EP0032960A1 - Verfahren zum Elektroplattieren eines porösen Körpers - Google Patents

Verfahren zum Elektroplattieren eines porösen Körpers Download PDF

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Publication number
EP0032960A1
EP0032960A1 EP80100351A EP80100351A EP0032960A1 EP 0032960 A1 EP0032960 A1 EP 0032960A1 EP 80100351 A EP80100351 A EP 80100351A EP 80100351 A EP80100351 A EP 80100351A EP 0032960 A1 EP0032960 A1 EP 0032960A1
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EP
European Patent Office
Prior art keywords
porous body
plating
porous
solution
current
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP80100351A
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English (en)
French (fr)
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EP0032960B1 (de
Inventor
James Arthur Mcintyre
Robert Floyd Phillips
Joseph Donald Lefevre
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Dow Chemical Co
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Dow Chemical Co
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Publication date
Application filed by Dow Chemical Co filed Critical Dow Chemical Co
Priority to EP80100351A priority Critical patent/EP0032960B1/de
Priority to DE8080100351T priority patent/DE3065335D1/de
Publication of EP0032960A1 publication Critical patent/EP0032960A1/de
Application granted granted Critical
Publication of EP0032960B1 publication Critical patent/EP0032960B1/de
Expired legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D7/00—Electroplating characterised by the article coated
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/03—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form perforated or foraminous
    • C25B11/031—Porous electrodes
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/08—Electroplating with moving electrolyte e.g. jet electroplating

Definitions

  • Porous bodies are known to be difficult to electroplate interiorly.
  • the problem is intensified with an increasing diminishment of the voids interiorly of a porous body where the plating deposit is desired to be made on the enclosing wall surfaces thereof.
  • This is particularly so in cases where the body to be interiorly plated is a porous electrode intended for electrochemical usage, and which contains an abundance of exceedingly fine, internal pores many of which are of miniscule size of less than 10 microns to as small as 0.1 micron.
  • the present invention essentially resides in a process for electroplating porous bodies. More particularly, the present invention resides in a process for electroplating porous electrodes for use in electro-chemical processes, particularly for the use in chlor-alkali cells. Electroplating is performed in such a way as to preclude or minimize the deposition of a coating on the exterior surfaces of the porous body so as to cause a substantial and excessive blockage of the pores on the outer surface of the porous body.
  • the process of the present invention provides for improved economy and deposition of an adequate and effective quantity of a uniformly thin plating layer on the interior surfaces of the porous body.
  • the present invention also resides in a process for applying a coating on the interior wall surfaces of at least a portion of a porous electroconductive body having a multiplicity of void spaces comprising the steps of at least substantially filling the void spaces in the porous body with a plating solution having dispersed therein an electrodepositable substance which forms said coating when the porous body is subjected to passage therethrough of an electrical current; immersing the porous body in an electroductive non--plating liquid medium, and applying a direct current electrical potential to said porous body to cause current to flow through said electroconductive liquid medium and porous body to apply said coating on the internal wall surfaces of said porous body.
  • porous bodies are interiorly electroplated by providing substantially the entire volume of a plating bath from which the coating is to be deposited within all or at least a substantial portion of the porous body during the time that an electroplating current is applied to thereby effect the desired plate deposition on the wall surfaces of the internal voids in the porous body.
  • an efficient, effective and sparing application of the plating is made on only the desired wall surfaces within the porous body such that the plating exhibits good uniformity and quality.
  • exterior surface plating is minimized to substantially reduce pore blockage which is normally associated with prior electroplating procedures. The latter problem can be a serious detriment to porous bodies, particularly where such porous bodies are used as electrodes in electrochemical applications.
  • the article to be plated is placed in a solution which contains the ion of the metal to be plated.
  • the anode is made of the same metal as the metal to be deposited as a coating on the porous body by electroplating such as a silver plating one a silver anode.
  • This material ly helps to keep a constant concentration of metal ions in solution through anode dissolution as metal ions plate out on the cathode. Since metal ion migration into the interstices of a porous body is relatively slow and is retarded by pores of a decreasingly smaller size, the concentration of metal ions within the body voids decreases with time during the plating as compared to the concentration of metal ions of the plating bath. Unavoidably, the plating rate is much faster on the exterior body surfaces where metal ions in the bath, per se, are in proportionally greater abundance to cause a much heavier plating on the exterior surface compared to the internal voids.
  • An electroplatable metallic porous body (5) (such as an electrode) is suitably pretreated, if necessary, to ready it for the plating operation. This may include chemical treatments, for example, degreasing, washing and cleaning or drying.
  • Body (5) contains a plurality of internal voids (6) to give it a somewhat sponge-like structure. According to the present invention, it is intended to plate the wall surfaces of the voids within the porous body without sealing of the open pores on the exterior surface of the porous body. To this end, the electrode is immersed at a filling station (4) in a plating bath solution (7) within container (8).
  • the body (5) is preferably kept in the bath until the void spaces in the porous body are saturated with the plating solution. Accordingly, enough time should be allowed for immersion of the porous body in the solution to permit adequate penetration of and filling of the pores by the solution.
  • the body is shown in a vertical position, penetration of the solution into the pores is also facilitated by having the body tilted in any position other than the vertical to minimize or avoid air entrapment in the porous body.
  • the physical positioning of the body and/or vigorous circulation of the plating solution may also help to achieve more effective and quicker penetration of the solution into the porous body. Incomplete penetration and saturation of the solution into the pores of the body would result in less than total plating of the pore surfaces within the body.
  • an outer portion of the porous body may be saturated with the plating solution by immersion of the body into the solution for a predetermined limited time period without obtaining complete saturation of the plating solution into the pores of the body.
  • only a portion of the porous body may be immersed into the plating solution, such as one side or the lower portion of the body to saturate only that portion of the porous body before proceeding with the electrolytic plating procedure in accordance with the process of the present invention.
  • the porous body can be formed of any desired electroplatable material depending substantially on the particular use to which the body is subjected.
  • Porous bodies for use as electrodes are frequently fabricated from metals such as iron, steel alloys (particularly the corrosion-resisting or so-called “stainless steel” types) copper, titanium or alloys of these metals, although there obviously is no limitation on the metals used for electrodes or any other porous bodies to be plated.
  • metals such as iron, steel alloys (particularly the corrosion-resisting or so-called "stainless steel” types) copper, titanium or alloys of these metals, although there obviously is no limitation on the metals used for electrodes or any other porous bodies to be plated.
  • any suitable and compatible plating solution may be employed depending on the substrate of the porous body to be plated.
  • the porous body After the porous body has been immersed into the plating solution for a predetermined period of time, it is transferred from the filling station (4) to a plating station (9). Care should be taken in this transfer to prevent or minimize the loss of plating solution due to leakage or spillage of the solution from the pores of the body (6). This can be accomplished by holding the body in a position to minimize such loss when taking the body out of the plating solution. Alternatively, a covering member may be held closely against the pore openings on the exposed surfaces of the body to prevent or minimize the leakage of the plating solution from the pores of the body. Bodies, such as electrodes, having extremely small pores are not too troublesome and can be manipulated without leakage or spilling of the plating solution when they are outside of the plating bath.
  • a non-plating, electroconductive liquid (10) is provided in a vessel or container (11).
  • the current-carrying liquid (10) is an appropriately formulated aqueous saline solution, i.e., one containing a sufficient amount of a suitable and compatible ionizable salt that does not react with the plating solution and is adapted to adequately transport and conduct the electrical current necessary for plating.
  • the saline solution (10) is intended to more or less function as a fluid electrical brush for the porous body to be plated and it should be substantially if not entirely free from reducible ions that would tend to interfere with the desired internal plating procedure.
  • An anode (12) is positioned inside of vessel (11) together with means (not shown) to receive and mount the porous body saturated with the plating solution.
  • An electrical circuit is established between the anode and the porous body, which functions as the cathode through electric line (14) connected to a suitable direct current power source (13) which, in turn, is connected by electric line (15) to the anode (12). It is preferred to completely submerge the saturated body in the saline solution (10) for the plating procedure, although there are circumstances when only partial immersion will suffice such as while the porous body is saturated with the plating solution over a portion of its surface.
  • the electrode counter to the porous body being plated (which, as is primarily described-, is anodic although that is not necessarily the case) be inert.
  • the counterelectrode should not dissolve in the saline solution so as to yield platable ions in the solution.
  • the counterelectrode material should be selected so as to be capable of allowing for gas evolution or some other non-interference-provoking reaction in the electrolysis process.
  • a plating current is applied to the porous body to cause a deposition of the metal ions from the plating solution within the void spaces or pores (6) of the saturated porous body onto the interior walls of the pores.
  • the current is applied through the saline solution (10) for a period of time sufficient to accomplish plating and at a relatively lower current level as compared to the current level used in conventional electroplating. Reduction generally being such that the current rate in the practice of the present invention is from 5 to 40 percent, preferably less than 10 percent, of normally utilized electroplating currents in standard plating procedures utilizing the same metal substrate and plating materials. However, the current density should be sufficient to perform the plating quickly enough to minimize or avoid diffusion the plating solution of (7) into the saline solution (10) and vice versa, during the plating procedure.
  • a current density of at least about 0.05 amp/in 2 (0.008 amp/cm 2 ).
  • a current density at a level much lower than 0.05 amp/in 2 may require too much time to allow for deleterious plating solution/saline solution diffusion and mixing.
  • Upper acceptable current density levels are reached where excessive formation and evolution of hydrogen occurs.
  • a current density of about 0.1 amp/in (0.015 amp/cm 2 ) is found satisfactory. It will be understood, however, that the precise current level to be employed for any given situation is readily determinable by persons skilled in the art.
  • the plated porous body is removed from the saline solution (10) and given a washing, drying or other post-plating treatment such as may be needed to finish the porous body for final intended use.
  • the quantity of the coating applied to the porous body, a single-pass plating procedure may not be adequate.
  • the desired thickness of the plating deposit can easily be achieved by a repetition of the plating procedure for as many times as necessary to achieve the desired results.
  • a flat, disc-like body of porous nickel having a 2 1/2 inch (6.35 cm) diameter was washed thoroughly with acetone and air dried at about 110°C.
  • the porous body (made of a commercial, pressed and sintered powdered nickel electrode stock) had a thickness of 70 mils (0.178 cm) and an average diameter pore size of 10 microns. It had a porosity of 80 percent by volume.
  • the porous body was saturated in an aqueous plating solution containing 50 g/1 AgCN (silver cyanide) and 100 g/1 KCN (Potassium cyanide).
  • the porous body saturated with the solution was electrically connected as the cathode in an electrolytic cell containing as the current carrying medium a 1/loth molar (0.1 M) aqueous solution of sodium perchlorate (NaClO 4 ).
  • a platinum (Pt) electrode was inserted into the cell to serve as the anode.
  • An electric current of 0.1 amp/in 2 was passed for 30 minutes through the cell to deposit a silver coating on the inner walls of the pores in the nickel body.
  • the plated and thus catalyzed electrode was tested in an experimental cell along with an unplated electrode made of the same porous nickel stock.
  • Each of the electrodes was mounted for evaluation as a depolarized cathode in a standard electrolytic test cell having an expanded titanium mesh anode provided with a coating of titanium oxide and ruthenium oxide.
  • Anode-to-cathode spacing was 9/32 inch (0.714 cm) with an intermediate "Nafion" ion exchange membrane separator in the cell.
  • the anolyte was 300 g/1 NaCl and the catholyte 100 g/1 NaOH; with the cell operated at a temperature of about 60°C and at a gas pressure on the back side of the cathode maintained at between 2 and -2-1/2 psig.
  • the applied current density was 0.5 amp/in 2 .
  • the test was carried out to determine the performance of the electrode over increasing time periods amd the voltage savings realized in comparing cell operation with both nitrogen and oxygen gases applied to the electrode.
  • the differences arrived at by subtraction of the voltage values obtained from nitrogen (i.e., inert gas) operation at any given point of measure and those from oxygen (i.e., active gas) operation at the same point of measure provided a reliable indication of voltage savings obtained as well as a corresponding depolarization effect upon use of the electrode as a cathode.
  • Figure 2 particularly shows the performance of uncatalyzed (uncoated) porous nickel as a depolarized cathode while Figure 3 illustrates the perfomance of a porous nickel body coated in accordance with the practice of the present invention.
  • plating procedure of the present invention is applicable to materials other than the metals specifically identified herein.
  • coating solutions other than the solutions specifically identified herein and which may even be organic in nature but which are electro-depositable from such appropriate solutions and suspensions are useable in the plating procedure, particularly in electroplating procedures, of the present invention.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Electroplating Methods And Accessories (AREA)
EP80100351A 1980-01-23 1980-01-23 Verfahren zum Elektroplattieren eines porösen Körpers Expired EP0032960B1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP80100351A EP0032960B1 (de) 1980-01-23 1980-01-23 Verfahren zum Elektroplattieren eines porösen Körpers
DE8080100351T DE3065335D1 (en) 1980-01-23 1980-01-23 Method of electroplating a porous body

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP80100351A EP0032960B1 (de) 1980-01-23 1980-01-23 Verfahren zum Elektroplattieren eines porösen Körpers

Publications (2)

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EP0032960A1 true EP0032960A1 (de) 1981-08-05
EP0032960B1 EP0032960B1 (de) 1983-10-19

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DE (1) DE3065335D1 (de)

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2019568C (en) * 1990-06-21 1998-11-24 Hieu C. Truong Coins coated with nickel, copper and nickel and process for making such coins

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1915859A1 (de) * 1969-03-28 1970-10-22 Waldemar Witte Akkumulator mit Traegergeruestelektroden und Herstellungsverfahren hierzu
FR2105024A1 (de) * 1969-09-15 1972-04-28 United Aircraft Corp
US4045303A (en) * 1976-08-05 1977-08-30 Billings Energy Corporation Process of electroplating porous substrates
FR2422737A1 (fr) * 1978-04-14 1979-11-09 Bbc Brown Boveri & Cie Procede pour le depot electrolytique de metaux

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1915859A1 (de) * 1969-03-28 1970-10-22 Waldemar Witte Akkumulator mit Traegergeruestelektroden und Herstellungsverfahren hierzu
FR2105024A1 (de) * 1969-09-15 1972-04-28 United Aircraft Corp
US4045303A (en) * 1976-08-05 1977-08-30 Billings Energy Corporation Process of electroplating porous substrates
FR2422737A1 (fr) * 1978-04-14 1979-11-09 Bbc Brown Boveri & Cie Procede pour le depot electrolytique de metaux

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Publication number Publication date
DE3065335D1 (en) 1983-11-24
EP0032960B1 (de) 1983-10-19

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