Comparison of the Solubility of ZnFe2O4, Fe3O4 and Fe2O3 in High Temperature Water

As the solubility is a direct measure of stability, this study compares the solubilities of ZnFe2O4, Fe3O4 and Fe2O3 in high temperature water. Through literature analysis and formula derivation, it is shown that it is reasonable to assume ZnFe2O4 and Fe(OH)3 coexist when ZnFe2O4 is dissolved in water. Results indicated that the solubility of ZnFe2O4 is much lower than that of Fe2O3 or Fe3O4. The low solubility of ZnFe2O4 indicates that it is more protectively stable as an anticorrosion phase. Moreover, the gap between the solubility of ZnFe2O4 and that of Fe3O4 or Fe2O3 was enlarged with an increase of temperature. This means that ZnFe2O4 is more protective at higher temperatures. Further analysis indicated that with the increase of temperature, the solubility of ZnFe2O4 changed little while those of Fe2O3 or Fe3O4 changed a lot. Little change of the solubility of ZnFe2O4 with increase of temperature showed that ZnFe2O4 is stable. The very low and constant solubility of ZnFe2O4 suggests that it is more protective than Fe2O3 and Fe3O4, especially in water at higher temperature.