Corrosion Testing
Corrosion testing is a series of tests used to measure the corrosion resistance of various materials. It is important to understand the potential for corrosion in industrial products, components, and structures so that the proper mitigation measures can be taken before costly damage and safety risks occur. Corrosion testing, also known as accelerated corrosion testing, is an important part of product development and failure analysis. By simulating the actual environmental conditions a material will experience, the performance of the material under those conditions can be determined.
Corrosion tests can be divided into two main categories: accelerated testing and field testing. Accelerated testing creates a controlled and accelerated environment in the laboratory in which to assess the performance and durability o f materials. Field testing is performed in a real-world environment, measuring corrosion over an extended period of time.
Accelerated corrosion testing is typically used to assess the corrosion resistance of components and materials in the laboratory. This testing is typically done in unison with a material supplier or corrosion consultant to choose the most corrosion resistant material, optimize coating systems, or to determine aging and environmental degradation performance. This testing is typically done in enclosed environmental chambers that are designed to accurately control humidity, temperature, and atmospheric composition.
The most common types of accelerated corrosion tests are accelerated salt spray tests, cyclic corrosion tests, and neutral salt fog tests.
The accelerated salt spray (fog) test is the most widely used accelerated corrosion test and was designed to mimic natural atmospheric corrosion. In this test, the part to be tested is exposed to a salt mist in a chamber heated to between 95°F and 100°F. This test involves exposing the part to a high-humidity sodium chloride solution sprayed over the part. The part is monitored over a period of time and the absorbed percentage of salt solution is measured as a sign of corrosion.
The cyclic corrosion test simulates specific cyclic environmental effects on materials and components. This test is done by cycling the test article between a chamber environment of high humidity and a dry hot temperature. This technique can be used to simulate rapid weathering cycles.
The neutral salt fog test is used to evaluate the corrosion performance of metals and other materials. This test measures the corrosion resistance of a material by exposing it to an acidic or basic salt solution that has been aerosolized with pressurized air. The solution is sprayed onto the material and the corrosion rate is measured over a period of time until a predetermined criteria is met.
Field testing is used to assess the corrosion performance of material when exposed to natural environmental conditions over an extended period of time. This testing is typically done in a real-world environment, such as an industrial site, in order to accurately determine the corrosion performance of materials when exposed to the elements. Monitoring panels, also known as corrosion coupons, are used to measure the corrosion rate of various materials. These coupons are placed in the natural environment, protected or unprotected, and observed over time for the effects of corrosion. This testing is typically done by placing a number of coupons into plastic bags, with the coupons exposed to the air, and then buried in the soil. The coupons are then monitored regularly and photographed in order to determine the level of corrosion.
Overall, corrosion testing is a necessary component of research and development for industrial products. This testing gives industrial engineers the ability to control the environment of a sample in order to accurately gauge the performance and durability of materials under different conditions. Through accelerated corrosion testing and field testing, materials can be properly matched to their intended use and corrosion-resistant coatings can be properly evaluated and optimized.
