US3649489A - Process for electrolytically stripping coatings and bath therefor - Google Patents
Process for electrolytically stripping coatings and bath therefor Download PDFInfo
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- US3649489A US3649489A US38568A US3649489DA US3649489A US 3649489 A US3649489 A US 3649489A US 38568 A US38568 A US 38568A US 3649489D A US3649489D A US 3649489DA US 3649489 A US3649489 A US 3649489A
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- 238000000034 method Methods 0.000 title abstract description 20
- 238000000576 coating method Methods 0.000 title description 20
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 abstract description 23
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 abstract description 22
- 239000002253 acid Substances 0.000 abstract description 21
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 abstract description 18
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 16
- 229910052804 chromium Inorganic materials 0.000 abstract description 16
- 239000011651 chromium Substances 0.000 abstract description 16
- JVTAAEKCZFNVCJ-UHFFFAOYSA-N lactic acid Chemical compound CC(O)C(O)=O JVTAAEKCZFNVCJ-UHFFFAOYSA-N 0.000 abstract description 12
- 150000001875 compounds Chemical class 0.000 abstract description 8
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 abstract description 6
- 150000007513 acids Chemical class 0.000 abstract description 6
- 239000004310 lactic acid Substances 0.000 abstract description 6
- 235000014655 lactic acid Nutrition 0.000 abstract description 6
- 235000006408 oxalic acid Nutrition 0.000 abstract description 6
- 229910052708 sodium Inorganic materials 0.000 abstract description 6
- 239000011734 sodium Substances 0.000 abstract description 6
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 abstract description 5
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 abstract description 5
- 235000015165 citric acid Nutrition 0.000 abstract description 5
- 229910052700 potassium Inorganic materials 0.000 abstract description 5
- 239000011591 potassium Substances 0.000 abstract description 5
- 239000010953 base metal Substances 0.000 abstract description 4
- LSNNMFCWUKXFEE-UHFFFAOYSA-M Bisulfite Chemical compound OS([O-])=O LSNNMFCWUKXFEE-UHFFFAOYSA-M 0.000 abstract description 3
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 34
- 229910052759 nickel Inorganic materials 0.000 description 17
- -1 aryl sulfonic acid Chemical compound 0.000 description 15
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 12
- 229910052751 metal Inorganic materials 0.000 description 12
- 239000002184 metal Substances 0.000 description 12
- 150000003839 salts Chemical class 0.000 description 9
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 4
- FEWJPZIEWOKRBE-UHFFFAOYSA-N Tartaric Acid Chemical compound [H+].[H+].[O-]C(=O)C(O)C(O)C([O-])=O FEWJPZIEWOKRBE-UHFFFAOYSA-N 0.000 description 4
- 229910052802 copper Inorganic materials 0.000 description 4
- 239000010949 copper Substances 0.000 description 4
- 229960003975 potassium Drugs 0.000 description 4
- 239000000758 substrate Substances 0.000 description 4
- 125000000217 alkyl group Chemical group 0.000 description 3
- 239000011248 coating agent Substances 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 239000011975 tartaric acid Substances 0.000 description 3
- 235000002906 tartaric acid Nutrition 0.000 description 3
- HWTDMFJYBAURQR-UHFFFAOYSA-N 80-82-0 Chemical compound OS(=O)(=O)C1=CC=CC=C1[N+]([O-])=O HWTDMFJYBAURQR-UHFFFAOYSA-N 0.000 description 2
- FEWJPZIEWOKRBE-JCYAYHJZSA-N Dextrotartaric acid Chemical compound OC(=O)[C@H](O)[C@@H](O)C(O)=O FEWJPZIEWOKRBE-JCYAYHJZSA-N 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- AFVFQIVMOAPDHO-UHFFFAOYSA-N Methanesulfonic acid Chemical compound CS(O)(=O)=O AFVFQIVMOAPDHO-UHFFFAOYSA-N 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 239000010970 precious metal Substances 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- JIRHAGAOHOYLNO-UHFFFAOYSA-N (3-cyclopentyloxy-4-methoxyphenyl)methanol Chemical compound COC1=CC=C(CO)C=C1OC1CCCC1 JIRHAGAOHOYLNO-UHFFFAOYSA-N 0.000 description 1
- LBLYYCQCTBFVLH-UHFFFAOYSA-N 2-Methylbenzenesulfonic acid Chemical compound CC1=CC=CC=C1S(O)(=O)=O LBLYYCQCTBFVLH-UHFFFAOYSA-N 0.000 description 1
- CYDQOEWLBCCFJZ-UHFFFAOYSA-N 4-(4-fluorophenyl)oxane-4-carboxylic acid Chemical compound C=1C=C(F)C=CC=1C1(C(=O)O)CCOCC1 CYDQOEWLBCCFJZ-UHFFFAOYSA-N 0.000 description 1
- PXRKCOCTEMYUEG-UHFFFAOYSA-N 5-aminoisoindole-1,3-dione Chemical compound NC1=CC=C2C(=O)NC(=O)C2=C1 PXRKCOCTEMYUEG-UHFFFAOYSA-N 0.000 description 1
- 239000004251 Ammonium lactate Substances 0.000 description 1
- 229910001369 Brass Inorganic materials 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 1
- 150000001412 amines Chemical class 0.000 description 1
- 235000019286 ammonium lactate Nutrition 0.000 description 1
- 229940059265 ammonium lactate Drugs 0.000 description 1
- VBIXEXWLHSRNKB-UHFFFAOYSA-N ammonium oxalate Chemical compound [NH4+].[NH4+].[O-]C(=O)C([O-])=O VBIXEXWLHSRNKB-UHFFFAOYSA-N 0.000 description 1
- RZOBLYBZQXQGFY-HSHFZTNMSA-N azanium;(2r)-2-hydroxypropanoate Chemical compound [NH4+].C[C@@H](O)C([O-])=O RZOBLYBZQXQGFY-HSHFZTNMSA-N 0.000 description 1
- SRSXLGNVWSONIS-UHFFFAOYSA-N benzenesulfonic acid Chemical compound OS(=O)(=O)C1=CC=CC=C1 SRSXLGNVWSONIS-UHFFFAOYSA-N 0.000 description 1
- 229940092714 benzenesulfonic acid Drugs 0.000 description 1
- 239000010951 brass Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- IRXRGVFLQOSHOH-UHFFFAOYSA-L dipotassium;oxalate Chemical compound [K+].[K+].[O-]C(=O)C([O-])=O IRXRGVFLQOSHOH-UHFFFAOYSA-L 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- CCIVGXIOQKPBKL-UHFFFAOYSA-M ethanesulfonate Chemical compound CCS([O-])(=O)=O CCIVGXIOQKPBKL-UHFFFAOYSA-M 0.000 description 1
- 235000011187 glycerol Nutrition 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229940098779 methanesulfonic acid Drugs 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 235000005985 organic acids Nutrition 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 239000001508 potassium citrate Substances 0.000 description 1
- 229960002635 potassium citrate Drugs 0.000 description 1
- QEEAPRPFLLJWCF-UHFFFAOYSA-K potassium citrate (anhydrous) Chemical compound [K+].[K+].[K+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O QEEAPRPFLLJWCF-UHFFFAOYSA-K 0.000 description 1
- 235000011082 potassium citrates Nutrition 0.000 description 1
- PHZLMBHDXVLRIX-UHFFFAOYSA-M potassium lactate Chemical compound [K+].CC(O)C([O-])=O PHZLMBHDXVLRIX-UHFFFAOYSA-M 0.000 description 1
- 239000001521 potassium lactate Substances 0.000 description 1
- 235000011085 potassium lactate Nutrition 0.000 description 1
- 229960001304 potassium lactate Drugs 0.000 description 1
- 238000011536 re-plating Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000004332 silver Substances 0.000 description 1
- 239000001509 sodium citrate Substances 0.000 description 1
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 1
- 229960001790 sodium citrate Drugs 0.000 description 1
- 235000011083 sodium citrates Nutrition 0.000 description 1
- 239000001540 sodium lactate Substances 0.000 description 1
- 229940005581 sodium lactate Drugs 0.000 description 1
- 235000011088 sodium lactate Nutrition 0.000 description 1
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 description 1
- 229940039790 sodium oxalate Drugs 0.000 description 1
- 150000003460 sulfonic acids Chemical class 0.000 description 1
- 239000011593 sulfur Substances 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- YWYZEGXAUVWDED-UHFFFAOYSA-N triammonium citrate Chemical compound [NH4+].[NH4+].[NH4+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O YWYZEGXAUVWDED-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
- C25F5/00—Electrolytic stripping of metallic layers or coatings
Definitions
- ABSTRACT OF THE DISCLOSURE Process and aqueous bath for rapid stripping of thick nickel and/ or chromium coatings from non-ferrous base metals, the coated non-ferrous base being connected as an anode under a voltage of about 8-15 volts at a current density of about 10-25 amperes per square decimeter and at a temperature of between and 80 C., the aqueous stripping containing from 50-95% of sulfuric acid or water-soluble alkyl or aryl sulfonic acid and 50-100 grams per liter of polycarboxylic acid compound selected from citric acid, lactic acid, oxalic acid, and water-soluble salts of said acids, e.g. the sodium, potassium, ammonium, and amine salts.
- polycarboxylic acid compound selected from citric acid, lactic acid, oxalic acid, and water-soluble salts of said acids, e.g. the sodium, potassium, ammonium, and amine salts.
- the invention relates to an aqueous electrolytic stripping bath for the electrolytic stripping of metal coatings composed of nickel and/ or chromium from a metal substrate of non-ferrous metal and to a method of stripping nickel and chromium from non-ferrous substrates using said bath.
- the bath is intended especially for rapid stripping of thick coatings of nickel and/ or chromium which are provided, for example, in the manufacture of dishes, cups, and other so-called hollow ware, which are given a thin silver or precious metal plating over the thick nickel or chromium plate.
- the novel process and bath used herein are characterized by the rapid stripping of thick nickel and/ or chromium coatings from non-ferrous base metals in an aqueous stripping medium containing from 50-95%, preferably 60-85%, of sulfuric acid or water-soluble alkyl or aryl sulfonic acid and from 50-100 grams per liter of polycarboxylic acid compound selected from the group consisting of citric acid, and water-soluble salts of these acids, such as sodium, potassium, ammonium and amine salts, with the coated non-ferrous base being connected as an anode under a voltage of about 8-15 volts, at a current 0 density of about 10 to about amperes per square decimeter, and at a temperature of about 20 to 80 C preferably C.
- the present invention is based on the discovery that a bath combining sulfuric acid and polycarboxylic acid for the electrolytic separation of coatings made of nickel and/ or chromium from base bodies of non-ferrous metals, especially copper and copper alloys, will achieve a very rapid stripping of the coatings and does not attack the non-ferrous base bodies.
- this effect is achieved b means of a bath which consists of -95%, preferably -85%, sulfuric acid or water-soluble alkyl or aryl sulfonic acid and of one or more of the polycarboxylic acids or their salts.
- water-soluble alkyl sulfonic acids are methane sulfonic acid and ethane sulfonic acid.
- water-soluble aryl sulfonic acids are benzene sulfonic acid, toluene sulfonic acid (ortho, meta and para isomers), nitrobenzene sulfonic acid (ortho, meta and para isomers), and xylene sulfonic acid.
- the bath consists of 60-85% sulfuric or sulfonic acid and of 50-100 grams of citric, lactic, or oxalic acid, or their salts, per liter of sulfuric or sulfonic acid, whereby sodium oxalate, potassium oxalate, ammonium oxalate, sodium lactate, potassium lactate, ammonium lactate, sodium citrate, potassium citrate and/or ammonium citrate can be used as salts.
- the invention relates to the process for quick electrolytic stripping of metal coatings from base bodies with the use of the previously described bath, and the process is characterized in accordance with the invention by the fact that one operates at a bath temperature of 20-80 C., preferably 30 C., at a voltage between 8 and 15 volts and a current density of 10-25 amperes per square decimeter, and that no corrosion of the underlying non-ferrous base results from such rapid stripping.
- the base body from which the coating is stripped is connected as the anode, as is well-known.
- EXAMPLE I Composition of the bath sulfuric acidl liter Sodium citrategrams Conditions for the process Voltage-12 volts Current density15 amperes/dm. Bath temperature-30 C.
- EXAMPLE III Composition of the bath 75% nitrobenzenesulfonic acid-1 liter Lactic acid-50 cm.
- Water-soluble salts may be used; these being the sodium, potassium, ammonium, and amine salts.
- An aqueous electrolytic stripping bath for the rapid removal of coatings composed of nickel and/ or chromium from substrates of non-ferrous metals, comprising from 60-85% of a water-soluble sulfur-containing acid selected from the group consisting of sulfuric acid, alkyl sulfonic acid and aryl sulfonic acid as the stripping component and, as the accelerator for said stripping component, from 50-80 grams per liter of a polycarboxylic acid compound 4 selected from the group consisting of citric acid, lactic acid, tartaric acid, oxalic acid, and water-soluble salts of these acids, said bath adapted to rapidly strip thick coatings at a current density of 10-25 amperes per square decimeter at a temperature of 20-80 C.
- a process for electrolytically stripping coatings of nickel and/or chromium from substances on non-ferrous metals comprising inserting a non-ferrous article coated with nickel or chromium into a stripping bath and passing an electric current at 8-15 volts from said article serving as anode to a cathode at a current density of between 10 to 25 amperes per square decimenter and at a temperature of 20-80 C., said stripping bath consisting essentially of from -95% of a water-soluble sulfurcontaining acid selected from the group consisting of sulfuric acid, alkyl sulfonic acid and aryl sulfonic acid as the stripping component and, as the accelerator for said stripping component, from 50-100 grams per liter of a polycarboxylic acid compound selected from the group consisting of citric acid, lactic acid, tartaric acid, oxalic acid, and water-soluble salts of these acids.
- said acid is nitrobenzene sulfonic acid in a strength of 75 and said polycarboxylic acid compound is lactic acid.
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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)
- ing And Chemical Polishing (AREA)
- Electroplating Methods And Accessories (AREA)
- Electroplating And Plating Baths Therefor (AREA)
- Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
Abstract
PROCESS AND AQUEOUS BATH FOR RAPID STRIPPING OF THICK NICKEL AND/OR CHROMIUM COATINGS FROM NON-FERROUS BASE METALS, THE COATED NON-FERROUS BASE BEING CONNECTED AS AN ANODE UNDER A VOLTAGE OF ABOUT 8-15 VOLTS AT A CURRENT DENSITY OF ABOUT 10-25 AMPERES PER SQUARE DECIMETER AND AT A TEMPERATURE OF BETWEEN 20 TO 80*C., THE AQUEOUS STRIPPING CONTAINING FROM 50-95% OF SULFURIC ACID OR WATER-SOLUBLE ALKYL OR ARYL SULFONIC ACID AND 50-100 GRAMS PER LITER OF POLYCARBOXYLIC ACID COMPOUND SELECTED FROM CITRIC ACID, LACTIC ACID, OXALIC ACID, AND WATER-SOLUBLE SALTS OF SAID ACIDS, E.G. THE SODIUM, POTASSIUM, AMMONIUM, AND AMINE SALTS.
Description
United States Patent 3,649,489 PROCESS FOR ELECTROLYTICALLY STRIPPING COATIYGS AND BATH THEREFOR Horst Dillenberg, 26 Kaiser-Wilhelm-Allee, 56 Wuppertal-Elberfeld, Germany No Drawing. Filed May 18, 1970, Ser. No. 38,568 Claims priority, application Germany, May 22, 1969, P 19 26 228.3 Int. Cl. B01k N00 US. Cl. 204-146 5 Claims ABSTRACT OF THE DISCLOSURE Process and aqueous bath for rapid stripping of thick nickel and/ or chromium coatings from non-ferrous base metals, the coated non-ferrous base being connected as an anode under a voltage of about 8-15 volts at a current density of about 10-25 amperes per square decimeter and at a temperature of between and 80 C., the aqueous stripping containing from 50-95% of sulfuric acid or water-soluble alkyl or aryl sulfonic acid and 50-100 grams per liter of polycarboxylic acid compound selected from citric acid, lactic acid, oxalic acid, and water-soluble salts of said acids, e.g. the sodium, potassium, ammonium, and amine salts.
The invention relates to an aqueous electrolytic stripping bath for the electrolytic stripping of metal coatings composed of nickel and/ or chromium from a metal substrate of non-ferrous metal and to a method of stripping nickel and chromium from non-ferrous substrates using said bath. The bath is intended especially for rapid stripping of thick coatings of nickel and/ or chromium which are provided, for example, in the manufacture of dishes, cups, and other so-called hollow ware, which are given a thin silver or precious metal plating over the thick nickel or chromium plate.
The novel process and bath used herein are characterized by the rapid stripping of thick nickel and/ or chromium coatings from non-ferrous base metals in an aqueous stripping medium containing from 50-95%, preferably 60-85%, of sulfuric acid or water-soluble alkyl or aryl sulfonic acid and from 50-100 grams per liter of polycarboxylic acid compound selected from the group consisting of citric acid, and water-soluble salts of these acids, such as sodium, potassium, ammonium and amine salts, with the coated non-ferrous base being connected as an anode under a voltage of about 8-15 volts, at a current 0 density of about 10 to about amperes per square decimeter, and at a temperature of about 20 to 80 C preferably C.
There is a need to remove chemically defective or mechanically damaged nickel or chromium coatings from hollow Ware and similar articles in order to permit the articles to be re-coated and thereafter plated with precious metals, and there is a further need to carry out the stripping process quickly without damaging the non-ferrous metal substrate.
The chemical separation processes used in the prior art have been too slow to gain present commercial acceptance and the present commercial practice is to employ electrolytic stripping to shorten the time in preparing the article for replating. One such commercial method used employs a sulfuric acid bath having a density of 1.57, equivalent to 65% sulfuric acid, for the removal of nickel or chromium coatings from copper base metal, and the etching of the base or damage to the base is inhibited, in this commercial method, by adding small amounts of glycerin, especially when nickel is removed. This sulfuric 3,649,489 Patented Mar. 14, 1972 ICC acid electrolytic stripping method is very slow when thick coatings are to be removed.
In another known electrolytic process for stripping chromium coatings from nickel which covers iron, as described in British Pat. No. 336,532, the chromium is separated from the nickel layer by using an aqueous bath containing a polycarboxylic acid, such as oxalic, tartaric or citric acid. This bath has only limited utility because it strips chromium only and nickel cannot be removed electrolytically using these organic acids.
The present invention is based on the discovery that a bath combining sulfuric acid and polycarboxylic acid for the electrolytic separation of coatings made of nickel and/ or chromium from base bodies of non-ferrous metals, especially copper and copper alloys, will achieve a very rapid stripping of the coatings and does not attack the non-ferrous base bodies. According to the present invention, this effect is achieved b means of a bath which consists of -95%, preferably -85%, sulfuric acid or water-soluble alkyl or aryl sulfonic acid and of one or more of the polycarboxylic acids or their salts.
Illustrative examples of water-soluble alkyl sulfonic acids are methane sulfonic acid and ethane sulfonic acid.
Illustrative examples of water-soluble aryl sulfonic acids are benzene sulfonic acid, toluene sulfonic acid (ortho, meta and para isomers), nitrobenzene sulfonic acid (ortho, meta and para isomers), and xylene sulfonic acid.
Preferably, the bath consists of 60-85% sulfuric or sulfonic acid and of 50-100 grams of citric, lactic, or oxalic acid, or their salts, per liter of sulfuric or sulfonic acid, whereby sodium oxalate, potassium oxalate, ammonium oxalate, sodium lactate, potassium lactate, ammonium lactate, sodium citrate, potassium citrate and/or ammonium citrate can be used as salts.
Furthermore, the invention relates to the process for quick electrolytic stripping of metal coatings from base bodies with the use of the previously described bath, and the process is characterized in accordance with the invention by the fact that one operates at a bath temperature of 20-80 C., preferably 30 C., at a voltage between 8 and 15 volts and a current density of 10-25 amperes per square decimeter, and that no corrosion of the underlying non-ferrous base results from such rapid stripping. The base body from which the coating is stripped is connected as the anode, as is well-known.
Practical tests have shown that all of the above-mentioned coating metals can be separated very rapidly with the bath according to the invention, without attack of the base body made of non-ferrous metal. The stripped metals are deposited as oxides and they must be removed at certain intervals in time from the container for the bath.
Three particularly preferred baths are given by Way of illustration in the following examples:
EXAMPLE I Composition of the bath sulfuric acidl liter Sodium citrategrams Conditions for the process Voltage-12 volts Current density15 amperes/dm. Bath temperature-30 C.
Result With the above bath, nickel coatings of a thickness of microns were completely separated from a base body made of copper within twenty minutes without the base body having been attacked.
3 EXAMPLE II Composition of the bath 75% sulfuric acid-1 liter Citric acid-80 grams Conditions for the process Voltage-12 volts Current density 'amperes/dm. Bath temperature-50 C.
Results With the bath of this example, approximately 8 microns thickness of a layer of metal coating were removed per minute from a base body made of copper.
EXAMPLE III Composition of the bath 75% nitrobenzenesulfonic acid-1 liter Lactic acid-50 cm.
Conditions for the process Voltage-12 volts Current density-20 amperes/dm. Bath temperature40 C.
Results Approximately 6 microns thickness per minute were stripped from a base body made of brass.
From the foregoing examples, it can be seen that coatings of 10 to 200 microns in thickness can be removed in a short time span of from 1 to minutes, a result which cannot be achieved with the prior art electrolytic stripping baths and processes. Despite the rapidity of stripping, no corrosion or chemical attack of the underlying non-ferrous base is observed.
To increase the solubility of the organic sulfonic acids, Water-soluble salts may be used; these being the sodium, potassium, ammonium, and amine salts.
I claim:
1. An aqueous electrolytic stripping bath for the rapid removal of coatings composed of nickel and/ or chromium from substrates of non-ferrous metals, comprising from 60-85% of a water-soluble sulfur-containing acid selected from the group consisting of sulfuric acid, alkyl sulfonic acid and aryl sulfonic acid as the stripping component and, as the accelerator for said stripping component, from 50-80 grams per liter of a polycarboxylic acid compound 4 selected from the group consisting of citric acid, lactic acid, tartaric acid, oxalic acid, and water-soluble salts of these acids, said bath adapted to rapidly strip thick coatings at a current density of 10-25 amperes per square decimeter at a temperature of 20-80 C.
2. A stripping bath as claimed in claim 1, wherein said water-soluble salts of said polycarboxylic acid compounds contain a cation selected from the group consisting of sodium, potassium, ammonium and amine.
3. A process for electrolytically stripping coatings of nickel and/or chromium from substances on non-ferrous metals comprising inserting a non-ferrous article coated with nickel or chromium into a stripping bath and passing an electric current at 8-15 volts from said article serving as anode to a cathode at a current density of between 10 to 25 amperes per square decimenter and at a temperature of 20-80 C., said stripping bath consisting essentially of from -95% of a water-soluble sulfurcontaining acid selected from the group consisting of sulfuric acid, alkyl sulfonic acid and aryl sulfonic acid as the stripping component and, as the accelerator for said stripping component, from 50-100 grams per liter of a polycarboxylic acid compound selected from the group consisting of citric acid, lactic acid, tartaric acid, oxalic acid, and water-soluble salts of these acids.
4. A process as claimed in claim 3, wherein said temperature is from 30-50 C., said acid is sulfuric acid in a concentration of between and and said polycarboxylic acid compound is citric acid.
5. A process as claimed in claim 3, wherein said temperature is 30-50 C. said acid is nitrobenzene sulfonic acid in a strength of 75 and said polycarboxylic acid compound is lactic acid.
References Cited UNITED STATES PATENTS 2,840,521 6/ 1958 Wasserman 204-146 3,260,659 '7/1966 Willing, et a1 204-146 1,863,868 6/1932 McCullough 204-146 OTHER REFERENCES Products Finishing, January 1942, pp. 50, 51, 54-56.
JOHN H. MACK, Primary Examiner T. TUFARIELLO, Assistant Examiner
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE1926228A DE1926228C3 (en) | 1969-05-22 | 1969-05-22 | Bath for the electrolytic removal of metal coatings made of nickel or chrome from base bodies made of non-ferrous metal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| US3649489A true US3649489A (en) | 1972-03-14 |
Family
ID=5734922
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| US38568A Expired - Lifetime US3649489A (en) | 1969-05-22 | 1970-05-18 | Process for electrolytically stripping coatings and bath therefor |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US3649489A (en) |
| AT (1) | AT290943B (en) |
| BR (1) | BR7019185D0 (en) |
| CH (1) | CH508053A (en) |
| DE (1) | DE1926228C3 (en) |
| FR (1) | FR2043620B1 (en) |
| GB (1) | GB1283463A (en) |
| NL (1) | NL7007038A (en) |
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4111767A (en) * | 1977-12-07 | 1978-09-05 | Okuno Chemical Industry Co., Ltd. | Electrolytic stripping bath for removing metal coatings from stainless steel base materials |
| US4221648A (en) * | 1978-07-14 | 1980-09-09 | Petrolite Corporation | Media regeneration in electrofiltration |
| US4233124A (en) * | 1979-10-29 | 1980-11-11 | Oxy Metal Industries Corporation | Electrolytic stripping bath and process |
| US4261804A (en) * | 1979-11-13 | 1981-04-14 | United Technologies Corporation | Selective removal of nickel-based alloys from ferrous-based metals |
| US4264420A (en) * | 1979-10-29 | 1981-04-28 | Oxy Metal Industries Corporation | Electrolytic stripping bath and process |
| US4324626A (en) * | 1979-11-13 | 1982-04-13 | United Technologies Corporation | Selective removal of nickel-based braze alloy from nickel-based metals |
| US4400248A (en) * | 1982-03-08 | 1983-08-23 | Occidental Chemical Corporation | Electrolytic stripping process |
| DE3318598A1 (en) * | 1982-05-27 | 1983-12-01 | Occidental Chemical Corp., 48089 Warren, Mich. | BATH AND METHOD FOR THE ELECTROLYTIC REMOVAL OF COATS FROM COPPER, COPPER ALLOY OR CHROME FROM A FERROUS BASE METAL |
| US4539087A (en) * | 1982-10-29 | 1985-09-03 | Latszereszeti Eszkozok Gyara | Method for electrolytic removal of galvanic nickel, chromium or gold layers from the surface of a copper or copper alloy base and apparatus for carrying out the method |
| US4668355A (en) * | 1985-09-09 | 1987-05-26 | Olin Corporation | Solutions for extracting magnetic particles |
| US4678552A (en) * | 1986-04-22 | 1987-07-07 | Pennwalt Corporation | Selective electrolytic stripping of metal coatings from base metal substrates |
| US4720332A (en) * | 1986-04-21 | 1988-01-19 | Coffey Barry W | Nickel strip formulation |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA1185152A (en) * | 1982-01-22 | 1985-04-09 | Thomas W. Bleeks | Selective chemical removal of hard surface coatings from superalloy substrates |
| EP0214644A3 (en) * | 1985-09-09 | 1988-10-05 | Olin Corporation | Method of producing ferromagnetic particles |
-
1969
- 1969-05-22 DE DE1926228A patent/DE1926228C3/en not_active Expired
-
1970
- 1970-04-29 AT AT390470A patent/AT290943B/en not_active IP Right Cessation
- 1970-04-29 GB GB20693/70A patent/GB1283463A/en not_active Expired
- 1970-05-08 CH CH690770A patent/CH508053A/en not_active IP Right Cessation
- 1970-05-15 NL NL7007038A patent/NL7007038A/xx unknown
- 1970-05-18 US US38568A patent/US3649489A/en not_active Expired - Lifetime
- 1970-05-21 BR BR219185/70A patent/BR7019185D0/en unknown
- 1970-05-22 FR FR7018731A patent/FR2043620B1/fr not_active Expired
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4111767A (en) * | 1977-12-07 | 1978-09-05 | Okuno Chemical Industry Co., Ltd. | Electrolytic stripping bath for removing metal coatings from stainless steel base materials |
| US4221648A (en) * | 1978-07-14 | 1980-09-09 | Petrolite Corporation | Media regeneration in electrofiltration |
| US4233124A (en) * | 1979-10-29 | 1980-11-11 | Oxy Metal Industries Corporation | Electrolytic stripping bath and process |
| US4264420A (en) * | 1979-10-29 | 1981-04-28 | Oxy Metal Industries Corporation | Electrolytic stripping bath and process |
| US4261804A (en) * | 1979-11-13 | 1981-04-14 | United Technologies Corporation | Selective removal of nickel-based alloys from ferrous-based metals |
| US4324626A (en) * | 1979-11-13 | 1982-04-13 | United Technologies Corporation | Selective removal of nickel-based braze alloy from nickel-based metals |
| US4400248A (en) * | 1982-03-08 | 1983-08-23 | Occidental Chemical Corporation | Electrolytic stripping process |
| DE3318598A1 (en) * | 1982-05-27 | 1983-12-01 | Occidental Chemical Corp., 48089 Warren, Mich. | BATH AND METHOD FOR THE ELECTROLYTIC REMOVAL OF COATS FROM COPPER, COPPER ALLOY OR CHROME FROM A FERROUS BASE METAL |
| US4539087A (en) * | 1982-10-29 | 1985-09-03 | Latszereszeti Eszkozok Gyara | Method for electrolytic removal of galvanic nickel, chromium or gold layers from the surface of a copper or copper alloy base and apparatus for carrying out the method |
| US4668355A (en) * | 1985-09-09 | 1987-05-26 | Olin Corporation | Solutions for extracting magnetic particles |
| US4720332A (en) * | 1986-04-21 | 1988-01-19 | Coffey Barry W | Nickel strip formulation |
| US4678552A (en) * | 1986-04-22 | 1987-07-07 | Pennwalt Corporation | Selective electrolytic stripping of metal coatings from base metal substrates |
Also Published As
| Publication number | Publication date |
|---|---|
| CH508053A (en) | 1971-05-31 |
| GB1283463A (en) | 1972-07-26 |
| AT290943B (en) | 1971-06-25 |
| FR2043620A1 (en) | 1971-02-19 |
| FR2043620B1 (en) | 1974-05-24 |
| NL7007038A (en) | 1970-11-24 |
| DE1926228C3 (en) | 1974-02-21 |
| BR7019185D0 (en) | 1973-04-17 |
| DE1926228B2 (en) | 1973-07-05 |
| DE1926228A1 (en) | 1970-11-26 |
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