Some of the factors leading to corrosion damage can be reproduced relatively easily, by creating a situation favorable to their occurrence. However, other factors depend entirely on the development of local defects that often become visible only after long and highly variable periods of exposure, such as the effects caused by the neutral salt spray test commonly known as ASTM B117 (Method for Salt Spray Fog Testing). When an experiment or test is planned, many factors have to be considered. The following list enumerates some of the most standard considerations for the design of a test program:
What are the objectives of the test?
How should the results be interpreted?
How can the information be integrated to earlier or other tests?
How many specimens are available, what is their production schedule (batch, sequential)?
How many factors control the specimen's behavior?
How many factors are to be included in the tests?
Which of these factors interact and which have negligible interaction?
What type of data is to be measured?
Is the sample homogeneous?
How representative is the sample?
Are the tests destructive?
How expensive are the tests and/or specimens?
How much control is there over testing?
How difficult would it be to include human errors of different kinds in the planning?
With such a long list of questions and the continuously increasing number of testing methods, it is important to simplify the design of test plans by adopting a testing strategy relating requirements with the main test parameters. The decision tree presented here has been developed to facilitate the selection of tests designed to verify the susceptibility of steels to various forms of stress corrosion cracking (SCC).