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rates can be correlated with the predicted stability of metastable iron sulfide phases.
conditions under which the stable and metastable iron sulfides can be formed.
product C, then a transformation A→B→C is likely to occur.
pressures up to 1 kbar and compositions up to 30 mol/kg.
reduction, complexation, acid-base transformations and precipitation.
aqueous phase and all possible solid phases.
In the second step, thermodynamic conditions are defined for the thermodynamic simulation.
to real (e.g., concentrated) solutions. They have been described in detail by Anderko et al.
are varied in addition to pH.
sulfides, it is necessary to consider simultaneously iron and sulfur in various oxidation states.
) are used as independent variables, they are varied within predetermined ranges.
The computations provide the equilibrium activities of all species as functions of independent variables.
structure, oxidation states, stoichiometry and charges of all species in the chemical speciation model.
for the electrochemical and chemical diagrams, respectively.
stable species. In this work, this method is used for predicting the replacement sequence of iron sulfides.
is the likely precursor for the formation of more stable sulfides.
relationship could not be quantitatively evaluated.
environments (Meyer et al., 1958).
involves an iron monosulfide precursor.
S-containing environments. In particular, Meyer et al.
pressure will somewhat increase the stability areas of various iron sulfides.
vapor phase should be large so that its composition practically does not change as a result of reactions.
increases beyond a certain limit.
diagram with the amount of oxygen as an independent variable has been generated.
, 0.1 m corresponds to 1,000 ppmv etc.
increases, the iron sulfides cease to be stable and the corrosion rate increases.
With a small increase in oxygen concentrations, mackinawite is predicted to convert into greigite.
pitting is not likely varies from 1 to 50 ppmv depending on the amount of dissolved iron.
The stability diagrams are also useful for simulating experiments performed in flowing solutions.
) at higher pH values.
because iron sulfides would then become stable.
iron sulfide formation in solutions and on the surface of corroding iron.
in corrosion rate can be explained using the predicted stability of iron sulfides.
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(5) Volume as a function of temperature and pressure.
up to 1000 °C and 5 kbar.
been tabulated for large numbers of ions, complexes and neutral, both inorganic and organic, molecules.
the Gibbs energy, enthalpy and entropy at reference temperature and pressure as integration constants.
estimation techniques have been reviewed in detail by Rafal et al.
of an expression developed by Bromley.
estimated using a correlation with entropies of ions.
Figure 1. Overall structure of the program for generating stability diagrams.
Figure 2. Stability diagram constructed by including all Fe-S species (see Captions).
Figure 3. Stability diagram constructed by excluding pyrite (FEIIS2PPT) and troilite (FEIISPPT).
Marcasite and mackinawite are shown as the metastable iron sulfide species.
Figure 3. Mackinawite and greigite are shown as the metastable iron sulfide species.
precursors for iron sulfide formation.
O and 100 mol of neutral gas phase.
are shown in shaded circles.
Corrosion rates in mpy (Lyle, 1997) are shown in shaded circles.
rates in mpy (Lyle, 1997) are shown in shaded circles.

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