficial to the uniform corrosion of the anode material, prevent the formation of passivation layer and more uniform current distribution. By changing the proportion of each component in the packing material, the percolation of the packing material can be adjusted and the soil resistivity around the anode can be reduced slightly.

The main functions of the packing material are as follows: (1) The sacrificial anode is changed from the state of direct adjacent to the soil to the state of adjacent to the anode and the packing material. The interface state and working environment of the anode can be improved by selecting the appropriate packing material components. (2) The ground resistance of the anode can be significantly reduced and the output current of the anode can be increased because of the reasonable packing material formula. (3) Due to the rapid dissolution of the anodic corrosion products in the packing material, the deposition layer with high resistance will not be formed, and the anode surface is activated and the anodic surface is formed to form a passivation layer, which reduces the polarization of the anode. (4) It can make the protection current more evenly distributed, so that its working environment can be kept wet for a long time. ⑤ Make the corrosion of the sacrificial anode itself uniform, improve the efficiency of the current, prolong the service life of the anode.

The basic requirements for the packing material composed of chemical agents are: ① Good interface performance with the anode; ② The resistivity is low; ③ Good permeability; ④ It is not easy to lose; ⑤ Strong moisture retention.