US3649489A - Process for electrolytically stripping coatings and bath therefor - Google Patents

Process for electrolytically stripping coatings and bath therefor Download PDF

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Publication number
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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acid
bath
stripping
water
coatings
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US38568A
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English (en)
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Horst Dillenberg
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    • CCHEMISTRY; METALLURGY
    • C25ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25FPROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F5/00Electrolytic 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 And Plating Baths Therefor (AREA)
  • Electroplating Methods And Accessories (AREA)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
US38568A 1969-05-22 1970-05-18 Process for electrolytically stripping coatings and bath therefor Expired - Lifetime US3649489A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE1926228A DE1926228C3 (de) 1969-05-22 1969-05-22 Bad zum elektrolytischen Ablösen von Metallüberzügen aus Nickel oder Chrom von Grundkörpern aus Buntmetall

Publications (1)

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US3649489A true US3649489A (en) 1972-03-14

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US38568A Expired - Lifetime US3649489A (en) 1969-05-22 1970-05-18 Process for electrolytically stripping coatings and bath therefor

Country Status (8)

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US (1) US3649489A (enExample)
AT (1) AT290943B (enExample)
BR (1) BR7019185D0 (enExample)
CH (1) CH508053A (enExample)
DE (1) DE1926228C3 (enExample)
FR (1) FR2043620B1 (enExample)
GB (1) GB1283463A (enExample)
NL (1) NL7007038A (enExample)

Cited By (12)

* Cited by examiner, † Cited by third party
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 (de) * 1982-05-27 1983-12-01 Occidental Chemical Corp., 48089 Warren, Mich. Bad und verfahren fuer die elektrolytische entfernung von ueberzuegen aus kupfer, kupferlegierung oder chrom von einem eisenhaltigen grundmetall
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)

* Cited by examiner, † Cited by third party
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

Cited By (12)

* Cited by examiner, † Cited by third party
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 (de) * 1982-05-27 1983-12-01 Occidental Chemical Corp., 48089 Warren, Mich. Bad und verfahren fuer die elektrolytische entfernung von ueberzuegen aus kupfer, kupferlegierung oder chrom von einem eisenhaltigen grundmetall
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
FR2043620B1 (enExample) 1974-05-24
NL7007038A (enExample) 1970-11-24
CH508053A (de) 1971-05-31
AT290943B (de) 1971-06-25
DE1926228A1 (de) 1970-11-26
FR2043620A1 (enExample) 1971-02-19
BR7019185D0 (pt) 1973-04-17
DE1926228C3 (de) 1974-02-21
DE1926228B2 (de) 1973-07-05
GB1283463A (en) 1972-07-26

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