DD208486A3 - METHOD FOR METALLIZING ALUMINUM AND ALUMINUM-SUBSTANTIAL SURFACES - Google Patents

Abstract

The invention relates to a method for metallizing aluminum and aluminum. Surface and can be used in particular in the electroless and electrodeposition of metals. The aim of the invention is to obtain adherent metal layers on aluminum-containing surfaces. The object of the invention is the development of a simple process for the metallization of aluminum and aluminum-containing surfaces, which frees this surface of oxidic cover layers with a few process steps and protects against introduction into a metallization from renewed oxide or hydroxide formation. According to the invention, these surfaces are produced by treating them with solutions of organic acids, preferably polybasic hydroxy and / or carboxylic acids, in water or other polar solvents in the temperature range from room temperature to 513K u. then be introduced into a metallizing bath with a liquid layer containing the treatment solution.

Description

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Process for the metallization of aluminum and aluminum-containing surfaces

Field of application of the invention

The invention relates to processes for the metallization of aluminum and aluminum-containing surfaces and can be used in particular in the electroless and galvanic deposition of metals. The deposited metal layers can serve both decorative purposes for functional purposes and enable the deposition of further metal layers.

Characteristic of the known technical solutions

The metallization of aluminum (Al) and Alu'niniumlegierungen is indispensable for certain Anwendungszivecke on the one hand = due to the position of Al in the eiek-irochsmischen voltage series, the amphoteric behavior of Al and its oxides, its high O ₀ -Affinitat and one in comparison to common metallization layers (eg _o H ± _: Ag ₅ Cu ϋ ₍ 3 ₍ ) ₍ high thermal expansion coefficient not unproblematic »

The previous explanations for the metallization of Al materials include cleaning the surface by organic solvents, treatment in inorganic acids or alkalis (pickling) to remove oxides or ligation residues and activation of the surface by applying a thin metallic layer by means of dip deposition ^ as the basis for the actual electroless or electrolytic deposition and a subsequent current

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Loose or electrolytic reinforcement is used, / WP C 23 C / 219 066, DDR, 19Sl; OS 2 512 339, FRG 1975 /. This procedure requires an economically unacceptably high number of process steps ^; n and one additional by the activation step. Use of materials, sometimes also of precious or Oefizitrnetallen. Furthermore, it has a disadvantageous effect that the oxide layer which was removed during the pickling process immediately arises again on the surface when the object to be coated is removed from the pickling bath and the action of adhering acid residues is rinsed with water , Dip separation problems occur with the adhesion of the metallization layers * Because of the use of aggressive chemicals for surface preparation (z, B, HNO_., HF u »a") it is necessary - special measures das.Health and safety to make »

Other embodiments are concerned with the metallization of Al materials via a porous oxide layer selectively applied by anodic treatment / Lashmors, D.S., Metal Finishing (1980) 4, -S, 21-24; Lashmore, D * S "Plating and Surface. Finishing (1981) 4, 43-51; U.S. Patent 4,115,211, Sept.,

This is intended to provide a more even distribution of low-density coatings. "Although these methods provide some advantages over those described above," 3, lower cost of chemicals, cyanide-free electrolytes, etc., are not as widespread as those previously mentioned. The reason for this is, inter alia, represent ± _n} that a modified pre-treatment is required for almost any Legierungszusaramensatzung that required for sufficient adhesion pores are inhomogeneously distributed in the oxide layer is in R.ealfall and thus can lead to Haftfestigkeitsprobleinen "The energy required for the AnodisierungsprozeE is quite high * and infoige of a dielectric interlayer must be expected with an adverse effect on the transfer resistance of the substrate / metallization, which completely excludes the method for certain Amvendungszwecka in Slektrotachnik / Elaktronik.

For elimination o, g. Disadvantages would be to strive for a direct metallization of Al materials without metallic or dielectric intermediate layers. Feldstein / RCA Reviev Ouni 1970, -S, 317-329 / describes, for example, a process for direct electroless nickel plating of aluminum. However, this method refers only to pure aluminum and is limited to a nickel bath with dimethylamine borane as the reducing agent.

Object of the invention

The aim of the invention is to provide a method step reduced surface treatment method, which succeeds to produce adherent metal layers on aluminum and aluminum-containing surfaces.

Explanation of the essence of the invention

The invention is based on the object to develop a method that sait few process steps without intermetallic layers and without anodized oxide layers and without additional activation of aluminum and Alurainiumlegierungen of oxide topcoats and sparingly soluble alloying freed and the surface to the introduction into a metallizing, in particular a stroraloses nickel plating SBAD, broadly protects against re-covering with oxides or hydroxides "ErfindungsgeraäS is by this process the aluminum surface with a solution of an organic acid or einetn mixture of organic acids, preferably malic acid j-malonic acid, succinic acid, - tartaric acid or citric acid without strong Metal removal at elevated temperatures in Teraperaturintervall from room temperature to 513 K, - in particular 303 - 458 K etched so that oxide cover layers, partly peel off as a result of undercutting and a sau bere active metal surface is obtained, the etching is not present buttocks by displacing the etching solution with water but substantially slowed by lowering the temperature so that the reaction products of the etching reaction Vierden further maintained complex in solution and a

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Hydroxide coverage of the surface due to hydrolysis is largely prevented,

According to the invention, the surfaces thus pretreated with an adherent liquid film which contains sufficient complexing agent for aluminum ions are introduced directly into the Meta.llbeschichtungs.bad which contains in many cases even organic acids as complexing agents and largely insensitive to an entry of the etching solution However, Hs is also "possible by a washdown of the pretreated surfaces in a solution containing alkali or ammonium salts of the organic acids used and optionally ammonia, to adjust the pH of the surface-adhering liquid film and the metal coating bath Process according to the invention can also be advantageously carried out with solutions of organic acids in monohydric or polyhydric alcohols or other nonaqueous polar solvents or in mixtures of these solvents with ultrasound, optionally with superposition of ultrasound It should be emphasized that it is possible with the erfiridungsg.emäS / en method, not only aluminum, but also a wide range of different composite alloys without modification of the pretreatment directly electrolessly, preferably by applying an electroless nickel layer.

The application is not limited to a nickel bath. limited to a particular reducing agent, but it is possible through the choice of'educing agent to make a targeted influence of mechanical-physical and electrical layer properties.

24 yy 6-6: 0

embodiments

There are solid aluminum or aluminum alloys with Fe, Cu ₁ 3i, Mg and Zn as alloying ingredients

1. in a solution of 1000 g of tartaric acid in 100 ml of H ₂ O '. treated at 363 ° <2 min and without intermediate rinsing after briefly wiping off the adhering liquid in a nickel bath according to Feldstein / RCA Review, 3une 197O ₁ p. 317-329 / electrolessly containing 0.4, coated with nickel in 10 min;

2. in a solution of

500 g tartaric acid in 50 ml H ₂ O.

50 ml of ethanol and 900 ml of glycerol

treated at 343 K for 5 min, then 40 s in a solution of 270 g of ammonium tartrate

300 g of ammonia solution 25% in 200 ml H ₃ O and

80 g of ethanol at 333 K

and ultrasound exposure and then without intermediate rinsing at 368 K in 7.5 min in a 3ad Epifanowa-f- W.3. et al / Saschita metallow 1978, S »226-228 / at a pH value of 9, provided with a 0,5μm thick nickel layer;

3 × in a solution of 50 g malonic acid

200 g of citric acid and 800 g of tartaric acid in 100 ml of water

pretreated at 370 K for 3 minutes and then coated in a bath to Epifanowa, L "C, at a pH of 4 for 5 min with 0.4y μm nickel»

All nickel layers were adherent and crack-free even after repeated deformation by bending.

Claims (2)

24 0 Invention claim  1, process for the metallization of aluminum and aluminum-containing / surfaces, characterized in that the surface dia by solutions of organic acids, preferably polybasic hydroxy and carboxylic acids, in water or other polar solvents or mixtures thereof in the temperature range from room temperature to 513 K, in particular 303 up to 458 K, optionally under the influence of ultrasound and then either immediately with. a liquid layer containing the Beh.andlungslösung be introduced into a metallization or previously dipped in order to equalize the pH of this liquid layer with the metallization in_ a solution containing alkali metal or ammonium salts of these organic acids and optionally ammonia, 2, Method according to claim 1, characterized gekannzeichnet that are preferably used as organic acids malic acid, malonic acid, succinic acid, citric acid, tartaric acid and lactic acid or mixtures of these acids. Λ i! 1 ί. _ ,, ΓΓΟ.Λ L \ 't \