A corrosion inhibitor or anti-corrosive is a chemical compound that, when added to a liquid or gas, decreases the corrosion rate of a material, typically a metal or an alloy, that comes into contact with the fluid. The effectiveness of a corrosion inhibitor depends on fluid composition, quantity of water, and flow regime. Corrosion inhibitors are common in industry, and also found in over-the-counter products, typically in spray form in combination with a lubricant and sometimes a penetrating oil. They may be added to water to prevent leaching of lead or copper from pipes.
A common mechanism for inhibiting corrosion involves formation of a coating, often a passivation layer, which prevents access of the corrosive substance to the metal. Permanent treatments such as chrome plating are not generally considered inhibitors, however: corrosion inhibitors are additives to the fluids that surround the metal or related object.
Benzotriazole inhibits corrosion of copper by forming an inert layer of this polymer on the metal's surface
The nature of the corrosive inhibitor depends on (i) the material being protected, which are most commonly metal objects, and (ii) on the corrosive agent(s) to be neutralized. The corrosive agents are generally oxygen, hydrogen sulfide, and carbon dioxide. Oxygen is generally removed by reductive inhibitors such as amines and hydrazines:
The suitability of any given chemical for a task in hand depends on many factors, including their operating temperature.
Volatile amines are used in boilers to minimize the effects of acid. In some cases, the amines form a protective film on the steel surface and, at the same time, act as an anodic inhibitor. An inhibitor that acts both in a cathodic and anodic manner is termed a mixed inhibitor.
Corrosion inhibitors are often added to paints. A pigment with anticorrosive properties is zinc phosphate. Compounds derived from tannic acid or zinc salts of organonitrogens (e.g. Alcophor 827) can be used together with anticorrosive pigments. Other corrosion inhibitors are Anticor 70, Albaex, Ferrophos, and Molywhite MZAP.
"Corrosion Resistance - DECC Company". www.decc.com. Retrieved 2015-10-15.*"Nitriding for Corrosion and Wear Fatigue Resistance". Corrosionpedia. Retrieved 2018-06-19.
^Hubert Gräfen, Elmar-Manfred Horn, Hartmut Schlecker, Helmut Schindler "Corrosion" Ullmann's Encyclopedia of Industrial Chemistry, Wiley-VCH: Weinheim, 2002. doi:10.1002/14356007.b01_08
^ ab"Optimal Corrosion Control Treatment Evaluation Technical Recommendations for Primacy Agencies and Public Water Systems" (PDF). United States Environmental Protection Agency. 2019.
^Ma, I. A. Wonnie; Ammar, Sh.; Kumar, Sachin S. A.; Ramesh, K.; Ramesh, S. (2022-01-01). "A concise review on corrosion inhibitors: types, mechanisms and electrochemical evaluation studies". Journal of Coatings Technology and Research. 19 (1): 241–268. doi:10.1007/s11998-021-00547-0. ISSN 1935-3804. S2CID 244716439.
^M. Finšgarand and I. Milošev "Inhibition of copper corrosion by 1,2,3-benzotriazole: A review" Corrosion Science 2010, Volume 52, Pages 2737-2749 doi:10.1016/j.corsci.2010.05.002
^Octel-Starreon Refinery Fuel Additives Corrosion Inhibitors for hydrocarbon fuels - corrosion inhibitor and corrosion protection to fuel distribution system
Corrosion control informations and documents
Developing corrosion inhibitor models – A paper on corrosion inhibition modeling
Corrosion inhibition, Norman Hackerman,(August, 2006), Electrochemistry Encyclopedia[dead link]