EP0026482A1 - A method for producing an insoluble electrode for electroplating - Google Patents

A method for producing an insoluble electrode for electroplating Download PDF

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Publication number
EP0026482A1
EP0026482A1 EP80105832A EP80105832A EP0026482A1 EP 0026482 A1 EP0026482 A1 EP 0026482A1 EP 80105832 A EP80105832 A EP 80105832A EP 80105832 A EP80105832 A EP 80105832A EP 0026482 A1 EP0026482 A1 EP 0026482A1
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EP
European Patent Office
Prior art keywords
coating
metal
platinum
platinum group
electroplating
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.)
Withdrawn
Application number
EP80105832A
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German (de)
English (en)
French (fr)
Inventor
Hajime Nitto
Kango Sakai
Katsushi Saito
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
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Nippon Steel Corp
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Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Publication of EP0026482A1 publication Critical patent/EP0026482A1/en
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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
    • C25D5/00—Electroplating characterised by the process; Pretreatment or after-treatment of workpieces
    • C25D5/48—After-treatment of electroplated surfaces
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
    • C25D17/10—Electrodes, e.g. composition, counter electrode

Definitions

  • the present invention relates to a method for preparing a durable electrode material usable as an insoluble anode usable for electrolysis in a bath containing chlorine compounds and sulfur compounds, which comprises coating a current-conductive material, such as titanium, with a metal diffusion film such as of a metal of the platinum group.
  • the concentration of metal ions in the electroplating bath gradually increases due to the difference between the deposition efficiency of the cathode which is usually from 94% to 97% and the dissolution efficiency of the anode which is usually from 100% to 103%.
  • the soluble anode is partially replaced by an insoluble anode so as to control the concentration of the metal ion, and at the same time, to cause deposition of the metal for a desired amount of electroplating so as to optionally control the metal ion concentration.
  • the amount of dissolution of the anode varies from portion to portion of the electrode, thus differing between the right side and left side of the electrode, and between the upper portion and the lower portion of the electrode.
  • this dissolution amount changes when the relative distance between the anode and the cathode changes or when the electrical resistance in the current path changes. Therefore, it is necessary to maintain a considerable distance between the cathode and the anode.
  • the distance is usually 25 mm to 35 mm,' and the loss of energy by the bath resistance is large.
  • a soluble anode for example, a tin anode, 200 to 300 cast tin anodes, each weighing about 10 kg, are used in one electroplating line.
  • the anodes must be supplemented to make up for the consumption (dissolution) of the anodes. Therefore, repeated heavy labour and complicated handling-in or handling-out of the anodes for such supplementation are required.
  • the anode must be insoluble.
  • Japanese Patent Publication No. Sho 38-10515 discloses an insoluble anode prepared by electroplating a titanium base with platinum, heating this coated material at a temperature not lower than 400°C in an inert gas or in vacuum of not higher than 10 -5 mmHg to alloy the titanium base with the platinum coating.
  • Japanese Patent Publication No. Sho 39-20910 discloses a method comprising electro-deposition of platinum in a thickness of 2 to 3 micron on a base material, heating in an inert gas in the temperature range from 400°C to 800°C, surface activating treatment, and further platinum plating in a thickness of 3 to 5 micron.
  • Japanese Patent Publication No. Sho 48-43267 (1973) discloses the preparation of non-corrosible electrodes which comprises inpinging rare gas ions on to the surface of a titanium cathode, coating the surface of the titanium cathode with a metal of the platinum group in an atmosphere substantially free from oxygen, and further applying a coating of ruthenium oxide on the platinum coating.
  • Japanese Patent Publication No. Sho 49-7789 discloses a method of producing anodes for electrolysis which comprises electroplating of platinum or rhodium in a thickness of 0.2 micron or more on the electrode base, further electroplating with ruthenium, and firing at a temperature not lower than 500°C in an oxidizing atmosphere.
  • the important technical object of these prior art anodes is to obtain better adhesion of the platinum coating and to eliminate defects of the coated film.
  • the base materials such as titanium are converted into nitrides and oxides when heated to 600°C or higher, so that their mechanical strength and current conductivity are lowered.
  • the alloying between platinum and the titanium base and between the platinum coating and ruthenium is very poor and only partial.
  • Japanese Patent Publication No.Sho 48-3954 discloses an electrode in which the oxide of a metal selected from the platinum group consisting of platinum, iridium, rhodium, ruthenium and osmium is used.
  • Japanese Patent Publication No. Sho 45-11014 discloses a method for electrolysis of an aqueous solution of alkali metal chlorides which comprises electrolysing the solution with an anode potential of 1.36V or lower using an anode made of an alloy of 20% to 50% platinum and 80% to 50 % palladium or an anode coated with the alloy.
  • titanium base material when oxides of platinum group metals or platinum group metals are to be directly coated on titanium base material and the like, no or only partial alloying with the titanium base material is obtained at the temperatures which cause the thermal decomposition of the chlorides and nitrides in the case of oxide films and platinum films, so that titanium oxide appears at non-coated portions.
  • the prior art insoluble anodes have been chiefly used in the chloralkali electrolysis, and although these prior art anodes can satisfactorily stand for the electrolysing conditions in a chlorine bath, such as electrolysis of sodium chloride, these prior art anodes have been found to have very little durability in a metal electroplating in a sulfuric acid bath, for example, which is performed under intermittent electrolysing conditions, because oxide films . such as TiO 2 filmsreadily dissolve. due to their reverse position in the electromotive force series.
  • the insoluble anodes to be used for continuous electroplating of steel strips such as in tin-plating in ferrostan baths and halogen baths, and in zinc-plating in chloride baths and sulfuric acid baths must stand for various electrolysing conditions including the current passing methods, and the bath compositions.
  • the prior art anodes have been unsuccessful in electroplating of steel strips.
  • the object of the present invention is to provide an insoluble anode satisfactorily usuable in continuous electroplating of steel strips and to provide a method for preparation thereof.
  • an insoluble electrode with a coating film free from defects can be obtained.
  • the features of the present invention lie in that a current conductive material is coated with at least one metal of the platinum group by electroplating, then a compound or salt of the platinum group metals, such as Ir, Ru, Ph and Pt is applied on the coating previously applied and is decomposed by heating in a reducing or non-oxidizing atmosphere to make up defects of the electroplated coating. At the same time, a metal of the platinum group which is active at the thermal decomposition of the salt is diffused into the electroplated coating at a temperature not higher than 600°C to avoid nitrization of the base metal. In this way, an electrode coated with a metal of the platinum group and having a continuous, thin diffusion film is obtained.
  • a further coating of a metal and/or oxide of the platinum group may be applied by electroplating or non-electrolytic coating on the thermally diffused coating.
  • the reducing atmosphere for thermal decomposition of the compound or salt of the platinum group metals in the present invention includes a reducing flame, and an atmosphere containing a reducing gas, such as hydrogen and carbon monoxide.
  • a reducing gas such as hydrogen and carbon monoxide.
  • the non-oxidizing atmosphere includes an inert gas, such as nitrogen gas, desirably in the form of gas stream.
  • inert gases contain. a small amount of oxygen, and the thermal decomposition can be satisfactorily done in a gas stream containing up to 1000 ppm of oxygen as usually contained in a device or furnace for maintaining the inert gas atmosphere.
  • the platinum group metals used in the present invention include the elements belonging to the 8th group of the Periodic Table. Among these elements platinum is easiest to electroplate.
  • the titanium base material is acid-pickled to clean the surface, coated with platinum by a conventional method.
  • the bath composition for the electroplating of the platinum group metals various bath compositions may be used, such as an ammonia alkali bath containing diamine platinum nitrite.
  • a typical bath composition and plating conditions are shown below:
  • the thickness of the electroplated coating must be at least 0.1 micron. In the case of the platinum coating, the coating defects still remain even if the thickness is increased as described hereinbefore. Therefore, from the . aspect of economy, it is desirable to maintain the coating thickness up to 3 micron. The most desirable range is from 0.2 to 1.0 micron.
  • the concentration of various metal compounds may be varied within their dissolution range, but a preferable range is from 0.01% to 0.1%.
  • the application of the solution may be done by immersion, spraying or roll brushing.
  • a higher corrosion resistance can be obtained by a larger proportion of Ir and Pt.
  • 60% Ir - 20% Ru - 20% Rh (by weight) is preferable.
  • the thickness of coating required for making up the coating defects must be 0.1 micron at least, and a preferable range is from 0.2 to 1.0 micron.
  • the thermal decomposition is performed by passing the coated electrode through the reducing flames at a speed of about lm/minute. After the thermal decomposition, the electrode is heated at about 500°C to 600°C, preferably 500°C to 550°C in an oxidizing atmosphere for about one hour to take away non-decomposed chlorine. In this way, the final anode can be obtained.
  • titanium alloys As the base material for the anode according to the present invention, titanium alloys, tantalum, tantalum alloys, zirconium and zirconium alloys may be used in addition to titanium.
  • an aqueous solution of one or more of compounds of the platinum group elements such as NO, N0 2 NOC1 compounds may be used.
  • these elements may be in any form which is soluble in water or other solvent.
  • Fig. 1 shows the cross section of an electrode according to the present invention.
  • This electrode was prepared by electroplating a titanium base 3 with 1 micron platinum, then applying to this electroplated titanium base a coating of a chloride of Ir, Rh and Ru and thermally decomposing the chloride under reducing flames.
  • the diffusion film 1 of Ir-Ru-Rh is formed at the portion at which the platinum coating is made.
  • the film 2 formed by the thermal decomposition of the chlorides of Ir, Ru and Rh makes up the coating defects.
  • Ir, Rh and Ru are diffused into the platinum coating, and as shown in Fig. 3, the diffusion film of Ir-Ru-Rh formed by the thermal -decomposition is present at the portion where no platinum coating is present, namely the defect of the platinum coating.
  • the coating on the titanium base obtained by the process of the present invention has a diffusion structure of Ir-Ru-Rh and of Pt-Ir-Ru-Rh free from pin holes.
  • two or more solutions of salts of the platinum group metals may be simultaneously applied, or a first solution of one salt of the platinum group metal is applied and heated, and then a second solution of another salt is applied and heated.
  • a plurality of the platinum group metals can be diffused simultaneously or one after another successively to form an alloyed layer which covers the pin holes of the electroplated coating. In either way, an electrode having excellent corrosion resistance can be obtained.
  • the coating or film formed by the thermal decomposition of the compound or salts of the platinum group metals it is necessary that the application of the solution, and the heating are repeated until a desired thickness of the coating or film can be obtained, because a single application of the solution and thermal decomposition gives only a very thin coating or film although it depends on the concentration of the solution. As mentioned hereinbefore, 40 cycles of application of the solution and heating are required for obtaining 1 micron coating or film.
  • the electroplating and the non-electrolytic coating are repeated, better results can be obtained when they are repeated more times for the purpose of eliminating the pin holes, although there is no specific limitation therefor.
  • the more desired result can be obtained by repeating the electroplating and the non-electrolytic coating under the specified conditions.
  • an electrode having very little pin holes can be obtained a total thickness of 0.8 micron composed of by electroplating of 0.2 micron platinum, diffusion coating of 0.2 micron platinum group metal, and electroplating of 0.2 micron platinum.
  • the electroplating coating may range from 0.1 to 1.0 micron in thickness, and the diffusion coating may range from 0.02 to 1.0 micron in thickness.
  • a coating of a platinum group metal diffused with a platinum group metal which is extremely free from pin holes, can be obtained by the combination of the electroplating of a platinum group metal and the thermal decomposition of a compound or salt of a platinum group metal.
  • the coating according to the present invention shows very excellent corrosion resistance as compared with the conventional electroplating or spray coating of a platinum group metal alone. This excellent corrosion resistance can still be improved by the following modification of the present invention.
  • salt of the platinum group metal such as Ir, Ru, Rh, Pt is applied on the electroplated coating and thermally decomposed in a non-oxidizing atmosphere so as to cover the defect portions of the coating, and further one or more metals of the platinum group is electroplated or coated by non-electrolytic method and/or an oxide film is formed to provide a multiple-layer coating. In this way, the corrosion resistance can be still enhanced.
  • the underlying coating layer is already a pin-hole free coating of a platinum group metal, so that it is easy to obtain a continuous coating having good adhesion under . conventional electroplating conditions.
  • the upper-most coating layer of a multiple coating is applied by a non-electrolytical method and thermal decomposition
  • compounds of the platinum group metals are applied and thermally decomposed in a reducing or substantially non-oxidizing atmosphere to deposit the metals, part or whole of which is diffused into the underlying coating.
  • the upper-most layer may be partially or wholly of oxide.
  • the oxide can be formed by heating the metal after deposition in an oxidizing atmosphere, or by bringing the deposiaed metal into contact with an oxidizing atmosphere during the thermal decomposition step. Further, the oxide may be applied by spattering.
  • the oxide may be an oxide of a platinum group metal, or an oxide of a metal other than the platinum group, such as titanium oxide and zirconium oxide, or a mixture of these oxides.
  • the most important feature of the present invention is that the defects and disadvantages of the prior art have been solved by making up the defects of the platinum coating by the formation of thermally decomposed product and diffusion at relatively low temperatures of the thermally decomposed products into the platinum coating for continuity with the platinum coating.
  • the corrosion resistance of the coating is improved by a multiple coating layer.
  • Fig. 4(a) showing the surface EPMA of the conventional titanium anode coated with platinum by electroplating
  • the weakness of a single uniform film which is peculier to the platinum electroplating produces the surface defects
  • the non-deposition of platinum is shown by the PtLa ccharacteristics X ray.
  • Fig. 6 showing the progress by time of deterioration of a titanium insoluble anode coated with 3 micron platinum at the stages after 30 days, 45 days, 60 days, 75 days and 90 days of electroplating, the peelings off of the platinum coating expand from the coating defects until they connect to each other, thus increasing the non-conductive portions on the electrode.
  • Fig. 7(a) showing the surface EPMA of the anode according to the present invention in which a mixture of salts of Ir, Rh and Ru is applied in an amount equivalent to 1 micron thick on 1 micron platinum coating, and thermally decomposed and diffused into the platinum coating
  • Fig. 7(b) showing the PtLa characteristics X ray
  • the salts of the platinum group elements diffuse into the electroplated platinum coating, while there is almost no diffusion or alloying is seen between the electroplated platinum coating and the base titanium.
  • the coating obtained by the present invention is in fact a diffused and alloyed coating which is completely free from defects and has excellent corrosion resistance.
  • Fig. 10 the polarization of a conventional anode electroplated only with 1 micron platinum is shown and in Fig.11 the polarization of an anode electroplated with 1 micron platinum and further with a diffusion layer of 1 micron Ir-Rh-Ru according to the present invention.
  • the loss of the anode weight during electrolysis is shown in Fig. 12.
  • the electrolysis was done under the following conditions.
  • the insoluble anode and the cathode made of iron were opposingly placed in a bath containing 200 g/l Na 2 S0 4 with pH of 1.0 and the electrolysis was done at 50°C and 30 A/ dm 2 . The total weight loss of the anode was measured and the weight losses by hours were shown.
  • the electrode according to the present invention can be well used an insoluble anode for electroplating of steel strips, but is also applicable to ordinary electroplating and electrolysis industries.
  • the electrode of the present invention may be used as insoluble anodes in a vertical electrolytic tank having electrodes positioned across the steel strip, or in a horizontal electrolytic tank having electrodes positioned above and below the steel strip.
  • the electrode of the present invention can be used as an insoluble anode in a horizontal, linear-type plating tank in which the electrolyte is forcedly circulated at a high velocity between the steel strip and upper and lower in electrodes as disclosed Japanese Patent Publication No. Sho 50-8020, or in a drum-type electrolytic tank in which the electrolyte is forcedly circulated between the strip closely contacting a drum immersed in the electrolyte and the electrodes arranged around the strip as disclosed in U.S.Patent No. 3,483,113.

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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)
  • Electrodes For Compound Or Non-Metal Manufacture (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
EP80105832A 1979-09-25 1980-09-25 A method for producing an insoluble electrode for electroplating Withdrawn EP0026482A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP12198179A JPS5647597A (en) 1979-09-25 1979-09-25 Insoluble electrode for electroplating and preparation thereof
JP121981/79 1979-09-25

Publications (1)

Publication Number Publication Date
EP0026482A1 true EP0026482A1 (en) 1981-04-08

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EP80105832A Withdrawn EP0026482A1 (en) 1979-09-25 1980-09-25 A method for producing an insoluble electrode for electroplating

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EP (1) EP0026482A1 (ja)
JP (1) JPS5647597A (ja)
AU (1) AU6271880A (ja)
BR (1) BR8006157A (ja)
ES (1) ES8106770A1 (ja)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0215649A1 (en) * 1985-09-13 1987-03-25 Engelhard Corporation Platinum/ECA-1500 combination anode coating for low pH high current density electrochemical process anodes
US4913973A (en) * 1985-09-13 1990-04-03 Engelhard Corporation Platinum-containing multilayer anode coating for low pH, high current density electrochemical process anodes
DE4029125A1 (de) * 1989-09-14 1991-03-28 Permelec Electrode Ltd Elektroden-schutz-einrichtung

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57140879A (en) * 1981-02-23 1982-08-31 Nippon Steel Corp Production of long life insoluble electrode
JPS62174394A (ja) * 1986-10-31 1987-07-31 Ishifuku Kinzoku Kogyo Kk 電解用電極の製造方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3055811A (en) * 1961-05-08 1962-09-25 Universal Oil Prod Co Electrolysis with improved platinum plated titanium anode and manufacture thereof
GB1171407A (en) * 1966-06-07 1969-11-19 Engelhard Min & Chem Electrode and Method of Preparation
US3497426A (en) * 1964-07-02 1970-02-24 Nippon Carbide Kogyo Kk Manufacture of electrode
US3663414A (en) * 1969-06-27 1972-05-16 Ppg Industries Inc Electrode coating
FR2120011A1 (ja) * 1970-12-26 1972-08-11 Asahi Chemical Ind
GB1351742A (en) * 1970-03-25 1974-05-01 Marston Excelsior Ltd Electrodes
JPS53123633A (en) * 1977-04-04 1978-10-28 Mitsubishi Electric Corp Information transfer system

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS497782A (ja) * 1972-05-12 1974-01-23

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3055811A (en) * 1961-05-08 1962-09-25 Universal Oil Prod Co Electrolysis with improved platinum plated titanium anode and manufacture thereof
US3497426A (en) * 1964-07-02 1970-02-24 Nippon Carbide Kogyo Kk Manufacture of electrode
GB1171407A (en) * 1966-06-07 1969-11-19 Engelhard Min & Chem Electrode and Method of Preparation
US3663414A (en) * 1969-06-27 1972-05-16 Ppg Industries Inc Electrode coating
GB1351742A (en) * 1970-03-25 1974-05-01 Marston Excelsior Ltd Electrodes
FR2120011A1 (ja) * 1970-12-26 1972-08-11 Asahi Chemical Ind
JPS53123633A (en) * 1977-04-04 1978-10-28 Mitsubishi Electric Corp Information transfer system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
MET FIN ABSTRACTS, Vol. 21, No. 2, March-April 1979 & JP-A-53 123 633 (NIPPON STEEL) 31-03-1977. *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0215649A1 (en) * 1985-09-13 1987-03-25 Engelhard Corporation Platinum/ECA-1500 combination anode coating for low pH high current density electrochemical process anodes
US4913973A (en) * 1985-09-13 1990-04-03 Engelhard Corporation Platinum-containing multilayer anode coating for low pH, high current density electrochemical process anodes
DE4029125A1 (de) * 1989-09-14 1991-03-28 Permelec Electrode Ltd Elektroden-schutz-einrichtung

Also Published As

Publication number Publication date
JPS5749636B2 (ja) 1982-10-22
JPS5647597A (en) 1981-04-30
ES495299A0 (es) 1981-09-01
BR8006157A (pt) 1981-04-07
ES8106770A1 (es) 1981-09-01
AU6271880A (en) 1981-04-09

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