Corrosion Rules of Thumb - Material Selection Considerations for Various Forms of Corrosion

In order to prevent corrosion related failure modes from occurring they should be considered during the design and material selection stages of system development. Accounting for many of the issues that are correlated with corrosion, including test, design, and metallurgical factors facilitates the development of an inherently corrosion resistant design. This article addresses the major considerations for the common forms of corrosion that factor into design and material selection, and presents some general ‘rules of thumb’ used in selecting materials for corrosion resistance.

The ‘rules of thumb’ are contained in the following sections that address each of the main forms of corrosion. The sections identify the major failure modes, followed by discussions of the test, design, and metallurgical considerations. With respect to test and design considerations, the primary properties used for quantitative measurement, if there are any, are identified. For many forms of corrosion, there are no quantitative measurement techniques, and thus materials are only rated based upon their relative susceptibilities. Additional design features that are conducive to the creation of corrosive microenvironments are highlighted. The primary metallurgical factors for each form of corrosion are also identified. Some of the major material classes are discussed as to their relative susceptibility and resistance to the form of corrosion under consideration. Together, this information provides a basis for the down-selection of candidate materials. The information discussed above has been organized into six categories for each form of correction including  :

1. measurement
2. design considerations
3. misapplication of data
4. metallurgical features
5. susceptible alloys
6. resistant alloys.

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