Briefly describe the two techniques that are used for galvanic protection.

Galvanic protection is a corrosion protection method that involves applying a direct electrical current to a metal structure to counteract the electrochemical process causing corrosion. The two principal techniques for galvanic protection are sacrificial anodes and impressed current cathodic protection.

Sacrificial anodes are made of a more reactive metal than the metal structure they protect. They are connected to the structure, creating a galvanic cell. The sacrificial anode corrodes preferentially, sacrificing itself and preventing corrosion on the protected structure. Examples of commonly used anodic materials include zinc, magnesium, and aluminum.

To apply sacrificial anodes: 1. Identify the type of metal to protect and select appropriate anodic material. 2. Determine the required number and size of sacrificial anodes based on the surface area of the structure to protect and the expected life of the anodes. 3. Connect the anodes to the structure using metallic connectors or cables to ensure good electrical contact. 4. Regularly inspect and replace the sacrificial anodes when they have corroded significantly to maintain effective protection.

In impressed current cathodic protection, an external power source provides a direct current to the protected structure. This direct current drives the electrochemical potential of the structure more negative, preventing corrosion. The system uses inert anodes, typically made of materials like titanium or graphite, that do not corrode during the process.

To apply impressed current cathodic protection: 1. Design the ICCP system considering factors like the size and geometry of the structure, current requirements, and power source types. 2. Install the inert anodes in the appropriate positions around the structure, ensuring good electrical contact. 3. Connect the anodes and structure to a rectifier or other power source that converts alternating current to direct current. 4. Monitor and adjust the applied current as needed to maintain adequate protection and prevent over-protection that can cause hydrogen embrittlement or other issues. 5. Periodically inspect and maintain the ICCP components to ensure effective long-term corrosion protection. By applying these techniques, galvanic protection effectively prevents corrosion on metallic structures, prolonging their service life and reducing maintenance costs.