Types of Corrosion Inhibitor

 A Corrosion Inhibitor is a chemical solution which is applied in a given state of affairs to reduce the rate of corrosion of the metal which is subjected to that circumstantial environment, like air or water. The corrosion inhibitor is abbreviated to CI. This can also be defined as a chemical compound that can be added to liquids or gases and used to drop-off the corrosion rate of a given material.

One method for the controlling of corrosion would be the addition of a coating on the surface of the metal which acts as a passivation layer and forbids access to the surface of the metal. Corrosion Inhibitor Paints have a wide range of uses in commercial, process, and industrial surrounds. Some of these uses are listed below.


  • Corrosion Inhibitors are used to prevent rusting and anodic corrosion of metals. This is implied through the coating of the metal surface with a chromate layer.
  • Oxygen scavengers can be used as CI substances to react with dissolved oxygen in the environment and can help in preventing cathodic corrosion.
  • It is very important to forbid rusting and corrosion of fuel pipelines. Therefore, Corrosion Inhibitor Paints are very important in shielding these pipelines and reducing the risk of accidents.


Let us look at the type of  inhibitors for corrosion:

1.    Cathodic Inhibitor: these substances can work to slow the cathodic reaction down or they can work to selectively precipitate on the cathodic areas of the metal in order to restrict the diffusion to the metal surface of the components that are eroded. Some examples of cathodic inhibitors include sulfite and bisulfite ions which react with oxygen and take the form of sulphates. Another instance of a cathodic inhibitor is a catalyzed redox reaction by nickel.

2.    Anodic Inhibitor: These types of corrosion inhibitors form a thin preventive layer made up of oxides on the surface of the metal. This reaction leads to a huge anodic shift, turning the metallic surface into a passivation surface. This passivation area aids in reducing the corrosion of the metal. Some of the instances of anodic inhibitors include chromates, nitrites, ortho-phosphates, and molybdates.

3.    Volatile Corrosion Inhibitor: these inhibitors are used to halt the corrosion of condenser tubes in boilers. They are also called as vapour phase inhibitors or VPIs. These work by changing the pH of the exterior atmosphere to lesser acidic medium in order to control corrosion. some examples are inclusive of morpholine and hydrazine that are used to control the corrosion of the condenser pipes in boilers.

4.    Mixed Inhibitors: These types of corrosion inhibitors also form a firm film on the surface of the metal. They work to minimize cationic reactions as well as anionic reactions. This is done via the formation of a precipitate on the metal surfaces. This category include silicates and phosphates which are used as water softeners to prevent rusting of water.

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