The first use of corrosion inhibitors is not well documented, but it is known that in the early 1900’s calcium in the form of Lime was being used to treat particularly clean potable water networks, so that a thick protective calcareous deposit would develop on the inner surfaces of the systems pipework.
By the mid 1940’s the use of inhibitors had become widespread and was used with aircraft, aluminum equipment, boilers, engines and oil refineries. Today corrosion inhibitors are used extensively throughout all industry sectors and particularly in logistics, transportation and storage where control of corrosion is required.
A corrosion inhibitor can easily be defined and as ‘A substance which retards corrosion when added to an environment is small concentrations’
Volatile corrosion inhibitor, also known as “vapor corrosion inhibitor,” (VCI) are inhibitors supplied in many forms but typically as liquids, powders, films, papers and foams.
When exposed to an enclosed gaseous environment the inhibitor evaporates and diffuses into the surrounding environment until a uniform concentration is achieved. When the now gaseous inhibitor comes to rest on a metal surface it will be adsorbed onto the surface creating a corrosion protecting thin film coating. The inhibitor or the film does not change the property of the metal on which it rests, but it blocks other corrosive elements such as oxygen and moisture reaching the surface of the metal and causing corrosion. Similarly, inhibitors added to contained liquids act the same, they mix/diffuse through the liquid coming to rest on the metallic surfaces requiring protection and are adsorbed to create a protective film.
Corrosion inhibitors act in three basic ways, they are either:
Often corrosion inhibitors may combine more than one of these actions.
Corrosion inhibitors can be supplied and applied in the form of gases, liquids, or powders to meet the requirements of individual applications or user needs.
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