Surface-Behavior Diagrams

XPS was used to determine the surface composition of the anodized aluminum substrate during exposure to warm, moist environments. The information obtained was used to construct surface behavior diagrams that showed that hydration of the surface involved three steps [38]. Step one, which was reversible, consisted of adsorption of water onto the AIPO4 monolayer. The second step, which was rate-controlling, involves dissolution of the phosphate followed by rapid hydration... 

Fig. 8. Surface behavior diagram showing hydration of the PAA surface. Hydration occurs in three stages 1, reversible adsorption of moisture II, hydration of the AHOr to AlOOH and 111, further hydration to Al(OH)s. The numbers represent hours of exposure to high humidity. Adapted from Refs. 138,40].

Davis, G. D., Moshier, W. C. and Aheam, J. S. 1987. Corrosion of aluminum in dilute sulfate-solutions studies by surface behavior diagrams. Surface and Interface Analysis,... 

Figure 13. (HgCd)-Te02-(HgCd)Te surface behavior diagram of Hgo8Cdo2Te with a 1600 A thick anodic oxide. The superimposed depth scale gives the equivalent thickness of oxide for an abrupt interface and a mean free path of 16 A. The dashed line represents the depth profile path for a stoichiometric oxide and semiconductor. (With permission of Elsevier Science Publishers.)...

Davis GD (2003) Durability of adhesive joints. In Mittal KL, Pizzi A (eds) Handbook of adhesive technology, 2nd edn. Marcel Dekker, New York, p 273 Davis GD, Sun TS, Aheam JS, Venables JD (1982) Application of surface behavior diagrams to the study of hydration of PAA surfaces. J Mater Sci 17 1807... 

M. Pourbaix [5] has devised a compact summary of thermodynamic data of potential - pH diagrams related to corrosion behavior of any metal in water. These diagrams are now available for most common metals. Diagram (Fig. 1.4) shows specific conditions of potentiai and pH under which the metal either does not react (immunity) or is able to react to form specific oxides or complex ions. These data indicate the conditions under which diffusion-barrier films may form on the electrode surface. The diagram outlines the nature of stoichiometric compounds into which any less stable compounds... 

FIGURE 1.62. Kinetic case diagram for linear sweep voltammetry applied to redox switching in a finite-diffusion space. Regions 1, 2, and 3 denote reversible, quasi-reversible, and irreversible charge percolation kinetics, respectively, whereas A, B, and C represent regions corresponding to infinite diffusion, finite diffusion, and surface behavior, respectively. (Adapted from Ref. 179.)... 

With increasing humidity, growth of the amount of water adsorbed may occur in a continuous way or via the surface phase transitions, such as layering and prewetting, described in Section 2.1. Obviously, the presence of water clusters, water layer(s), or macroscopic water film on the surface essentially modifies the system properties. To predict water behavior near various surfaces, it is, therefore, important to analyze in a systematic way all possible scenarios of water adsorption and to relate them with the thermodynamic conditions and with the properties of a surface. Analysis of the surface phase transitions of water at hydrophilic surfaces (this section) and at hydrophobic surfaces (Section 2.3) will be finalized by constructing the surface phase diagram of water in Section 2.4. 

A comprehensive list of standard potentials is found in Ref. 7. Table 2-3 gives a few values for redox reactions. Since most metal ions react with OH ions to form solid corrosion products giving protective surface films, it is appropriate to represent the corrosion behavior of metals in aqueous solutions in terms of pH and Ufj. Figure 2-2 shows a Pourbaix diagram for the system Fe/HjO. The boundary lines correspond to the equilibria ... 

The oxidation products are almost insoluble and lead to the formation of protective films. They promote aeration cells if these products do not cover the metal surface uniformly. Ions of soluble salts play an important role in these cells. In the schematic diagram in Fig. 4-1 it is assumed that from the start the two corrosion partial reactions are taking place at two entirely separate locations. This process must quickly come to a complete standstill if soluble salts are absent, because otherwise the ions produced according to Eqs. (2-21) and (2-17) would form a local space charge. Corrosion in salt-free water is only possible if the two partial reactions are not spatially separated, but occur at the same place with equivalent current densities. The reaction products then react according to Eq. (4-2) and in the subsequent reactions (4-3a) and (4-3b) to form protective films. Similar behavior occurs in salt-free sandy soils. 

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