Pitting corrosion occurs in grooves, narrow gaps under bolts, under deposits, and in areas of the system where the solution (electrolyte) is stagnant or dead. Due to the corrosive liquid being trapped between the grooves, the corrosion reaction in the groove is accelerated and severe localized corrosion will occur.

Pitting corrosion is a type of localized corrosion that causes holes in the metal, resulting in pitting and deterioration. This type of corrosion is much more dangerous than uniform corrosion because pitting is difficult to detect and predict, and the holes are sometimes isolated and sometimes so close together that they create a rough surface on the metal.

Galvanic corrosion occurs when two dissimilar metals (with different electrochemical potentials) are placed next to each other in an electrolyte so that there is electrical contact between them.

Uniform corrosion is the most common type of corrosion, which occurs over the entire surface of the metal due to contact with the corrosive environment, resulting in a uniform reduction in metal thickness. This type of corrosion is schematically shown in the figure below. In this type of corrosion, the reduction in metal dimensions due to corrosion is completely uniform, so the corrosion rate is expressed in terms of the reduction in dimensions per unit time.

Downhole corrosion is one of the most important problems facing the oil and gas industry. By using various methods such as selecting appropriate materials, surface coating, use of corrosion inhibitors and cathodic protection, the corrosion rate can be significantly reduced. A better understanding of corrosion mechanisms and the development of new technologies can help improve efficiency and reduce costs in this industry.

The set of factors affecting metal corrosion can be divided into two main categories: environmental factors and intrinsic factors of the metal.

The incidence of each type of metal corrosion varies, and the importance of each type will vary across systems and environments. On the other hand, there are striking similarities in the distribution of corrosion damage across similar industries, and by comparing them, it can be seen that corrosion problems in similar industries are very similar.

In general, it can be said that the corrosion process will never stop, but it can be controlled to a large extent by implementing a corrosion management program. In fact, by implementing corrosion management, organizations can proactively plan to improve the way they design, operate, and maintain their critical assets, thereby reducing the cost of controlling damage and unexpected failures caused by corrosion.

Corrosion is a phenomenon that occurs in most environments, so no industry can be safe from the costs of corrosion. For example, the oil, gas and petrochemical industries, factories and heavy manufacturing industries (iron smelting, steelmaking, etc.), transportation, water and wastewater, are among the industries that are severely affected by this phenomenon. This section attempts to briefly examine corrosion in several important industries.

The destructive phenomenon of corrosion has a very long history, and mankind has always dealt with the problems caused by it, but scientific approach and study in this field do not have much history. In the middle of the 18th century, the phenomenon of corrosion was noticed, but no solution was presented to solve the problems caused by it.

In general, to facilitate the study of corrosion problems and to compare different metals with each other, the best method is to express the speed or rate of the corrosion reaction. Corrosion measurement units are used to express corrosion rates.

Metals are subject to corrosion in most chemical environments, for example, metals corrode in contact with water, moisture, acids, bases, salts, oils, gaseous substances and other chemicals. In general, minerals are more corrosive than organic substances. For example, corrosion in the oil, gas and petrochemical industries is often caused by the effects of minerals such as chlorine, sulfur, etc., rather than by organic substances such as oil, petroleum and diesel.

Failure to pay attention to corrosion problems in any industrial and manufacturing unit results in hidden costs that are impossible to avoid. Economic considerations are essential in each of the corrosion control methods. Of course, there is no need to choose the most expensive corrosion control methods, because the costs incurred may not be economically justified and waste capital.

In an effort to develop new materials, humans have succeeded in producing synthetic materials using organic materials (mainly hydrocarbons) found in nature. These materials mainly contain the elements carbon, hydrogen, oxygen, nitrogen, and sulfur and are known as polymeric materials.

Corrosion is often not uniform along the length of a member and is usually confined to the middle or ends of the member. In the case of piles, corrosion may be severe above the waterline and mild or absent below. This area of ​​maximum corrosion is often further away from the sections of maximum anchorage and shear forces, but rebar may be uniform throughout the member.

Corrosion inhibitors are substances that, when added in small amounts to a corrosive environment, slow down the rate of corrosion. In fact, an inhibitor can be considered a retarding catalyst. There are many inhibitors available with different compositions.