US3617456A - Bath for the electrolytic stripping of galvanic coatings made of nickel, chromium or gold from base bodies made of copper, copper alloys, silver, zinc or titanium - Google Patents

Bath for the electrolytic stripping of galvanic coatings made of nickel, chromium or gold from base bodies made of copper, copper alloys, silver, zinc or titanium Download PDF

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Publication number
US3617456A
US3617456A US771349A US3617456DA US3617456A US 3617456 A US3617456 A US 3617456A US 771349 A US771349 A US 771349A US 3617456D A US3617456D A US 3617456DA US 3617456 A US3617456 A US 3617456A
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Prior art keywords
phenol
bath
stripping
copper
silver
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US771349A
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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

  • the present invention relates to a novel electrolyticstripping bath for the detachment of galvanic deposits of chromium, nickel or gold from base metal bodies made of copper and copper alloys, silver, zinc, or titanium, the main stripping component of the bath consisting of an aqueous solution of a water-soluble salt of thiocyanic acid,-preferably a solution of ammonium thiocyanate, in the presence of a watersoluble phenol.
  • the water -soluble phenol is selected from the group consisting of phenol, pyrocatechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, oxyhydroquinone, nitrophenol, dinitrophenol, nitropyrocatechol, cresol, nitrocresol, thymol, nitrothymol, xylenol and nitroxylenol.
  • the amount of phenol which is employed is lessthan the amount of ammonium thiocyanate. Without the phenol, the electrolytic stripping is inefficient because the base metal is pitted and corroded by the electrolytic-stripping solution.
  • lt is known to strip copper, silver, zinc or titanium objects of their defective coatings of the above-mentioned types by dipping them into a suitable chemical bath, e.g., a strong 1 mineral acid.
  • a suitable chemical bath e.g., a strong 1 mineral acid.
  • such chemical baths require long coatings electrolytically in strong sulfuric acid but, in this case, the base material is substantially attacked and the stripping time is much too long.
  • the defective coatings of the above-mentioned types can be detached more effectively and more rapidly by the electrolytic method, whereby the object that is to be treated is dipped into a galvanic bath as the anode and the bath is adjusted with a pitting preventative agent consisting of a water-soluble phenol which is present in anamount less than the dry weight of the thiocyanate salt.
  • the present invention thus provides a galvanic bath for the electrolytic detachment of galvanic coatings of chromium, nickel, or gold from base bodies of copper, copper alloys, silver, zinc or titanium which overcomes the disadvantages of the known thiocyanate salt baths.
  • the present invention also provides the advantage that a waterrepellent layer permeable to the stripping current is formed on the base material consisting of copper, copper alloys, silver, zinc or titanium during the detaching process and this layer prevents corrosion of the base body.
  • the protective layer can be removed later on by dipping the base body into a diluted caustic soda solution.
  • phenol C H OH and/or nitrophenol C I-LNOOH are preferred to use since these phenols have good solubility and are of relatively low cost.
  • dihydroxybenzene Panechol, resorcinol, hydroquinone
  • trihydroxybenzene pyrogallol, phloroglucinol, oxyhydroxyquinone
  • their nitro compounds especially nitropyrocatechol C,l-l,N0,(0H dinitrophenol C H,(NO ),Ol-I, as additive to the bath.
  • the homologues of the phenol for example, cresol, thymol or xylenol, and their nitro compounds are also suitable as additives to the bath.
  • All of the foregoing phenols of the invention are seen to be water-soluble aromatic hydroxyl compounds with at least one unsubstituted hydroxyl in the benzene ring.
  • those baths have proven to be particularly suitable which contain 50 to 300 grams of ammonium thiocyanate and 5 to grams of a phenol, such as C l-LOH, per liter of liquid bath. 7
  • the base body made of copper, copper alloys, silver, zinc or titanium, which is to be freed of its metallic coating, dull-finish nickel for an example, is immersed in the bath and connected as an anode.
  • a stainless steel metal sheet can be used as cathode.
  • 8 ampere/dm. is provided.
  • the pH value of the bath lies 6 to 6.5 and does not need to be regulated by the addition of any buffers or other acidity regulating chemicals.
  • EXAMPLE A solution consisting of 75 g. of ammonium thiocyanate and 50 g. of phenol per one liter of water was produced.
  • the base body was connected as the anode and a metal plate made of stainless steel was used as cathode.
  • An aqueous electrolytic stripping bath to remove nickel, chromium, or gold coatings from copper, copper alloys, silver, zinc or titanium metal articles comprising water-soluble thiocyanate as the stripping component in an amount of 50-300 grams per liter and a phenol which is a water-soluble aromatic hydroxyl compound with at least one unsubstituted hydroxyl in the benzene ring to accelerate the stripping and reduce corrosion of the base metal in an amount of 5-80 grams per liter.
  • phenol is selected from the group consisting of phenol, pyrocatechol, resorcinol, hydroquinone, pyrogallol, phloroglucinol, oxyhydroquinone, nitrophenol, dinitrophenol,
  • a stripping bath as claimed in claim 1 phenol is xylenol.

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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)
  • Prevention Of Electric Corrosion (AREA)
US771349A 1968-10-15 1968-10-28 Bath for the electrolytic stripping of galvanic coatings made of nickel, chromium or gold from base bodies made of copper, copper alloys, silver, zinc or titanium Expired - Lifetime US3617456A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
BE722317 1968-10-15
FR171185 1968-10-24
US77134968A 1968-10-28 1968-10-28

Publications (1)

Publication Number Publication Date
US3617456A true US3617456A (en) 1971-11-02

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US771349A Expired - Lifetime US3617456A (en) 1968-10-15 1968-10-28 Bath for the electrolytic stripping of galvanic coatings made of nickel, chromium or gold from base bodies made of copper, copper alloys, silver, zinc or titanium

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US (1) US3617456A (sv)
BE (1) BE722317A (sv)
FR (1) FR1589902A (sv)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793172A (en) * 1972-09-01 1974-02-19 Western Electric Co Processes and baths for electro-stripping plated metal deposits from articles
US3819494A (en) * 1973-03-29 1974-06-25 Fountain Plating Co Inc Method of removing braze
US4233124A (en) * 1979-10-29 1980-11-11 Oxy Metal Industries Corporation Electrolytic stripping bath and process
US4264419A (en) * 1979-10-09 1981-04-28 Olin Corporation Electrochemical detinning of copper base alloys
US4264420A (en) * 1979-10-29 1981-04-28 Oxy Metal Industries Corporation Electrolytic stripping bath and 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
CN106149042A (zh) * 2016-06-24 2016-11-23 惠州市博美环保新材料有限公司 一种锌合金电解剥铜剂

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US908937A (en) * 1908-02-18 1909-01-05 Kings Norton Metal Company Ltd Removal of metallic plating, coating, or fouling from metallic or other surfaces.
US2200782A (en) * 1935-05-23 1940-05-14 Metal & Thermit Corp Detinning
US2463190A (en) * 1946-07-01 1949-03-01 Crowell Collier Publishing Com Method of producing nickel powder from printing press plates and the like
US2596307A (en) * 1947-11-05 1952-05-13 Charles Litzenberg Process of electrostripping electrodeposited metals
US2706171A (en) * 1953-03-09 1955-04-12 Enthone Stripping chromium plating from zinc electrolytically
US2735810A (en) * 1956-02-21 Cathode

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2735810A (en) * 1956-02-21 Cathode
US908937A (en) * 1908-02-18 1909-01-05 Kings Norton Metal Company Ltd Removal of metallic plating, coating, or fouling from metallic or other surfaces.
US2200782A (en) * 1935-05-23 1940-05-14 Metal & Thermit Corp Detinning
US2463190A (en) * 1946-07-01 1949-03-01 Crowell Collier Publishing Com Method of producing nickel powder from printing press plates and the like
US2596307A (en) * 1947-11-05 1952-05-13 Charles Litzenberg Process of electrostripping electrodeposited metals
US2706171A (en) * 1953-03-09 1955-04-12 Enthone Stripping chromium plating from zinc electrolytically

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3793172A (en) * 1972-09-01 1974-02-19 Western Electric Co Processes and baths for electro-stripping plated metal deposits from articles
US3819494A (en) * 1973-03-29 1974-06-25 Fountain Plating Co Inc Method of removing braze
US4264419A (en) * 1979-10-09 1981-04-28 Olin Corporation Electrochemical detinning of copper base alloys
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
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
CN106149042A (zh) * 2016-06-24 2016-11-23 惠州市博美环保新材料有限公司 一种锌合金电解剥铜剂

Also Published As

Publication number Publication date
FR1589902A (sv) 1970-04-06
BE722317A (sv) 1969-03-14

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