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Introduction of Sacrificial Anode Cathodic Protection

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Types of cathodic protection methods

Element Secrificial anode system Impressed current system
types of cathodic protection methods Mg Anode, Al Anode, Zn Anode H.S.C.I Anode, M.M.O Anode
construction method - Deep Well Bed, Shallow Bed
pros
  • Time and space-efficient
  • No artificial maintenance required
  • No need for electricity
  • No problem when installing hazardous area
  • Can be installed on existing facilities
  • No need for a separate installation location
  • Uniform current distribution
  • No concerns about over-protection
  • No impact on adjacent facilities
  • Long anode lifespan due to use of wear-resistant anode
  • Artificial control of current is possible
  • Useful in narrow spaces
  • Automation is possible
  • Effective in high-resistance environments
  • Wide range of application methods
cons
  • Current control is not possible after installation.
  • Limited range of application methods.
  • Requires many installation locations.
  • Economically inefficient in high-resistance areas.
  • Unable to adjust current according to environmental changes.
  • Limited space requiring a long lifespan becomes difficult to install due to increased volume of anodes.
  • Always requires power supply.
  • Continuous expenditure on electricity.
  • Requires ongoing maintenance.
  • Requires land allocation for installation.
  • May cause interference with adjacent structures.

Secrificial Anode Cathodic Protection

By connecting the metal with lower potential to the protected strcutre within the corrosive environment, either directly or through a wire, an electrochemical reaction occurs between the two metals. This results in the extraction of metal ions from the anode, generating a current. The lower potential metal, serving as the sacrificial anode, is consumed sacrificially instead of the protected structure, preventing corrosion.

Sacrificial anode construction procedure

By connecting the metal with lower potential to the protected strcutre within the corrosive environment, either directly or through a wire, an electrochemical reaction occurs between the two metals. This results in the extraction of metal ions from the anode, generating a current. The lower potential metal, serving as the sacrificial anode, is consumed sacrificially instead of the protected structure, preventing corrosion.

1. CAD WELDING

  1. Identify the wire to be cad welded and the welded body (protected structure) to determine the size of the mold that matches the size of the welding powder.
  2. Determine the welding area, remove the coating around 5cm in all directions, and clean the surface with sand paper or other tools.
  3. Remove about 25mm of the insulation cover of the wire.
  4. If there is moisture on the surface, welding will not work well, so heat it with a torch to remove the moisture.
  5. Remove any rust generated during heating with torch.
  6. Place the wire in the correct position.
  7. Place the mold and add disk, welding powder, and ignition powder.
  8. Ignite the IGNITION POWDER (welding occurs when flames appear).
  9. Separate the mold and visually inspect the welding condition. If it is satisfactory, lightly strike 4-5 times with a 1 pound hammer.
    If the welding joint moves during this process, consider it defective. Repeat the above procedure until the joint is satisfactory.

2. Mg-ANODE

  1. Before applying cathodic protection to the U/G pipeline, underground piping must be installed first.
  2. Arrange Mg-anodes at regular intervals.
  3. Connect the main cable and Mg-anode lead cable using a splice kit.
  4. The main cable shall be connected to the negative(-) cable in the test box.

3. Procedure for Potential Measurement

  • Natural Potential Measurement
    (Record a result)

  • Protective Potential Measurement
    (Record a result)

4. Potential Measurement Method

Potential measurement is performed using a potential measuring instrument (multi-meter) and a reference electrode and is measured as follows.

  1. Connect the lead cable of the Ref. Electrode to the (-) terminal of the measuring instrument.
  2. Connect the measuring lead cable of the pipe to the (+) terminal of the measuring instrument.
  3. Ensure that the reference electrode makes contact with the surface layer of the ground directly beneath the pipeline (In case of using portable ref. electrode).

5. Protective Potential Range

The potential criteria for Cu/CuSO4 Ref. Electrode are set to be below (-)0.85V (increasing in numerical value), and the limits for the minimum and maximum values are as follows:

Minimum value: Below (-)850[mV] / Maximum value: (-)2,500[mV]