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Corrosion & Erosion

Common Corrosion & Erosion Types, Causes, and Solutions

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Corrosion is a defect common in metallic and non-metallic assets, commonly resulting from the natural breakdown of a refined metal through oxidation or another chemical process.

Results from an industry study found that the total estimated annual costs directly related to corrosion in the United States alone is nearly $300 billion dollars. Difficult to predict and costly to repair, MISTRAS’ clients must contend with corrosion’s damaging effects on a daily basis.

Corrosion comes in different forms, with different causes. Below is a list of some of the most common types of corrosion our customers deal with, which MISTRAS is an industry expert in detecting, diagnosing, repairing, and preventing.

General Corrosion

Corrosion occurs due to environmental interactions, most often when a material comes into contact with oxygen or sulfates, causing it to gradually deteriorate. Though commonly associated only with metals, certain forms of corrosion can occur in non-metallic materials as well.

Depending on the material, the corrosion process can be accelerated due to increased exposure to air, water, or other substances. Since it includes a structural breakdown of the metal, corrosion is a serious concern for metallic and non-metallic assets in any facility.

Over time, corrosion results in wall thinning, decreased strength, increased permeability to liquids and gasses, and other degradation of the material’s useful properties. Corrosion damage can cause cracking, leaking, pitting, and eventual asset failure if remained untreated, making sufficient detection, identification, removal, and prevention essential in maintaining sound facility health and integrity.

Corrosion Under Insulation (CUI)

Insulated assets can hide corrosion degradation from view, risking the buildup of serious corrosion damage before other physical signs are shown.

Corrosion Under Insulation (CUI) refers to any corrosion that occurs under the surface of insulation due to a buildup of moisture on the external surfaces of the asset. It attacks primarily attacks carbon and low-alloy steels, but can affect any insulated asset.

CUI is caused by insulation collecting and retaining water between a metal surface and thermal insulation, making it incredibly difficult to prevent. Any break in the insulation system of an asset makes it susceptible to CUI within the metallic material, frequently found in piping, vessels, or any other asset with an insulation coating.

Click here to learn about our special emphasis programs for detecting and preventing CUI.

Sulfidation Corrosion

Sulfidation corrosion is a naturally-occurring result of chemical reactions in crude oil, attacking carbon steel and other alloys used in refining equipment. It can occur in both the liquid and vapor phase. Sulfidation can cause corrosion failures in your piping, heater tubes, pressure vessels, and other oil refining equipment.

According to API RP 939-C and API RP 571, carbon steel and other alloys can suffer from corrosion when they react with sulfur components in high-temperature environments above 400°F (204°C).

The presence of hydrogen accelerates sulfidation, and hydrogen in hydrogen sulfide (H2S) streams increases the severity of high-temperature sulfidation corrosion at temperatures above 500 °F (260 °C). While piping containing no or low silicon content has been shown to have high sulfidation corrosion rates, the addition of chrome increases a material’s resistance to sulfidation.

Click here to learn about our special emphasis programs for detecting and preventing sulfidation corrosion.

Microbiologically Induced Corrosion (MIC)

Microbial corrosion is a naturally-occurring form of corrosion caused by biological growth within a material. Bacteria can arise from a variety of sources, but assets that come in contact with natural, unfiltered waters or direct contact with oils and emulsions are especially at risk from the bacteria within these sources.

This type of corrosion specifically attacks steel assets, including carbon and stainless steel, frequently used in:

  • Piping
  • Vessels
  • Storage Tanks
  • Wiring
  • Tubing

The pitting caused by MIC has a serious impact on the strength and soundness of steel assets, making its early detection and repair a critical investment for your facility.

Erosion Corrosion

Erosion Corrosion is the combined effect of both erosion and corrosion on a metal surface, with the two effects accelerating each other to produce higher levels of damage and degradation.

Erosion Corrosion is especially present within piping and tubing, since the erosion is triggered by high rates of flow over a metallic surface. Corrosion causes pitting, which in turn increases the turbulence of a liquid, and can make the effects of erosion more intense.

The presence of this corrosion frequently causes wall thinning, material degradation, leaking, and other associated effects.

Touch Point Corrosion (TPC)

Touch Point Corrosion (TPC) is a form of corrosion that results from the interaction of wooden and metal objects to create corrosion cells within the metal.

This type of corrosion is common in piping, occurring at the point of contact between the pipe and its support, or wherever a pipe comes into contact with another pipe or object. Water and corrosives can become trapped in the crevice between the pipe and the support, and movement between pipe and support dislodges scale which would retard corrosion.

Corrosion at this location is difficult to monitor and measure, as it is often not visible without lifting the pipe to inspect.

Uniform Surface Attack

Uniform surface attack is the most common type of corrosion found in aerospace components. When paint or other protective coatings are worn off a material, the exposure of metallic surfaces to the moisture and oxygen in the air can result in corrosion. The intense conditions that aerospace assets undergo accelerate this damage, creating a huge risk for the safety and integrity of affected materials.

MISTRAS Corrosion Services

MISTRAS offers inspection, maintenance, engineering consulting, and monitoring solutions to detect, diagnose, and prevent corrosion.

We utilize traditional and advanced non-destructive testing (NDT) inspection techniques to detect corrosion in your assets, including in hard-to-reach areas where corrosion is often allowed to proliferate in between scheduled evaluations. Our corrosion engineers help to diagnose where corrosion is most likely to form, and provide recommendations for mitigating it.

MISTRAS performs coating and corrosion removal services, and monitoring solutions to inform operators of corrosion performing before it worsens.

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