Let's understand Cathodic Protection

Cathodic protection is a method used to prevent or mitigate the corrosion of metal structures like pipelines, tanks, and offshore platforms. It involves applying a direct current (DC) to the metal surface to counteract the electrochemical reactions responsible for corrosion.

Corrosion is an electrochemical process where metals interact with their surroundings, often in the presence of moisture and oxygen, leading to the metal's deterioration. In the context of cathodic protection, corrosion is seen as an oxidation reaction where metal atoms lose electrons and become metal ions.

Cathodic protection functions by applying a negative potential (cathodic polarization) to the metal surface, shifting its electrochemical potential to a more negative level. This negative potential hinders the oxidation (corrosion) process by decreasing the driving force for the electrochemical reactions.

There are two main methods of cathodic protection:

1. Galvanic Cathodic Protection (Galvanic Anode): This technique uses a more reactive metal, called a sacrificial anode, which is connected to the structure needing protection. The anode corrodes sacrificially instead of the protected metal. Common sacrificial anode materials include zinc, aluminum, and magnesium. The anode material is chosen based on its electrochemical characteristics and the environment of the protected structure.

2. Impressed Current Cathodic Protection (ICCP): This method uses an external power source, such as a rectifier, to deliver a continuous direct current to the structure. In ICCP, inert anodes, often made from materials like mixed metal oxide (MMO) coated titanium, supply the protective current to the metal structure. The external power source allows for better control of the cathodic protection system, making it suitable for larger structures or more demanding environments.

The choice of the appropriate cathodic protection system depends on several factors, including the size and shape of the structure, the environment it faces, and the anticipated corrosion rate.