Corrosion

Corrosion is a process marked by the deterioration of a solid material’s physical integrity as the result of environmental conditions. One of its most familiar manifestations affects metal, which can oxidize when exposed to water or high levels of moisture in the air. This oxidation is widely known as rust, and it can be used to illustrate one of the most widely misunderstood aspects of corrosion. It is common for the terms rust and corrosion to be used interchangeably, but this is technically inaccurate. Specific to metal, corrosion refers to the progressive process of moisture-triggered deterioration, while rust is the result of that process. Thus, rust is more accurately described as corrosion damage.

While corrosion is most frequently associated with metal, the process can affect a wide range of different materials, including polymers, ceramics, and composite products composed of multiple base materials with differing physical properties. There are also many different types of corrosion, which are generally classified according to where the corrosion damage is localized on a given piece of material or by the root cause of the damage.

Background

Much of the scientific literature about corrosion focuses on its effects on metals, but the International Union of Pure and Applied Chemistry (IUPAC) has published a more inclusive technical definition that has been widely adopted by scientific agencies around the world. The IUPAC definition is as follows: “Corrosion is an irreversible interfacial reaction of a material (metal, polymer, ceramic) with its environment which results in consumption of the material or in dissolution into the material of a component of the environment. Often, but not necessarily, corrosion results in effects detrimental to the usage of the material considered. Exclusively physical or mechanical processes such as melting or evaporation, abrasion, or mechanical fracture are not included in the term corrosion.” Put more simply, corrosion is caused by a variety of damaging environmental agents and can affect a wide range of metal, polymer, and ceramic materials. It cannot be reversed, and in some cases, corrosion damage may result in the affected material being partially or entirely absorbed by the triggering material in the external environment.

As the IUPAC definition notes, corrosion can compromise the functional integrity of the affected material, and for this reason, industrial engineering efforts prioritize corrosion prevention as a primary objective. According to a study by NACE International, which became part of the Association for Materials Protection and Performance (AMPP) in 2021, corrosion costs the global economy   about $2.5 trillion each year, representing approximately 3.4 percent of global gross domestic product, and available corrosion-control practices could reduce those costs by 15 to 35 percent.

Beyond the economic costs, corrosion can also pose serious risks to human health and safety. Corrosion-related failure has been cited as a primary or secondary cause of many bridge collapses, industrial accidents, and oil and gas pipeline explosions. Prominent examples include an El Paso, Texas, pipeline explosion that killed twelve people in the summer of 2000 and a dangerous tank leak detected in 2013 at a nuclear power plant in Fukushima, Japan. Because of corrosion, a ride at the Ohio State Fair in 2017 collapsed, killing one person and injuring seven others.

Overview

In metals, corrosion results from prolonged exposure to a combination of moisture, oxygen, and other environmental irritants. Beyond these variables, metal also corrodes because of surface processes marked by electrochemical changes that accelerate the development of corrosion damage. One such electrochemical process is known as galvanic action, which occurs when two different metals, positioned in prolonged, close contact with one another, generate low levels of electrical current, causing the continuous erosion of the structure’s physical integrity. Crevices and cracks that form in a metal material’s surface can promote a form of localized attack known as crevice corrosion. Corrosion imposes hundreds of billions of dollars in annual costs on the United States through maintenance, repair, replacement, and infrastructure degradation.

There are many other specific subtypes of corrosion, including uniform, localized, selective, pitting, intergranular, transgranular, exfoliation, and waterline corrosion. Uniform corrosion is defined as a corrosive chemical reaction that begins on a material’s surface and extends across that surface in an even (uniform) manner. Localized corrosion, by contrast, affects only the base layers of the material or certain isolated areas on the material’s surface. Selective corrosion is similar to localized corrosion, except that it affects only certain specific structural components of a given material. Pitting corrosion is characterized by the formation of pits on a material’s surface. Intergranular and transgranular corrosion are types of corrosion damage that affect the interior layers of a material rather than its surface. Exfoliation corrosion is a type of damage that results in the differing layers of a material becoming physically separated, and it usually affects irregular or misshapen objects. Finally, waterline corrosion is a form of corrosion damage that can occur in marine environments, particularly in splash zones and tidal zones where materials are exposed to both water and air.

While corrosion is irreversible, its progress can be slowed or even stopped altogether with the proper techniques. In industrial environments, corrosion prevention and management typically take one or more of six main forms, including modifications to the environment, the selection of materials with inherent corrosion resistance properties, electrochemical protection, and the application of corrosion inhibitors and/or coating and plating compounds that protect the material from the damaging effects of moisture, oxygen, and harsh chemicals. Key prevention principles include removing the material from the corrosive environment, or altering the environment to be less corrosive. For example, storing a metal drum outdoors will make it more prone to corrosion from rain exposure. Moving the metal drum indoors, where it will remain dry, can prevent it from developing rust and other forms of corrosion damage. Similarly, hard water contains alkaline agents that can corrode metal. Adding softening agents to the water will make it less corrosive, thus reducing the likelihood of the immersed metal suffering corrosion damage.

Protective coatings, such as urethane, acrylic, and epoxy polymer coatings, can be applied to metal surfaces to increase their ability to resist corrosive agents. Some self-healing coatings are designed to release corrosion inhibitors or repair small coating defects when damage occurs. This strategy is commonly used in industrial material handling applications, such as oil and gas pipelines or storage drums. A technique known as plating, which involves the application of a metallic coating, can also be used to improve corrosion resistance.

Bibliography

Association for Materials Protection and Performance. “AMPP Unveils New Guide to Enhance Pipeline Safety Through Corrosion Control.” Pipeline & Gas Journal, 8 Apr. 2024, pgjonline.com/news/2024/april/ampp-unveils-new-guide-to-enhance-pipeline-safety-through-corrosion-control. Accessed 5 June 2026.

Bahadori, Alireza. Corrosion and Materials Selection: A Guide for the Chemical and Petroleum Industries. John Wiley & Sons, 2014.

“Corrosion Science.” American Galvanizers Association, www.galvanizeit.org/corrosion/corrosion-science. Accessed 5 June 2026.

“Economic Impact.” NACE International, impact.nace.org/economic-impact.aspx. Accessed 5 June 2026.

“The High Cost of Corrosion.” Tri-Council Development Fund, 11 Nov. 2021, tcdfillinois.org/news/the-high-cost-of-corrosion/. Accessed 5 June 2026.

“NACE Study Estimates Global Cost of Corrosion at $2.5 Trillion Annually.” Inspectioneering, 8 Mar. 2016, inspectioneering.com/news/2016-03-08/5202/nace-study-estimates-global-cost-of-corrosion-at-25-trillion-ann. Accessed 5 June 2026.

“NEW Association for Materials Protection and Performance (AMPP) Launches Today.” Association for Materials Protection and Performance, 6 Jan. 2021, www.ampp.org/blogs/webmasternaceorg/2021/01/06/new-association-for-materials-protection-and-perfo. Accessed 5 June 2026.

Pianoforte, Kerry. “New Interpon Redox Primers Help US Specifiers Fight $3 Trillion Global Corrosion Challenge.” Coatings World, 6 Sept. 2023, www.coatingsworld.com/issues/2023-10-01/view_breaking-news/new-interpon-redox-primers-help-us-specifiers-fight-3-trillion-global-corrosion-challenge/. Accessed 5 June 2026.

Popov, Branko N. Corrosion Engineering: Principles and Solved Problems. Elsevier, 2015.

Revie, R. Winston, and Herbert H. Uhlig. Corrosion and Corrosion Control. 5th ed., John Wiley & Sons, 2025.

Tiwari, Atul, et al., editors. Intelligent Coatings for Corrosion Control. Butterworth-Heinemann, 2014.

Zhang, Yue, et al. “Self-Healing Coatings Based on Stimuli-Responsive Release of Corrosion Inhibitors: A Review.” Frontiers in Materials, vol. 8, 2021, doi:10.3389/fmats.2021.795397. Accessed 5 June 2026.