What You Need to Know about Cathodic Protection?

What You Need to Know about Cathodic Protection?

Cathodic protection is a method used for controlling or mitigating the corrosion of a metallic structure by turning the structure into a cathode. This can be accomplished either passively or actively; passively by connecting the metal structure to another metal that corrodes rather than the structure (galvanic anodes), or actively by applying direct current to an anode connected to a structure (impressed current). Both methods cause the structure to become cathodic and mitigate corrosion.

When to Use Cathodic Protection
Not all structures require cathodic protection, and cathodic protection cannot be installed in every situation. CP is required when a structure is susceptible to deterioration to environmental conditions, such as immersion and burial.
While some waters and soils are less likely to cause corrosion, many of these environments are more aggressive—and therefore there is a higher probability that corrosion will occur. For new structures, samples are collected and chemically analyzed for elements such as chlorides, in addition to measuring the conductivity and performing soil resistivity surveys to aid in determining the need for cathodic protection. For existing immersed structures, it is recommended to add CP when corrosion such as galvanic, pitting, and uniform corrosion is observed. Buried structures cannot be visually inspected and, therefore, it is recommended that CP be added to the structure if feasible. Corrosion experts should be consulted to determine if there is a need for additional corrosion mitigation measures and if it is feasible to add CP to a structure.

Cathodic Protion Application:
Common applications for cathodic protection are steel water or fuel pipelines and steel storage tanks such as home water heaters; steel pier piles; ship and boat hulls; offshore oil platforms and onshore oil well casings; offshore wind farm foundations and metal reinforcement bars in concrete buildings and structures. Another common application is in galvanized steel, in which a sacrificial coating of zinc on steel parts protects them from rust.