Electrodes monel

Ti electrodes have appeared on the market, offering better durability and performance than conventional graphite electrodes Alloys Steels, Monels... 

The most important applications of nickel metal involve its use in numerous alloys. Such alloys are used to construct various equipment, reaction vessels, plumbing parts, missile, and aerospace components. Such nickel-based alloys include Monel, Inconel, HasteUoy, Nichrome, Duranickel, Udinet, Incoloy and many other alloys under various other trade names. The metal itself has some major uses. Nickel anodes are used for nickel plating of many base metals to enhance their resistance to corrosion. Nickel-plated metals are used in various equipment, machine parts, printing plates, and many household items such as scissors, keys, clips, pins, and decorative pieces. Nickel powder is used as porous electrodes in storage batteries and fuel cells. 

The electrode material for electrofluo-rination processes is important, and new materials with high conductivity but chemically inert surface characteristics are desirable. Materials such as Ni, Monel, or HastaUoy are commonly employed [46] and the use of Pt has been pioneered by Schmidt [47]. Boron-doped diamond is a novel electrode material with a chemically highly inert surface suitable for... 

The chemistry of fluorine is dominated by its electronegativity, which is the highest of all elements. The colorless gas F2 has an estimated standard electrode potential E° (Chapter 15) of +2.85 V for reduction to F (cf. + 1.36 V for Cl2 to Cl-), and thus F2 immediately oxidizes water to oxygen (E° = +1.23 V), and 2% aqueous NaOH to the gas F20. Obviously, F2 cannot be made by electrolysis of aqueous NaF. The usual preparation involves electrolysis of HF-KF melts in a Monel (Cu-Ni alloy) or copper apparatus. 

The partial electrochemical fluorination of benzene (I), phenol, chlorobenzene (2), ethylbenzene (3), and naphthalene (4) was investigated31 in a cell with a platinum anode (3x17 cm) and a Monel cathode (distances between the electrodes 1.5 to 2.0 mm), in Et3N 3HF as electrolyte with a voltage of 3 to 5 V (5 mA cm-2). The electrolyte was pumped through a degasifier with a HF resistant flow inducer (30 to 50 mL min-1). The reaction mixture was dissolved in HzO and extracted with CH2C12. The products are indicated below. 

Several, different, electrochemical oxidations of 26 to 27 have been reported. Using a variety of electrodes (copper, Monel metal, nickel, or silver), 26 was oxidized in aqueous potassium hydroxide solution containing potassium chromate or potassium permanganate, to afford 27 in 70-85% yield.118,119 This electrochemical oxidation has been conducted in aqueous, alkaline solution in the presence of a surfactant, but with added metal catalyst, to give 27 in 85-95% yield.120 Alternatively, the oxidation has been performed by using an anode on which nickel oxide was deposited. This anode, in a solution of 26 at pH >9, with or without nickel salts, afforded 27 in >90% yield.121 A number of additional publications described122-140 other modifications of the... 

With the diaphragm in position, electrolysis is carried out using the monel-metal pot as the cathode. If the potassium bifluoride has been well purified, fluorine will be produced at the nickel electrode soon after the current starts to flow. If the source of electricity is a 110-volt direct-current line, a simple rheostat to allow the control of the current may be made from one 500- and two 1000-watt electric heater units. 

Cut a rectangle 9%" x 73 " from the monel woven wire cloth (mesh) for the positive electrode mesh. This allows an overlap of about 34" so that the two surfaces can be tabbed together with nickel foil tabs. 

An electrolyzer consists of two electrodes, usually made of pure nickel, a nickel iron alloy, stainless steel, monel, or Raney nickel. One electrode is connected to the positive source of the DC power supply and the other electrode is connected to the negative source of the DC power supply. 

Another alternative for electrodes is fine mesh screen. This provides more surface area than the flat plate and is not as easily clogged up as is the case with nickel sponge. Either 316 stainless steel, monel or nickel screen can be used. Nickel screen is expensive, so the 316 or monel is a more cost effective choice. The best choice is the monel, an alloy of 65% nickel, 33% copper and 2% iron. This alloy has excellent corrosion resistance in alkaline solutions and will last a long time. 

Experiments with a variety of materials led to the conclusion that monel is a perfect choice for electrodes in an electrolyzer designed for intermittent power supplies. It has an electrical resistance of about 42 micro ohms-cen-timeters at 20°C. This is much higher than, for instance, nickel, which has a resistance of 11. With higher resistance, more heat is generated as the current passes through the electrodes and electrolyte solution. 

Cut a 6"x 9V2" inch piece from the Monel wire cloth according to the layout on page 108. This will be the outer oxygen electrode and will follow closely the inside surface of the PVC pipe. 

Layout for cutting the positive and negative electrodes from a 12"x 12" piece of monel screen... 

Cut the monel wire mesh for the negative electrode to dimensions as shown in the diagram on the previous page. This will give you a 6"x 93/8" piece with a /4" wide... 

Insert the electrode connector screws from the inside, though a nickel washer, then the Monel screen,... 

Examples of metals that are passive under Definition 1, on the other hand, include chromium, nickel, molybdenum, titanium, zirconium, the stainless steels, 70%Ni-30% Cu alloys (Monel), and several other metals and alloys. Also included are metals that become passive in passivator solutions, such as iron in dissolved chromates. Metals and alloys in this category show a marked tendency to polarize anodicaUy. Pronounced anodic polarization reduces observed reaction rates, so that metals passive under Definition 1 usually conform as well to Definition 2 based on low corrosion rates. The corrosion potentials of metals passive by Definition 1 approach the open-circuit cathode potentials (e.g., the oxygen electrode) hence, as components of galvanic cells, they exhibit potentials near those of the noble metals. 

Electrodes are commonly made of platinum, although other noble or passive metals may be used including gold, silver, titanium, monel, stainless steel, and tungsten. The nonmetal graphite is also used because it is inexpensive, inert, and conductive. 

Flow measurement is by magnetic meters with ethylene-propylene-diene elastomer (EPDM) lining and Hastelloy C electrodes. The control valve can be a rubber-lined butterfly valve with a rubber-coated or Monel disc. 

The electrolytic cells used are very similar to the cells used for the production of elemental fluorine [4, 5, 7] cf. Fluorine Suppl. Vol. 2,1980, pp. 4/10. An electrolytic cell suitable for NF3 production on a pilot-plant scale having a capacity of about 25 kg of electrolyte was described by Massonne [5]. The cell and the gas separation skirt were made of Monel the cell cover and the cathode were made of mild steel. The anode was composed of nickel or carbon with an efficient surface of ca. 800 cm. Thus, a current density of 0.15 A/cm was possible at a current of 120 A. On the top of the cell cover there were holes for the release of Hg, the anode gas, inlets for HF, NH3, and Ng, and for the electrodes. The cell was electrically heated and a water-cooling system was attached to remove the heat at high current densities. 

Halogen-containing substances are usually electrolytically reduced on mercury electrodes but there is also a possibility of reducing them at lead, platinum or monel electrodes. The reduction of ethyl bromide at a lead cathode yields tetraethyl lead in a preparative reaction. Still, solid electrodes are usually not used for voltammetric measurements. 

Figure 15. Potentiodynamic polarization curve for a specimen of Monel alloy A in pH 10 solution at 25 C. All voltages are given with respect to the standard calomel electrode. The alloy was first exposed to open circuit corrosion for 1 h prior to the voltage sweep.

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