The electrochemical anticorrosion method of sacrificial anode is based on the reductive sacrifice of the metal and the anode metal connected to the positive pole of the external power supply, so that the cathode metal connected to the negative pole of the external power supply can be protected by electrons. Generally speaking, the electrode potential of the sacrificial anode metal is required to be negative than that of the protected metal, the anode capacitance is large, and the theoretical electricity generation is large, and then the anode metal is required to have high current efficiency to improve the protection rate of the cathode metal. In addition, the anode metal is required to be a metal material with low price and abundant reserves, and the product produced by electrolysis should be non-toxic and pollution-free.
Magnesium alloy is the mainstream material of sacrificial anode. Mg-Mn series alloy, Mg-Al-Zn-Mn series alloy and magnesium coated aluminum are widely used in industrial production. Magnesium-coated zinc bimetallic composites. Manganese in magnesium alloy can eliminate the effect of impurities on magnesium self-corrosion rate, which is equivalent to the existence of "purifying agent", but excessive manganese will lead to the decrease of corrosion resistance and plasticity of magnesium alloy. Some studies have shown that the corrosion rate of magnesium alloy in soil decreases, and from the sediment on the surface of magnesium alloy, it can be inferred that it is due to the action of calcium salt and magnesium salt in soil, so adding appropriate amount of calcium to magnesium alloy can delay the self-corrosion of magnesium alloy. Aluminum and magnesium are the main elements of the alloy, but the presence of aluminum will accelerate the self-corrosion of magnesium, and the addition of zinc can greatly slow down the corrosion rate, so most of the magnesium alloys commonly used in industrial production contain manganese, aluminum, zinc and other elements. People can get the best content ratio of each element by changing the content of each element. even so, the content of impurities still needs to be controlled to reduce impurities in order to improve the current efficiency.
The sacrificial anode method can effectively prolong the protection period of cathode metal, and the cost is less than other protection measures, so the sacrificial anode method has a high utilization rate in anti-corrosion engineering. Magnesium alloy sacrificial anode materials are also widely used in all kinds of anti-corrosion projects, such as anti-corrosion protection of urban underground gas pipelines and oil transportation pipelines, and anti-corrosion protection of equipment in biochemical engineering. Anti-corrosion protection of fresh water heat exchangers in thermal power plants and petrochemical plants, anti-corrosion protection of sewage gates in rivers and reservoirs, etc.
