Corrosion Inhibitor

Definition - What does Corrosion Inhibitor mean?

A corrosion inhibitor is a chemical substance that inhibits or reduces the corrosion rate of a metal when it's added to its surrounding corrosive environment. A corrosion inhibitor is of different types namely, anodic, cathodic, and mixed inhibitors. Corrosion is a rampant problem in buried pipelines resulting in damage and failure of pipelines. This can be especially catastrophic when the pipelines transport hazardous material such as oil, gas, sewage or chemicals.

It's necessary to carry out regular inspection of pipes prone to corrosion using closed-circuit-television cameras (CCTV) and robotic cameras.

Trenchlesspedia explains Corrosion Inhibitor

The different types of corrosion inhibitors mentioned above work differently and are effective in reducing the rate at which a metal corrodes.

Anodic inhibitors are used in environments where salts, oxides or hydroxides are formed sparingly. They are also called passivating inhibitors and facilitate the formation of passivating films that inhibit the anodic reaction. Insufficient amount of anodic inhibitor can accelerate the rate of corrosion.

Cathodic inhibitors work either by decreasing the reduction rate or by precipitating on the cathodic areas. Cathodic poisons such as sulfides and selenides can cause hydrogen blisters, hydrogen embrittlement and hydrogen induced cracking because of the absorption of hydrogen into the metal especially in acidic environment. Cathodic inhibitors such as carbonates of calcium and magnesium work by increasing the alkalinity at cathodic sites.

Mixed inhibitors are those that cannot be specifically classified as anodic or cathodic. They protect the metal by adsorption, film formation and chemisorption. Silicates and phosphates are commonly used mixed inhibitors.

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