A corrosion inhibitor reduces the corrosion rate of a metal exposed to that environment. An inhibitor is a substance that slows down a chemical reaction (in the present context, a corrosion reaction). Corrosion inhibitors are commonly added in small amounts to acids, cooling waters, steam, and many other environments—either continuously or intermittently—to reduce the intensity of corrosion. Corrosion inhibitors are generally applied to clean surfaces and allowed to penetrate and dry.
Inhibition can be used internally with carbon steel pipes and vessels as an economic corrosion control alternative to stainless steels and alloys, coatings, or non-metallic composites, and can often be implemented without disrupting a process. Inhibitors can also be used to protect against the corrosion of reinforced steel bars (rebar) within concrete. Major businesses using corrosion inhibitors include many within oil and gas exploration and production, petroleum refining, chemical manufacturing, heavy manufacturing, water treatment, and the product additive industries.
The total consumption of corrosion inhibitors in the United States doubled from approximately $600 million in 1982 to nearly $1.1 billion in 1998, according to NACE research.