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A corrosion inhibitor is a chemical compound which is designed to protect a metal or alloy from corrosion. While corrosion inhibitors will not halt or completely prevent corrosion, they can reduce the rate at which corrosion occurs, and block early corrosion damage. A wide variety of chemicals can be used for this purpose, although many are toxic, and must therefore be used with care to protect the environment.
One form of corrosion inhibitor is a compound added to a fluid such as a fuel or lubricant. In this case, the corrosion inhibitor travels with the fluid, providing protection to the systems the fluid moves through. Commonly, it forms a thin film which prevents reactions between compounds in the fluid and systems such as pipes. This type of corrosion inhibitor may be blended into the fluid continuously, or added periodically to maintain a protective film.
Corrosion inhibitors can also be sprayed or painted on to create a thin layer which will provide protection from corrosion. Many people do this on a regular basis when they oil locks and hinges to prevent them from rusting and to keep them moving smoothly. The thin layer of oil acts as a corrosion inhibitor to prevent oxidation, so that rusting cannot occur. In order to work effectively, the surface needs to be clean when the chemical is applied, as otherwise corrosive reactions can take place underneath the corrosion inhibitor.
Once corrosion has already started, a corrosion inhibitor may be used to slow the rate of damage, depending on the corrosives involved and the situation. Some corrosion inhibitors will also remove surface layers of corrosion to help restore a material to its original finish before depositing a layer of protection. It is a good idea to regularly inspect systems treated with corrosion inhibitors to confirm that the system is still protected and to check for signs of corrosion and system failure.
The choice of which corrosion inhibitor to use varies, depending on the application. Different chemicals can resist different types of corrosives, and may be more suitable for various applications, depending on which corrosives and metals are involved. It is also important to consider issues such as the safety of the system when selecting a product. Some products are highly effective, but very dangerous, and the safety risks may not be worth the high level of protection conferred by the toxic compound in a system which could release pollutants into the environment.
I have read a little about big problems with corrosion inhibitors not working as expected and this caused corrosion on machine parts on cars and in factory machinery.
There are experts in the field of metal corrosion and the products that are used to prevent corrosion on connectors and other parts of machinery. If the corrosion inhibitor doesn't work, the machinery malfunctions. The expert tries to find out why the inhibitor isn't working, and he/she may act as an expert witness in court cases.
It's really too bad that our metals are prone to corrosion when they are so useful for so many of our needs.
Unfortunately, if you want to protect metals from corrosion or remove it after corrosion has started, there are problems. The products that work well are also dangerous to handle and the toxins may get into the air.
What can be done so we don't have to use corrosion inhibitors?
I only know of one substitute for metal. We could use more plastic. The change from copper pipes to plastic has been a good one.