Chapter 1
Accelerated aging vs. corrosion
Accelerated aging is a broad type of testing that uses amplified adverse conditions to increase the rate of aging of materials and products. This guide focuses on corrosion testing. Corrosion testing is one specific type of accelerated aging, and there are many tests to choose from in that category.
WHAT IS ACCELERATED AGING?
Amplified conditions, faster answers
Amplified adverse conditions may be environmental (such as sunlight/UV, heat, cold, humidity, and salt water), mechanical (shocks and vibrations), wear-related, or a combination thereof. The goal is to quickly estimate the expected service life of products and materials or to understand unexpected field failures.
The accelerated aging approach used will vary depending on the material or product, its intended use, and the conditions it will experience in service.
Accelerated aging often involves a combination of environmental and mechanical stresses. Since these aging mechanisms will often compound themselves synergistically, we sometimes combine test methods at our facility. For example, ASTM D5894, also known as the Cyclic Salt Fog/UV Exposure of Painted Metal Test, combines cyclic corrosion and UV exposure in a single test.
Given the diversity of applications, it is often impossible to simulate every aging parameter and interaction at once, even with today’s technology. From a development standpoint, it may be better to simulate a limited number of parameters at a time, so that each aging mechanism can be isolated and evaluated more clearly.
The six categories of accelerated aging
Surface abrasion and mechanical wear that degrades materials over time.
Photochemical degradation of coatings, polymers, and surface treatments from ultraviolet radiation.
Chemical or electrochemical reactions between a material and its environment — the primary focus of this guide.
Thermal cycling, condensation, and high-humidity exposure that stress materials and coatings.
NOx, SOx, and other atmospheric contaminants that accelerate corrosion in urban and industrial environments.
Mechanical stresses that can initiate cracking, fretting, and fatigue — often compounding corrosion damage.
AFTER THE AGING RUNS
Once the aging process is over
Once the aging process is over, physical or mechanical measurements are performed on the samples to assess whether the products’ properties were adversely compromised compared to those of the unaged product.
Taking measurements while the aging process is occurring can also be extremely helpful to:
Save time if early failures are observed
If a product fails significantly before the end of the planned test duration, stopping early avoids wasting resources on a result that is already clear.
Provide a better understanding of material behaviour trends
Corrosion rarely progresses linearly. Multiple data points across the test duration reveal the actual degradation curve rather than just the endpoint.
Improve interpretation by comparing results side by side
Comparing against a reference product or material with known characteristics gives context that makes results far more actionable.