Localized corrosion occurs on metals that are coated with rutile layers. This can be caused by defects or breakage of the rutile layer. Attacking ions such as chloride cause the rutile layer to break down at weak points on the metal surface. In this case, the bulk of the metal is in a rutile state while small localized areas of it are in an active state.

Today, due to the understanding of the metal-electrolyte system, it has become common to prevent corrosion with the help of corrosion inhibitors. Inhibitors are chemicals that, when added in small amounts to a corrosive environment, greatly reduce the rate of corrosion. The composition and types of inhibitors are very diverse. One of the most important ways to classify these materials is based on their mechanism of action and composition.

Large factories, especially in the oil, gas and petrochemical industries, have engineering groups that work directly with designers to reduce corrosion. Materials engineers have a good understanding of the processes and corrosion issues that exist in manufacturing plants. They come to designers to advise on design problems.

Changing the corrosive environment is a common method for reducing and preventing corrosion. Environmental changes are affected by parameters such as temperature changes, oxygen concentration changes, velocity changes, concentration changes, composition changes, and moisture content changes.

Some of the coatings used today include materials made using nanotechnology. These methods include composite thin film coatings, topcoat coatings, and surface passivation layers. They are called nanocoatings.

The use of nanoparticles in the manufacture of anti-corrosion coatings is one of the most important achievements of nanotechnology. Important functions of nanoparticles in corrosion control include improving barrier properties, cathodic protection, anodic protection, and increasing the adhesion properties of the coating.

Organic coatings protect metal from the environment in the form of a very thin layer. Varnishes, paints, enamels, bituminous rubbers, and plastics are organic coatings that can partially cut off the metal from the environment and thus protect metals. An important factor in the development of organic coatings is the petroleum industry, which produces the main components of chemical resins.

These coatings, which are used to protect against corrosion, contain mineral compounds and are often made of glass and cement. The most common mineral anti-corrosion coatings are glass glazes.

Another way to protect metal from corrosion is to use corrosion-resistant coatings. Coatings refer to thin layers of materials that are applied to the surface of a metal to achieve goals such as improving surface strength, improving corrosion resistance, aesthetic appearance, and thermal insulation.

Another way to protect metal from corrosion is to use corrosion-resistant coatings. Coatings refer to thin layers of materials that are applied to the surface of a metal to achieve goals such as improving surface strength, improving corrosion resistance, aesthetic appearance, and thermal insulation.

The increasing expansion of various industries, including factories, power plants, refineries, automotive industries, cable manufacturing, etc., has made it more necessary to understand the types of materials and their performance against corrosive environments. The importance of choosing the right materials in different corrosive environments is such that it has become the most important and common tool for controlling corrosion.

In the cathodic protection method, by applying a direct electric current to the metal or by contacting it with a sacrificial anode, the corrosion rate is reduced. In this case, on the metal surface where both cathodic and anodic regions exist, the anodic regions become cathodes, and as a result, the desired system or equipment becomes completely cathodic.

Corrosion engineers or technicians must determine which method to use for cathodic protection under different conditions. The project manager must be able to compare the various factors affecting the two cathodic protection methods and select the best one.

In anodic protection, the applied electric current is usually equal to the amount of corrosion of the structure being protected. Therefore, it is not only a protection method but also a method of measuring the instantaneous corrosion rate.

Microbial corrosion is a term used as an abbreviation in Persian. The exact term for this corrosion is microbiologically influenced corrosion and is abbreviated as MIC. Therefore, microbial corrosion can be defined as a type of corrosion that is exacerbated by the presence and activity of specific microorganisms.

This type of corrosion progresses laterally from the corrosion initiation sites on the surface and usually continues intergranularly along planes parallel to the surface. Corrosion products produced at the grain boundaries force the metal out of the underlying layer, ultimately resulting in delamination or flaking of the metal.