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Application

Sacrificial Anode Protection: Electrochemical protection achieved by obtaining a protective current from a corrosion cell formed by connecting an auxiliary anode to the protected metal.

This method is commonly used to prevent rust. Sacrificial anode protection essentially involves attaching a piece of more reactive metal, typically zinc or magnesium. In other words, it allows the more active metal to be oxidized, forming metal ions, thereby reducing iron and preventing it from turning into iron hydroxide (rust). Thus, the more reactive metal "sacrifices" itself for the iron. This is a widely used method, often employed to prevent large steel structures, such as underground pipelines and oil tankers, from rusting.

System Requirements

Sacrificial anodes are typically only economically applied to structures requiring small protective currents and in environments with low soil resistivity. Additionally, they are valuable when there is no power supply or when it is not economically feasible.

Sacrificial anode materials suitable for soil are primarily magnesium, while zinc and aluminum are used in seawater. To maintain stable current output and reduce anode grounding resistance, sacrificial anodes in soil should be surrounded by chemical backfill, mainly composed of 75% calcium sulfate, 20% bentonite, and 5% sodium sulfate. Sacrificial anodes should not be buried in coke. When used in groups, the spacing between anodes should be at least 3m. The soil cover thickness above the anode should be at least 0.6m. To measure the off-potential, sacrificial anodes should be connected to the pipeline through a test box. When used near AC traction systems, the continuous AC induced voltage on the anode body should not exceed 20V.

Anode Requirements

1. The potential should be sufficiently negative but not too negative to avoid hydrogen evolution reactions in the cathode area;

2. The anode polarization rate should be low, and the potential and current output should be stable;

3. The anode material should have a high electrical capacity;

4. It must have high current efficiency;

5. It should dissolve uniformly and detach easily;

6. The material should be inexpensive and readily available;

7. The corrosion products produced should be non-toxic, harmless, non-polluting, and pose no environmental hazards.

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