Plate anodes

Finally there are large plate anodes up to 1 m square with cable connections as hangers. Such anodes serve to drain stray currents in ships in fitting out or repairs (see Section 15.6). 

For pipelines, so-called bracelets are used (see Section 16.6). They consist of groups of plate anodes of more or less large breadth, partly curved, which are secured near to one another on an iron band support like links of a bracelet and laid around pipelines. With the same objective, half-shells are used which are fixed in pairs under stress around the pipe and then welded. 

Although rod anodes screwed into the side walls of containers are preferred, plate anodes and basket anodes are mostly necessary on the base. They are particularly suitable for large containers without being built in. Plate anodes are supplied with a flat plastic holder to which the cable conductor is attached and... 

In such cases basket anodes are frequently used. These have a relatively large surface and work at a low driving voltage due to their special construction. A cylinder of platinized titanium-expanded metal serves as the basket to which a titanium rod is welded. This serves as the current lead and carrier, and ends in a plastic foot that contains the cable lead and at the same time serves as the mounting plate. The expanded metal anode exhibits a very uniform anode current density distribution, even at large dimensions, in contrast to the plate anode. The reason is the many comers and edges of the metal that make the point effect only evident at the outer edges of the anode. 

Plate anodes were used for corrosion protection in order to avoid damage due to erosion and cavitation. These consisted of enamelled steel bodies in which a metal oxide-coated titanium anode 1 dm in surface area was fitted. The enamel... 

Figure 21 -3 shows a schematic diagram of the turbine in which the black areas are CrNi steel. The plate anodes are situated in the region of the suction manifold (A 1 to A3) in a triangular arrangement in the impeller ring (A4 to A6) and distributed in the vicinity of the segmented water inlet ring (A7 to A10) (see Fig. 21-4). These four anodes were individually connected to the transformer-rectifier with chloride-resistant pressure-resistant cable.

Fig. 21-4 Mounted plate anode (see text) on the CrNi-siainless steel water inlet ring between stator and rotor.

The protection current requirement is determined mainly by the uncoated surfaces of the stainless steel whose protection potential is a few tenths of a volt more positive than that of the plain carbon steel, to avoid pitting (sec Section 2.4). The protection current requirement for the turbine section is about 10 A so that the plate anodes are only loaded to about 1 A. 

Suda and coworkers described the anodic oxidation of 2-silyl-l,3-dithianes which have two sulfur atoms on the carbon adjacent to silicon [42], In this case, however, the C Si bond is not cleaved, but the C-S bonds are cleaved to give the corresponding acylsilanes (Scheme 12). Although the detailed mechanism has not been clarified as yet, the difference in the anode material seems to be responsible for the different pathway of the reaction. In fact, a platinum plate anode is used in this reaction, although a carbon anode is usually used for the oxidative cleavage of the C-Si bond. In the anodic oxidation of 2-silyl-l,3-dithianes the use of a carbon anode results in a significant decrease in the yield of acylsilanes. The effects of the nature of the solvent and the supporting electrolyte may also be important for the fate of the initially formed cation radical intermediate. Since various 2-alkyl-2-silyl-l,3-dithianes can be readily synthesized, this reaction provides a convenient route to acylsilanes. 

The work on the electrochemical generation of a solution of ceric sulphate from slurry of cerous sulphate in 1-2 M sulphuric acid was abandoned by BCR due to difficulties encountered in handling slurried reactants. A 6kW pilot reactor operated at 50 °C using a Ti plate anode and a tungsten wire cathode (electrolyte velocity about 2ms 1) produced 0.5 M Ce(S04)2 on the anode with a current efficiency of 60%. The usefulness of Ce(IV) has been limited by the counter anions [131,132], Problems include instability to oxidation, reactivity with organic substrates and low solubility. Grace found that use of cerium salts of methane sulfonate avoids the above problems. Walsh has summarized the process history, Scheme 6 [133],... 

Potassium manganate obtained above is oxidized to the permanganate either by electrolysis or by chemical oxidation. Electrolytic oxidation is more common. Electrolytic cells have cathodes made of iron rods and nickel-plated anodes. Potassium manganate melt is extracted with water prior to its electrolysis and then electrolyzed at a cell voltage of 2.3V and current of about 1,400 amp. Permanganate is produced at the anode and water is reduced to gaseous hydrogen and hydroxyl ions at the cathode ... 

The semi-dry blotting apparatus consists of two plates (anode and cathode) made from graphite, glassy carbon, or stainless steel and a sandwich consisting of buffer-soaked filter paper, transfer... 

A second effect of high fly ash resistivity is observed when the difference in potential across the collected dust layer rises to too high a value. A back corona can form as the EMF differential breaks down due to sparking across the dust layer. High currents flow between the wire cathode and plate anode thereby destroying the ability of the ESP to charge particulates. 

The general procedure for the electrochemical preparation of (10) is as follows. A solution of (9) (3 mmol) in wet acetonitrile (40 ml, 5 vol.% of H20) containing sodium perchlorate (0.25 m) was placed in an undivided electrolysis cell equipped with a platinum plate anode and a platinum plate cathode. The system was subjected to a constant current electrolysis (300 mA current density, 20mAcnr2) at ambient temperature. After 4 faradays per mole of (9) had been consumed, the electrolysed solution was poured into water (50 ml) and extracted with dichloromethane (3 X 30 ml). The organic layer was dried with magnesium sulfate and concentrated under reduced pressure. The residue was chromatographed on silica gel to afford (10) in an excellent yield. 

In an undivided cell equipped with both a graphite plate anode and cathode and a Teflon stirrer bar was placed an McCN solution (10 mL) containing the 4-(trimethylsilyl)azctidin-2-one 10 (0.5 mmol) and Et,N 3 HF (0.37 mol dm ). A constant electric current of 50 mA was applied to the solution. After... 

FIGURE 1.11 Schematic of the electrochemical cell and circuit arrangements for anodic oxidation of a titanium metal plate under hydrothermal conditions. (A) Counter electrode (platinum plate), cathode (B) thermocouple (C) stirrer (D) reference electrode (platinum plate) (E) working electrode (titanium plate), anode. 

Fig. 14.23 Microtiter plate anodic electrooxidation from lb to form 3ba in the presence of CH3OH, c(lb) = 4mM, c(lu) = 50mM, c(CH3OH) = 2M, electrolysis potential E = +0.4 V vs. id fc+ (a) steady-state microdisk electrode (d = 25 pm) cyclic voltammetry during electrolysis, v = 0.02 V s 1, times after start of electrolysis indicated, (b) current development during electrolysis, (c) steady-state voltammograms before (1) and after 900 s of electrolysis with (3) and without (2) mixing by convection. (Figure reprinted from Markle et al.72). Copyright Elsevier Ltd. (2005)...

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