It refers to general or localized corrosion of carbon steels and other metals caused by dissolved salts, gases, organic compounds, or microbiological activity.

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.

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.

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 additives that control corrosion by altering the metal surface, the environment, or both. Their mode of action is to alter the anodic, cathodic, or both reactions. There are many corrosion inhibitors available with different compositions. Most of these materials have been discovered and refined through experimental testing, and many of them are sold under trade names and their chemical composition is kept secret.