Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Metal-electrolyte potential difference

For these situations, IR 0 and Aelectron-source and -sink areas. In general, however, the sink-to-source distance is on the order of microns or less, in which case the conducting path in the solution and therefore IR becomes negligible. Thus, the A(j>so is virtually equal to A(f>u, and any negligible difference that exists occurs over distances too small to be resolved by the probe used to measure the potential difference between the metal and the solution (Fig. 12.14). [Pg.141]

As discussed above, concentration gradients will produce a potential drop. Because of the electrode reaction even at equilibrium, that is, with no current flow, there will be a potential drop. The formation of this metal-electrolyte potential difference, which is based on a metal-ion potential, arises from the transfer of metal ions from the metal into the electrolyte, and vice versa. This transfer of metal ions through the electric double layer (here assumed infinitely thin) takes place simultaneously in both directions. The amount of this transference is generally not equal in both directions and gives rise to the metal-electrolyte potential difference. This electrode potential is the potential difference that forms at the boundaries of the two phases. [Pg.363]

It is worth noting that, in whatever way a pit nucleus was bom, its further development to form a pit embryo (growing metastable pit) depends on the electrolyte concentration which locally sets up in the electrolyte when the metal dissolves. The development of the pit embryo implies the local stabilization of an acidic corrosive medium, differing from the surrounding one. This local acidification induces a local dissolution of the metal in the active state, which is compensated only by the diffusion of the corrosion products. This dissolution in turn provokes an acidification due to the hydrolysis reactions and the process is self-sustained, provided that fire diffusion or the electromigration is slow enough in the electrolyte. Formally [3h,5d], if Jis the anodic current andXrepresents the concentration in corrosion products, one has dX/dt = KJ V, X) - DX, where the metal-electrolyte potential difference F is a control parameter (J increases with V) and parameters K and D represent respectively the production in corrosion products by the anodic dissolution and their dilution into the electrolyte by a diffusion process. The steady state conditions write dX/dt = 0. The system is locally stable when... [Pg.341]

The analysis of the process of measuring potential differences across phase boundaries demonstrates the impossibility of using standard potential measuring devices to determine the value of a single metal-solution potential difference. The electrochemist proceeds, therefore, somewhat humbled but not defeated. He or she must ask how much information about the potential difference across an elec-trode/electrolyte interface can be obtained. [Pg.94]

Vanadium is obtained from many of the extracts, either by precipitation as ferrous vanadate or calcium vanadate or by electrolytic deposition. If ferrous sulfate is used, it must be present in considerable excess in order to prevent loss of vanadium. The electrolytic deposition has some advantages over the precipitation methods, but it does not produce a pure product. If ferrous vanadate is desired, a nearly neutral solution is used, the anode is iron and the cathode almost any metal. A potential difference between the electrodes of four volts is suffi-... [Pg.209]

In addition to potential differences between two metals in an electrolyte, potential differences also arise whenever two solutions of different composition or concentration come into contact. The potential difference is called the liquid... [Pg.33]

The term ( p- p.)is the ohmic potential difference (IR i drop) which is completely located in the electrolytic phase. It is the only measurable potential difference on the right side of Eq. 11. The other terms represent Galvani potential differences (Galvani tensions [1]). The metal-solution potential difference - p) is usually designated as electrode potential. [Pg.8]

The surface tension of an electrode in contact with an electrolyte depends on the metal-solution potential difference, A ( ). The equation describing this dependence is called the electrocapiilary equation. It follows by simple logic from the Gibbs adsorption isotherm. Thus, the sum X Tjdp in Eq. (9.6) should represent the surface excess (or deficiency, i.e. negative surface excess) of all the species in the interphase. On the solution side there are terms of the type (Fcr dpd-) and (Frh dp,RH) charged and neutral species, respectively, where the subscript "RH stands for an unspecified organic molecule). On the metal side, the surface excess is... [Pg.130]

In addition to the case of a metal in contact with its ions in solution there are other cases in which a Galvani potential difference between two phases may be found. One case is the innnersion of an inert electrode, such as platinum metal, into an electrolyte solution containing a substance S that can exist m either an oxidized or reduced fomi tlirough the loss or gain of electrons from the electrode. In the sunplest case, we have... [Pg.598]

When two conducting phases come into contact with each other, a redistribution of charge occurs as a result of any electron energy level difference between the phases. If the two phases are metals, electrons flow from one metal to the other until the electron levels equiUbrate. When an electrode, ie, electronic conductor, is immersed in an electrolyte, ie, ionic conductor, an electrical double layer forms at the electrode—solution interface resulting from the unequal tendency for distribution of electrical charges in the two phases. Because overall electrical neutrality must be maintained, this separation of charge between the electrode and solution gives rise to a potential difference between the two phases, equal to that needed to ensure equiUbrium. [Pg.510]

This handbook deals only with systems involving metallic materials and electrolytes. Both partners to the reaction are conductors. In corrosion reactions a partial electrochemical step occurs that is influenced by electrical variables. These include the electric current I flowing through the metal/electrolyte phase boundary, and the potential difference A( = 0, - arising at the interface. and represent the electric potentials of the partners to the reaction immediately at the interface. The potential difference A0 is not directly measurable. Therefore, instead the voltage U of the cell Me /metal/electrolyte/reference electrode/Me is measured as the conventional electrode potential of the metal. The connection to the voltmeter is made of the same conductor metal Me. The potential difference - 0 is negligibly small then since A0g = 0b - 0ei ... [Pg.29]

A particular type of anodic danger arises in the interiors of pipes and storage tanks that are filled with an electrolyte and consist of similar or different metals, which, however, are electrically separated by insulating units. Potential differences are produced from external cathodic protection and are active in the interior [29,30]. These processes are dealt with in more detail in Sections 10.3.5,20.1.4, and 24.4.6. [Pg.150]

Galvanic corrosion is the enhanced corrosion of one metal by contact with a more noble metal. The two metals require only being in electrical contact with each other and exposing to the same electrolyte environment. By virtue of the potential difference that exists between the two metals, a current flows between them, as in the case of copper and zinc in a Daniell cell. This current dissolves the more reactive metal (zinc in this case), simultaneously reducing the corrosion rate of the less reactive metal. This principle is exploited in the cathodic protection (Section 53.7.2) of steel structures by the sacrificial loss of aluminum or zinc anodes. [Pg.893]


See other pages where Metal-electrolyte potential difference is mentioned: [Pg.445]    [Pg.263]    [Pg.265]    [Pg.266]    [Pg.445]    [Pg.224]    [Pg.445]    [Pg.263]    [Pg.265]    [Pg.266]    [Pg.445]    [Pg.224]    [Pg.550]    [Pg.14]    [Pg.9]    [Pg.7]    [Pg.14]    [Pg.90]    [Pg.148]    [Pg.173]    [Pg.258]    [Pg.55]    [Pg.358]    [Pg.305]    [Pg.652]    [Pg.550]    [Pg.432]    [Pg.362]    [Pg.13]    [Pg.864]    [Pg.22]    [Pg.589]    [Pg.597]    [Pg.600]    [Pg.306]    [Pg.307]    [Pg.311]    [Pg.277]    [Pg.38]    [Pg.456]    [Pg.893]    [Pg.662]   
See also in sourсe #XX -- [ Pg.167 ]




SEARCH



Difference potential

Electrolytic potential

Metal potential

Metal-electrolyte interface contact potentials difference

Potential electrolytes

© 2024 chempedia.info