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A corrosion inhibitor is a chemical compound that, when added in small concentration, stops or slows down corrosion of metals and alloys.
A typical good corrosion inhibitor will give 95% inhibition at concentration of 80 ppm, and 90% at 40 ppm. One of the mechanisms of its effect is formation of a passivation layer, a thin film on the surface of the material that stops access of the corrosive substance to the metal.
Some corrosion inhibitors are hexamine, phenylenediamine, dimethylethanolamine, sodium nitrite, cinnamaldehyde, and others. The suitability of any given chemical for a task in hand depends on many factors, from the material of the system they have to act in, to the nature of the substances they are added into and their operating temperature.
Corrosion inhibitors are commonly added to coolants, fuels, hydraulic fluids, boiler water and many other fluids used in industry.
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