Cathodic protection is primarily for protection against what?

Cathodic protection is primarily a technique used to prevent corrosion on metal surfaces that are buried in soil or submerged in water. This method safeguards these surfaces by creating a cathodic (negative) charge on the metal, which greatly reduces the electrochemical reactions that cause corrosion.

In the context of pipelines, tanks, or other structures exposed to corrosive environments, cathodic protection works by introducing another metal (a sacrificial anode) or applying an external electric current to reduce the oxidation reactions that lead to corrosion. By mitigating these reactions, the integrity and longevity of the metal structures are preserved, preventing deterioration that can lead to leaks or failures.

The other options pertain to different issues: heat could refer to thermal expansion or stress, pressure relates to mechanical stress on materials, and vibration pertains to structural stability and resonance effects. However, none of these are the primary concern that cathodic protection addresses. Therefore, corrosion is the correct context for understanding the application and necessity of cathodic protection techniques.