Fig. 2: E-pH diagram with stoichiometric oxides. | npj Materials Degradation

Fig. 2: E-pH diagram with stoichiometric oxides.

From: Potential-pH diagrams considering complex oxide solution phases for understanding aqueous corrosion of multi-principal element alloys

Fig. 2

The heterogeneous interaction system contains 10−2 mol of FCC single-phase Cr22 MPEA and 1 kg of water with 0.6 m NaCl at 25 °C and 1 atm ambient pressure. The dashed lines are reversible potentials for hydrogen and oxygen evolution with the stable region for water in between with a width of 1.23 V. The gray region indicates the conditions for immunity (of all alloying elements) while the light green region indicates the predominance of metal ions or active corrosion. The white regions contain one of the more thermodynamically stable oxides, hydroxides, or oxy-hydroxides. Protectiveness of solid reaction products cannot be predicted based on the existence of stable phases.

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