Material selection method of cathodic protection

In the process of cathodic protection design, the selection of cathodic protection materials is a very important content, which is related to the success or failure of the whole project. In theory, any metal that is more active than the protected metal can be used as sacrificial anode.

However, in practice, some metals are too active, such as potassium, calcium and sodium, which can react violently with air or water, so they can't be used. In fact, the common sacrificial anodes that can be used are magnesium, aluminum and zinc.

Magnesium anode can be used in a wide range of environments. Basically, it can be used in most environments. Another advantage is that it will not produce harmful cations. It can be used in drinking water tanks and water heaters. However, because magnesium is more active, self-corrosion is more severe, current efficiency is not high, and the price is high, so it is not very economical to use.

Magnesium anode is suitable for the environment with high resistivity in soil or fresh water. In order to reduce grounding resistance, reduce self-corrosion and increase current output, magnesium anode in soil is required to be placed in the filling material, which is a mixture of gypsum powder and bentonite.

Pure aluminum is not suitable for sacrificial anode material, because its surface will produce passivation film to prevent electrochemical reaction. By adding trace metal elements, such as zinc, indium and so on, the passive film can be prevented from forming and play an initial activation role. Aluminum anode is usually used in seawater or saline soil environment. Aluminum anode is widely used in ocean engineering because of its light weight, large unit capacitance and low price. The aluminum anode is used in water and is directly fixed on the protected structure without filler.

Zinc anode is one of the most commonly used anodes in seawater and soil. There are many types of zinc anodes. Ordinary zinc anodes can not be used in the environment above 54 ℃, because the polarity of zinc anode will be reversed and the potential will be corrected compared with steel. The zinc anode will become a cathode at this time. However, there are special types of zinc anode that can be used in high temperature environment. Generally speaking, the current efficiency of zinc anode is high. High purity zinc can be used in soil or fresh water with resistivity below 20 Ω. M. Zinc anode used in soil requires to be placed in the packing material, which uses gypsum powder, bentonite, industrial sodium sulfate and other mixtures.

Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing cathodic protection technology, engineering design, installation and technical services.