Most of them are used for cathodic protection of metal structures or the bottom plate of crude oil storage tanks in seawater environments, and cannot be used in soil environments with low chloride ion content (for indium-containing anodes, chloride ion content is greater than 1000ppm; Mercury anode 10000ppm). The electrode potential is -1.05V CSE. When the temperature is higher than 49℃, the capacitance decreases with the temperature, which can be referred to the formula: Z=2500-27 (T-20), (T anode operating temperature ℃). In salt water, the current capacity may be reduced by half. The aluminum anode is fixed directly to the protected structure without filler