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

• the present invention relates to an electrolytic bath for removing metallic coatings, such as nickel, chromium, zinc, tin, copper, cadmium or silver plate, from steel parts, the bath containing, in aqueous solution, nitric acid and/or its salts with inorganic and/or organic bases, organic acids and/or their salts, and a watersoluble halogen compound.
• metallic coatings such as nickel, chromium, zinc, tin, copper, cadmium or silver plate
• German published Specification Offenlegungsschrift l 963 415 describes an electrolytic demetallizing bath containing amines, nitrates, organic acids and water-soluble chlorine compounds.
• the above baths contain amines or aminoalcohols, especially those which have up to carbon atoms.
• the amines include primary, secondary and tertiary amines, such as trimethylamine, diethyland triethylamines, ethylene triamines, mono-, diand triethanol.
• the organic solvents used in the above baths are formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, lactic acid and citric acid, or the alkali metal and/or ammonium salts thereof.
• the chlorine or bromine compounds are accelerators necessary to effect the removal of metal layers, particularly semi-polished nickel, within a reasonable period of time.
• they are activators of considerably increased corrosiveness for the base metal. Needless to say, it is practically impossible completely to inhibit corrosion of the base material, in an anodicelectrolytic operation.
• the object of the present invention can unexpectedly be achieved with the use of a bath, wherein the halogen compound is a soluble iodine compound, preferably an iodide.
• the baths of the present invention contain, as further known constituents, nitric acid and/or its salts with an alkali metal hydroxide or ammonium hydroxide or with an aliphatic amine or aminoalcohol or a blend of these salts, in proportions within the range 15 and 60 g/l, as well as organic acids, such as formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, lactic acid or citric acid, or blends thereof, their salts or salt blends, in preferred proportions within the range 10 and 40 g/l.
• organic acids such as formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, lactic acid or citric acid, or blends thereof, their salts or salt blends, in preferred proportions within the range 10 and 40 g/l.
• the difficultly soluble iodine compounds can be used in the form of solid phase material lying on the bottom of the bath, or to be placed in anode bags, for example, which'are suspended from a holder and continually contacted with the electrolyte.
• the electrolytic demetallization being critically determined by the addition of the halogen compound, it is absolutely necessary to avoid overfeeding of the bath with halogen.
• difficultly soluble iodine compounds e.g. copper-I-iodide, which produce a bath wherein the iodine content need not be controlled analytically. Overfeeding with iodine is practically excluded as the bath having the difficultly soluble iodine compounds therein is a self-controlling demetallization bath which is easy to handle.
• Baths containing soluble iodine compounds enable metal coatings to be removed from steel at least as rapidly as with the use of analogous baths containing chlorine or bromine compounds, and they combine this with considerably reduced corrosiveness for the steel itself.
• Baths containing readily and difficultly soluble chlorine and bromine compounds, respectively, and baths containing difficultly soluble iodine compounds are compared with each other hereinafter.
• the basic electrolyte was composed of: g/l of triethanolamine, 48 g/l of HNO of 63 strength, and
• EXAMPLE 2 The basic electrolyte and the electrolytic conditions were the same as those used in Example 1, save that the base material was stainless steel (material No. I4 571 (German Industrial Standard X CrNiMoTi 1810)).
• Electrolytic bath for removing metallic coatings, such as nickel, chromium, zinc, tin, copper, cadmium or silver plate, from steel parts the bath containing, in aqueous solution,
• a at least one substance selected from the group consisting of nitric acid and its salts with inorganic and organic bases;
• a water-soluble halogen compound being characterized in that the halogen compound is a soluble iodine compound.
• an organic acid being selected from the group consisting of formic acid, acetic acid, propionic acid, oxalic acid, malonic acid, lactic acid or citric acid.
• the bath as claimed in claim 13 having a pH-value between 6.5 and 7.5.

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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 And Plating Baths Therefor (AREA)
• Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
• ing And Chemical Polishing (AREA)

Applications Claiming Priority (1)

Publications (1)

Family

ID=5901294

Family Applications (1)

Country Status (9)

Cited By (13)

Families Citing this family (1)

Citations (4)

• 1973
  • 1973-12-20 DE DE2363352A patent/DE2363352C3/de not_active Expired
• 1974
  • 1974-12-11 CH CH1648374A patent/CH603833A5/xx not_active IP Right Cessation
  • 1974-12-17 US US533719A patent/US3912603A/en not_active Expired - Lifetime
  • 1974-12-18 SE SE7415930A patent/SE7415930L/xx unknown
  • 1974-12-18 IT IT54626/74A patent/IT1026066B/it active
  • 1974-12-18 GB GB5461474A patent/GB1444699A/en not_active Expired
  • 1974-12-20 FR FR7442318A patent/FR2255397B1/fr not_active Expired
  • 1974-12-20 BE BE151780A patent/BE823676A/xx not_active IP Right Cessation
  • 1974-12-20 NL NL7416696A patent/NL7416696A/xx not_active Application Discontinuation

Patent Citations (4)

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