DE102008023079A1 - Method for compacting a component made of aluminum and / or an aluminum alloy - Google Patents

Abstract

The invention relates to a method for compacting a component made of aluminum and / or an aluminum alloy, which has an oxide layer uniformly produced by anodization on the surface. The densification process involves densifying the component in a bath of demineralised water using overpressure for at least one minute. The application of pressure accelerates the compaction process and increases the capacity of the anodizing unit.

Description

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

in the Exterior and interior of many vehicles are located high-gloss, matt-glossy or silky-glossy Trim parts made of aluminum sheets or aluminum profiles are. The decorative surfaces are polished by polishing and gloss anodizing produced. These may also be colored Surfaces are visually sophisticated and meet a high quality standard. They are surfaces, which in contrast to painted surfaces a completely have uniform layer thickness and neither undulations nor edge structures or edge alignment have. They feel metallic and therefore high-quality An, one speaks of the so-called "cool touch". You also have, by a combination of cold and heat compression processes, about a good corrosion resistance.

Improvements in the compaction process were aimed in particular at increasing the corrosion resistance of anodized and compacted components, in particular in the alkaline range. From the European patent application EP 1 407 935 A1 For example, a process is known in which uncompressed glosseloxal surfaces are coated with a transparent "varnish" (Aluceram), ie the anodizing process is followed by a varnishing process. 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 contamination of the parts. Furthermore, only the visible sides are coated for procedural and cost reasons. This results in an increased tendency of the back side to corrode, especially in combination with other metals or free carbon-containing materials, which are in direct contact with the un- or partially compacted back surface in the presence of a conductive electrolyte, for example a saline solution. The parts coated in this way corrode to varying degrees on visible and non-visible surfaces, so that an inhomogeneous overall picture can arise.

Of There were also attempts by additives during the cold sealing process the corrosion resistance increase. In a combination of a Kaltsealing- and a Heißwasserverdichtungsverfahren, wherein in the cold sealing process z. B. nickel fluoride-containing products are added and the hot water compression with demineralized water in combination with nickel acetates and possibly another hot water compacting step is carried out, corrosion stabilities can be up to pH values of 13.5. The pores of the anodization layer are in this case closed or covered by a cover layer, the next to the alumina hydrate (boehmite) nickel-containing Contains compounds. 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 load to eliminate this Layer leads, what then the increased corrosion resistance destroys and thus for use in components in the automotive sector is unsuitable.

From the unpublished German patent application DE 10 2007 057 777.1-45 is the production of a stabilized, glassy-modified Eloxalschicht known. In this method, components with a very high corrosion resistance against acidic and alkaline media, in particular an alkali resistant at pH values of 13.5 are achieved.

Known Furthermore, it is a vapor compression, resulting in temperatures above the boiling point of the water. However, there is no possibility substances, z. B. silicates, by means of the steam in the compression layer, since these substances are not carried in the vapor.

at All known compression method for the treatment of components made of aluminum and / or aluminum alloys with a high compaction quality and in particular a high corrosion resistance usually made several compression steps. At a Eloxalanlage for the treatment of the components are next to the Anodisierbecken and possibly different tanks for pretreatment, various Provide sink and several compaction basins. For a hot compression, usually becomes the longest Compaction time needed, so that in an anodizing line for a continuous flow of the products several Hot compaction tank are provided.

The object of the invention is to provide a method for compacting components made of aluminum or an aluminum alloy with high compaction quality, in particular good corrosion resistance. Another task is to accelerate the compression process and thus the Anlagenka increase capacity and reduce unit costs.

These The object is achieved by a method having the features of the claim 1 solved.

These improved compression replaces the commonly used Hot water compression and leads in addition to a shortening of the necessary process time. In the first Step of the compression method according to the invention becomes the porous oxide layer obtained in the anodization, which as a rule has a layer thickness of 2 to 30 μm, preferably in natural-colored parts a layer thickness of 5 to 7 microns and dyed parts one layer thickness from 12 to 15 μm, subjected to a known cold sealing step. In this case, sealing products with nickel fluoride are preferably added.

Subsequently becomes after repeated flushing in demineralized water one Hot water compression made.

These Hot water compression according to the invention takes place at elevated temperatures and under application of overpressure. The temperatures are in a range from 100 ° C, preferably in a range between 100 ° C to 140 ° C. The increased temperature serves to increase the reaction rate.

The overpressure is preferably 1 bar to 2 bar. At a lower overpressure than 1 bar is the shortening of the Heißverdichtungszeit not so significant that the additional investment costs would be worthwhile for the pressure generation. pressures of more than 2 bar have the disadvantage that the plant technical Expenditure by the high acting forces disproportionately elevated. The optimum operating pressure must vary depending on the used Chemicals, substrates and layer thicknesses are determined.

These Hot compression can be done in different pH ranges be performed. In a preferred embodiment the pH values are in the range of 6.0 to 7.0. On the other hand pH values in the basic range for a silicate compaction, because the dissolved silicates are basic.

The Compaction bath contains demineralized water. It can known surfactants are added. To increase the resistance in the alkaline range may additionally glassy Substances of one or more such alkali metal silicates in the cover layer be introduced. These glassy substances are preferably as an aqueous solution in concentrations of 5 to 20 g / l introduced into the heat sealing bath.

In In this case, the parts thus compressed show in one test acidic medium with a pH of 1.0 for 10 minutes and a downstream test in an alkaline medium a pH of 13.5 for 10 minutes no attack.

The Compression time is at an inventive Hot compression at 1 bar overpressure and temperatures of 120 ° C per 1 micron layer thickness of the anodization between 0.5 to 3 min. Comparing this with the known hot compression without pressure application, where the compaction time per 1 μm layer thickness the anodization layer is between 2 to 6 minutes, the Reduction of the compaction time significantly.

The Hot water compression according to the invention is done in place of a known hot water compression. It will, as already described, the throughput times of components reduced in an anodizing and at the same time the goodness the compression improved. The by the inventive Method achieved compaction layer is complete and extends to the bottom of the pores of the anodizing layer. This will be with the inventive method a very achieved homogeneous sealing of the pores with alumina hydrate. The conventional known hot water compression achieved this goal is not or not always, u. a. due to process heretics Residual amounts of chemicals, eg. B. acids from the Glänzbad, which can collect in the capillary bottoms of the pores and not displaced, but rather trapped in the layer become. In the method according to the invention is the compression medium, z. B. demineralized water or when added of alkali silicates also these, improved by the pressure in the Pores registered. Residual amounts of treatment substances deposited in the pores, which is not removed by the various rinsing processes became, are displaced or assimilated. By the possible increased process temperature above 100 ° C, the usual boiling point of the water at normal pressure, In addition, the reaction speed and completeness elevated. Thus, the compression times of about 1-3 reach min / μm, causing a shortening of up to corresponds to 50%.

Comparative Example 1a:

One Aluminum sheet piece with the dimensions 40 × 100 × 2 mm from a A199.9Mg0.8 alloy is mechanically polished and in known manner chemically pretreated.

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 Sealingzeit: 4-8 min Additive: 4-8 g / l compaction agent (sealing salt with nickel fluoride),

By a hot water compression a re-compaction takes place. Temperature: 95-100 ° C PH value: 6.2 ± 0.2 Sealingzeit: 21 min sealing bath: completely desalinated water 2-3 ml / l antifriction agent

Comparative Example 1b:

A similar piece of aluminum sheet is treated as in Comparative Example 1a, with only the hot densification being different,
namely a first hot water compression under the following conditions: Temperature: 70-80 ° C PH value: 5.7 ± 0.3 Sealingzeit: 3 min sealing bath: completely desalinated water 15-20 g / l.Nickelacetat and a second hot water compression for recompression under the following conditions: Temperature: 95-100 ° C PH value: 6.2 ± 0.2 Sealingzeit: 21 min sealing bath: completely desalinated water 2-3 ml / l antifriction agent

Inventive embodiment 1:

One the same piece of aluminum sheet is as in the comparative example 1, where only the hot compression differs.

It is followed by the new hot water compression, which is carried out under the following conditions: Temperature: 120 ° C Print: 1 bar overpressure PH value: 6.2 ± 0.2 Sealingzeit: 14 min sealing bath: completely desalinated water 2-3 ml / l surfactant mixture (scale inhibitor)

comparing one the hot water sealing times, then becomes the favorable one Reduction of the treatment time from 21 minutes or 24 minutes to 14 minutes clear.

Comparative Example 2:

One Aluminum sheet piece with the dimensions 40 × 100 × 2 mm from a A199.9Mg0.8 alloy is mechanically polished and in known manner chemically pretreated. Subsequently, will during a DC sulfuric acid treatment generated anodized oxide layer on this piece. The component B is additionally an electrolytic and fed adsorptive dyeing process. The layer thickness is 15 μm. After rinsing the component For example, the porous oxide layer is subjected to a cold sealing step in Comparative Example 1.

By a hot water compression a re-compaction takes place. Temperature: 95-100 ° C PH value: 6.2 ± 0.2 Sealingzeit: 45 min sealing bath: completely desalinated water 2-3 ml / l antifriction agent

Inventive embodiment 2:

One the same piece of aluminum sheet is as in the comparative example 3 treated, with only the hot compression differs.

It is followed by the new hot water compression, which is carried out under the following conditions: Temperature: 120 ° C Print: 1 bar overpressure PH value: 6.2 ± 0.2 Sealingzeit: 30 min sealing bath: completely desalinated water 8 g / l sodium and potassium silicate mixture 0.2-0.3 ml / l surfactant mixture

comparing one the hot water sealing times, then becomes the favorable one Reduced treatment time from 45 min to 30 min significantly.

Comparative Example 3

One Aluminum sheet piece with the dimensions 40 × 100 × 2 mm from a A199.9Mg0.8 alloy is mechanically polished and in known manner chemically pretreated. Subsequently, will during a DC sulfuric acid treatment generated anodized oxide layer on this piece. The layer thickness is 7 μm. After rinsing of the component, the porous oxide layer becomes a cold sealing step as in Comparative Example 1 subjected.

By a hot water compression a re-compaction takes place. Temperature: 94-100 ° C PH value: 10.4 to 10.8 Sealingzeit: 21 min sealing bath: completely desalinated water 8 g / l sodium silicate 0.2-0.3 ml / l surfactant mixture

Inventive embodiment 3:

One the same piece of aluminum sheet is as in the comparative example 4 treated, with only the hot compression differs.

It joins the new hot water compression, which is done under the following conditions :.

It is followed by the new hot water compression, which is carried out under the following conditions. Temperature: 120 ° C Print: 1 bar overpressure PH value: 10.4 to 10.8 Sealingzeit: 14 min sealing bath: completely desalinated water 8 g / l sodium and potassium silicate mixture 2-3 ml / l surfactant mixture

comparing one the hot water sealing times, then becomes the favorable one Reduced treatment time from 21 min to 14 min significantly.

There Water is known to be under a higher pressure Boiling point than under normal conditions, the inventive Compression at temperatures of 100 ° C or higher be made, which increases the reaction rate, whereby the reaction underlying the compression faster and also more complete. By the applied pressure results in an improved and more homogeneous Compression. Any remaining in the pores of the anodizing Remains of treatment media are better displaced and Thus, no local microscopic compression errors occur on the finished product which are considered weak points in terms of corrosion resistance Act. In example 3 according to the invention, the silicate compression, which is during the hot water compression added glassy substance by the pressure and the temperature better introduced into the pores of the oxide layer and / or on the Built oxide layer.

Test for heat cracking resistance:

All Components of both the comparative examples and the invention Embodiments are stored at 100 ° C for 60 min. All components optically show no heat cracks.

Test for acid resistance and combined Acid / heat / alkali load:

All construction parts become 5 cycles of the Kesternichtests after DIN 50018 Subjected to KFW 2.0S. After that, no part has any visual changes. The components of the invention exhibit in a test after Standard TL 182 Volkswagen AG, namely a treatment for 10 minutes in an acidic medium, which has a pH of 1.0, a subsequent thermal aging and a 10-minute immersion in a medium with a pH of 13.5 and no changes , The test also consists of the components of Comparative Examples 1b and 3, but not if an abrasion test has already been carried out beforehand. In contrast, the protective effect in the case of the components treated according to the invention is retained even in the case of a preceding abrasion test since the protective effect is not built up not only on the surface but also in the pores. The components of Comparative Examples 1a and 2 are completely omitted in this test.

Test for resistance saline media:

All components undergo a salt spray test DIN 50017 SS exposed for over 480 hours. After that, no part has any visual changes.

Alkali resistance test:

All components are stored in an alkaline test solution with a stoichiometric pH of 13.5 at temperatures of 18-20 ° C for 10 min. The alkaline test solution consists of a 0.317 molar solution, in which 11 solution
12.7 g of sodium hydroxide
4.64 g of sodium phosphate dodecahydrate (equivalent to 2 g of sodium phosphate)
0.33 g of sodium chloride
and the rest of distilled water are contained.

The erfindungsgenäßen components and components from Comparative Examples 1b and 3 show after 10 minutes no or wegpolierbare changes. The Eloxalschicht is at virtually unchanged Schichtdi not damaged compared to the initial state.

The Component from Comparative Example 1a changes after 4 min and the component from Comparative Example 2 to 3-4 minute The transparent compaction layer becomes cloudy, partially is the anodized layer after the entire test period of 10 completely removed.

Alkali resistance test after previous mechanical load:

The Components of Comparative Example 3 and the invention Embodiments 1, 2 and 3 are by a device led to Amtec-Kistler, which is a car wash simulation represents. There are 10 double strokes on the surface each component exercised. Subsequently, the Components in the alkaline test solution described above with a measured pH of 13.5 at temperatures of 18-20 ° C stored for 10 min.

The Component of Comparative Example 3 and the components of the invention Embodiments 1 and 3 show after 10 min a slight, By polishing almost completely reversible change. The Component according to the embodiment of the invention 2 passes the test at a pH of 12.5, whereas the comparative example 2 the test is at a pH of 11.5.

All Components can be used as trim or functional parts because they are a heat resistant and corrosion resistant Have surface. The invention treated Components show the same good or better properties as those in Comparative method treated components. The better part Properties in the components according to the invention are achieved due to the improved compaction. The invention treated Components get a significantly shorter process time receive.

With treated by the method according to the invention Components are trim parts with high compaction quality, especially high corrosion resistance at the same time shortened process time of the anodizing process for Available.

The Invention is not described in the embodiment Limited process conditions. these can be varied according to the application of the component. So For example, the layer thickness of the anodization of a Ornamental parts are between 2 and 30 microns, resulting in treatment times change.

By the improved compacting quality with reduced processing time the capacity of an anodizing unit can be passed through increase faster throughput times of the components to be treated. The heat-compression step is conventional the step that takes the longest in the overall procedure, so that in anodized plants constructed by known methods more Hot compaction tank are provided. With a faster one Hot compression according to the invention Procedures can be less hot compacting tanks be provided in an anodizing plant. In contrast stands the increased plant outlay for one Compaction under increased pressure and increased Temperature. The energy balance is in the inventive Process by the reduced throughput times despite the increased Energy input favorable.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• EP 1407935 A1 [0003]
• - DE 102007057777 [0005]

Cited non-patent literature

• - DIN 50018 [0039]
• - Standard TL 182 [0039]
• - DIN 50017 SS [0040]

Claims (10)

Method for compacting a component made of aluminum and / or an aluminum alloy with one by anodization the surface of the component evenly produced oxide layer with a layer thickness of 2 to 30 microns, full at least the step: - Hot compacting of Component in a bath of demineralized water at temperatures of at least 100 ° C and when applying overpressure for a minimum of 1 min. Method according to claim 1, characterized in that that in addition to the hot water compression in addition Cold-sealing of the component in a bath of demineralized water, preferably with the addition of a nickel fluoride-containing compaction agent, at temperatures of 25 to 35 ° C and pH values from 6 to 7 for a minimum of 4 minutes. Method according to claim 1 or 2, characterized that temperatures of 100 to 140 ° C are used, preferably temperatures of 100 to 120 ° C. Method according to one of claims 1 to 3, characterized in that an overpressure of 1 bar to 2 bar is applied. Method according to one of claims 1 to 4, characterized in that the Heißwasserverdichtungszeit 0.5 to 3 min per micron layer thickness of the anodized oxide layer is. Method according to one of claims 1 to 5, characterized in that the Heißwasserverdichtungsbad To achieve a particularly high resistance to alkali a glassy Substance is added. Method according to one of claims 1 to 3, characterized in that as vitreous substance, a compound one or more alkali silicates in the hot water compacting bath, preferably sodium silicate and / or potassium silicate, more preferably as an aqueous solution in a concentration of 8 to 16 g of silicate per liter of demineralized water is added. Method according to one or more of the claims 1 to 7, characterized in that the hot water compression at pH values of 10 to 11, preferably at pH 10.4 to 10.8 is performed. Method according to one or more of the claims 1 to 8, characterized in that the component after the anodizing and before compacting an electrolytic and / or adsorptive Staining step is subjected. Method according to one of claims 1 to 9, characterized in that the Heißwasserverdichtungsbad one or more surfactants are added.