Corrosion inhibitors

A corrosion inhibitor is a chemical compound which, when added at low concentration to the corrosive medium, slows or stops the corrosion process of a metal placed in contact with this medium.

While such a definition is by no means perfect, it avoids the risk of considering as inhibitors additives which, while meeting the second condition (reduction of corrosion rate), do not meet the first (for example, pH adjustment by adding base or acid does not constitute a means of inhibition within the meaning of the definition). On the other hand, certain compounds which should be strictly excluded by the definition can nevertheless be considered as inhibitors (oxygen-consuming additives = scavengers). Finally, the meaning given by this definition to the term inhibitor prevents corrosion inhibition from being interpreted in an overly semantic sense as the slowing down, by whatever means, of a metal's corrosion process (e.g. the incorporation of an alloying element into a metal: chromium is not an iron inhibitor when used in the composition of stainless steel).