Abstract
To investigate the behavior of molybdenum dissolution products in systems that approximate localized
corrosion environments, solubility of Mo(III) in equilibrium with solid MoO2 has been determined at
80 C as a function of solution acidity, chloride concentration and partial pressure of hydrogen. The measurements
indicate a strong increase in solubility with acidity and chloride concentration and a weak
effect of hydrogen partial pressure. The obtained results have been combined with literature data for systems
containing Mo(III), Mo(IV), and Mo(VI) in solutions to develop a comprehensive thermodynamic
model of aqueous molybdenum chemistry. The model is based on a previously developed framework
for simulating the properties of electrolyte systems ranging from infinite dilution to solid saturation or
fused salt limit. To reproduce the measurements, the model assumes the presence of a chloride complex
of Mo(III) (i.e., MoCl2+) and hydrolyzed species (MoOH2+, Mo(OH)2
+, and Mo(OH)3
0) in addition to the
Mo3+ ion. The model generally reproduces the experimental data within experimental scattering and provides
a tool for predicting the phase behavior and speciation in complex, concentrated aqueous solutions.
Thus, it provides a foundation for simulating the behavior of molybdenum species in localized corrosion
environments.