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What are the most common types of corrosion?

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Corrosion is the deterioration of a material, usually a metal, due to a chemical or electrochemical reaction with its environment. Corrosion can cause serious damage to structures, equipment, and products, resulting in safety hazards, economic losses, and environmental impacts. As a chemical engineer, you need to understand the different types of corrosion and how to prevent or control them. In this article, we will discuss the most common types of corrosion and some examples of where they occur.

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Alireza Salehi

Senior Material, Corrosion and Welding Engineer at Subsea7
Milad Mojtahedi

Assistant Professor of Materials Science & Metallurgical Engineering, Razi University
Damon Yang

Uniteam Group - Special Projects - Sales project manager

1 Uniform corrosion

Uniform corrosion is the most simple and predictable type of corrosion, where the material loses its mass evenly over the entire surface. This type of corrosion can be easily measured and monitored by weight loss or thickness reduction. Uniform corrosion can be prevented or reduced by using corrosion-resistant materials, coatings, inhibitors, cathodic protection, or changing the environmental conditions. An example of uniform corrosion is the rusting of iron exposed to moist air.

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Damon Yang

Uniteam Group - Special Projects - Sales project manager
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Uniform corrosion: This corrosion occurs uniformly on the surface of the metal and is usually related to factors such as the composition of the metal, environmental conditions and exposure time. Crevice corrosion: metal in crevices or hidden areas, usually caused by concentration of oxygen, moisture, and corrosive ions. Contact corrosion: Corrosion that occurs when two different metals come into contact, usually as a result of an electrochemical reaction. Stress corrosion: Corrosion that occurs as a result of metal being subjected to tensile stress, usually under specific environmental conditions, such as chloride environments with high humidity. Fatigue corrosion: metal under alternating stress, usually on cyclically loaded parts.

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Alireza Salehi

Senior Material, Corrosion and Welding Engineer at Subsea7
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As specified, Atmospheric corrosion which is the most common type of uniform corrosion and it should be known as the most common type of corrosion. All of the assets made of carbon steel or any other types of metallic alloys exposed to atmosphere are prone to this type of corrosion, and ahuge amount of money per year is expensed each year to protect different types and millions of structures against this type of corrosion.

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2 Galvanic corrosion

Galvanic corrosion is the accelerated corrosion of a metal in contact with a more noble metal in the presence of an electrolyte. The less noble metal acts as the anode and sacrifices itself to protect the more noble metal, which acts as the cathode. The electrolyte provides a medium for the flow of ions and electrons between the two metals. Galvanic corrosion can be prevented or reduced by avoiding dissimilar metals, isolating the metals with insulators, reducing the electrolyte concentration, or applying cathodic protection. An example of galvanic corrosion is the pitting of aluminum in contact with copper in seawater.

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Alireza Salehi

Senior Material, Corrosion and Welding Engineer at Subsea7
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Galvanic corrosion is known as a hidden threat everywhere when two different types of materials or components are connected together. It is not only necessery to have two types of alloys concerned together to have galvanic corrosion. Even two types of components with simillar base material and different coating types and thicknesses are known as anodes and cathods and galvanic corrosion might happen in such cases.

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3 Pitting corrosion

Pitting corrosion is the localized corrosion of a metal surface, where small holes or pits form due to the breakdown of the protective layer. Pitting corrosion can be very dangerous, as it can penetrate the material rapidly and cause failure without significant weight loss or surface damage. Pitting corrosion can be prevented or reduced by using materials with high resistance to chloride or other aggressive ions, maintaining a high pH or low oxygen level, applying inhibitors or coatings, or performing regular inspection and cleaning. An example of pitting corrosion is the perforation of stainless steel pipes in chlorinated water systems.

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Alireza Salehi

Senior Material, Corrosion and Welding Engineer at Subsea7
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Pitting corrosion is a corrosion morphology which might happen due to different reasons. If I wanted to name the most common types of corrosion, I would defenitely consider seawater corrosion as one of the most common types which is destroying many of human assets each year and human is investing a huge money each year to prevent it. There are many corrosion mechanisms responsible in sewater corrosion but one of the most common types of corrosion in sewater is pitting corrosion.

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4 Crevice corrosion

Crevice corrosion is the localized corrosion of a metal surface in a narrow gap or crevice, where the stagnant solution becomes more acidic and corrosive due to the depletion of oxygen and the accumulation of metal ions. Crevice corrosion can occur in joints, seams, flanges, gaskets, fasteners, or other areas where there is a small space between two surfaces. Crevice corrosion can be prevented or reduced by eliminating or minimizing crevices, using sealants or gaskets that resist corrosion, improving the ventilation or circulation of the solution, or applying inhibitors or coatings. An example of crevice corrosion is the deterioration of aluminum alloy plates in marine environments.

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Alireza Salehi

Senior Material, Corrosion and Welding Engineer at Subsea7
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If I wanted to name a corrosion type even more common than Crevise corrosion, I would defenitely consider CO2 Corrosion which is the the most common type of corrosion in the many process streams and equipment. All of the pressurized assets in oil and gas industry are dealing with CO2 corrosion and it is damaging many assets each year.

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5 Intergranular corrosion

Intergranular corrosion is the selective corrosion of the grain boundaries of a metal, where the grains remain intact but the boundaries are weakened or dissolved. Intergranular corrosion can occur due to the segregation of impurities, alloying elements, or precipitates at the grain boundaries, which makes them more susceptible to corrosion than the grains. Intergranular corrosion can be prevented or reduced by controlling the composition, heat treatment, or welding conditions of the metal, or applying inhibitors or coatings. An example of intergranular corrosion is the cracking of stainless steel welds due to the formation of chromium carbides at the grain boundaries.

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6 Stress corrosion cracking

Stress corrosion cracking is the cracking of a metal due to the combined effect of tensile stress and a corrosive environment. The stress can be applied externally, such as by loading or bending, or internally, such as by thermal expansion or residual stress. The corrosive environment can be specific to the metal, such as chloride for stainless steel or ammonia for copper. Stress corrosion cracking can be prevented or reduced by reducing the stress level or frequency, changing the material or the environment, or applying inhibitors or coatings. An example of stress corrosion cracking is the failure of brass fittings in ammonia refrigeration systems.

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Alireza Salehi

Senior Material, Corrosion and Welding Engineer at Subsea7
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SCC should be known as of the most dangerous or disasterous types of corrosion because it is so difficult and sometimes impossible to be detected before happening. There are many types of SCC known in the process industry among which the most common types are: - Sulfide Stress Corrosion Cracking - Amine Stress Corrosion Cracking - Ammonia Stress Corrosion Cracking - Chloride Stress Corrosion Cracking - Carbonate Stress Corrosion Cracking

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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Milad Mojtahedi

Assistant Professor of Materials Science & Metallurgical Engineering, Razi University
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A scientific answer requires a statistical analysis of the occurrence of various types of corrosion in different industries. However, looking from the point of view of materials can be helpful. In the case of stainless steels, mechanisms such as pitting, crevice corrosion or GB corrosion (in the welded parts) can be important. Some types of corrosion are also associated with specific materials, such as exfoliation in some aluminum alloys or dezincification in Brasses. But the most commonly used metallic material in industries (in terms of weight) is by far carbon steel. This material is simply subjected to uniform corrosion. Therefore, uniform corrosion can be considered as the most common type of corrosion in the industry and construction.

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What are the most common types of corrosion?

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1 Uniform corrosion

2 Galvanic corrosion

3 Pitting corrosion

4 Crevice corrosion

5 Intergranular corrosion

6 Stress corrosion cracking

7 Here’s what else to consider

Chemical Engineering

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