DE19858034A1 - Improved compaction process for anodized metal surfaces - Google Patents

Abstract

The invention relates to a method for the subsequent treatment of anodized metal surfaces, whereby the metal surfaces are brought into contact with an aqueous solution for sealing or after sealing. Said solution has a pH value ranging from 1 to 14 and contains 0.01 to 10 g/l of one or more acids having fluoroalkyl groups with 2 to 22 carbon atoms and/or of fluorinated polymers or copolymers of acrylic acid and/or methacrylic acid or of each of the salts of these acids. The invention also relates to the use of acids having fluoroalkyl groups with 2 to 22 carbon atoms and/or of fluoroalkyl with 2 to 22 C atoms and/or of fluorinated polymers or copolymers of acrylic acid and/or methacrylic acid or of each of the salts of these acids in order to reduce the soil adherence to anodized metal surfaces.

Description

The invention is in the field of producing anti-corrosion and / or decorative coatings on metals by anodic oxidation. she relates to an improved method for compressing the electrochemically generated porous anodizing layers to further improve their properties, especially to reduce dirt adhesion.

The electrochemical anodic oxidation of metals in suitable Electrolytes is a widely used process for the formation of Corrosion-protecting and / or decorative coatings on suitable ones Metals. These processes are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition, Vol. 9 (1987), pp. 174-176 briefly characterized. Accordingly, titanium, magnesium and aluminum and their alloys anodizable, the anodizing of aluminum and its alloys has the greatest technical importance. The electrolytically generated anodizing layer ten protect the aluminum surfaces from the effects of weather and other corrosive media. Anodizing layers are also applied, to get a harder surface and therefore an increased surface To achieve wear resistance of the aluminum. Due to the inherent color of the Leave anodizing layers or by absorptive or electrolytic coloring achieve special decorative effects. Anodizing aluminum takes place in an acidic electrolyte, with sulfuric acid being the most common is. Other suitable electrolytes are phosphoric acid, oxalic acid and Chromic acid. The properties of the anodizing layers can be determined by the  Choice of the electrolyte, its temperature as well as the current density and the Anodizing times vary within wide limits. Usually this is done Anodization with direct current or with an alternating current superimposed on direct current electricity.

The fresh anodizing layers can be dipped in solutions suitable dye or by an AC treatment in one metal salt-containing, preferably subsequently in a tin-containing electrolyte be colored. As an alternative to the subsequent coloring, colored ones can be used Anodizing layers obtained by so-called color anodization processes, for what one, for example, the anodization in solutions of organic acids, in particular special sulfophthalic acid or sulfanilic acid, optionally in each case Mix with sulfuric acid.

These anodically generated protective layers, the structure of which is scientific Investigations are available (R. Kniep, P. Lamparter and S. Steeb: "Structure of Anodic Oxide Coatings on Aluminum "Angew. Chem. Adv. Mater 101 (7), pp. 975-977 (1989)), are often referred to as "oxide layers". The above However, the aforementioned study has shown that these layers are glass-like and contain tetrahedrally coordinated aluminum. Octahedrally coordinated Aluminum as in the aluminum oxides was not found. Therefore in this patent application the more general term "anodizing layers" instead of the misleading term "oxide layers" used.

However, these layers do not yet meet all the requirements with regard to the Corrosion protection because they still have a porous structure. For this Basically, it is necessary to compact the anodizing layers. This Compression is often done with hot or boiling water, alternatively with Water vapor, made and referred to as "sealing". This will make the The pores are closed and the corrosion protection is considerably increased. About this Compaction process there is extensive literature. For example called sei: S. Wernick, R. Pinner and P. G. Sheasby: "The Surface Treatment and Finishing of Aluminum and its Alloys "(Vol. 2, 5th Edition, Chapter 11:" Sealing  Anodic Oxide Coatings "), ASM International (Metals Park, Ohio, USA) and Fi nishing Publications LTD (Teddington, Middlesex, England) 1987.

When compacting the anodizing layers, however, not only the pores become closed, but a more or forms on the entire surface less strong velvety covering, the so-called sealing covering. This one out Covered hydrated aluminum oxide is optically disturbing, reduced the adhesive strength when bonding such aluminum parts and promotes later Pollution and corrosion. Since the subsequent removal of this Sealing coverings by hand, mechanically or chemically, are complex is attempted by chemical additives to the sealing bath training to prevent this sealing topping. According to DE-C-26 50 989 are for this Additions of cyclic polycarboxylic acids with 4 to 6 carboxyl groups in the molecule, in particular cyclohexane hexacarboxylic acid. According to DE-A-38 20 650 certain phosphonic acids, for example the 1- Use phosphonopropane-1,2,3-tricarboxylic acid. From EP-A-122 129 is the Known use of further phosphonic acids. DE-C-22 11 553 describes a method for compacting anodic oxide layers on aluminum and Aluminum alloys in aqueous, phosphonic acids or their salts and Solutions containing calcium ions, the molar ratio of calcium ions Phosphonic acid is set to at least 2: 1. Preferably a higher ratio of calcium ions: phosphonic acids from about 5: 1 to about 500: 1 used. Examples of suitable phosphonic acids are: 1- Hydroxypropane, 1-hydroxybutane, 1-hydroxypentane, 1-hydroxyhexane-1,1- diphosphonic acid and 1-hydroxy-1-phenylmethane-1,1-diphosphonic acid and preferably 1-hydroxyethane-1,1-diphosphonic acid, 1-aminoethane, 1-amino-1- phenylmethane, dimethylaminoethane, dimethylaminobutane, Diethylaminomethane, propyl and butylaminomethane-1,1-diphosphonic acid, Aminotrimethylenephosphonic acid, ethylenediaminetetramethylenephosphonic acid, Diethylenetriaminepentamethylenephosphonic acid, aminotri- (2-propylene-2- phosphonic acid), phosphonosuccinic acid, 1-phosphono-1- methyl succinic acid and 2-phosphonobutane-1,2,4-tricarboxylic acid. According to the Embodiments of this patent are conventional  Hot compression process with compression times between 60 and 70 minutes with anodizing layer thicknesses between approximately 18 and approximately 22 μm. The Compression time is about 3 minutes per µm of layer thickness.

When using water other than the sealingbe mentioned Anti-sag agents contain no other additives are for effective compaction high temperatures (at least 90 ° C) and relatively long treatment times in of the order of about 1 hour with an anodizing layer of about 20 µm required. This corresponds to a compression time of about 3 minutes each Micrometer anodizing layer thickness. The compression process is very much so energy consuming and because of its duration can be a bottleneck for the Show production speed. Therefore, additives were already used for Compression bath sought to support the compression process, so that this at lower temperatures (so-called cold compression or cold sealing) and / or expires with shorter treatment times. As additives, the one Compression in the temperature range below 90 ° C was possible suggested for example: nickel salts, in particular fluorides, some of which are contained in used in practice (EP 171 799), nitrosylpentacyanoferrate, complex Fluorides of titanium and zirconium as well as chromates or chromic acid, if necessary in conjunction with other additives. As an alternative to one The actual compression was achieved by means of hydrophobicizing the oxide layer long chain carboxylic acids or waxes recommended as well as treatment with Acrylamides to be polymerized in the pore space. More details the above-mentioned literature by S. Wernick et al. be removed. With the exception of the Do not enforce compression with nickel compounds in practice.

A short-term hot compression process is known from US-A-5 411 607 which the anodized metal parts are immersed in a lithium-containing aqueous solution become. The lithium concentration is preferably in the range from 0.01 to 50 g / l and especially in the range of 0.01 to 5 g / l. It is also proposed that the compaction solution additionally contains a sealant inhibitor. This is preferably present in a concentration between 0.1 and 10 g / l  and is preferably an aromatic disulfonate. According to US-A-5,478 415, which has the same priority as US-A-5 411 607 cited above decreases, a short-term hot compression with an aqueous solution take place, the at least 0.01 g / l of lithium ions and from 0.1 to 10 g / l of one Contains anti-sealant. Here, too, is the sealant preventing agent preferably an aromatic disulfonate. From DE-A-195 38 777 is a Short-term hot compression process known, in which the anodized Metal parts in contact with an anodizing solution, the total of 0.1 to 5 g / l one or more alkali metal and / or alkaline earth metal ions and in total 0.0005 to 0.2 g / l of a sealing deposit inhibitor in the form of phosphonic acids or contains cyclic polycarboxylic acids.

The teaching of the last three documents enables a significant reduction in hot compression times. DE-A-196 21 819 points in a similar direction. It relates to a method for compacting anodized metal surfaces, characterized in that the anodized metal is in contact with an aqueous solution for a period of between 0.5 and 2 minutes per micrometer of anodizing layer thickness brings, which has a temperature between 75 ° C and the boiling point and a pH in the range of 5.5 to 8.5 and the

• a) a total of 0.0001 to 0.01 g / l of one or more alkali metal and / or Alkaline earth metal ions and
• b) a total of 0.0005 to 0.5 g / l of one or more organic acids selected from cyclic polycarboxylic acids with 3 to 6 carboxyl groups and / or phosphonic acids

contains, the solution containing a larger amount of the metal ions of group a) contains, as required for the complete neutralization of the acids of group b) is.

DE-A-196 21 818 teaches a method for compacting anodized metal surfaces, characterized in that the anodized metal is brought into contact with an aqueous solution which has a temperature of between 75 and 0.5 minutes per micrometer of anodizing layer thickness ° C and the boiling point and has a pH in the range of 5.5 to 8.5 and the

• a) a total of 0.0004 to 0.05 g / l, preferably 0.005 to 0.02 g / l, one or several cationic, anionic or nonionic surfactants and
• b) a total of 0.0005 to 0.5 g / l, one or more organic acids selected from cyclic polycarboxylic acids with 3 to 6 carboxyl groups and / or phosphonic acids

contains.

Despite the state of the art, there is a need for compaction processes that either reduce the effort for the compression or that give densified anodizing layers improved properties. To the Properties of densified anodizing layers in need of improvement especially the soiling behavior and the adhesion of the dirt. Anodized metal surfaces that are dirty on the surface are aesthetic ugly, which is particularly annoying when used in architecture is felt. On the other hand, layers of dirt accelerate corrosion. Therefore, there is a particular need for anodized metal surfaces to which dirt adheres poorly. As a result, dirt settles less quickly becomes solid and on the other hand is largely restored by precipitation washed.

In a first aspect, the present invention relates to a method for Aftertreatment of anodized metal surfaces, whereby the metal surfaces for densification or after densification in contact with an aqueous solution brings that has a pH in the range of 1 to 14 and the 0.01 to 10 g / l one or more acids with fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated polymers or copolymers of acrylic acid and / or methacrylic acid or each contains the salts of these acids.  

The monomeric and / or polymeric acids mentioned can also be used Fluoroalkyl groups - with the exception of additives for adjusting the pH - represent only active ingredients dissolved in the aqueous solution. For setting of the pH, if necessary, come in particular ammonia or Acetic acid in question. In principle, it is irrelevant whether the monomers and / or polymeric acids used as such or in the form of their salts become. Due to the adjustment of the pH value to the range mentioned the balance between free acid and acid anions according to the Acid constant corresponding to the respective acid.

In one embodiment of the method according to the invention, the mentioned fluorine-containing acids during the densification of the anodizing layers used. This embodiment of the invention is accordingly characterized characterized in that the anodized metal surfaces are compacted by the metal surfaces for a period between 0.5 and 4 minutes each Micrometer anodizing layer in contact with an aqueous solution which has a pH in the range from 5.5 to 8.5 and the 0.01 to 10 g / l or more acids with fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated polymers or copolymers of acrylic acid and / or methacrylic acid or each contains the salts of these acids.

The acids mentioned with fluoroalkyl groups can also be used together with other components, the beneficial effects of which are known when compacting anodizing layers and which can contribute, for example, to reducing the sealing coatings, lowering the sealing temperature and shortening the compression time. Examples of such substance groups and individual substances were enumerated in the description of the prior art. Accordingly, preferred embodiments of the present invention can consist in that the aqueous solution for compacting additionally contains one or more of the following constituents:

• a) a total of 0.0005 to 0.5 g / l of one or more organic acids without Fluoroalkyl groups selected from cyclic polycarboxylic acids with 3 to 6  Carboxyl groups and / or phosphonic acids,
• b) a total of 0.0004 to 0.05 g / l of one or more cationic, anionic or nonionic surfactants,
• c) a total of 0.0001 to 0.01 g / l of lithium and / or magnesium ions.
• d) 1.2 to 2.0 g / l, nickel ions and 0.5 to 0.8 g / l fluoride ions.

In a further embodiment of the method according to the invention, the anodizing layers are compacted according to one of the methods known in the prior art, which were described by way of example in the introduction. Following this compaction, if necessary after an intermediate rinsing with water, the anodized and compacted metal surfaces are brought into contact with the fluorine-containing acids already mentioned above. Accordingly, an alternative embodiment of the invention is to densify the anodized metal surfaces by contacting the metal surfaces with an aqueous solution having a pH in the range of 5 for a period of between 0.5 and 4 minutes per micron of anodizing layer thickness , 5 to 8.5 and which contains one or more of the following components:

• a) a total of 0.0005 to 0.5 g / l of one or more organic acids without Fluoroalkyl groups selected from cyclic polycarboxylic acids with 3 to 6 Carboxyl groups and / or phosphonic acids,
• b) a total of 0.0004 to 0.05 g / l, one or more cationic, anionic or nonionic surfactants,
• c) a total of 0.0001 to 0.01 g / l of lithium and / or magnesium ions,
• d) 1.2 to 2.0 nickel ions and 0.5 to 0.8 g / l, fluoride ions

and then for a period of time ranging from 5 seconds to 15 minutes an aqueous solution which has a pH in the range of 1 to 14 and which 0.01 to 10 g / l, one or more acids with Fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated polymers or Copolymers of acrylic acid and / or methacrylic acid or each of the salts contains these acids.

In these two embodiments, the organic acids are preferred the group a) selected from saturated, unsaturated or aromatic  carbocyclic six-ring carboxylic acids with 3 to 6 carboxyl groups.

Preferred examples of such acids are trimesic acid, trimellitic acid, Pyromellitic acid, mellitic acid and the most preferred Cyclohexane hexacarboxylic acid. The total amount of carboxylic acids is preferably in the range 0.001 to 0.05 g / l.

The preferred cyclohexane hexacarboxylic acid exists in the form different stereoisomers. As known from DE-A-26 50 989 preference is given to those cyclohexane hexacarboxylic acids which have 5 cis and 1 trans or the 4 cis and 2 trans carboxyl groups wear.

In a second special embodiment, the organic acids are Group a) selected from the phosphonic acids: 1-phosphonopropane-1,2,3- tricarboxylic acid, 1,1-diphosphonopropane-2,3-dicarboxylic acid, 1-hydroxypropane-1,1- diphosphonic acid, 1-hydroxybutane-1,1-diphosphonic acid, 1-hydroxy-1- phenylmethane-1,1-diphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, 1- Aminoethane-1,1-diphosphonic acid, 1-amino-1-phenylmethane-1,1-diphosphone acid, dimethylaminoethane-1,1-diphosphonic acid, propylaminoethane-1,1- diphosphonic acid, butylaminoethane-1,1-diphosphonic acid, aminotri (methylene phosphonic acid), ethylenediaminotetra (methylenephosphonic acid), diethylenetri aminopenta (methylenephosphonic acid), hexamethylene diaminotetra (methylene phosphonic acid), n-propyliminobis (methylenephosphonic acid), aminotri (2-propylene- 2-phosphonic acid), phosphonosuccinic acid, 1-phosphono-1-methyl succinic acid and 1-phosphonobutane-1,2,4-tricarboxylic acid. From this selection are the 1-phosphonopropane-1,2,3-tricarboxylic acid, 1,1-diphosphonopropane-2,3- dicarboxylic acid, aminotri (methylenephosphonic acid) are particularly preferred. The Group b) phosphonic acids are preferably used in an amount of 0.003 up to 0.05 g / l used. Polyphosphinocarboxylic acids are also suitable can be understood as copolymers of acrylic acid and hypophosphites. An example of this is Belclene® 500 from FMC Corporation, Great Britain.

Different groups of surfactants can be used as a further optional component in the process according to the invention. Cationic surfactants from group b) can be selected, for example, from quaternary ammonium salts in which at least one alkyl or arylalkyl radical has at least 8 carbon atoms. An example of this is C _12-14 - alkyldimethylbenzylammonium chloride. Pyridinium salts such as dodecylpyridinium chloride can also be used as cationic surfactants. Examples of anionic surfactants from group b) which can be used are alkyl or alkylaryl sulfates and sulfonates. Linear alkyl sulfates such as lauryl sulfate are preferred for environmental reasons. The anionic surfactants can be used as alkali or ammonium salts, with lithium salts being particularly preferred.

However, nonionic surfactants are preferably used as group b) surfactants on. These can be selected, for example, from alkoxylates such as for example ethoxylates and / or propoxylates of fatty alcohols or Fatty amines. Here, among fatty alcohols and fatty amines are compounds with understood an alkyl radical with at least 8 carbon atoms. Such substances can as pure substances with a defined alkyl radical or from Product mixtures consist of how they are obtained from natural fats and oils become. The alkoxylates can also be end group capped, i.e. H. on the terminal OH group must be etherified again. Examples of such Nonionic surfactants are octanol × 4 EO (EO = ethylene oxide) and octanol × 4.5 EO- Butyl ether. One uses as nonionic surfactants instead of the fatty alcohol ethoxylates Fat aminoxylates tend to give improved compaction results. The group b) nonionic surfactants are therefore preferably selected Fatty amine ethoxylates with 10 to 18 carbon atoms in the alkyl radical and with 3 to 15 Ethylene oxide units in the molecule. Specific examples are coconut fatty amine × 5 EO and coconut fatty amine × 12 EO.

Another preferred embodiment is that the aqueous solution additionally a total of 0.0001 to 0.01 g / l lithium and / or magnesium ions contains. The use of components a), b) and / or c) leads to that compression times can be selected in the lower half of the  specified period of time are between about 0.5 and about 2 minutes each µm anodizing layer thickness can be.

Regardless of the chosen embodiment of the invention, this can Compression bath 1, 2 to 2.0 g / l nickel ions and 0.5 to 0.8 g / l fluoride ions contain. This component allows the compression as a so-called Cold compaction, d. H. in the temperature range between about 15 and about 70 ° C operate. Without the addition of nickel fluoride or other additives that it allow the compression temperature in this so-called "cold compression area "can lower the compression in the so-called medium temperature range, i.e. from about 70 to about 90 ° C, or in the so-called hot temperature range, i.e. between 90 ° C and the boiling point of the compression bath be performed. These temperature specifications apply to the Compression process regardless of which of the two described Embodiments of the method according to the invention is used.

If you work according to the last described embodiment, in which the Treatment with the fluorine-containing acids after the actual one Compression takes place, so the aqueous solution of the fluorine-containing acids Temperature in the range between about 15 ° C and the boiling point of the solution exhibit. The amount of time that the compacted metal surfaces last brought into contact with the aqueous solution of the fluorine-containing carboxylic acids are chosen, the shorter the higher the temperature of this aqueous Solution is.

The acids to be used according to the invention with fluoroalkyl groups with 2 to 22 C atoms are preferably selected from fluorocarboxylic acids, Fluoroalkylphosphinic acids, fluoroalkylphosphonic acids, fluoroalkylphosphon acid esters with still free acid functions and from fluoroalkyl sulfonic acids. Here Those acids with fluoroalkyl groups are particularly preferred in which these fluoroalkyl groups represent perfluoroalkyl groups. However, this is not the case to understand that the entire acid molecule must be perfluorinated. Much more it can also carry unfluorinated methylene or methyl groups.  

Rather, this statement should mean that whenever a Carbon atom is bound to a fluorine atom, the other valences this Carbon atom, not through bonds to neighboring carbon atoms or heteroatoms of the acids are saturated by binding to fluorine atoms be saturated. In an alternative formulation, acids are preferred whose Carbon atoms do not carry both hydrogen atoms and fluorine atoms. In particular, those acids can be used in which the Acid function adjacent carbon atoms normal methylene groups represent, while more distant carbon atoms are either perfluoromethylene or represent perfluoromethyl groups. If you use fluorinated polymers or Copolymers of acrylic acid and / or methacrylic acid, is the distribution of the the individual C atoms bound F atoms and H atoms irrelevant.

In each of the described embodiments, the invention can Methods for the aftertreatment of anodized metal surfaces are used, where the thickness of the anodizing layer is in the normal range Anodizing layer thicknesses (about 15 to about 25 μm, in particular about 18 to about 22 µm) or in the area of thin film anodization (about 1 µm to about 15 µm).

The compression bath suitable for the compression process according to the invention with the fluorine-containing organic acids can in principle by dissolving the Components in - preferably fully demineralized - water in the required Concentration range are made on site. Preferably used for the preparation of the compression baths, however, an aqueous concentrate already all the necessary components of the compression bath in the right one Contains proportions and from which you can dilute with water for example by a factor between about 10 and about 1000 ready-to-use solution. If necessary, the pH must be included Ammonia or adjusted with acetic acid to the range of the invention become. The invention accordingly also comprises an aqueous concentrate for Preparation of the aqueous solution for use in the invention Compaction process whereby the concentrate is diluted with water  a factor between about 10 and about 1000 the ready-to-use aqueous Solution results.

The method according to the invention provides compressed anodizing layers, the Quality characteristics in the technical rules (for example those of Qualanod) matched. These compacted anodizing layers However, they also show a further property which is the case with the the anodizing layers produced in technology is less pronounced. Dirt particles adhere less well to the surface, making them underneath same conditions less quickly and the dirt relatively easy is removable. When used in the field of exterior architecture, this leads to that soiling on the anodized aftertreatment according to the invention Metal surfaces can be easily washed off by precipitation.

Accordingly, another aspect of the present invention is its use of acids with fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated Polymers or copolymers of acrylic acid and / or methacrylic acid or each the salts of these acids to reduce dirt adherence on anodized Metal surfaces. This use is that one of the above Acids with fluoroalkyl groups, for which the above mentioned details Comments apply in the context of one of the ones described in more detail above Post-treatment procedures. To reduce dirt adhesion Anodized metal surfaces are accordingly the above according to the invention specified acids with fluoroalkyl groups in the above described aftertreatment method used. In claims 9 to 12 the features of this use are summarized again.

It is for the compression method according to the invention or for the Use of the invention irrelevant whether the metal surfaces during or after anodizing and before compacting or not. The compression method according to the invention and the one according to the invention Accordingly, both colored and non-colored are used Anodizing layers applicable. A possible coloring can  electrochemical (e.g. conventional tin salt staining), as Integral coloring or with organic immersion colors.

Embodiments A) Fluorinated acids in the compression bath

Aluminum sheets of the type AlMg1 were prepared with a treatment sequence customary in the prior art:

Degreasing: P3-almeco® 18, 5%, 5 min. 70 ° C
Rinse: domestic water
Pickling: P3-almeco ^R 57, 3%, 1 min. 50 ° C
Rinse: domestic water
Deoxidize: Novox ^R 4902, 2%, 1 min., Room temperature
Rinse: demineralized water
Anodizing: sulfuric acid, 18%, 40 min., 18 ° C, 1.5 A / dm ² , 16 V
Rinse: demineralized water.

The anodized aluminum sheets with an anodizing layer thickness in the range from about 18 to about 20 μm were then compacted with compression solutions according to the tables below for 60 minutes at a temperature between 95 and 100 ° C. In all cases the surface appearance was judged to be good. The following were measured as quality parameters:

• 1. Acid removal in mg / dm ² , determined based on ISO 3210. For this purpose, the test sheet is weighed to the nearest 0.1 mg and then immersed for 15 minutes at 38 ° C. in an acid solution containing 35 ml of 85% per liter Contains phosphoric acid and 20 g of chromium (VI) oxide. At the end of the test period, the sample is rinsed with deionized water and dried in a drying cabinet at 60 ° C. for 15 minutes. The sample is then weighed again. The weight difference between the first and the second measurement is calculated and divided by the size of the surface in dm ² . Weight loss is expressed as Δ G in mg / dm ² (1 dm ² = 100 cm ² ) and should not exceed 30 mg / dm ² .
• 2. The apparent conductance Y ₂₀ was determined in accordance with German standard DIN 50 949 using an Anotest YD 8.1 measuring device from Fischer. The measuring system consists of two electrodes, one of which is conductively connected to the base material of the sample. The second electrode is immersed in an electrolyte cell that can be placed on the layer to be examined. This cell is designed as a rubber ring with an inner diameter of 13 mm and a thickness of approximately 5 mm, the ring surface of which is self-adhesive. The measuring area is 1.33 cm ² . A potassium sulfate solution (35 g / l) in deionized water is used as the electrolyte. The apparent conductance readable on the measuring device is converted according to the specifications of DIN 50 949 to a measuring temperature of 25 ° C and to a layer thickness of 20 µm. The values obtained, which should preferably be in the range between approximately 10 and approximately 20 μS, are entered in the table.
• 3. Paint drop test according to ISO 2143. Here it is checked how strong a Dye solution is absorbed on the anodized surface. For testing a drop of an acid solution (hexafluorosilicic acid or a Solution of potassium fluoride in sulfuric acid) at about 23 ° C on the clean, given a dry and level test surface and exactly one Leave on for a minute. Then the drop of acid is washed off and the Let the sample surface dry. Then the same place of the A drop of a dye solution (aluminum blue 2 EV or Sanodal Red B3 LW) with a pH in the range between about 5 and about 6 and a temperature of about 23 ° C and act for one minute to let. Then the drop of the dye solution is rinsed off and the Wipe the test surface with a damp cloth. Then will dried. The intensity of the color spot remaining on the test surface is visually compared to one specified in the test specification Comparison scale assessed. The intensity of the color is determined by a Grading scale expressed between 0 and 5, with the grade 0 for none Coloring (corresponding to a non-absorbent surface) and the grade 5 for strong coloring (corresponding to a fully absorbent  Anodizing layer). The lower the test grade, the better the compression the anodizing layer is viewed.
• 4. Soiling behavior. A 5% was used as test soiling Dispersion of ground fly ash (grain size about 10 µm) in demineralized water is used. A color measuring device was used for evaluation (Croma-Meter CR-300, Minolta) and a gloss meter (mikro-TRI-gloss, Gardner) used. Implementation and evaluation took place as follows:

execution

• a) L * a * b * value of the coated, not yet soiled test sheet with measure the colorimeter and the 60 ° gloss,
• b) Allow the test sheet to swell in deionized water for 15 minutes,
• c) Stir test dirt well, 2 ml with the disposable pipette on the almost distribute the test plate held vertically,
• d) completely dry the test sheet in the drying cabinet at 40 ° C (approx. 20 min),
• e) then rinse in a vessel with deionized water (10 times each before and move back),
• f) Dry the test sheet again at 40 ° C
• g) Measure the L * a * b * value of the soiled test sheet with the colorimeter as well as the 60 ° gloss.

evaluation

L * a * b * measurement with the Minolta colorimeter:
The Δ value is calculated in%:
ΔL * = (L * _dirty

/ L * _unpolluted

) × 100%
60 ° gloss measurement with the Gardner micro-TRI-gloss device
The Δ value is calculated in%:
ΔGE = (GE _spotted

/ GE _unpolluted

) × 100%
Repetition of steps 3b) to g) to ΔL * or ΔGE are constant or significantly larger than that of an uncoated test plate (zero plate).
Compression and quality parameters are summarized in Table 1.

Table 1: Compression and quality parameters

• a) Component according to the invention ("Comp 1"): perfluorinated monoalkyl phosphate (R _f H ₂ CH ₂ O) P (O) (ONH ₄ ) ₂ R _f = F (CF ₂ - CF ₂ ) _3-8 (Zonyl®FSP, DuPont company);
  optional additive: cyclohexane hexacarboxylic acid according to DE-A-26 50 989 ("CHHS")
  pH 5.5-6.0
  
• b) Component according to the invention ("Comp 1"): Perfluorinated dialkyl phosphate (R _f CH ₂ CH ₂ O) ₂ P (O) (ONH ₄ ), R _f = F (CF ₂ - CF ₂ ) _3-8 (Zonyl®FSE , DuPont company);
  optional additive: cyclohexane hexacarboxylic acid according to DE-A-26 50 989 ("CHHS")
  pH 5.5-6.0
  
• c) Component according to the invention ("Comp 1"): Perfluorinated mono- / dialkyl phosphate (R _f H ₂ CH ₂ O) P (O) (OH) ₂ + (R _f CH ₂ CH ₂ O) ₂ P (O) (OH ) R _f = F (CF ₂ - CF ₂ ) _3-8 (Zonyl®UR, DuPont);
  optional additive: cyclohexane hexacarboxylic acid according to DE-A-26 50 989 ("CHHS")
  pH 5.5-6.0
  

To test the soiling behavior, as described above, Sample sheets once soiled per test cycle, let dry and the Rinsed off dirt. After each test cycle, the change in color and the gloss value measured relative to the unpolluted sheet. Table 2 contains information on relative color value and relative gloss per soiling cycle, the use of perfluorinated monoalkyl according to the invention phosphate using the standard comparison Compression bath additive cyclohexane hexacarboxylic acid is compared. The Table 2 shows that color and Gloss values change only slightly from cycle to cycle, whereas with the Comparative sheets a significant deterioration occurs, the adherent Indicates dirt.  

Table 2: Soiling behavior. According to the invention: compressed with the addition of 35 mg / l perfluorinated monoalkyl phosphate (Zonyl®FSP); Comparison: compressed with the addition of 13.2 mg / l cyclohexane hexacarboxylic acid ("CHHS")

B) Post-treatment with fluorinated acids after compaction

Aluminum sheets were prepared as described under A). After that them according to a method according to the prior art in an aqueous solution of 13.2 mg / l cyclohexane hexacarboxylic acid with a temperature of 95 ° C and a pH in the range of 5, 5 to 6 compressed for 30 or 60 minutes. After that they were immersed in a solution containing 7 g / l Zonyl®FSP (see Table 1) contained, had room temperature and a pH of 7 exhibited. The sheets were then dried with compressed air. The Surface quality was tested according to Qualanod, as above under A) has been described. The results are shown in Table 3.  

Table 3: Treatment parameters and surface qualities for compaction and subsequent treatment with perfluorinated monoalkyl phosphate Zonyl®FSP

In a further series of tests, the sheet metal described above under B) described compressed and aftertreated with perfluorinated monoalkyl phosphate the influence of the variables: drug concentration, temperature and Treatment time on the surface coverage of the sample sheets with perfluorinated Monoalkyl phosphate examined. The sheets were compacted for 60 minutes been. The compacted test panels were each for one minute, 5 minutes and leave in the Zonyl®FSP solution for 15 minutes. As a measure of the The counting rate (in kilo pulses per second) was at a surface area X-ray fluorescence measurement used for phosphorus. The results are in Tables 5 to 7 included.  

Table 5: X-ray fluorescence pulse rate at different concentrations of Zonyl®FSP; pH = 7, room temperature

Table 6: X-ray fluorescence pulse rate for different temperatures of the Zonyl®FSP solution; Concentration 0.7% by weight, pH = 7

Table 7: X-ray fluorescence pulse rate at different pH of the Zonyl®FSP solution, adjusted with acetic acid or ammonia; Concentration 0.7% by weight, room temperature

Claims (12)

1. Process for post-treatment of anodized metal surfaces, wherein the Metal surfaces for compacting or after compacting with a brings into contact aqueous solution having a pH in the range of 1 to 14 has and the 0.01 to 10 g / l of one or more acids with Fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated polymers or Copolymers of acrylic acid and / or methacrylic acid or each of the salts contains these acids. 2. The method according to claim 1, characterized in that one anodized metal surfaces by making the metal surfaces for a time period between 0.5 and 4 minutes per micrometer Anodizing layer thickness in contact with an aqueous solution that one Has pH in the range of 5.5 to 8.5 and which is 0.01 to 10 g / l or several acids with fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated polymers or copolymers of acrylic acid and / or methacrylic acid or each contains the salts of these acids. 3. The method according to claim 2, characterized in that the aqueous solution additionally contains one or more of the following components:

• a) a total of 0.0005 to 0.5 g / l of one or more organic acids without fluoroalkyl groups, selected from cyclic polycarboxylic acids with 3 to 6 carboxyl groups and / or phosphonic acids,
• b) a total of 0.0004 to 0.05 g / l of one or more cationic, anionic or nonionic surfactants,
• c) a total of 0.0001 to 0.01 g / l, lithium and / or magnesium ions.
• d) 1.2 to 2.0 g / l of nickel ions and 0.5 to 0.8 g / l of fluoride ions.

4. The method according to claim 1, characterized in that the anodized metal surfaces are compacted by bringing the metal surfaces into contact with an aqueous solution having a pH in the range of for a period of between 0.5 and 4 minutes per micrometer of anodizing layer thickness 5.5 to 8.5 and which contains one or more of the following components:

• a) a total of 0.0005 to 0.5 g / l of one or more organic acids without fluoroalkyl groups, selected from cyclic polycarboxylic acids with 3 to 6 carboxyl groups and / or phosphonic acids,
• b) a total of 0.0004 to 0.05 g / l of one or more cationic, anionic or nonionic surfactants,
• c) a total of 0.0001 to 0.01 g / l of lithium and / or magnesium ions.
• d) 1.2 to 2.0 nickel ions and 0.5 to 0.8 g / l fluoride ions

and then for a period of time in the range of 5 seconds to 15 minutes in contact with an aqueous solution which has a pH in the range of 1 to 14 and which contains 0.01 to 10 g / l of one or more acids with fluoroalkyl groups Contains 2 to 22 carbon atoms and / or fluorinated polymers or copolymers of acrylic acid and / or methacrylic acid or each of the salts of these acids. 5. The method according to one or more of claims 1 to 4, characterized characterized in that the acids with fluoroalkyl groups having 2 to 22 carbon atoms selected are fluorocarboxylic acids, fluoroalkylphosphinic acids, Fluoroalkylphosphonic acids, fluoroalkylphosphoric esters and  Fluoroalkylsulfonic acids. 6. The method according to one or more of claims 1 to 5, characterized characterized in that the fluoroalkyl groups represent perfluoroalkyl groups. 7. Aqueous concentrate, which when diluted with water by a factor between 10 and 1000 and adjusting the pH if necessary results in aqueous solution in the process according to one or both of the Claims 2 and 3 can be used. 8. Use of acids with fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated polymers or copolymers of acrylic acid and / or Methacrylic acid or each of the salts of these acids to reduce the Dirt adherence on anodized metal surfaces. 9. Use according to claim 8, characterized in that the Metal surfaces for a period between 0.5 and 4 minutes each Micrometer anodizing layer thickness with an aqueous solution with a Temperature between 15 ° C and the boiling point that one Has pH in the range of 5.5 to 8.5 and 0.01 to 10 g / l of one or several acids with fluoroalkyl groups with 2 to 22 carbon atoms and / or fluorinated polymers or copolymers of acrylic acid and / or methacrylic acid or each contains the salts of these acids. 10. Use according to claim 9, characterized in that the aqueous solution additionally contains one or more of the following constituents:

• a) a total of 0.0005 to 0.5 g / l of one or more organic acids without fluoroalkyl groups, selected from cyclic polycarboxylic acids with 3 to 6 carboxyl groups and / or phosphonic acids,
• b) a total of 0.0004 to 0.05 g / l of one or more cationic, anionic or nonionic surfactants,
• c) a total of 0.0001 to 0.01 g / l, lithium and / or magnesium ions.
• d) 1.2 to 2.0 g / l of nickel ions and 0.5 to 0.8 g / l of fluoride ions.

11. Use according to claim 8, characterized in that the anodized metal surfaces are compacted by bringing the metal surfaces into contact with an aqueous solution having a pH in the range of from 0.5 to 4 minutes per micrometer of anodizing layer thickness 5.5 to 8.5 and which contains one or more of the following components:

• a) a total of 0.0005 to 0.5 g / l of one or more organic acids without fluoroalkyl groups, selected from cyclic polycarboxylic acids with 3 to 6 carboxyl groups and / or phosphonic acids,
• b) a total of 0.0004 to 0.05 g / l of one or more cationic, anionic or nonionic surfactants,
• c) a total of 0.0001 to 0.01 g / l of lithium and / or magnesium ions.
• d) 1.2 to 2.0 g / l of nickel ions and 0.5 to 0.8 g / l of fluoride ions

and then for a period of time in the range of 5 seconds to 15 minutes in contact with an aqueous solution which has a pH in the range of 1 to 14 and which contains 0.01 to 10 g / l of one or more acids with fluoroalkyl groups Contains 2 to 22 carbon atoms and / or fluorinated polymers or copolymers of acrylic acid and / or methacrylic acid or each of the salts of these acids. 12. Use according to one or more of claims 8 to 11, characterized characterized in that the acids with fluoroalkyl groups having 2 to 22 carbon atoms selected are fluorocarboxylic acids, fluoroalkylphosphinic acids,  Fluoroalkylphosphonic acids, fluoroalkylphosphoric esters and Fluoroalkylsulfonic acids.