Mixed potential diagram illustrating

Figure 3. Mixed potential diagram illustrating controls on the kinetics of corrosion at a pitted, oxide-covered metal. The potential range is from -700 to +300 mV/NHE. Arrows (B) corrosion current at the bottom of the pit, controlled by Fe Fe + (acid) and 2H - H2 (M) corrosion current at the mouth of the pit, controlled by the partial currents for Fe -> Fe2+ (passivated) and RX RH (Pit) corrosion current for the short-circuited pit, controlled by Fe Fe + (acid) and RX - RH. The three solid curves are generated using the Tafel equation and exchange current densities and Tafel slopes from reference (9). The dashed curve was measured at 5 mV s in pH 8.4 borate buffer, using methods described in reference (9).

In order to construct mixed-potential diagrams to model a corrosion situation, one must first gather (1) the information concerning the activation overpotential for each process that is potentially involved and (2) any additional information for processes that could be affected by concentration overpotential. The following examples of increasing complexity will illustrate the principles underlying the construction of mixed-potential diagrams. 

Abstract In the beginning, the mixed potential model, which is generally used to explain the adsorption of collectors on the sulphide minerals, is illustrated. And the collector flotation of several kinds of minerals such as copper sulphide minerals, lead sulphide minerals, zinc sulphide minerals and iron sulphide minerals is discussed in the aspect of pulp potential and the nature of hydrophobic entity is concluded from the dependence of flotation on pulp potential. In the following section, the electrochemical phase diagrams for butyl xanthate/water system and chalcocite/oxygen/xanthate system are all demonstrated from which some useful information about the hydrophobic species are obtained. And some instrumental methods including UV analysis, FTIR analysis and XPS analysis can also be used to investigated sulphide mineral-thio-collector sytem. And some examples about that are listed in the last part of this chapter. 

Figure 5.41 G-X diagram illustrating application of Darken s Quadratic Formalism to a binary join. Although mixing behavior of components 1 and 2 in phases a and ]8 is nonideal (heavy lines), in each of the simple regions it is modeled by an ideal mixing model (light lines) by means of an appropriate choice of the Active standard state potential /x. From Will and Powell (1992). Reprinted with permission of The Mineralogical Society of America.

Fig. 4 Phosphatation as a mixed potential process schematic diagram illustrating a simplified view of different chemical phenomena occurring during the growth of the phosphate film on an Fe surface in a trication phosphating bath.

Figure 3.2 Schematic Evans diagrams illustrating an example of mixed potential reactions associated with the chemical component of copper-CMP in an acidic medium. These diagrams only show the high overpotential (Tafel) trends of the Butler Volmer equation, and extrapolate the resulting lines through the low-overpotential regions, (a) shows how the cathodic step of reaction (3.9) couples to the anodic step of reaction (3.10). The solid lines in (b) indicate the resulting plot of the mixed reactions, while the dashed lines show the contributions of the individual reactions. The effects of a cathodic inhibitor (lowering of the values of both Ecotr and /corr) are displayed in (c).The mixed potential situation for bimetalhc corrosion is considered in (d).

Figure 3.8 Diagram illustrating mixed potential theory...

IT band. The correlation of these properties can be illustrated in a diagram plotting potential energy versus nuclear configuration for a symmetrical mixed-valence complex (Fig. 10). 

In terms of a potential energy surface, attractive release occurs in the valley of the reactants, as judged from the energy contours, repulsive release in that of the products, and mixed in the transition region. These concepts are illustrated in the reaction coordinate diagram, Fig. 1. 

The procedure by which multi-component mixtures of noble gas (He and Ar) isotopes and halogens can be represented in terms of 2 and 3 dimensional linear mixing diagrams is described in this section. The treatment is not intended to be exhaustive but to illustrate how potentially useful pieces of mineral deposit information can be extracted from the data. 

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