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

• the invention relates to a process for the electrolytic metal salt coloring of aluminum, in which a defined oxide layer is first generated by means of direct current in an acidic solution and this is then colored by means of alternating current using an acidic, preferably sulfuric acid, electrolyte containing tin (II) salts.
• anodized aluminum is colored in the aqueous phase with suitable organic and / or inorganic compounds without the influence of electricity.
• the process of electrolytic coloring can be carried out in one or two stages.
• aluminum is usually both anodized and colored using direct current in one process step, with sulfuric acid mixed with suitable organic acids, e.g. Maleic acid, oxalic acid, sulfosalicylic acid, sulfophthalic acid, is used.
• suitable organic acids e.g. Maleic acid, oxalic acid, sulfosalicylic acid, sulfophthalic acid
• the so-called electrolytic metal salt coloring a defined oxide layer is first generated in the first process step using direct current with sulfuric acid or sulfuric acid and oxalic acid as the electrolyte liquid.
• the anodized aluminum is then electrolytically colored in a second process step using alternating current and the use of solutions of certain metal salts or metal salt mixtures.
• the electrolytic coloring processes are mainly used for coloring aluminum due to their advantages such as higher light resistance and economy.
• the electrolytic metal salt coloring clearly outweighs the lower costs and therefore greater economy, with tin (II) sulfate-containing solutions preferably being used here.
• the present invention relates to the two-step process of electrolytic metal salt coloring.
• color tones can be produced between light silver, light, medium and dark bronze to black, which are resistant to light and are normal atmospheric influences.
• Sulfuric acid tin (II) sulfate-containing solutions such as those used for the electrolytic metal salt coloring of aluminum, however, increasingly separate tin compounds which are sparingly soluble and which are ineffective for coloring aluminum by hydrolysis and / or oxidation in accordance with the service life.
• the invention is therefore based on the object of finding compounds which do not have these disadvantages, and are therefore more environmentally friendly and as completely as possible prevent the formation of precipitates in tin (II) sulfate-containing solutions when standing.
• this object can be achieved in a simple manner by carrying out the electrolytic metal salt dyeing process with an electrolyte containing tin (II) salts which contains 1-10 g / l of one or more iron (II) salts (s) of acids from the group comprising sulfuric acid, a sulfonic acid having at most 8 carbon atoms and the amidosulfonic acid.
• an electrolyte containing tin (II) salts which contains 1-10 g / l of one or more iron (II) salts (s) of acids from the group comprising sulfuric acid, a sulfonic acid having at most 8 carbon atoms and the amidosulfonic acid.
• the additives are effective in an amount of 1 - 10 g / l.
• About 5 g / l of one or more of the compounds mentioned in the patent claim is preferably added to the sulfuric acid electrolyte containing tin (II) salts.
• coals hydrogen radical can be an optionally substituted alkyl, aryl or alkaryl radical.
• a particular advantage of the process according to the invention is that the addition of the aforementioned iron (II) salts, in addition to the suppression of the formation of sparingly soluble precipitates, results in a considerable color-enhancing effect in many cases.
• a particularly preferred embodiment of the process according to the invention in view of both the color-enhancing effect and the suppression of sparingly soluble tin-containing precipitates is therefore that the electrolyte containing iron (II) salts used is one which contains iron (II) sulfosalicylate and / or contains iron (II) sulfophthalate.
• the electrolytes used for the coloring and containing the additives according to the invention can contain further compounds as are known from the prior art. For example, it is possible to add amines or phenols or phenol derivatives to these solutions in a manner known per se.
• scmit succeeds in a simple and particularly economical manner in practically completely preventing the formation of sparingly soluble precipitates in sulfuric acid tin (II) salt solutions and at the same time achieving a deepening of color during the coloring of the aluminum.
• the efficacy of the compounds according to the invention contained in the electrolyte was determined by that 20 ml 0, sulfate of a tin sulfate solution containing sulfuric acid, as it is used for the electrolytic coloring of aluminum for use with 14 g of tin (II) and 16 g conc. Sulfuric acid / l as such or with the compounds additionally listed in the following table were left to stand for 1 week. The precipitates that formed were filtered off and determined by weight analysis.
• the electrolytic coloring of previously anodized aluminum was carried out with the individual solutions.
• the sanctities (L) of the colored aluminum sheets obtained in this way were determined after compression and drying using a color and color difference measuring device, the measuring device being scaled from 0-100 and meaning 100 white and O black. Differences in brightness could thus be correctly determined in an objective manner.
• Group I lists free acids and amines, phenolsulfonic acid, cresolsulfonic acid and amidosulfonic acid being added in accordance with the prior art to tin sulfate solutions containing sulfuric acid. With the exception of the environmentally harmful cresol sulfonic acid, the suppression of the formation of tin-containing precipitate is completely insufficient.
• the results of group II show that when compounds to be used according to the invention are added, the compound which forms tin-containing Kiederhchlag is practically negligible.
• the color depth of the colored aluminum is not affected.
• iron (II) sulfosalicylate and iron (II) sulfophthalate are used, the color intensity is additionally markedly increased, and when iron (II) sulfamate and iron (II) sulfonates are used, the color intensity is markedly increased.
• the additives according to group III in turn have the effect that practically no appreciable precipitate forms, while the color intensity of the colored aluminum is considerably increased in all cases. It follows from this that the iron (II) compounds mentioned according to the invention reliably suppress the formation of precipitates in solutions containing tin (II) sulfate, iron (II) sulfonates and iron (II) sulfamates as such or in combination with sulfosalicylic acid or sulfophthalic acid also lead to an intensification of the color intensity.
• Aluminum sheets (100 mm ⁇ 50 mm ⁇ 2 mm) were degreased in a known manner, alkaline and acid pickled, rinsing with water being carried out in each case between the individual operations, and using direct current with aqueous sulfuric acid (200 g conc. H 2 SO 4 / l) anodized as electrolyte liquid in such a way that an anodized layer of 20 ⁇ m was produced.
• Cathode material stainless steel; current density: 1.3 - 1.5 amp./dm 2
• current density 1.3 - 1.5 amp./dm 2
• S o anodized aluminum sheet was after rinsing with water in 300 ml of an electrolyte containing 14 g of tin (II) sulfate, 16 g conc. Contained sulfuric acid and 5 g of iron (II) sulfo-salicylate / l, immersed, the liquid being in a rectangular glass cell.
• the electrolytic metal salt coloring was carried out using two stainless steel electrodes after applying AC voltage and an electrolyte temperature of 18-20 ° C. within 5 minutes. The voltage was continuously raised to 15 volts within the first minute and kept constant for 4 minutes. The colored aluminum sheet was compacted in a known manner after the coloring process. The brightness value determined using the colorimeter was 12.7. The amount of precipitation of 200 ml of the same electrolyte fluid was 4 mg after 1 week of standing.
• Example 2 The procedure was analogous to Example 1, except that only a sulfuric acid tin (II) sulfate solution, the 14 g tin (II) sulfate and 16 g conc. Sulfuric acid / l contained, was used instead of the electrolyte liquid mentioned in Example 1.
• the brightness determined using the colorimeter was 22.0 and the amount of precipitation of 200 ml of this solution after 1 week of standing was 1000 mg.
• Example 2 The procedure was analogous to Example 1, with a solution containing 14 g of tin (II) sulfate, 16 g of conc. Contained sulfuric acid and 5 g of iron (II) sulfamate / 1 was used.
• the brightness determined using the colorimeter was 18.8.
• the amount of precipitation of 200 ml of this solution after 1 week of standing was 6 mg.
• Example 2 The procedure was analogous to Example 1, with a solution containing 14 g of tin (II) sulfate, 16 g of conc. Contains sulfuric acid, 5 g iron (II) sulfate and 5 g sulfophthalic acid / 1.
• the brightness determined with the color measuring device was 13.4.
• the amount of precipitation of 200 ml of this solution was 7 mg after standing for 1 week.
• Example 2 The procedure was analogous to Example 1, with a solution containing 14 g of tin (II) sulfate, 16 g of conc. Contains sulfuric acid and 5 g of iron (II) sulfamate and 10 g of aminoethylethanolamine / l.
• the brightness determined using the colorimeter was 18.1.
• the amount of precipitation of 200 ml of this solution was 46 mg after standing for 1 week.
• Example 2 The procedure was analogous to Example 1, with a solution containing 14 g of tin (II) sulfate, 16 g of conc. Contains sulfuric acid and 10 g aminoethylethanolamine / l was used.
• the brightness determined using the colorimeter was 19.0.
• the amount of precipitation of 200 ml of this solution was 820 mg after standing for 1 week.
• Example 2 The procedure was analogous to Example 1, with a solution containing 14 g of tin (II) sulfate and 16 g as the electrolyte liquid conc. Contains sulfuric acid, 10 g phenolsulfonic acid and 5 g ice (II) sulfamate / l.
• the brightness determined using the colorimeter was 15.8.
• the amount of precipitation of 200 ml of this solution was 66 mg after standing for 1 week.
• Example 2 The procedure was analogous to Example 1, with a solution containing 14 g of tin (II) sulfate, 16 g of conc. Contained sulfuric acid and 10 g phenolsulfonic acid / 1 was used.
• the brightness determined using the colorimeter was 16.5.
• the amount of precipitation of 200 ml of this solution was 420 mg after standing for 1 week.
• Example 2 The procedure was analogous to Example 1, with a solution containing 14 g of tin (II) sulfate, 16 g of conc. Containing sulfuric acid, 10 g cresol sulfonic acid and 5 g iron (II) sulfamate / 1 was used.
• the brightness determined using the colorimeter was 13.8.
• the amount of precipitation of 200 ml of this solution was 8 mg after standing for 1 week.
• the brightness determined using the colorimeter was 14.5.
• the amount of precipitation of 200 ml of this solution was 18 mg after standing for 1 week.

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• 1978
  • 1978-11-18 DE DE2850136A patent/DE2850136B2/de not_active Ceased
• 1979
  • 1979-09-05 AT AT79103288T patent/ATE87T1/de active
  • 1979-09-05 EP EP79103288A patent/EP0011097B1/fr not_active Expired
  • 1979-10-19 BR BR7906756A patent/BR7906756A/pt not_active IP Right Cessation
  • 1979-11-14 US US06/093,990 patent/US4401525A/en not_active Expired - Lifetime
  • 1979-11-16 DK DK486579A patent/DK486579A/da not_active Application Discontinuation

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