Cathodes, aluminum copper

Purification actually starts with the precipitation of the hydrous oxides of iron, alumina, siUca, and tin which carry along arsenic, antimony, and, to some extent, germanium. Lead and silver sulfates coprecipitate but lead is reintroduced into the electrolyte by anode corrosion, as is aluminum from the cathodes and copper by bus-bar corrosion. 

Another study (200) presented IR data for a number of hydride and deuteride species. Using matrix-isolation spectroscopy in conjunction with a hollow-cathode, sputtering source (the apparatus for which is shown in Fig. 36), the IR-active vibrations of the diatomic hydrides and deuterides of aluminum, copper, and nickel were observed. The vibra-... 

In nonaqueous, aprotic media, the hydrogen overvoltage does not play any role. Commonly used cathode materials are lead, aluminum, copper, titanium, steel, and carbon of all kinds. 

Milton and Hutton [21] evaluated aluminum, copper, silver, indium, lead, and tantalum as possible secondary cathode materials. The first three candidates (Al, Cu, and Ag) sputtered at rates too high to allow production of ions characteristic of the glass sample (i.e., tended to produce too thick a metallic layer). Indium and lead are soft materials that lead to the overcompression of the insulator-cathode-sample sandwich, consistently resulting in electrical short-circuiting between the anode and cathode. Finally, tantalum does indeed exhibit the desirable characteristics for application as secondary cathode materials. Although not explicitly required, the fact that Ta is a getter element is likely to provide some added benefits as well. 

The protecting Cl form a separate group (e.g. metal pigments like zinc, aluminum, copper) that promotes cathodic polarization of the metal with a more positive potential. These Cl liberate electrons while dissolving in electrolytes and shifting the metal electrode potential up to a negative value, at which the anodic reaction is suppressed fully. 

In hollow cathodes the cathode material can be sputtered by ion bombardment in the discharge. The metal vapor, consisting of atoms and ions, can be investigated by optogalvanic spectroscopy. Figure 1.43b illustrates a section of the optogalvanic spectrum of aluminum, copper, and iron atoms, and ions A1+, Fe , measured simultaneously in two hollow cathodes irradiated with a tunable pulsed dye laser [120]. 

FIGURE 21.14 Total (a) estimated energy consumption (MJ/kg battery) and (b) GHG emissions of BEV batteries made from virgin materials (solid black line) with recycled cathode materials with recycled aluminum with recycled copper and with recycled cathode material, copper, and aluminum. (For color version, refer to the plate section.)... 

Aldykiewicz Jr A.J., Davenport A.J., Isaacs H.S., (1995).Investigation of cerium as a cathodic inhibitor for aluminum-copper alloys. Journal of the Electrochemical Society, Vol. 142, No.lO, pp. 3342-3350. ISSN 0013-4651... 

The SVET was utilized to study the effect of phosphate ions and organic buffer on the corrosion of carbon steel in dilute solution of chlorides and sulfates (Franklin et al., 1992), and the influence of cerium as a cathodic inhibitor on the localized corrosion of aluminum-copper alloys (Aldyke-wicz et al., 1995). Franklin et al. (1992) in-... 

Voltammograms for the background electrolyte (LiF-LiCl eutectic) at 530 °C on various electrodes are shown in Figure 1.9.2a,b. The voltammograms for the background electrolyte show a sharp rise in cathodic current from -2.38 V versus Ag/AgCl for tungsten electrodes, which is due to the deposition of lithium [3, 11]. For aluminum, copper, and Al-Cu alloy electrodes, small cathodic currents were observed at around -2.0 V versus... 

Aldykewicz AJ Jr, Isaacs HS, Davenport AJ (1995) The investigation of Cerium as a Cathodic Inhibitor for Aluminum-Copper Alloys , Journal of the Electrochemical Society, 142,10, 3342-3350. 

For aluminum-copper alloys (2000 series) dilute aluminum alloys such as 1230, 6003, or 6053, containing small amounts of manganese, chromium, or magnesium, may be used as cladding material. These have low-copper contents, less than 0.02%, and low-iron content, less than 0.2%. However these alloys are not sufficiently anodic with respect to the Al-Zn-Mg-Cu alloys of the 7000 series, and they do not provide cathodic protection in these cases. The 7000 series alloys are... 

The 2xxx (aluminum-copper) alloy series started to be used frequently with the development of 24S (2024) in 1933 for maximum solubility of alloying elements in the solid phase. Due to their high strength, toughness and fatigue resistance, modifications of 24S are widely used today for aircraft applications. However, the alloys of these series, in which the copper is major alloying element, are less corrosion-resistant than the alloys of other series. Copper increases the efficiency of the cathodic counter reaction of the corrosion, such as O2 and H+, reduction reaction and, thus, the presence of copper increases the corrosion rate. ... 

The rate of attadr depends on (a) the difference in corrosion potentials between the two metals, (b) the electrical resistance between the two metals, (c) the conductivity of the electrolyte, (d) the cathode-aiKxle area ratio, and (e) the polarization characteristics of the two metals. Although Fig. 4 can be used to predict which metal suffers galvanic attadc when compared with another, the extent of attack cannot be predicted because of polarization. For example, the potential difference between aluminum and stainless steel is greater than that between aluminum and copper (refer to Fig. 4), yet the galvanic influence of stainless steel on aluminum is much less because of polarization, while the aluminum-copper couple shows little... 

Step 2 When the pH reaches a value of 9, the aluminum is depassivated and dissolves, leading to the formation of a crevice. The cmrent distribution shows that the high cathodic current is restricted to the aluminum/copper interface, which explains that the dissolution of aluminum only occurs at the aluminum/copper interface, leading to the specific topography observed with scaiming electron microscopy. 

The electrorefining of many metals can be carried out using molten salt electrolytes, but these processes are usually expensive and have found Httie commercial use in spite of possible technical advantages. The only appHcation on an industrial scale is the electrorefining of aluminum by the three-layer process. The density of the molten salt electrolyte is adjusted so that a pure molten aluminum cathode floats on the electrolyte, which in turn floats on the impure anode consisting of a molten copper—aluminum alloy. The process is used to manufacture high purity aluminum. 

The potential of the reaction is given as = (cathodic — anodic reaction) = 0.337 — (—0.440) = +0.777 V. The positive value of the standard cell potential indicates that the reaction is spontaneous as written (see Electrochemical processing). In other words, at thermodynamic equihbrium the concentration of copper ion in the solution is very small. The standard cell potentials are, of course, only guides to be used in practice, as rarely are conditions sufftciendy controlled to be called standard. Other factors may alter the driving force of the reaction, eg, cementation using aluminum metal is usually quite anomalous. Aluminum tends to form a relatively inert oxide coating that can reduce actual cell potential. 

Vanadium is resistant to attack by hydrochloric or dilute sulfuric acid and to alkali solutions. It is also quite resistant to corrosion by seawater but is reactive toward nitric, hydrofluoric, or concentrated sulfuric acids. Galvanic corrosion tests mn in simulated seawater indicate that vanadium is anodic with respect to stainless steel and copper but cathodic to aluminum and magnesium. Vanadium exhibits corrosion resistance to Hquid metals, eg, bismuth and low oxygen sodium. 

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