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The additional cost usually associated with choosing increased corrosion resistance during the selection process is invariably less than that due to product contamination or lost production and high maintenance costs due to premature failure. Without adequate corrosion resistance, or corrosion allowance, components often fall short of the expected design life.
A common form of representing the corrosion resistance of materials is what is known as isocorrosion diagrams. These diagrams are two-dimensional representations of three dimensional corrosion data. Iso-corrosion diagrams present corrosion behavior as a function of corrosive concentration (usually the abscissa) and temperature. The use of the prefix "iso" refers to lines (or regions) of constant corrosion behavior across variations in concentration and temperature. A modern and comprehensive document on the subject is the second edition of the classic CORROSION BASICS textbook.
However, it should be emphasized that there are a number of determining criteria for corrosion to occur in actual process conditions which cannot be introduced in iso-corrosion diagrams . The result is that the use of such diagrams to select a material may be inaccurate and sometimes catastrophic. A more reliable methodology to select material and evaluate corrosion risks may be provided by software systems such as CorrIntel™.
