FR2574435A1 - ELECTROCHEMICAL PROCESS FOR THE PICKLING OF INSULATING MATERIALS - Google Patents

Abstract

THE SUBJECT OF THE INVENTION IS A PROCESS FOR PICKLING AN INSULATING MATERIAL CONTAINING IN PARTICULAR OXIDE LAYERS ON ITS SURFACE, CHARACTERIZED IN THAT A FIRST ELECTRODE 4 CONSTITUTED BY A WOOL BUFFER 1 IS APPLIED TO THE SURFACE TO BE PICKLED METALLIC 6 AS WELL AS AN ELECTROLYTE 3 IN WHICH A SECOND ELECTRODE 9 ALSO IMMERSES AND A VOLTAGE AND AN INTENSITY IS MAINTAINED BETWEEN THE TWO ELECTRODES 4 AND 9 SUCH AS THE FIRST ELECTRODE 4 IS POLARIZED CATHODICALLY CAUSING A CLEARING OF HYDROGEN.

Description

The present invention relates to a process for pickling a material

insulator comprising in particular

oxide layers on its surface.

  It is already known to carry out electrochemical polishing of the surface of a metal part or, conversely, the electrochemical deposition of a metal on this surface using an electrode constituted by a pad of metallic wool, the metallic part constituting the other electrode (A. Roos, Techniques

Metallographic, Dunod 1960).

  It has now been discovered that such electrodes can be used to strip insulating materials by an electrochemical method by

  using specific conditions.

  The subject of the present invention is a process for pickling an insulating material comprising in particular layers of oxides on its surface, characterized in that a first electrode consisting of a metallic wool pad is thus applied to the surface to be stripped. an electrolyte in which a second electrode is also immersed and a voltage and an intensity are maintained between the two electrodes such that the first electrode is cathodically polarized

  causing a release of hydrogen.

  In order to improve the pickling effect we can

  advantageously complete the purely electro-

  chemical by a mechanical effect of abrasion by rubbing

  the pad against the surface to be stripped.

  The metallic wool constituting the tampon can be formed from a metal such as stainless steel or from a more noble metal such as nickel or a precious metal. The other electrode can be formed of a wire

  of a metal such as nickel or a precious metal.

  2- The two electrodes can be attached to separate supports and held by hand. To make the pickling operation easier, the electrodes are preferably fixed to the same portable support, the electrode operating as an anode surrounding the working buffer.

in cathode.

  The electrode constituted by the metallic wool pad can in particular be housed in a tube in which the pad can slide under the action of a piston to compensate for the wear of the pad when the pad is rubbed

  against the surface to be stripped and / or to increase the work surface.

  The electrolyte can be applied by immersing the surface to be stripped in an electrolyte bath. It can also be simply deposited in the form of a film on the surface to be stripped. For this purpose it

  can be brought in particular through the buffer

killing the first electrode.

  The electrolyte advantageously contains a com-

  plexing metals and in particular cyanide.

  The alkaline electrolyte can be an electrolyte

  usually used for industrial alkaline cleaning

  triel of iron and steel surfaces.

  It advantageously contains: -KOH or NaOH 5 to 40% by mass - NaCN or KCN 60 to 120 g / l - Surfactant approximately 1% by weight As surfactant, it is possible to use in particular sodium alkyl aryl sulfonates or aryl sodium sulfonates. When deposits on the surface

  to be pickled are iron oxides we use advantageously-

  ment of Tiron (1,2-dihydroxy-benzene 3,5-sodium disulfonate) which is a colored reagent-of iron and can play the role of indicator of work and depletion of the cyanide bath. - 3 -

  You can adjust the intensity of the electro-

  lysis so as to regulate the release of hydro bubbles

  genes that act both chemically and mechanically.

  In practice with a cathode having a buffer diameter of 10 mm, one can operate with an intensity of 200

  at 400 mA at a voltage of 2 to 4 V. -

  The method according to the present invention can be used to strip different insulating materials such as

  than porcelain, ceramics, mineral materials

  corn, plastics, wood, fossils.

  The method according to the invention finds application

  cation especially in the restoration of objects

old insulators.

  - The invention will be explained in more detail using the appended drawings in which FIG. 1 is a schematic sectional view of an embodiment of the present invention, FIG. 2-is a partial sectional view of a set of electrodes usable in the present

invention.

  In Fig. 1 shows an embodiment using two electrodes fixed to supports

separate hand-held.

  On the surface 1 of a part to be treated in cer-

  mique, comprising a layer of iron oxide 2, a film 3 of alkaline electrolyte is applied, containing sodium cyanide and Tiron, which comes to cover the layer 2 to be removed. On this layer 2 we just apply -to the hand an electrode 4 comprising a Teflon tube 5 provided at its lower end with a plug 6 of stainless steel wool. Through a plug 7 closing the upper end of the tube 5 slides a metal piston 8 which leans against the pad 6. By pressing the piston-8 you can -4- move the pad 6. The piston rod 8 is connected to the negative pole of the current source and the electrode 4

  thus constitutes the cathode of the cell.

  The other electrode 9, constituting the anode

  takes a tube 10 of insulating material longitudinally crossed by a nickel rod 11 having a

  partially folded lower end 12; the extreme

  upper mite being connected to the pale positive of the

Power source.

  The electrode 9 is applied by hand in the vicinity of the electrode 4 and a voltage is applied between the electrodes 4 and 9 - The intensity is adjusted so that the

  Hydrogen bubbles are released in sufficient quantity.

  During the evolution of hydrogen we rub

  layer 2 with pad 6 to promote detachment

layer.

  There is shown in FIG. 2 a set

  electrodes carried by the same portable support.

  This set includes a central electrode

  13 similar to that shown in FIG. 1 and comp-

  including a tube 14 and a buffer 15.

  This tube 14 is surrounded by a second tube 16.

  Between the tubes 14 and 16 passes a nickel rod 17 whose lower end 18 is bent so

to surround the buffer 15.

  This set can be easily handled at

the hand.

- 5 -

Claims (7)

  1. Process for pickling an insulating material comprising in particular layers of oxides on its surface, characterized in that a first electrode (4) consisting of a metallic wool pad is applied to the surface to be stripped (1) (6) as well as an electrolyte (3) into which also a second   electrode (9) and it is maintained between the two elect   trodes (4 and 9) such a voltage and intensity   the first electrode (4) is cathode polarized-   by causing a release of hydrogen.   2. Method according to claim 1, characterized in that the pad (6) is rubbed against the surface to be stripped (2).   3. Method according to claim 1 or the res-   dication 2, characterized in that one uses   two electrodes (13,18) fixed to the same support.   4. Method according to claim 3, characterized in that the second electrode (18) surrounds the first electrode (13) constituted by the tampon (15) of wool metallic.   5. Method according to any one of the claims.   previous cations, characterized in that a tampon (6) of metallic wool housed in a tube (5) is used in which it can slide.   6. Method according to any one of the claims.   previous cations, characterized in that the electrolyte contains cyanide.   7. Method according to any one of the claims.   previous cations characterized in that the electrolyte contains Tiron.