Pourbaix diagrams are typically found in the literature for pure elements or only the most common alloys. As such, they often need to be determined experimentally, which can be costly and time consuming and still does not capture the composition variation that may be associated with an alloy. Using the Pourbaix Diagram Module, included in Thermo-Calc, it is possible to make such predictions specifying both the alloy composition and also the solution chemistry.
In this example, the calculation for a 2.25Cr-1Mo steel readily maps the regions associated with immunity (H2 Gas Reducing Area), passivity (Fe2O3 and Fe3O4), as well as the region where corrosion readily occurs. The results correspond well with the data found in traditional handbooks.