Zinc anodes use the properties of potential, current capacity and alloy quality to protect the metal surface from corrosion. When immersed in water, the zinc alloy sacrificial anode has a reduction potential of -1.05V compared to the reference electrode. When the zinc alloy sacrificial anode is in close proximity to another metal with a greater reduction potential, it makes the other metal the cathode of the electrochemical system. As the oxidizer erodes the metal surface, electrons flow through the system and are removed from the zinc alloy sacrificial anode rather than from the protected metal, as shown in the formula: Zn→Zn2++2e-
Therefore, the sacrificial anode of the zinc alloy is corroded by oxidation rather than by the protective metal surface. The more massive the zinc alloy sacrificial anode, the longer it can provide a protective current before it exhausts itself. An important indicator of a zinc alloy sacrificial anode is its utilization rate, which specifies how much the anode can be used before losing its protective properties. With these indicators, we can calculate the anode demand according to the formula. The quality of the zinc anode material is also important because impurities in the zinc metal can weaken its protective properties.
In fresh water, zinc alloy sacrificial anodes create a thin film of zinc hydroxide on the surface, preventing the flow of current. Because of this, zinc anodes are ineffective in fresh water and are used in salt water.
Impurity, not more than
Open circuit potential
Corrosion products are easy to fall off, and the surface is evenly dissolved
Note 1: Reference electrode - saturated calomel electrode
Note 2: Medium - seawater medium adopts artificial seawater; The soil medium is wet soil, and the filling material is added around the anode.