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geniusofha...
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geniusofhardwork  |  April 22, 2009 03:21 PM
According to wikipedia.com
"A corrosion inhibitor is a chemical compound that, when added to a fluid or gas, decreases the corrosion rate of a metal or an alloy.

The effectiveness, or corrosion inhibition efficiency, of a corrosion inhibitor is a function of many factors like: fluid composition, quantity of water, flow regime.... If the correct inhibitor and quantity is selected then is possible to achieve high, 90-99%, efficiency. Some of the mechanisms of its effect are formation of a passivation layer (a thin film on the surface of the material that stops access of the corrosive substance to the metal), inhibiting either the oxidation or reduction part of the redox corrosion system (anodic and cathodic inhibitors), or scavenging the dissolved oxygen.

Some corrosion inhibitors are hexamine, phenylenediamine, dimethylethanolamine, sodium nitrite, cinnamaldehyde, condensation products of aldehydes and amines (imines), chromates, nitrites, phosphates, hydrazine, ascorbic acid, 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.

An example of an anodic inhibitor is chromate which forms a passivation layer on aluminum and steel surfaces which prevents the oxidation of the metal. Unfortunately, chromate is carcinogenic in humans; the toxicity of chromates was featured in the film Erin Brockovich. Like hydrazine, the use of chromate to protect metal surfaces has been limited; for instance it is banned from some products."
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