Corrosion is a natural conversion process in which a metal part gradually deteriorates into a more chemically stable oxide. Rusting is the most common and recognizable form of corrosion.

Corrosion occurs as a result of electrochemical reactions between metallic elements and oxygen in the environment to which they’re exposed. As corrosion spreads, the affected metal will begin to lose its useful properties, such as its strength and durability.

A corrosion testing lab studies how corrosion affects different metals and alloys to understand how those metals will corrode in different environments. Corrosion testing is an extremely important form of quality assurance for virtually any product that incorporates metals in its construction. This is what you should know about how a corrosion testing lab works and why they’re essential.

What is a corrosion testing lab?

A corrosion testing lab is a facility that uses advanced equipment to simulate several different atmospheric conditions that may corrode metallic structures. They are used to test the resistance of a metal or metallic alloy to different corrosive environments to determine if the material is suitable for various applications.

Crucially, advanced corrosion testing labs, such as Secat’s, can create controlled environmental conditions where the corrosion effects occur at a greatly accelerated pace. This allows scientists to simulate the effects of years of exposure in a much shorter time frame.

Why is corrosion testing important?

When metal corrodes, it often loses the properties it needs to perform its function properly. Rusty metal may become brittle, for example, while local pitting may lead to cracking and failure. 

Under corroded conditions, the metal could break or otherwise fail, compromising the performance of the entire system the metal is part of. Corrosion can lead to dangerous structural failure and causes billions of dollars in product and infrastructural damage every year.

For example, metal corrosion as a result of prolonged exposure to salt water is a frequent cause of structural damage on ships and bridges. This corrosion can eventually cause shipwrecks and bridge collapses in the most extreme cases. In December 1999, corrosion led to the Maltese oil tanker the MV Erika spilling nearly 19,800 tons of oil in the ocean.

Therefore, whenever metal is used to construct anything, corrosion testing is an important part of its quality assurance testing. Experts need to test the metal in all the environments it will be exposed to during its regular operation to understand exactly how quickly corrosion will take effect and how it will affect the metal’s performance. For example, saltwater corrosion testing is performed on any metals that will be used in the construction of seaworthy ships.

How does corrosion testing work?

There are a wide variety of different corrosion tests used, depending on what kind of environmental effects the corrosion experts want to study. A corrosion testing lab is typically capable of performing a huge number of these tests using specialized equipment.

For example, the corrosion testing machine Secat uses in our laboratory, the Q-Fog CRH Tester, is capable of performing corrosion testing according to a suite of ASTM, ISO, NACE and other customer or industrial standard procedures. Further, the large chamber size of the Secat Q-Fog corrosion test machine enables the testing of many full-size components and assemblies, facilitating the evaluation of interactions between different metals— a process known as galvanic corrosion.

Salt spray corrosion testing

One of the most common forms of accelerated corrosion testing is the “salt spray test” or “salt fog test”, which is commonly conducted according to ASTM standard B117. This test involves placing the metallic sample at a specific angle inside a temperature and environmentally controlled test chamber and then exposing it with an acidic saline water solution for a set period.

Experts check for the appearance of corrosion effects such as rust or other oxides after a predetermined period of testing. The longer it takes for these effects to appear, the more corrosion resistance the metal or coating is considered to have.

Though salt spray testing is highly useful for comparing the corrosion resistance of different metals and coatings, it is not considered a useful way to predict how metals will resist corrosion in a real environment because it does not replicate environmental effects accurately.

Automated cyclic corrosion testing

Cyclic corrosion testing is a more complex form of corrosion testing. It involves automatically cycling the environment which the sample is subjected to, changing over time to test the metal’s reaction to changing environmental conditions. 

Cyclic corrosion testing was developed to test metals that are used in automotive vehicles, which is its most common use. Cyclic testing makes it possible to understand how metals will resist corrosion while exposed to widely varying temperatures over long or short periods of time, making it a more reliable method for accurately testing the use/life expectancy of these metals in real-world scenarios. Engineers may use standards like ASTM G85, to test metals under these conditions.

The specific environments a cyclic corrosion test subjects the sample to depends on the kind of corrosive effects the tests need to study. These may include phases similar to the salt spray test, air drying or heating phases, gradual or sudden condensation phases, humidity cycling phases, corrosive immersion phases, and more. Each phase is carefully timed and measured so experts can monitor and measure corrosive effects over time.

While large corrosion chambers like the Q-Fog CRH are often used to test actual products in various corrosive environments, metallurgists will also often use corrosion screening tests to evaluate the corrosion resistance of a specific alloy or composition.  For these tests, samples are typically submerged into different solutions with various PH’s over a period of about one day.  The samples are then sectioned and evaluated microscopically for the mode of corrosion, such as pitting, general, or intergranular.  During this evaluation, the depth of corrosion can also be quantitatively determined.  There are several ASTM standards that Secat uses for these evaluations, such as; G71, G110, G34, G67, G48, and B912.

Coupons exposed to corrosion may also be loaded under static or dynamic (fatigue) situations to determine how the corrosion will affect the mechanical performance.  These tests are critical for safely designing a metal component that will be exposed to corrosion in service.  

If you think you need corrosion testing, Secat’s experts are ready to help. Get in touch today and we can get started.