Corrosion is known as a state of deterioration of metals that is usually caused by oxidation or chemical reactions. Corrosion of metals in the industry of oil and gas is something that is bound to happen and something that is unavoidable. But measures can be taken to see that this doesn't happen excessively. As we all know, it is very important for the industry, public and the economy of the country to make sure that everything runs well. And since the occurrence of corrosion is something that is a result of the working of the industry for its actual purpose of production of crude oil, we cannot stop the process but only look for steps that help to inhibit them. Here comes the role of corrosion inhibitors in the industry of oil and gas.

What are corrosion inhibitors and how do they work?

Inhibitors are chemicals that are used to protect the surface of metals used in oil and gas industries to prevent corrosion. They protect the surface of metals either by merging with them or by reacting with the impurities in the environment that may cause pollution. The inhibitors are dispersed onto metals from a solution, they then form a thin layer or film on the surface of the metal thereby protecting them. What is behind the film in the protection of the metal and how do they work? Well, the inhibitors help:

By causing an increase in the anodic and the cathodic polarization behavior

An inhibitor prevents and reduces the ions from diffusing with the metallic surface

It also helps to create an electrical resistance through its metallic surface

It may seem easy to control the corrosion of metals by just the use of inhibitors. But, there are a few things that are very important and that must be taken into consideration.

Things to consider before using a corrosion inhibitor in the oil and gas industry:

• Toxicity

• Environment Friendliness

• Availability

• Cost

Looking into inhibitors a lot of literature and scientific studies prove that there are a number of chemicals that can produce the effect of protection against corrosion but there are only very few used in the industry today. The reason being, it is very necessary to make the right decision while choosing the right one with respect to the above criteria. Coming to the prevention of corrosion of the oil and gas industry, the effective way to avoid it depends on the materials used in the construction of various parts of the industry and the type of inhibitor used, based on the requirement.

Treating an oil plant with corrosion and prevention of corrosion is a tricky thing and needs a lot of wise thinking. For example, the materials used and the placement of the metal depends on the pressure, temperature, and the kind of impurities that they are exposed to. At places where there isn't much pressure and temperature, metals like steel and copper are used; in areas that are excessively exposed to impurities and environmental changes, stronger metals like titanium are used.

Corrosion Inhibitors used, fall into the following types based on their way of functioning:

• Vapor Phase

• Cathodic

• Anodic

• Passivating

• Film Forming

• Neutralizing and Reactive

There are two types of inhibitors - inorganic and organic. Inorganic inhibitors were previously in use in the earlier days. Inorganic inhibitors like sodium arsenite and sodium ferro cyanide were put to use to avoid corrosion due to CO2, but the results weren't very good. The use of such inorganic inhibitors required frequent treatment and the end results weren't always up to the mark. Later, organic inhibitors were introduced which were commonly made from amines and salts of amines.

The mid 1940s brought about a drastic change to the way people looked at the problem of corrosion. At that time, the major reason of concern was the expenses involved in the treatment and prevention of corrosion. When the situation went beyond control, the very idea of using this facility was abandoned. With the introduction of long chain polar compounds, the problems related to corrosion were solved. Many reservoirs and operational oil wells were almost abandoned because of their corrosion, while the production of large volumes of water with hydrocarbons were saved.

In simpler terms, a corrosive inhibitor acts on the metal by slowly precipitating out its environment, which could be water or hydrocarbons onto the surface of the metal benefiting it by protection. A recent change in the functioning of these inhibitors is by the production of protection films that stick to the surface of the metals and resist the flow of ions and electrons slowing the reaction of corrosion. As the years have passed from the first introduction of inhibitors there has been immense development in the field, as studies continue based on the formulation of the inhibitors and methods of applying them. Similarly the methods used to evaluate them have also advanced, eliminating the corrosion problem.