Accelerated Corrosion Testing of Aerospace Materials and Life Expectancy

A brief description of standard corrosion tests for evaluation of aerospace materials will be provided.  Quality control tests will also be discussed.  Specific attention will be given to scientific and technical concepts behind accelerated corrosion tests and their relationship with real-world service environments.  Acceleration factors are necessarily based on an accurate scientific description of the corrosion failure process.  Several requirements must be addressed in the usefulness of accelerated testing in life expectancy determination.  A primary requirement is that the corrosion failure mechanism(s) should be the same as those which occur under normal service conditions.  Otherwise, the test lacks validity with regard to simulating the service environment.  A second key requirement is that sufficient scientific understanding of the failure mechanism should be available so that the test data can be analyzed and interpreted in a physically meaningful way.  The shortcomings of the American Society for Testing and Materials’ ASTM B117-11 salt spray (fog) test as a predictor of the service lifetime of aerospace materials, and recent application of the ASTM B845-97(2008) mixed flowing gas environmental pollutant test to simulate the actual atmospheric exposure conditions of aerospace components, along with ASTM G71-81 galvanic corrosion testing and ASTM G44-99(2005) alternate immersion testing will be presented in detail.