RU56400U1 - COMPONENT ANODE WITH AN EXTENDED LIFE OF OPERATION - Google Patents

Abstract

The utility model relates to the field of electrochemical production, in particular, to the manufacture and repair of composite magnetite anodes for the electrolysis of aqueous media with pH = 2 ÷ 14. The objective of the utility model was to reduce the rate of growth of the burning voltage on the composite anodes and increase their life. The technical result is achieved by closing defects in the active coating with a filler in a gaseous or liquid state, followed by condensation and solidification (cooling, polymerization). As a filler, substances of organic and inorganic origin are used that have the necessary combination of physicochemical properties.

Description

The utility model relates to the field of electrochemical production, in particular, to the manufacture and repair of magnetite anodes for the processes of electrolysis of aqueous media with pH = 2-14 (industrial electrolysis, cathodic corrosion protection by external current, electrochemical wastewater treatment).

A composite anode for electrolysis is known with a valve metal base (aluminum, molybdenum, niobium, tantalum, titanium, tungsten, zirconium or their alloys) and an active coating of oxides of manganese, iron, cobalt, nickel with inclusions of particles of tin, antimony, manganese, valve metals [Pat. US No. 4243503, dated January 6, 1981].

Known composite anode for the electrolysis of alkaline solutions containing a base of titanium and an active coating of magnetite and glass enamel [US Pat. DE No. 1964999, dated 01/07/1971].

The closest analogue (prototype) of the proposed utility model is a composite anode for electrolysis of aqueous media containing a base of titanium and an active coating of magnetite [FR No. 2009337 (69 16957 nat. Reg.), From 01.30.1970].

Common disadvantages of all these devices are:

- an increase in the voltage drop across the anodes during operation, significantly limiting the period of their operation;

- the inability to use anodes having mechanical damage to the active coating (chips, peeling, cracks).

The objective of the proposed utility model was to reduce the rate of growth of the burning voltage on the composite anodes and increase their life.

The essence of the utility model is illustrated by the figure, which shows a fragment of the anode. A composite anode containing a base of titanium (1) and an active coating of magnetite (2) differs from the prototype in that the defects of the active coating (2) are filled with filler (3). An additional difference is that the filler material must have certain properties that provide a solution to the problem.

The active coating of magnetite, applied to the titanium base by a plasma method, sintering of pressed Fe ₃ O ₄ powder, or thermal decomposition of iron compounds, has significant porosity [Kudinov VV, Pekshev P.Yu., Belashchenko V.E., Solonenko O.P. ., Safiullin V.A. Plasma coating - M .: Nauka, 1990. - 408 p .;

Fioshin M.Ya., Smirnova M.G. Electrochemical systems in the synthesis of chemical products. - M.: Chemistry, 1985. - 256 p.]. In this case, the electrolysis process proceeds not only on the surface of the composite anode, but also on the surface of the pores [B. Khorishko. Anodic polarization of magnetite sputtering on titanium in a solution of sodium chloride. / Materials of the scientific and technical conference of the Novomoskovsk branch of the Moscow Art Theater. D.I. Mendeleev, Novomoskovsk, 1994 / M., 1994, part I, p. 120-122. Dep. at VINITI No. 2685-B95 dated 10/05/95]. Through macrodefects (chips, peeling, cracks) and microdefects (pores), oxygen of the aqueous medium and electrolysis products penetrate to the titanium base, which accelerates its oxidation. The accumulation of a certain amount of oxygen at the boundary of the titanium base - magnetite causes the anode current to be blocked on the resulting titanium oxide TiO ₂ . This leads to an increase in the voltage drop across the composite anode [Hayes M., Kuhn A.T. - J. Appl. Electrochem., 1978, v. 8, p. 327-332]. Thus, the composite anode becomes unsuitable for further operation. To inhibit the growth of the voltage drop across the composite anode, it is necessary to reduce the oxygen flux to the boundary of the titanium-magnetite base. As a technical solution to this problem, a useful model (Fig.)

It is proposed to fill the defects of the active coating (2) with a special material, it is also a filler (3) in a gaseous or liquid state, followed by condensation and solidification (cooling, polymerization). As filler (3), substances of organic and inorganic origin are used. First, macrodefects are filled, for which synthetic resins and organic polymers with good adhesion to the base and to the active coating are used. After hardening, these materials have their own porosity, therefore, like a porous active coating, they require filling - impregnation. To stop electrolysis in microdefects of the coating, as well as the penetration of the products of electrolysis and oxygen of the aqueous phase to the base, the impregnating substance, which is also a filler, must have a combination of the following properties:

- hydrophobicity;

- good adhesion to the material of the active coating;

- inertness under operating conditions;

- low viscosity in a liquid state;

- large electrical resistivity;

- the melting (boiling) temperature is lower than that of the active coating material, but higher than the temperature of storage and operation of the anode.

Information on substances combining the above properties is available in the technical literature [Yakimenko L.M. Electrode materials. - M.: Chemistry, 1977 .-- 246 p. or Otter F., Shtulik K., Yulanova E. Inversion voltammetry. - M .: Mir, 1980. - 280 s].

Example.

The tubular base (⌀ _ext. = 25 mm; l = 420 mm) of VT-0 titanium was previously subjected to jet-abrasive treatment, heated to 150 ° C in an argon atmosphere, and magnetically coated with a 2 mm thick layer

using a plasmatron. Argon served as the plasma gas. Next, the current supply and the inner surface of the base were isolated. To simulate damage to parts of composite anodes manufactured in this way, macrodefects were artificially created. The filling of macro- and microdefects was carried out by two substances in three versions: 1. epoxy resin ED-20; 2. molten mixture: paraffin + polyethylene; 3. sequentially: epoxy resin - mixture: paraffin + polyethylene. Composite anodes without filling defects (prototype) and filling (utility model) were subjected to anodic galvanostatic polarization in aqueous solutions: 0.5 M H ₂ SO ₄ ; 0.5 M Na ₂ SO ₄ ; 5.5 M NaOH; under conditions: Т≅298 К; P0101328 Nm ^-2 ; i _a = 500 A m ^-2 ; τ = 72000 min. The rate of change of potential (dE / dτ) was investigated. In each experiment, seven samples were studied. Research results with statistical processing parameters are shown in the table. The table shows that the proposed utility model solves the problem. Filling defects in a magnetite coating with a hydrophobic, non-conductive material more than an order of magnitude reduces the growth rate of the voltage drop across the composite anode, which significantly increases the duration of operation of the electrode.

Table The change in the potential of the composite anode during operation.
(Base material: VT-0; active coating Fe ₃ O ₄ δ = 2 mm; Т≅198 К; Р≅101325 N · m ^-2 ; τ = 72000 min; i _a = 500 A / m ² ) dE / dτ · 10 ⁶ , V / min, n = 7, α _d = 0.95 Water solution No impregnation Epoxy resin
ED-20 Mixture: paraffin + polyethylene Epoxy resin, paraffin + polyethylene 0.5 M H ₂ SO ₄ 63.4 ± 3.1 1.94 ± 0.18 0.89 ± 0.03 0.69 ± 0.02 0.5M Na ₂ SO ₄ 95.1 ± 4.0 2.53 ± 0.33 1.20 ± 0.17 0.71 ± 0.02 5M NaOH 131 ± 17 2.51 ± 0.31 1.04 ± 0.14 0.72 ± 0.03

Claims (2)

1. A composite anode for the electrolysis of aqueous media with a titanium base and an active coating of magnetite, characterized in that the defects of the active coating are filled with filler. 2. The composite anode according to claim 1, characterized in that hydrophobic, inert dielectrics are used as a filler, having a melting (boiling) temperature lower than that of the coating material and higher than the storage and operating temperature of the anode, low viscosity in the liquid state, good adhesion to coating materials and bases.