![]() AA þ mHþ þ ne bB þ cH2O ð1Þ where a, m, b and c are the number of moles, respectively, of the species A, H?, B and H2O in the reaction and n is the number of electrons transfer in the electrochemical reaction. The above four steps are illustrated in the following example of balancing the species chromium oxide Cr2O3 and Cr7C3 16 in the chemical reduction reaction of chromium carbide in contact with water.Ģ.2.1 E-pH-Dependent Reactions The following general E-pH-dependent reaction is used in the thermodynamic calculations for 298 K (25 C). Balancing a reaction consists of the following four steps which are constructed under chemical equilibrium: (1) the number of all atoms is balanced without considering the oxygen or charge, (2) the oxygen atoms are then added through water (H2O) on the appropriate side of the chemical equation, (3) the hydrogen ions (H?) are added on the appropriate side to balance the number of hydrogen atoms in the chemical equation and finally, (4) the charges are balanced by adding electrons to the appropriate side. The thermodynamic calculations are made for the reduction reactions to construct Pourbaix diagrams using the method described in the literature 11, 12, 16. Table 1 Thermodynamic input data of species at 298 K (25 C) L liquid substance, g gaseous substances, s solid substances and d dissolved substances 2.1 Balancing the Reactions of Two Selected Species The method of balancing the chemical reactions depending on the chemical species selected is described in this section. There are several considerations for developing Pourbaix diagram, and these are described below. The method of constructing Pourbaix diagrams is described in a number of publications 11, 12, 16, and these methods are followed in this work. All Pourbaix diagrams were calculated using a concentration of 10-6 M for all the aqueous species. 2 Thermodynamic Calculations The present work provides the details of thermodynamic calculations for the construction of Pourbaix diagrams for chromium carbides, Cr7C3, Cr23C6 and Cr3C2 at 298 K (25 C). The authors believe that this would result in more efficient development of hardfacing alloys. The final goal, as future work, is to be able to design hardfacing alloys containing carbides, and other compounds, of different materials by using the Pourbaix diagrams. It is expected that such analysis will provide guidance for applications and development of hardfacing alloys. ![]() ![]() The present work provides Pourbaix diagrams for chromium carbides that can be used to predict the range of use of these alloys and target electrochemical experiments to areas of interest. Pourbaix diagrams are useful in predicting the spontaneous direction of electrochemical reactions, identifying the corrosion products and predicting the changes in environment in terms of potential and pH that result in high or low corrosive attack 8. ![]()
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