Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
  • C25D11/02—Anodisation
  • C25D11/04—Anodisation of aluminium or alloys based thereon
  • C25D11/18—After-treatment, e.g. pore-sealing
  • C25D11/20—Electrolytic after-treatment
  • C25D11/22—Electrolytic after-treatment for colouring layers

Definitions

• ABSTRACT Method for electrolytic coloring of oxide layers produced by anodisation on aluminum and aluminum alloys consisting in using one coloring electrolyte which contains at least two metal salts of which each one renders different colors to the others, for example copper and tin salts, the different color sequences being obtained by adjusting the electrolysis AC-current voltage adequately.
• the counter electrode may be of the same metal that is dissolved in form of a salt in the electrolyte.
• salts of the following elements Fe, Co, Ni, Mn, Cr, Bi, As, Sb, Sn, Ag, Cu, Au, Cd, Mo, Ti, Ca, Mg, V, Pb and Zn were accordingly proposed as components of the colouring electrolytes, the various elements and groups of elements as, for example, 80,", N Cl, oxyacids such as from Te, B, Cr and P and organic acids and acid anions such as acetates, tartrates, oxalates and citrates being suggested as anionproducing components of such electroytes.
• NH amino and imino groups are also known as additional cationforming constituents of such electrolytes.
• Metals, metal hydroxides, metal oxides and metal salts have previously been mentioned as effective colouring substances which penetrate the oxide layers under these conditions.
• a typical colour is determined and produced by means of the bath composition and especially by choosing the specific colouring metal salt, the depth of colour being influenced by electrical conditions (voltage/current intensity) and/or the time of exposure to these electrical parameters of the piece to be coloured.
• the present invention concerns a process for the colouring of anodised, protective layers on aluminium and its alloys in a variety of colours by means of an electrolytic treatment of the protective layer with alternating current, using counter electrodes in acidiferous colouring metal salt electrolytes in which there is used a colouring electrolyte containing at least two colouring metal salts, each salt establishing its own variety of colours and that the said variety of colours are established during the said electrolytic treatment in one and the same colouring electrolyte by means of differing heights in electrical voltage.
• the colour to be produced in the anodised layer is selectable from two colour scales obtainable in one and the same colour electrolyte containing at least two colouring metal salts by adjusting the electrical current/voltage conditions and duration of treatment, whereby changing these conditions leads to the production of the other colour scale.
• the conventional colouring electrolytes comprising Ni or C0 salts, or the Sn salts, can only render one colour sequence.
• a successfully operating electrolyte comprising a combination of two colour metal salts is obtained if two colouring metal salts are selected whereby each renders its own individual colour and when those conventional parameters of anion kinds and pH values (easily discoverable by routine methods) are applied by which each of the two said metal salts of the colouring electrolyte can produce its own colouring effects in anodised layers.
• the latter condition is quite easily accomplished provided that each of the two metal salts is individually colour-electrolytic effective in equal or similar pH ranges.
• such suitable parameters can also be determined and applied by selecting and adding suitable anion-producing means or coloured complex compound materials or other means including buffer substances which all said means result in a modification in the composition of the bath thereby making it suitable for the formation of two different coloured pigments.
• the one kind of metal ion and also its degree of valency is essentially responsible for one colour scale, the other metal ion type for another, similarly obtainable, colour scale. Consequently concentrations of kinds of metallic ions have to be selected by experiment, according to the aim to be achieved, since any excessively low concentration or activity of one metallic ion kind makes the production of two different colour scales according to the invention by means of one and the same colour electrolyte impossible.
• the time program for applying the selected voltage steps, the duration as such, and the final voltage value all influence the colours of the two different colour scales produced according to the invention and can easily be determined for the present purposes by tests.
• the length of treatment time influences the depth of colour although it noticeably less influences the kind of obtainable colour scale, similarly to the known methods for procuring only one colour sequence.
• the concentration of further additions determines the appearance of both colour scales.
• the expert may select, for the method according to the invention, the most practicable material for the counter electrode as for example graphite, aluminium or metal carbides or for example a counter electrode of a metal which represents, as a composition, part of the colouring electrolyte.
• the suitable adjustment of pl-l value and temperature of the colouring electrolyte will also be selected by means of tests or by theoretical calculations for each specific combination of metal salts which will render the desired two colour sequences.
• anodised layers produced by any conventional methods may be coloured according to the invention process. Excellent results were found for example on anodised layers produced in baths which contain, as main component, acids of the sulfuric, chromic and sulfamic group.
• a preferred embodiment of the method according to the invention rendering two characteristic colour scales was found when a colouring electrolyte containing at least two kinds of differently colouring ions of the metals in the Cu, Ag, Cd, Mn. Sn, Ni, Co and Mo group and anion-forming acids or acid radicals containing one acid or one salt of the citric, tartaric, maleic, succinic, fumaric, adipic, acetic, lactic, malonic, phthalic, sulfuric, selenic, phosphoric, fluoboric, formic, sulfamic, sulfosalicylic, sulfanilic and phenosulfonic acids group.
• the sulfuric acid may be totally or partially replaced by other acids, for example, by tartaric, oxalic, succinic, phthalic, sulfamic, sulfosalicylic, citric acids and otherst
• colouring electrolytes are used which, as anion-producing acids or acid radicals, contain at least two different acids or their salts from the group of acids specified in the previous paragraph.
• Another, especiallyadvantageous embodiment of the present invention consists of utilizing a colouring electrolyte containing at least copper and tin ions, and as anion-producing acids at least one acid or one salt of the citric, tartaric, maleic, succinic, fumaric, adipic, acetic, lactic, malonic, phthalic acids group (1), and at least one additional acid from the sulfuric, selenic, phosphoric, fluoboric, formic, sulfamic, sulfosalycilic, sulfanilic, phenolsulfonic acids group (2).
• a colouring electrolyte may contain for example:
• the colouring electrolyte contains the following concentrations: Preferably:
• the following organic acids under observance of all other necessary requirements, render no' colouring or only one colour sequence: hydrofluoric acid, nitric acid, chromic acid.
• the colouring electrolyte contains:
• said colour- .ing electrolyte contains at least two kinds of differently colouring ions of the metals in the Cu, Ag, Cd, Mn, Sn, Ni, Co and Mo group and as anion-producing acids at least one acid or one salt of the citric, tartaric, maleic, succinic fumaric, adipic, acetic, lactic,malonic,phthalic, sulfuric, selenic, phosphoric, fluoboric, formic, sulfamic, sulfosalicylic, phenolsulfonic acids group.
• the said colouring electrolyte contains at least Cu ions and tin ions, and as anion-producing acids at least one acid or one salt of the acids of the citric, tartaric, maleic, succinic, fumaric, adipic, acetic, lactic, malonic, phthalic acids group and at least one further acid or salt of an acid of the sulfuric, selenic, phosphoric, fluoboric, formic, su'lfamic, sulfo-salicylic, sulfanic, phenosulfonic acids group.
• a colouring louring electrolyte containing: electrolyte is used containing 0.5 up to 100 g/l tin-ll-sulfate 13 up to 17 g/l tin-ll-sulfate 0.5 up to 70 g/l CuSO 5 H 0 5 up to g/l CuSO; 5 H O 0.5 up to 100 g/l citric acid I 8 up to l2 g/l citric acid 0.5 up to 100 g/l sulfuric acid cone. 8 up to 12 g/l sulfuric acid. 6.
• electrolyte is used containing: electrolyte is used containing 0.5 up to 100 g/l tin-ll-sulfate 13 up to 17 g/l tin-ll-sulfate 0.5 up to 70 g/l CuSO 5 H 0 5 up to g/l CuSO; 5 H O 0.5 up to 100 g/l citric acid I 8 up to l2 g/l citric acid 0.5 up to 100

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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)
• Electroplating Methods And Accessories (AREA)
• Electrochemical Coating By Surface Reaction (AREA)

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Cited By (16)

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Citations (4)

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• 1970
  • 1970-04-02 CH CH486770A patent/CH535835A/de not_active IP Right Cessation
• 1971
  • 1971-03-26 SE SE7103984A patent/SE373607B/xx unknown
  • 1971-03-29 BE BE764954A patent/BE764954A/xx not_active IP Right Cessation
  • 1971-03-31 DK DK152971A patent/DK144481C/da active
  • 1971-04-01 AT AT279671A patent/AT323497B/de not_active IP Right Cessation
  • 1971-04-01 NO NO1246/71A patent/NO131551C/no unknown
  • 1971-04-01 FI FI710923A patent/FI51501C/fi active
  • 1971-04-01 US US00130484A patent/US3787295A/en not_active Expired - Lifetime
  • 1971-04-01 FR FR7111554A patent/FR2085799B1/fr not_active Expired
  • 1971-04-02 DE DE19712116251 patent/DE2116251B2/de not_active Ceased
  • 1971-04-02 NL NLAANVRAGE7104433,A patent/NL175200C/xx not_active IP Right Cessation
  • 1971-04-19 GB GB2637671*A patent/GB1342776A/en not_active Expired

Patent Citations (4)

Non-Patent Citations (2)

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