Solid corrosion products reaction equilibrium

These redox reaction boundaries and their computed equilibrium Eh values for pH = 7.0 are summarized in Table 11.3. The Eh/pH equations generally have different slopes so that when plotted on an Eh-pH diagram some of the reaction boundaries cross above or below pH = 7. To illustrate the importance of this effect, Fig. 11.11 shows that for constant Eh and increasing pH, the solubilities of solids of Se, Tc, and U (radioelements important in nuclear waste disposal) may reverse in order, and also become more or less soluble than the corrosion products of possible waste-container metals Cu, Fe, and Ni. 

The physical nature of the process stream. Is it single-phase or two-phase Is it liquid, solid, vapor or slurry What is its temperature and pressure at the sampling point, and how far can these be allowed to change during sampling What is its viscosity at the appropriate sample measurement temperature The chemical nature of the process stream. Is it at equilibrium (a final product) or is it to be measured mid-reaction Is sample transport possible, or must the sample be measured in situ Is it corrosive, and what material and metallurgical constraints exist ... 

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