Grade selection to avoid localised forms of corrosion
With appropriate grade selection, stainless steels, will give good corrosion resistance. However, the choice of an inappropriate grade can result in failure by perforation or catastrophic cracking in shorter times than failure by uniform corrosion in ‘lower resistant’ alloys such as ordinary, carbon steels.
Selection of the appropriate grade of stainless steel is of course a balance between attaining the appropriate degree of corrosion resistance whilst minimising cost. An appreciation of the possible failure mechanisms does help avoid unnecessary and possibly costly failures.
To help in the selection of the correct grade, corrosion tables are listed in references such as the Outokumpu Stainless Corrosion Handbook. Here a wide range of chemical environments, (concentration of chemical species and temperature), are listed. These indicate corrosion rates by weight loss and also give an indication of the additional risk of localised corrosion such as pitting or stress corrosion cracking.
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