Corrosion potential values phases

Table 3.2 Typical corrosion potential values [17] for common magnesium second phases (after 2h in de-aerated 5% NaCI solution saturated with Mg(OH)2 (pH 10.5))...

Figure 17.14 Ohmic-resistance-corrected Bode plots for the AZ91 alloy at the corrosion potential after different immersion times in 0.1 M NaCI, with values adjusted for the electrolyte resistance following equation (17.4) a) phase angle and b) modulus. (Taken from Orazem et al. ° and reproduced with permission of The Electrochemical Society.)...

Pourbaix diagram for Fe shows that the corrosion region extends into mid-pH values at moderate potentials. The phase field for Cr203 overlays much of this territory, allowing for an enhancement in the passivity of Fe alloys by the addition of Cr. 

Let us mention some examples, that is, the passivation potential at which a metal surface suddenly changes from an active to a passive state, and the activation potential at which a metal surface that is passivated resumes active dissolution. In these cases, a drastic change in the corrosion rate is observed before and after the characteristic value of electrode potential. We can see such phenomena in thermodynamic phase transitions, e.g., from solid to liquid, from ferromagnetism to paramagnetism, and vice versa.3 All these phenomena are characterized by certain values... 

The alkaline fuel cell (AFC) with its liqnid alkaline electrolyte KOH uses gas diffusion electrodes with a hydrophobic porous part, which is not flooded by the alkaline electrolyte, and a hydrophilic part containing electrolyte and thus leading to a three-dimensional three-phase boundary layer. As the electrode potentials in alkaline electrolyte are shifted towards more negative values, corrosion is less problematic. Raney Nickel and silver are the state-of-the-art catalysts. The practical use... 

A practical limitation on the operation of RPIP chromatography concerns the corrosive activity of many of the counter-ions on the bonded phase of the columns, notably at pH values outside of the range of 2-8.5. It may be anticipated that in the near future the use of non-silica-based stationary phases will result in an increase in the potential applications of ion-pair chromatography. 

This first-principles electrochanical model was directly applied to investigate the corrosion and destahUization of copper. A series of geometry optimizations was performed for a model Cu(111)-H20 interface, with the potentials made successively more anodic at each step [77]. The model was, therefore, setup in an equivalent way to a voltammetry experiment, although kinetic processes were not explicitly taken into account. When the resulting geometries were plotted, it could he seen that, at various values for the surface charge density, phase... 

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