WO2009068168A1 - Component made of aluminum and/or an aluminum alloy having very high corrosion resistance and method for the production thereof - Google Patents

Abstract

The invention relates to a component made of aluminum and/or an aluminum alloy, particularly a decorative or functional part, having very high corrosion resistance, and to a method for the production thereof. The high corrosion resistance, particularly high alkali resistance, is achieved in that the surface of the component comprises an oxide layer created evenly by anodization and a cover layer sealing and evenly covering the porous oxide layer. The cover layer is created by an oxide layer hydrate compound sealing the pores of the oxide layer and by an additional inclusion of glass-like substances and application thereof on the oxide layer at the same time.

Description

 Component of aluminum and / or an aluminum alloy with a very high corrosion resistance and method for its production

The invention relates to a component made of aluminum and / or an aluminum alloy, in particular a trim or functional part, with a very high corrosion resistance and a method for its preparation.

In the exterior and interior of many motor vehicles are high or matt or silk gloss trim parts, which are made of aluminum sheets or aluminum profiles. The decorative surfaces are obtained by polishing and gloss anodizing. These possibly also colored surfaces are visually demanding and fulfill a high quality standard. These are surfaces which, in contrast to painted surfaces, have a completely uniform layer thickness and have neither ripples nor edge structures or edge alignments. They also have good corrosion resistance through a combination of cold and heat compression processes. Thus, aluminum components produced by such a method, such as a component made of an AlMgO, 8 alloy, are stable in the alkaline range up to pH values of 11.5. When using a component made of an AlMgSiO, 5 alloy, even a resistance up to pH values of 12.5 is proven. The alkali resistance of anodized surfaces is specified for example in a standard TL 212 of Volkswagen AG. In addition, according to special test standards, acidic resistance was achieved at pH values of 1.5 and above. The resistance to acidic media is tested with the so-called Kesternichtest, DIN 50018 KfW 2, OS. This pH range of 1, 5 to 1 1, 5 and 12.5 represents a very wide range of corrosion resistance. However, the components are often exposed to higher loads. Thus, especially in the US, but also increasingly in Europe, brush and flapless washing systems, which clean non-contact vehicles, are increasingly used. In these Washing systems are used cleaners, especially in the area of soaking before the actual wash, which can reach pH values of 13.5. If vehicles with anodized components are exposed to such cleaners, the compacted anodised layer, which is transparent in the undamaged state, quickly becomes milky and unsightly due to corrosion processes. This change may even continue until complete damage to the anodization surface.

There are several ways to increase the corrosion resistance of such components, especially in the alkaline range.

1. European patent application EP 1 407 935 A1 discloses a method in which partially compacted glosseloxal surfaces are coated with a transparent lacquer (Cerapaint, Aluceram), ie the painting process is followed by the anodizing process. For procedural reasons, only the visible sides are coated. The anodising surface provided with the transparent lacquer (Cerapaint, Aluceram) can have excellent corrosion properties; for example, it is stable in the pH range from 1 to 13.5 according to Audi TLI 82. The surface may have this corrosion resistance even after mechanical stress, ie, for example, after a load of 10 double strokes of a device according to Amtec-Kistler, which represents a washing-road simulation. This means that it is also mechanically stable. The disadvantage is that uncompressed or partially compressed anodized goods can not be arbitrarily transported and handled before coating with these paints, since the capillary action of the open pores causes irreversible fouling of the parts. Furthermore, only the visible sides are coated for procedural and cost reasons. This results in an increased tendency of the backside to corrode, especially in combination with other metals or free carbon containing materials, which are in direct contact with the un- or partially densified backside in the presence of a conductive electrolyte, for example, a saline solution. 2. Furthermore, there are approaches to make the anodizing layer more corrosion-resistant by expanding the sealing activities. After the formation of the anodized layer, the pores are usually closed by cold sealing (by nickel felurid) and hot water sealing (deionized water plus scale inhibitor). The expansion of the sealing activities then consists either of an elevated temperature nickel acetate treatment, which is switched between cold sealing and hot water sealing, or nickel acetate treatment, which replaces hot water sealing. Corrosion stabilities up to pH values of 13.5 can be achieved in this way. In this case, the pores of the anodization layer are closed or covered by a cover layer which contains nickel-containing compounds in addition to the aluminum oxide hydrate (boehmite). This cover layer ensures that highly alkaline solutions can not attack. However, this nickel-containing cover layer is mechanically less stable, so that a low mechanical stress leads to the elimination of this layer, which then nullifies the increased corrosion resistance and is therefore unsuitable for use in components in the automotive sector.

The object of the invention is to provide a process for the production of components made of aluminum or an aluminum alloy with improved corrosion resistance in order to be able to produce improved components by means of this process, which in particular achieve an alkali resistance up to pH values of 13.5, without the other positive properties of an anodizing surface, such as their corrosion resistance to salt and acid contamination, their weathering and scratch resistance, to name but a few, be changed negatively. A further object of the invention is to design the method so that the coating can be carried out as an in-line process, ie wet in wet, in order to keep costs as low as possible. This object is achieved with components having the features of claim 1. In these components made of aluminum and / or an aluminum alloy, such as decorative and / or functional parts, in particular of motor vehicles, a high corrosion resistance against acidic or alkaline media could be achieved, in particular a high resistance to alkali. Thus, these aluminum components were stored at temperatures of 1 8 to 20 ⁰ C in a solution with a pH of 13.5 and were able to withstand these test conditions for at least 10 minutes without optical change.

In addition, the components have a high hot crack resistance, namely a resistance to high temperatures without heat cracks occur. The components of the invention were stored at 100 ° C for at least 60 minutes and then tested. It could optically no heat cracks are detected.

High-gloss trim parts are characterized by the use of particularly pure aluminum or particularly pure aluminum alloys, which are made of e.g. the known grades A199.9MgSiO, 5 or A199.9Mg0.8. The decorative area of the surface of the component can be adjusted by appropriate pretreatment between high-gloss and matt. It can, like known motor vehicle trim parts, be colored electrolytically and / or adsorptively.

The inventive components of pure aluminum and / or an aluminum alloy, based on high purity aluminum, have a uniform oxide layer produced by anodization and one of the pores of the

Oxide layer closing and even covering cover layer. Unlike known corrosion resistant decorative components, these are

Cover layer not exclusively of aluminum oxide and hydrated oxide (boehmite layer) in the pores or of an anodized layer covering

Lackschicht or ceramic-like layer, but the pores of the oxide layer are closed both by a Oxydhydratverdichtung and by a covered glassy layer. This combination of the compaction layer and the vitreous layer in the cover layer, on the one hand, causes the high corrosion resistance and, on the other hand, the consistently high heat-resistance.

This sealing is achieved after the anodization by a three-stage compaction. In the first step, the porous oxide layer obtained in the anodization, which usually have layer thicknesses of natural colored parts of 5-7 μm and, in the case of colored parts, layer thicknesses of 12-15 μm, is subjected to a cold sealing process. In this case, sealing products with nickel fluoride should be added. The process conditions for this cold sealing step are:

Total concentration of compaction agent 4.0-8.0 g / l, preferably 5.5-7.7 g / l,

PH 6.0-7.0, preferably 6.0-6.7,

Temperature 28-32 ° C,

• time 4 - 8 min, preferably 4-6 min.

Subsequently, after repeated rinsing in demineralized water, a conventional hot water sealing is carried out. The process conditions for hot water sealing are:

Concentration of phosphate and silicate (PO4 and SiO3) <8 ppm, pH 5.8-6.6, preferably 5.8-6.2,

• conductivity> 650 μS / cm,

Temperature T> 95 ° C, preferably 95-100 ° C,

Time t> 3min / μm layer thickness of the anodization layer,

• demineralized water, if necessary with the addition of anti-topping agents in a concentration of 2-3 ml / l. This is followed by a conversion treatment with an aqueous solution of hexaflourosilic acid and / or chromophosphoric acid, which prepares the surface for the subsequent treatment. The process conditions are for this conversion step:

Temperature 45-70 ° C, preferably 55-60 ° C,

• time 7 - 15min, preferably 10- 12min,

Concentration of conversion agent 20-200g / l, preferably 30-60 g / l,

PH 6.0-7.0, preferably 6.4-6.6.

The following second hot water compression is carried out at pH values of 10.5 to 1 1, 2 with the addition of alkali metal silicates, such as sodium silicate or potassium silicate. The process conditions for this hot water sealing are:

Time 21-45 min, preferably 3min / μm layer thickness of the anodization layer,

Concentration of alkali silicate 5 to 60 g / l, preferably 8 to 30 g / l potassium silicate or sodium silicate, pH 10.5 to 1 1, 2,

• possibly addition of surfactant mixture 0.2 to 0.3 ml / 1,

• temperature T> 95 ⁰ C, preferably 95- 100 ⁰ C

Glassy substances of one or more such alkali metal silicates can be introduced into the cover layer (anodized layer) and simultaneously applied to it. These glassy substances are preferably introduced into the compression bath as an aqueous solution.

The last two steps can be repeated several times to increase the resistance and the layer thickness of the silicate layer. For further protection of the vitreous-sealed anodized layer, in a particularly preferred embodiment, strongly hydrophobicizing polymers, such as siloxane / silicone resins having longer side chains (to C 16), aminosiloxanes having a reactive epoxy group or siloxanes / silicones having a reactive center, chemically bonded directly to the silanol groups of the glassy surface, preferably this coating is carried out by dipping or spraying.

Comparative Example 1

An aluminum sheet piece A measuring 40 × 100 × 2 mm made of A199.9MgO, 8 alloy is mechanically polished and chemically pretreated in a known manner. Subsequently, during a DC sulfuric acid treatment, an anodically generated oxide layer is formed on this piece. The layer thickness is 7 μm. After rinsing the component A, the porous oxide layer is subjected to a cold sealing step.

• temperature: 28-32 ° C, pH value: 6.2-7.0, • sealing time: 4-8min,

Concentration of the densifying agent: 4-8 g / l,

• Bath composition: nickel feluride dissolved in demineralized water.

By a hot water compression a re-compaction takes place.

Temperature: 95-100 ° C,

PH: 6.2 ± 0.2,

Sealing time: 3 min / μm layer thickness of the anodization layer,

• Compression bath composition: deionized water, anti-scale agent in the concentration of 2-3ml / l. Comparative Example 2:

An aluminum sheet piece B measuring 40 × 100 × 2 mm made of A199.9MgO, 8 alloy is mechanically polished and chemically pretreated in a known manner. Subsequently, during a DC sulfuric acid treatment, an anodically generated oxide layer is formed on this piece. The component B is additionally supplied to an electrolytic and adsorptive dyeing process. The layer thickness is 15 μm. After rinsing the component A, the porous oxide layer is subjected to a cold sealing step.

Temperature: 28-32 ° C, pH: 6.2-7.0,

• Sealing time: 4-8min, • Concentration of the compaction agent: 4-8g / l,

• Bath composition: nickel feluride dissolved in demineralized water.

By a hot water compression a re-compaction takes place.

Temperature: 95-100 ° C,

PH: 6.2 ± 0.2,

Sealing time: 3 min / μm layer thickness of the anodization layer,

• Compression bath composition: deionized water, anti-scale agent in the concentration of 2-3ml / l.

Comparative Example 3

An aluminum sheet piece C with the dimensions 40 × 100 × 2 mm made of an A199.9MgO, 8 alloy is mechanically polished and chemically pretreated in a known manner. Subsequently, during a DC sulfuric acid treatment, an anodic oxide layer is formed on this piece generated. The layer thickness is 7 μm. After rinsing the component C, the porous oxide layer is subjected to a cold sealing step.

Temperature: 28-32 ° C. • pH value: 6.2-7.0.

• Sealing time: 4-8min.

• Concentration of the densifier: 4-8g / l.

• Bath composition: nickel feluride dissolved in demineralized water.

By a first hot water compression another compression step takes place:

Temperature: 70-80 ° C,

• pH value: 5.7 ± 0.3, • Sealing time: 2-5 min,

• Compression bath composition: deionized water, 15-20 g / l nickel acetate.

By a second hot water compression a re-compaction takes place.

Temperature: 95-100 ° C, pH: 6.2 ± 0.2,

Sealing time: 3 min / μm layer thickness of the anodization layer,

• Compression bath composition: deionized water, anti-scale agent in the concentration of 2-3ml / l.

Inventive Embodiment 1:

An aluminum sheet piece D with the dimensions 40 × 100 × 2 mm of a A199.9MgO, 8 alloy is mechanically polished and chemically pretreated in a known manner. Subsequently, during a DC sulfuric acid treatment, an anodized oxide layer is formed on this piece generated. The layer thickness is 7 μm. After rinsing the component D, the porous oxide layer is subjected to a cold sealing step.

Temperature: 28-32 ° C, pH: 6.0-6.7,

• Sealing time: 4-6min,

Concentration of the compaction agent Metachem K14P: 5.5 - 7.7 g / l,

By a hot water compression a re-compaction takes place.

Temperature: 95-100 ° C, pH: 6.0 ± 0.2,

Sealing time: 3 min / μm layer thickness of the anodization layer,

• Compression bath composition: deionized water, anti-scale agent Henkel Seal SL in the concentration of 2-3ml / l.

This is followed by a conversion treatment with hexaflourosilicic acid, which prepares the surface for subsequent treatment.

Temperature T = 55 ° C,

• time t = 10- 12 min,

• Hexafluorosilicic acid concentration c = 60g / l, pH 6.4.

By a second hot water compression a re-compaction takes place.

Temperature T = 95 to 100 ° C,

• pH: = 10.5 to 1 1, 2,

• Sealing time: 3min. / μm layer thickness of the anodization layer, • compaction bath composition: demineralized water, 15 to 22 g / l sodium or potassium silicate and 0.2 to 0.3 ml / 1 surfactant mixture Clariant Liogen WL. The last two steps are performed twice in alternation.

Thereafter, the surface is sprayed by spraying with a solution containing an aminosiloxane having a reactive epoxy group and crosslinked by annealing.

Embodiment 2 of the invention:

An aluminum sheet piece E measuring 40 × 100 × 2 mm made of A199.9MgO, 8 alloy is mechanically polished and chemically pretreated in a known manner. Subsequently, during a DC sulfuric acid treatment, an anodically generated oxide layer is formed on this piece. The component E is additionally supplied to an electrolytic and adsorptive dyeing process. The layer thickness is 15 μm. After rinsing the component A, the porous oxide layer is subjected to a cold sealing step.

Temperature: 28-32 ° C, pH: 6.0-6.7,

• Sealing time: 4-6min,

• Concentration of the compaction agent Metachem Kl 4P: 5.5 - 7.7 g / l.

By a hot water compression a re-compaction takes place.

Temperature: 95-100 ° C,

PH: 6.0 ± 0.2,

Sealing time: 3 min / μm layer thickness of the anodization layer,

• Compression bath composition: demineralized water, anti-scale Henkel Seal SL in the concentration of 2-3ml / l, This is followed by a conversion treatment with hexaflourosilicic acid, which prepares the surface for subsequent treatment.

• temperature T = 55 ° C, 5 • time t = 10-12 min,

• Hexafluorosilicic acid concentration c = 60g / l, pH 6.4.

By a second hot water compression a re-compaction takes place. I O

Temperature T = 95 to 100 ° C, pH = 10.5 to 11, 2,

Sealing time: 3 min / μm layer thickness of the anodization layer,

• Compression bath composition: deionized water, 15 to 22 15 g / l sodium or potassium silicate and 0.2 to 0.3 ml / 1 surfactant mixture

Clariant Liogen WL.

The last two steps are performed twice in alternation. After that, the surface is sprayed by spraying with a solution containing an aminosiloxane having a reactive epoxy group and crosslinked by annealing.

In the case of the components D, E according to the invention, the porous oxide layer 5 is compacted and a vitreous substance is introduced into the pores of the oxide layer and simultaneously built up on the oxide layer. This type of seal is a combination of one cold sealing step and two

Hot compacting steps, wherein the individual steps (conversion treatment with

Hexaflourkieselsäure and silicate treatment) were carried out twice in Wechsel0. The components can be anodized in a known manner, ie the layer thicknesses of the porous oxide layers are in the usual range of 5 to 15 microns. The oxide layers can after the anodization and / or an electrolytic and / or adsorptive coloring in the manner according to the invention are sealed. To further protect the above-mentioned anodized layer, it is additionally possible to apply strongly hydrophobicizing polymers, such as, for example, aminosiloxanes having a reactive epoxy group, to name only one, by dipping or spraying.

Test for heat cracking resistance:

Parts A, B, C, D, E are stored at 100 ° C. for 60 minutes. All components optically show no heat cracks.

Test for acid resistance:

The components A, B, C, D, E are subjected to 5 cycles of Kesternichtests to DIN 50018 KFW 2, OS. After that, no part has any visual changes.

Test for resistance to saline media:

The components A, B, C, D, E are exposed to a salt spray test according to DIN 50017 SS over 480h. After that, no part has any visual changes.

Alkali resistance test:

Storage of parts A, B, C, D, E in an alkaline test solution with a stoichiometric pH of 13.5 at temperatures of 18-20 ⁰ C for 10 min. The alkaline test solution consists of a 0.317 molar solution containing 11 g of sodium hydroxide, 4.64 g of sodium phosphate dodecahydrate (equivalent to 2 g of sodium phosphate), 0.33 g of sodium chloride distilled water.

Parts C, D, E show no change after 10 min. Part A changes after 4 minutes and Part B changes after 3-4 minutes. The transparent layer becomes cloudy, in some cases the anodized layer is completely removed after the entire test period of 10 minutes.

Alkali resistance test after previous mechanical stress:

Parts A, B, C, D, E are passed through an Amtec-Kistler device, which is a car wash simulation. There are 10 double strokes on the surface of each component. Subsequently, the components are stored in the alkaline test solution described above with a measured pH of 13.5 at temperatures of 18-20 ° C for 10 min.

The parts D, E according to the invention show after 10 minutes a slight, by polishing almost entirely reversible change.

Part A changes after 2-3 minutes and part B also after 2-3 minutes. The transparent compaction layer becomes cloudy, the anodized layer is completely removed after the entire test period of 10 minutes.

Part C, which showed excellent corrosion resistance without mechanical stress, now changes after only 4 minutes. irreversible.

All components A, B, C, D, E can be used as trim or functional parts, as they have a heat-resistant and corrosion-resistant surface. However, this corrosion resistance differs for the

Components A, B, C (comparative examples) and the components of the invention

D, E in their alkali resistance, especially after mechanical stress, essential. This is effected in the components according to the invention due to the covering layer covering the porous oxide layer uniformly. The

Since the pH value is a logarithmic representation of the hydrogen ion concentration (pH = -log c [H3O ⁺ ]), the change is significant: the Resistance is from currently pH = 12.5 (anodized on substrate, for example of the type A199.9MgSiO, 5) or of pH = ll, 5 (anodized on substrate, for example of the type A199.9MgO, 8) to pH = 13, 5, which corresponds to a factor of 10 or 100, respectively. The cover layer formed consists of compounds which have been applied to the oxide layer by the compression and incorporation of the ceramic particles, namely aluminum oxides and / or aluminum hydrates and / or alumina hydrates, caused by the KaIt- and / or hot compression and alkali silicates and / or Aluminosilicates, caused by the incorporation of the ceramic particles in the cover layer and optionally of a thin film of hydrophobierenden Aminosiloxanen. In particular, no nickel compounds are detectable in the cover layer.

With these components according to the invention are for the first time trim parts with high corrosion resistance, in particular an alkali resistance to pH values of

13.5 with simultaneously high heat resistance and mechanical strength

(Abrasion resistance) available. Furthermore, it can be emphasized as a particular advantage that the abovementioned method steps, which lead to the particularly corrosion-resistant surface, can also be carried out as an in-line process.

The invention is not limited to the features described in the embodiment of the components D, E. These can be varied according to the purpose of the component. For example, the layer thickness of the anodization layer of a trim part can be between 2 and 30 μm.

Claims

Claims : 1 . Component of aluminum and / or an aluminum alloy, in particular a trim part or functional part, having a high corrosion resistance against acidic and alkaline media, in particular an alkali resistance at pH values of 13.5 and temperatures of 18 to 20 ° C. for at least 10 minutes, having a high heat-resisting strength, namely a resistance without occurrence of heat cracks at 100 ° C. for at least 60 minutes, wherein the surface of the aluminum and / or the aluminum alloy is a uniformly produced by anodization oxide layer and the pores of the oxide layer occluding and evenly covering Covering layer has, wherein the cover layer is formed by an oxide hydrate compound occluding the pores of the oxide layer and by an additional incorporation of vitreous substances into the pores of the oxide layer and a simultaneous buildup thereof on the oxide layer and optionally additionally containing a hydrophobizing polymer. 2. Component according to claim 1, characterized in that the component is a high-gloss component of a high-purity aluminum, in particular of an aluminum material with a weight fraction of 99.9% aluminum or an aluminum alloy, such as AlMgSiO.5 or AlMgO.8 exists. 3. Component according to claim 2, characterized in that the surface of the component has a gloss range of high gloss to matt. 4. Component according to one or more of claims 1 to 3, characterized in that the surface of the aluminum and / or the aluminum alloy is colored. 5. Component according to one of claims 1 to 4, characterized in that the oxide hydrate compaction by a cold compression and a Hot compression is effected. 6. Component according to one of claims 1 to 5, characterized in that the glassy substance is a compound of one or more alkali metal silicates. 7. Component according to one of claims 1 to 6, characterized in that the cover layer exclusively comprises aluminum oxides and / or aluminum hydrates and / or alumina hydrates and alkali metal silicates and / or aluminosilicates. 8. Component according to one of claims 1 to 6, characterized in that the cover layer additionally contains a hydrophobizing polymer, namely a cross-linked with the top layer siloxane compound. 9. A method for producing a component from aluminum and / or an aluminum alloy, in particular a trim part or functional part, having a high corrosion resistance against acidic and alkaline media, in particular an alkali resistance at pH values of 13.5 and temperatures of 18 to 20 ° C. for at least 10 minutes, having a high heat-resisting strength, namely a resistance without occurrence of heat cracks at 100 ° C. for at least 60 minutes, comprising at least the steps: Anodization of the component, wherein the surface of the aluminum and / or the aluminum alloy receives a uniformly generated oxide layer of a layer thickness of 2 to 30 microns, Cold sealing of the component in a deionized water bath with the addition of a nickel flourylide-containing densifier at temperatures of 28 ° C to 32 ° C and pHs of 6.0 to 7.0 for a time of at least 4 minutes and Hot water sealing of the component in a bath of demineralized water at a temperature of 95 ° C to lOO ° C, a pH of 5.8 to 6.6, a sealing time of 3 min per micron of the generated oxide layer thickness with the addition of anti-tarnish in one concentration from 2 to 3ml / l, Conversion treatment of the component with hexaflourosilicic acid and / or chromophosphoric acid as a conversion agent at a temperature of 45 ° C to 70 ° C, a period of 7 to 15 minutes and a concentration of the conversion agent of 20 to 200g / l in an aqueous solution, second hot compressing the component in a bath of deionized water with the addition of a glassy substance at temperatures of 95 ° C to 100 ° C and pH values of 10.5 to 1 1, 2 for a time of at least 3 min per micron of the oxide produced layer thickness. 10. The method according to claim 9, characterized in that as a glassy substance, a compound of one or more alkali metal silicates is added to the Heißverdichtungsbad in an amount of 5 to 60g / l. 1 1. A method according to claim 10, characterized in that sodium silicate and / or potassium silicate is added to the Heißverdichtungsbad, preferably as an aqueous solution. 12. The method according to one or more of claims 9 to 1 1, characterized in that the component is subjected to anodizing and before all Sealingschritten an electrolytic and / or adsorptive dyeing step. 13. The method according to one or more of claims 9 to 12, characterized in that for further protection, the component is additionally coated with a hydrophobic polymer, preferably with a siloxane compound. 14. The method according to one or more of claims 9 to 13, characterized in that all process step proceed as inline process.