Application principle of corrosion inhibitor？

The application principle of corrosion inhibitors involves several key mechanisms designed to prevent or slow down the corrosion process of metals. These principles are applied across various industries to protect infrastructure, equipment, and systems. Here are the main principles and mechanisms:

1. Formation of a Protective Film

Adsorption: Corrosion inhibitors often work by adsorbing onto the metal surface to form a thin, protective film. This film acts as a barrier that prevents corrosive agents (like oxygen, water, and chlorides) from reaching the metal surface.

Organic inhibitors: Many organic inhibitors, such as amines and azoles, adsorb onto the metal surface due to their polar groups that bond with metal atoms, creating a hydrophobic layer.

Inorganic inhibitors: Compounds like chromates and phosphates form protective oxide layers on metals like aluminum and iron (Avista Membrane Treatment Solutions).

2. Alteration of the Environment

pH Adjustment: Some corrosion inhibitors work by altering the pH of the environment to a level where the metal is less susceptible to corrosion.

Alkaline inhibitors: Such as sodium hydroxide, increase the pH, making the environment less acidic and less aggressive towards metals like iron and aluminum (Solenis Chem Solvers).

Buffering agents: These maintain a stable pH, preventing fluctuations that can accelerate corrosion.

3. Cathodic and Anodic Inhibition

Cathodic inhibitors: These work by reducing the rate of the cathodic reaction in the corrosion process. They often provide electrons to the cathodic areas, preventing the reduction reactions that contribute to corrosion.

Examples: Zinc salts, polyphosphates, and rare earth compounds.

Anodic inhibitors: These inhibit the anodic reaction by forming an insoluble compound with metal ions at the anode, thereby blocking the active sites.

Examples: Chromates, nitrates, and molybdates (Avista Membrane Treatment Solutions).

4. Complexation of Metal Ions

Chelation: Corrosion inhibitors can form complexes with metal ions, making them less available for participating in corrosion reactions.

Chelating agents: Such as EDTA and HEDP, bind with metal ions like Fe²⁺ and Cu²⁺, reducing their activity in the corrosion process.

5. Oxygen Scavenging

Oxygen removal: Some inhibitors work by removing dissolved oxygen in the environment, which is a primary driver of corrosion, especially in aqueous systems.

Examples: Sulfites and hydrazine are common oxygen scavengers used in boiler water treatment (Solenis Chem Solvers).

Applications in Industry

Water treatment: In cooling towers, boilers, and desalination plants, inhibitors are added to prevent scale and corrosion.

Oil and gas: Inhibitors are used in pipelines and refineries to protect against the corrosive effects of water, CO₂, H₂S, and other corrosive agents.

Automotive: Inhibitors are used in engine coolants and lubricants to protect engine components from corrosion.

Construction: Rebar in concrete is often protected with inhibitors to extend the lifespan of structures.

Conclusion

Corrosion inhibitorsplay a crucial role in protecting metals from corrosive environments by forming protective films, altering environmental conditions, inhibiting cathodic and anodic reactions, complexing with metal ions, and removing oxygen. Their application across various industries helps in maintaining the integrity and longevity of metallic structures and components (Solenis Chem Solvers) (Avista Membrane Treatment Solutions).