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WO2004035876A1 - Procede pour nettoyer et passiver des surfaces d'alliages legers - Google Patents

Procede pour nettoyer et passiver des surfaces d'alliages legers Download PDF

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Publication number
WO2004035876A1
WO2004035876A1 PCT/EP2002/011299 EP0211299W WO2004035876A1 WO 2004035876 A1 WO2004035876 A1 WO 2004035876A1 EP 0211299 W EP0211299 W EP 0211299W WO 2004035876 A1 WO2004035876 A1 WO 2004035876A1
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WO
WIPO (PCT)
Prior art keywords
phosphoric acid
solution
light metal
metal alloy
alcohol
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/EP2002/011299
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German (de)
English (en)
Inventor
Wolf-Dieter Franz
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Individual
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Individual
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Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to AU2002338880A priority Critical patent/AU2002338880A1/en
Priority to PCT/EP2002/011299 priority patent/WO2004035876A1/fr
Publication of WO2004035876A1 publication Critical patent/WO2004035876A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25F—PROCESSES FOR THE ELECTROLYTIC REMOVAL OF MATERIALS FROM OBJECTS; APPARATUS THEREFOR
    • C25F1/00—Electrolytic cleaning, degreasing, pickling or descaling
    • 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

Definitions

  • This invention relates to a new method for treating surfaces of light metal alloys.
  • the aim of the treatment is to clean and preserve the cleaned surface to a certain extent.
  • the light metal alloys to which this invention is directed contain a substantial proportion of Al and / or a substantial proportion of Mg.
  • oxidation is to be understood in a general chemical sense here, so it includes, in addition to the reaction with oxygen, which is suitable for alloys with a high Al content, also a reaction with fluoride ions for alloys with a higher Mg content.
  • the known cleaning and passivation processes are disadvantageous in part because they contain substances which are problematic to health, such as nitric acid, which releases nitrous gases.
  • this invention is based on the technical problem of specifying a method for cleaning and passivating light metal alloy surfaces which is efficient both in terms of its cleaning properties and in terms of its insensitivity to the alloy composition and in economic terms.
  • the invention relates to a method for cleaning light metal alloy surfaces, in which the surface is passivated by an oxidation step, characterized by a treatment step in a solution containing phosphoric acid and an alcohol, in which the surface is anodically switched.
  • the anodic cleaning method according to the invention achieves a very thorough and at the same time broad cleaning effect.
  • the anodic cleaning step in the solution with phosphoric acid and the alcohol has a good efficiency in terms of degreasing and etching the surface and is also able to remove problematic residues such as polysilane release agents.
  • a certain inhibiting effect is inherent in the cleaning method according to the invention, in that excessive removal of material is prevented by anodic oxygen reactions of the light metal surface.
  • the cleaning effect and in particular the etching effect can be set in detail by the choice of the electrical parameters of the anodic cleaning operation and thus optimized depending on the alloy in question. For example, a certain anodic current density can be used. This gives you an optimization parameter that does not change the composition of the solution. It is therefore possible to work optimally with different alloys even with the same solution. Of course, the composition of the solution can also be optimized depending on the alloy, although the inventors have not found any critical dependencies here.
  • alcohols such as methanol, ethanol, propanol, butanol and higher alcohols and their derivatives such as isopropanol come into consideration as alcohol. But also diols, polyethers and other alcohols. A cheap choice are butanol and isopropanol. Of course, two or more alcohols can also occur in a mixture.
  • fluoride ions are used to achieve passivation of the surface.
  • the fluoride ions are used in a solution also containing phosphoric acid, the surface also being anodized in this treatment step.
  • This treatment step can also coincide with the treatment step already described in the solution containing phosphoric acid and the alcohol, the solution thus containing phosphoric acid, the alcohol and also fluoride ions.
  • the steps can also be separated, the step with the solution containing fluoride ions taking place after the step described initially.
  • the solution can also contain one or another alcohol (or the other alcohol mixture) in addition to the phosphoric acid and the fluoride ions in order to optimize its cleaning properties.
  • the fluoride ions can be present in a wide variety of ways, for example as alkali metal fluoride, ammonium (bi) fluoride or as hydrofluoric acid.
  • the treatment with the fluoride ion solution is particularly suitable for light metal alloys with a significant Mg content, in which MgF 2 is then or in the Passivation layer is created.
  • the step with the fluoride ions is particularly preferred when the light metal alloy has a Mg content of 50 percent by weight and above.
  • the fluoride ion step is preferred for light metal alloys with an Si content, preferably if this is 0.1, in particular 0.5 or 1 or 2 percent by weight and above. At low Si concentrations one will choose rather low fluoride concentrations.
  • the fluoride ion step can therefore also be advantageous in the case of light metal alloys with a low or vanishing Mg content.
  • the cleaning and passivation method according to the invention can advantageously be concluded with an alkaline rinsing step, for example in alkalized water with a pH of preferably 10 and above.
  • the alkaline rinsing step is particularly favorable when the passivation surface is dominated by MgF 2 and less favorable when it is dominated by Al 2 0 3 , at least at the high pH values mentioned.
  • further treatment steps can be followed by an additional passivation step in an aqueous oxidizing agent.
  • This oxidizing agent can be, for example, a persulfate solution or a solution of peroxomonosulphuric acid (Caro's acid).
  • the passivation step in the oxidizing agent should take place after a possible treatment step in a fluoride solution.
  • the oxidation step is not necessary on a fluoride-coated surface of a light metal alloy with a high Mg content. If done in too acidic a range, it can also damage fluoride passivation (around pH 6 and below).
  • the fluoride ion content in the overall solution in question can have a value between 0.1 and 0.3 or have 0.5% by weight as the lower limit and 30, 20 or 10% by weight as the upper limit.
  • the anodic current density on the anodically polarized light metal alloy surface can advantageously be between 10, 30 or 50 A / m 2 as the lower limit and 500 A / m 2 as the upper limit and, as already explained above, is an optimization parameter depending on the alloy composition, the justifiable material removal and the required cleaning effect.
  • the total treatment time of the anodic cleaning steps can be between 10 seconds and 5 minutes, for example, and depends heavily on the set current density, the justifiable material removal and the degree of contamination.
  • the proportion of phosphoric acid in the solutions for the anodic cleaning steps is 30-90% by volume, and the phosphoric acid can be 50-95% by weight within this proportion by volume.
  • This relates in particular to solutions with an alcohol content which, apart from the volume fraction of phosphoric acid of 30-90% by volume mentioned, advantageously consists essentially of the alcohol (mixture) and optionally the fluoride.
  • the cleaning effect of the process according to the invention is so thorough and broad that chemical pretreatment steps prior to incorporation into the solution containing phosphoric acid and alcohol can be dispensed with and should also advantageously be eliminated for reasons of economy.
  • the surfaces to be treated can therefore be applied directly and dry.
  • a particular advantage of the invention is that good results can be achieved even on regenerated light metal alloys, in particular no sludge is formed.
  • the metallic contamination of regenerated material has caused considerable problems in cleaning in conventional processes. leads and often completely prevents cleaning and subsequent good coating.
  • Even with a larger proportion of Al, the surfaces in the anodic baths according to the invention remain shiny metallic, so that the subsequent oxidation mentioned can also take place free of nitric acid.
  • a preferred application of the invention lies in the preparation of light metal alloy surfaces for a subsequent coating of any kind.
  • the quality of the coating depends on the cleanliness of the surface, both with regard to the optical properties and the resilience of the coating.
  • the invention relates to a subsequent metallization, which should preferably be carried out without external current.
  • the invention is also directed to the overall process from the cleaning and passivation described and the subsequent coating, in particular metallization.
  • AZ91 is chosen as a typical example of an alloy with a higher Mg content, AM50 or AZ31 also being possible.
  • the AZ91 alloy is introduced dry into a bath of 60 percent phosphoric acid (H3PO4) with 40 vol.% Butanol without further chemical cleaning, and anodically poled.
  • the current density is, for example, 20 A / m 2 at a temperature of 25 ° C. and a treatment time that can be approximately 30 s.
  • the AZ91 alloy is then placed in a second bath which has a composition identical to the composition mentioned, but which also contains 2% by weight of ammonium bifluoride. A further anodic cleaning takes place with the same current density for a further 20s.
  • the AZ91 parts are then rinsed in alkalized water (pH slightly above 10).
  • the AZ91 surface is now passivated by a fluoride layer and can be metallized in a conventional manner.
  • a chemical conversion coating with Zn, Ni or Cu or an alloy selected from it is then rinsed in alkalized water (pH slightly above 10).
  • the second embodiment is directed to an alloy with a high Al content, i.e. technical aluminum, namely GdAISi8Cu3. Since this alloy contains Si, the fluoride bath mentioned in the first exemplary embodiment is also used here. The same quantitative parameters can be selected, but the rinsing step in the alkalized water is omitted. Instead, it is rinsed with neutral water (pH about 7) and then additionally oxidized with a persulfate solution to strengthen the passivation layer. This treatment also applies to GdAI-Si9Cu3.
  • the parts treated in this way can then in turn be chemically galvanized, nickel-plated or copper-plated or coated with alloys thereof.
  • the passivation layers are loosened or converted, so that there is good and direct contact between the metals.
  • a particular advantage is that the final oxidation of the Al alloy can be carried out without nitric acid, since there is a bright metallic surface. This means that there are no nitrous gases as with conventional processes, which means that there is no technical effort for extraction and exhaust gas purification and that there is no need for approval according to the relevant regulations (in Germany BlmschG).
  • the light metal alloys come from a die casting process, they are usually contaminated with mold release agents. These are also reliably and completely removed in the cleaning processes shown.

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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)
  • Cleaning And De-Greasing Of Metallic Materials By Chemical Methods (AREA)
  • Chemical Treatment Of Metals (AREA)

Abstract

L'invention concerne un nouveau procédé de nettoyage et de passivation destiné aux surfaces d'alliages légers qui contiennent Al ou Mg. Le procédé selon l'invention convient notamment à la préparation d'un revêtement, par exemple d'une métallisation sans courant externe.
PCT/EP2002/011299 2002-10-09 2002-10-09 Procede pour nettoyer et passiver des surfaces d'alliages legers Ceased WO2004035876A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU2002338880A AU2002338880A1 (en) 2002-10-09 2002-10-09 Method for cleaning and passivating light alloy surfaces
PCT/EP2002/011299 WO2004035876A1 (fr) 2002-10-09 2002-10-09 Procede pour nettoyer et passiver des surfaces d'alliages legers

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2002/011299 WO2004035876A1 (fr) 2002-10-09 2002-10-09 Procede pour nettoyer et passiver des surfaces d'alliages legers

Publications (1)

Publication Number Publication Date
WO2004035876A1 true WO2004035876A1 (fr) 2004-04-29

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Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2002/011299 Ceased WO2004035876A1 (fr) 2002-10-09 2002-10-09 Procede pour nettoyer et passiver des surfaces d'alliages legers

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AU (1) AU2002338880A1 (fr)
WO (1) WO2004035876A1 (fr)

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB829716A (en) * 1956-08-22 1960-03-02 Canadian Ind Electrolytic coating on articles of magnesium or magnesium base alloys
DE2601861A1 (de) * 1975-01-22 1976-07-29 Pechiney Aluminium Verfahren zur herstellung eines kontaktdrahtes mit geringem uebergangswiderstand aus aluminium oder einer aluminiumlegierung
DE19756845A1 (de) * 1997-12-19 1999-06-24 Alfred R Franz Fa Verfahren zur Aktivierung und Inhibierung der Oberflächen von zu galvanisierenden Gegenständen aus Magnesiumlegierungen
US5997721A (en) * 1994-12-19 1999-12-07 Alcan International Limited Cleaning aluminum workpieces
EP1270767A1 (fr) * 2001-06-20 2003-01-02 Wolf-Dieter Franz Procédé pour le nettoyage et la passivation de surfaces d'alliages de métaux légers
WO2003033777A1 (fr) * 2001-10-11 2003-04-24 Franz Oberflächentechnik Gmbh & Co. Kg Procede d'enduction pour surfaces en alliage leger

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB829716A (en) * 1956-08-22 1960-03-02 Canadian Ind Electrolytic coating on articles of magnesium or magnesium base alloys
DE2601861A1 (de) * 1975-01-22 1976-07-29 Pechiney Aluminium Verfahren zur herstellung eines kontaktdrahtes mit geringem uebergangswiderstand aus aluminium oder einer aluminiumlegierung
US5997721A (en) * 1994-12-19 1999-12-07 Alcan International Limited Cleaning aluminum workpieces
DE19756845A1 (de) * 1997-12-19 1999-06-24 Alfred R Franz Fa Verfahren zur Aktivierung und Inhibierung der Oberflächen von zu galvanisierenden Gegenständen aus Magnesiumlegierungen
EP1270767A1 (fr) * 2001-06-20 2003-01-02 Wolf-Dieter Franz Procédé pour le nettoyage et la passivation de surfaces d'alliages de métaux légers
WO2003033777A1 (fr) * 2001-10-11 2003-04-24 Franz Oberflächentechnik Gmbh & Co. Kg Procede d'enduction pour surfaces en alliage leger

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
DATABASE CA CHEMICAL ABSTRACTS SERVICE, COLUMBUS, OHIO, US; LARKE, L.W. ET AL.: "A method for electrolytic polishing and etching of some aluminum-silver alloys, commercial pure aluminum, and pure magnesium", XP002186406 *
METALLURGIA, vol. 41, 1950, pages 172 - 174 *

Also Published As

Publication number Publication date
AU2002338880A1 (en) 2004-05-04

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