JP2003535220A - Method of treating or pretreating a component having an aluminum surface - Google Patents

Abstract

(57) The present invention provides a method for forming a member, profile, strip or wire comprising a surface comprising aluminum or an aluminum-containing alloy, optionally having a surface comprising another metal or alloy. A method of treating or pre-treating with an aqueous acid solution containing fluoride and phosphate, wherein the fluoride is present in solution at least partially as free fluoride, and The free fluoride content of the phosphating solution in it is maintained in a concentration range of 5-500 mg / l of F _free and a concentration range of aluminum ions (including complexed Al) of 100 mg / l or less. Wherein the rising aluminum content in the sedimentation tank is outside the phosphating bath, from the phosphating bath to the sedimentation tank and From the circulation of a phosphating solution to phosphating bath drops content of less Al ions 100 mg / l in the bath.

Description

Detailed Description of the Invention

The present invention relates to a method of treating or pretreating a component having an aluminum surface.

The phosphating processes of aluminum and aluminum alloys are known in principle. In industrial practice, the fluoride-modified phosphating process with at least 150 mg / l of free fluoride is particularly demonstrated. These methods are
It is of particular importance in the automobile industry and is used especially when a substrate mix (Mix) of various metals or alloys is fed through the installation.

However, these processes are based on a high fluoride content, and a higher amount of cryolite (Na ₃ AlF ₆ ) or / and related precipitation products precipitates in the phosphating bath and Some of the product cannot be removed from it by a simple rinsing process and also deposits on the phosphated surface, with the increased roughness even after subsequent painting. It has the serious drawback that it occurs on pretreated surfaces that act in the way of their roughness.

DE-A1-197 35 314 has an aluminum surface—optionally a magnesium surface, a steel surface or / and a zinc surface—the component is placed in a phosphating facility. A method for pretreatment is described, in which the component is degreased with a degreasing solution, phosphating by treatment with a phosphating solution containing fluoride, and subsequently a passivating solution. Passivated by treatment with. The proportion of aluminum or / and magnesium surface to the total surface to be treated of the component is then at least 10%. At this time, the fluoride of the phosphate treatment solution is
It should be added exclusively as complexed fluoride and the content of free fluoride ions formed from it in the phosphating solution depends on the steel without phosphating the aluminum surface and / or the magnesium surface. It should be kept below 100 mg / l for phosphating the surface and / or the zinc surface. In addition, the passivating solution is used to passivate a phosphated steel surface or / and a zinc surface and a conversion layer (Konversio) on an aluminum surface or / and a magnesium surface.
nsschicht) should be formed.

However, this method can only be used in a relatively small area proportion relative to the aluminum surface, usually up to about 20 area% of the total surface to be treated, for a combination of substrates. It has the drawback that it can only be done. In addition, cryolite or / and related precipitation products are still formed in the pretreatment bath, and especially the layer-forming reaction on the iron and steel surfaces is dependent on the increased aluminum content of the phosphating solution. Due to the disadvantage of being hindered in some cases, all combinations of substrates of different metal and alloy surfaces can no longer be coated uniformly and well in the bath.

The object of the present invention is, in the case of an increased proportion of aluminum-containing surfaces of the component to be treated or pretreated, a good conversion layer which can be applied on an industrial scale and / or a corresponding non-conformity. A passivation layer on the surface of the aluminum or aluminum-containing alloy-
Proposal of a process for overcoming the disadvantages of the state of the art, and in particular for phosphating aluminum and aluminum-containing alloys, which makes it possible to apply-in combinations of substrates, possibly of different metals or alloys. Is.

The object is to have a surface made of aluminum or an aluminum-containing alloy--and optionally a surface made of another metal or alloy--a member,
It is solved by a method of treating or pre-treating a profile, strip or wire with an acidic aqueous solution containing fluoride and phosphate, the method wherein the fluoride is at least partly in solution as free fluoride. Existing and rising aluminum content in the precipitation tank is outside the phosphating bath, from the phosphating bath to the precipitation tank and from the precipitation tank to the phosphating bath. In the bath of the phosphating solution by reducing the content of Al ions in the bath to 100 mg / l or less under _free circulation, -Al ions (including complexed Al) are characterized by retaining an aluminum content in the concentration range up to 100 mg / l.

Alternatively or at the same time, in the case of the process according to the invention, the increasing aluminum content in the phosphating solution in separate zones of the phosphating bath results in Al ions 100
Care can be taken to reduce the content to below mg / l.

By pickling corrosion, aluminum is solubilized on the metal surface and the aluminum content is absorbed in the phosphating solution. However, the specific aluminum content is
It may also come from other sources into the phosphating solution, for example from the chemicals introduced in the post-rinse solution. The aluminum content can be reduced mainly or completely by precipitation, but also partly by complexation. The free fluoride content in the phosphating solution is preferably in the range 6 to 120 mg / l, particularly preferably 10 to 80.
It is kept in the range of mg / l, very particularly preferably in the range of 20-50 mg / l. The aluminum content in the phosphating solution is preferably kept at a value of ≦ 80 mg / l, particularly preferably ≦ 60 mg / l, very particularly preferably ≦ 30 mg / l.

The process according to the present invention is characterized in that aluminum in the phosphating solution is added in the precipitation tank or in a separate zone of the bath by addition of alkali metal ions, fluoride complexes or / and fluoride ions, in particular Na. - ions or K- or at least one easily dissociating fluoride in ion, e.g. _NaF, NH 4 F, NaHF ₂ or KF
It is also excellent to be precipitated in. The AlF _x complex may then already be present in a complexed form. It is advantageous to control the process according to the invention such that no increase in the free fluoride content in the bath occurs despite the F-addition. The content of alkali metal ions in the phosphating bath is preferably 1 to 20 g / l,
And, preferably, it is maintained within this range, particularly 3 to 10 g / l. In principle, the alkali metal ion content is much higher than the concentration of 20 g / l, eg 30 g / l.
It may be l. However, bath instability can often occur at such high alkali concentrations. In the case of coexisting mixtures of various alkali metal ions, a predominant content of sodium or / and potassium ions is preferred.

As a result, precipitated cryolite and related precipitation products, such as K ₂ NaAlF _6, are no longer or hardly present in the phosphating bath, rather rather or (mostly) exclusively. It is caused to occur in a separate zone of the bath or in the precipitation tank. Thereby, the precipitation product can no longer or hardly precipitate on the surface to be coated.

[0012] Advantageously, the free fluoride concentration of the phosphating solution in the phosphating bath is between 8 and.
80 mg / l and especially 10-50 mg / l, or 5-500 mg / l, especially 20-200 mg free fluoride in the precipitation tank or in a separate zone of the bath tank
/ L, particularly preferably 30 to 120 mg / l. Therefore, it is also preferable to keep these contents at these concentrations. Usually less than 5 mg / l does not cause pickling corrosion on aluminum due to free fluoride, and this pickling corrosion is required,
For example, chromate-containing compounds, titanium fluoride, zirconium fluoride, silane-based, soluble rare earth compounds-especially cerium-containing compounds, where scandium, yttrium and lanthanum are included in the concept of rare earth elements-, Phosphonate-based self-assembling molecules, phosphating as subsequent passivation with polymers soluble or / and dispersible in solvents is not sufficient for passivation alone. A small minimum content of free fluoride in solution is required. On the other hand, phosphoric acid is often present at a content of more than 120 mg / l of free fluoride, when the content of cations co-precipitated with phosphate, eg Zn, Cu, Ni, Fe, Mn, etc., is not very low. A closed phosphate layer from the salt treatment bath is formed on the metal surface. Formation of a phosphate layer on the aluminum surface is not absolutely necessary for reasons of corrosion protection. Therefore, free fluoride contents above 120 mg / l are
Despite this value being able to be manipulated according to the invention, it is usually not selected, in addition to it having higher chemical consumption and cryolite or / and related precipitation products. This is because it causes a larger amount of precipitated sludge. In addition, it is preferred to adjust and maintain a free fluoride concentration difference between 30 and 60 mg / l between the phosphating bath and the precipitation tank or a separate zone in the bath.

In many cases, the method according to the invention is utilized such that the residence time of the phosphating solution in the precipitation tank or in a separate precipitation zone is up to 1 h, often up to 0.5 h. The volume flow from the bath to the precipitation tank and from the precipitation tank to the bath is adjusted according to the selected volume or partial volume and the desired aluminum content in the phosphating bath.

The term “member” within the scope of the present application encompasses all types and shapes of sheets, strips and profiles, moldings, semi-finished products, components, assembly parts and the like.

Generally, the parts, profiles, strips and / or wires to be treated or to be pretreated in the process according to the invention are cleaned and rinsed before pickling / phosphating, And optionally, apart from the rinsing and cleaning steps, contact is made with an activating solution, for example based on colloidally dispersed titanium phosphate.

The treated or pretreated parts, profiles, strips and / or wires may be subjected to a pickling / phosphating treatment, in particular a chromate-containing compound, titanium fluoride,
Zirconium fluoride, soluble rare earth compounds-especially cerium-containing compounds, self-assembling molecules, such as those based on phosphonates, those based on silanes,
A passivating solution based on a polymer that is soluble or / and dispersible in a solvent,
It may be rinsed and / or passivated.

Treated or pretreated or / and passivated parts, profiles,
The strips and / or wires may be dried after pickling / phosphating or after passivation. However, in some cases drying is not necessary, for example in the case of immediate electrodeposition coating.

The precipitation of aluminum may be carried out under normal pressure and at a temperature in the range of room temperature to 70 ° C., in particular in the range of 40-60 ° C. In the case of the process according to the invention, the formation of the conversion or passivation layer may be carried out under normal pressure and at temperatures from room temperature to 70 ° C., preferably at 35-60 ° C. The pH value is usually within the range of 2-4. The pH value of the phosphating bath is in principle always in the range of around pH 3. pH ≧ 4.
At a value of 0, the bath is usually unstable, whereas at a value of pH ≤ 2.0, the bath is usually so stable that good layer formation does not occur, since This is because the pH value-displacement on the newly pickled metal surface is not sufficient for deposition of the chemical conversion layer.

Finally, the treated or pretreated or / and passivated parts, profiles, strips and / or wires can be paints, different types of organic coatings, foils and / or adhesives. It may be coated with layers, optionally printed and optionally deformed, the metal component so coated may additionally be glued together with other components, welding They may be joined together and / or otherwise joined together.

The product thus manufactured according to the present invention is used in the automobile industry, in the aircraft industry, in device assembly and machine assembly, in the furniture industry, in the building industry, in household appliances, electric appliances, measuring devices, control devices. For test equipment, structural elements, casings, linings, shelves, racks, frames, dividers, partitions, veneers, luminaires, guardrails, radiator elements or fence elements and for small parts, in particular car body members or car bodies , Can be used.

FIG. 1 shows a flow diagram that schematically illustrates one possible principle of separate aluminum-precipitations.

The phosphating process according to the invention differs from the processes described and practiced thus far in that sludges containing cryolite or / and related precipitation products are in separate precipitation zones or It has the advantage that it occurs significantly in a separate settling tank and from there can be waste treated. In addition, it is possible with the method according to the invention to treat or pretreat different metal substrates in one combination without disturbing, for example, the layer formation on steel. Due to the reduced content of free fluoride in the phosphating solution, there is also less pickling corrosion on the aluminium-containing surface, which also causes correspondingly less sludge formation. In addition, on the basis of the particles which are only slightly co-precipitated and deposited on the phosphated surface, indicia of interference after subsequent painting, such as roughness, streaking or other non-uniformity, are identified. What was not possible could be proved with the method according to the invention.

Significantly stable bath conditions are achieved with respect to the free fluoride and aluminum content in the phosphating bath and in separate zones or precipitation tanks, despite the very different concentrations of these contents. What I got was surprising.

[0024]   The subject of the invention is explained in more detail below on the basis of examples.

Example: The following experiment was carried out in order to calculate suitable precipitation conditions for an aluminum-containing phosphating solution in a phosphating bath according to the invention. Here, the effect of the concentrations of free fluoride, sodium and complexed fluoride on the aluminum precipitation rate was investigated, among others.

1. Experimental Design A computer-aided experimental design was used so that interactions that were potentially present with significant parameters could be better discriminated. I used the program Stavex
It was 4.3.

[0027] 2. Analysis equipment Fluoride measurement: Orion Model 960 with ion-selective electrode Aluminum: ICP.

A standard phosphating solution having the following composition was prepared from analytically pure chemicals: Zn: 1.5 g / l Mn: 1.0 g / l Ni: 1.0 g / l P ₂ O _{5: 14.0g / l NO 3:} 3.0g / l SiF 6: 1.0g / l FS: 2.0 free acid.

Starting from this solution, the content of SiF ₆ and Na ions and free fluoride was changed to another preparation.

3. Practical implementation: 0.5 l of the above phosphating solution is filled into a plastic beaker and adjusted to the desired higher content of silicofluoride with 24% H ₂ SiF ₆ solution. The free acid content was then calibrated by addition of NaOH. Na
- the content was adjusted with NaNO _3, the free fluoride content corresponding, ammonium bifluoride was diluted - adjusted with a solution. Aluminum 20 mg / l diluted aluminum nitrate solution was used to add to the bath. After 0, 15, 30 and 60 minutes, free fluoride was measured and a solution sample was drawn for aluminum determination.

In order to prevent the post-precipitation of aluminum in the extracted sample, it was carried out as follows: 5 ml of the sample filtered using a membrane filter was added to a strong hydrochloric acid complete desalted aqueous solution and 50 ml was replenished with demineralized water. This solution is
Was used to investigate the aluminum content.

[0032]   The results are summarized in Table 1.

[0033] Table 1: Precipitation test

[0034]

[Table 1]

Experiment 1 showed no precipitation of aluminum over a period of 5 days. In experiments 4, 8 and 15, a dramatic reduction in aluminum content was obtained even within 15 minutes. Increased alkali content may be preferred in compounds with increased free fluoride content. SiF ₆ is used for the stability of phosphating solutions and for the possibility of using combinations of various kinds of metal surfaces, in particular for avoiding spotting on galvanized or zinc-containing surfaces. Was added.

Following the evaluation of the values found in Example 1, the following exemplary calculations can be performed: Exemplary calculation of a volumetric flow or reaction tank Phosphating bath 200 m ³ Partial flow for precipitation in a precipitation tank 100 m ³ Al feed per hour 10 ppm This feed is between 50% aluminum surface percentage and contact time This corresponds to about 40 car bodies per hour with a pickling corrosion of about 1 g / m ² .

Calculation formula for the steady-state concentration of aluminum in the phosphating solution: Al [ppm] = (((200 m ³ −partial flow) × concentrated Al [ppm] after 1 h + (partial flow × after precipitation) Al [ppm])) / 200) + pickling corrosion / h feed Al [ppm] after passing.

From this it can be deduced that the volumetric flow to be treated should be a pool volume of at least 0.5 per hour so that a sufficiently high content of dissolved aluminum can be captured. It was This means that the average residence time of 30 min is 50 m
^This will be ³ reaction pool volumes. A residual content of about 5 ppm of aluminum in the effluent of the treatment pool resulted in a theoretical steady-state content of aluminum in the treatment bath of about 25 ppm. However, the actual dissolved aluminum content is adjusted to a lower value, since it should also be calculated in a treatment bath with a partial precipitation of aluminum (see, eg, Experiment 3 from Table 1): total precipitation product About 20% occurs in the phosphating bath and at steady state results in an Al content of about 20 ppm in the phosphating solution of the bath. About 80% of the total precipitated product settled in the settling tank.

[Brief description of drawings]

FIG. 1 is a flow diagram that schematically illustrates one possible principle of separate aluminum-precipitations.

[Procedure for Amendment] Submission for translation of Article 34 Amendment of Patent Cooperation Treaty

[Submission Date] August 16, 2002 (2002.16)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Contents of correction]

─────────────────────────────────────────────────── ─── Continued front page    (81) Designated countries EP (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE, I T, LU, MC, NL, PT, SE, TR), OA (BF , BJ, CF, CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG), AP (GH, G M, KE, LS, MW, MZ, SD, SL, SZ, TZ , UG, ZW), EA (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), AE, AL, AM, AT, AU, AZ, BA, BB, BG, BR, BY, CA, C H, CN, CR, CU, CZ, DE, DK, DM, EE , ES, FI, GB, GD, GE, GH, GM, HR, HU, ID, IL, IN, IS, JP, KE, KG, K P, KR, KZ, LC, LK, LR, LS, LT, LU , LV, MA, MD, MG, MK, MN, MW, MX, NO, NZ, PL, PT, RO, RU, SD, SE, S G, SI, SK, SL, TJ, TM, TR, TT, TZ , UA, UG, US, UZ, VN, YU, ZA, ZW (72) Inventor Jörg Heike             Federal Republic of Germany Eschborn             Strasse 5-7 (72) Inventor Thomas Kohlberg             Federal Republic of Germany Heppenheim Fa             Ilchenweg 7 (72) Inventor Peter Schubach             Federal Republic of Germany Nidderau / Winde             Becken an der Gensweide 18 (72) Inventor Harald Yashke             Federal Republic of Germany             Landrath-Remy-Strasse               Four (72) Inventor Christoph Croquet             Filsheim / Mu, Federal Republic of Germany             Nchsdorf Bachstraße 10 (72) Inventor Alfred Lutzka             Germany Mailing Columbe             Lumen ring 21 F term (reference) 4K026 AA09 AA22 AA24 AA25 BA03                       BA12 BB06 BB10 CA13 CA23                       CA28 CA32 EA11 EB02 EB03                       EB08

Claims (13)

[Claims] 1. A component, profile, strip or wire having a surface made of aluminum or an aluminum-containing alloy--optionally a surface made of another metal or alloy--is provided with fluoride and phosphoric acid. In the method of treating or pretreating with an acidic aqueous solution containing salt, the fluoride is at least partially present in the solution as free fluoride and the increasing aluminum content in the precipitation tank is Outside the treatment bath, under circulation of the phosphating solution from the phosphating bath to the precipitation tank and from the precipitation tank to the phosphating bath, the content of Al ions in the bath is reduced to 100 mg / l or less. by, in a bath of phosphating solution, (including complexed Al) free fluoride content and Al ions in the concentration range of F _free 5 to 500 mg / l 1 Characterized by holding the aluminum content of the following concentration range 0 mg / l, member, profiles, a method of the strip or wire, for processing or pre-treatment with an acidic aqueous solution containing fluoride and phosphate. 2. The method according to claim 1, wherein in a separate zone of the phosphating bath the increasing aluminum content in the phosphating solution is modified by reducing the content of Al ions to 100 mg / l or less. the method of. 3. In the tank or in a separate zone of the bath, by addition of alkali metal ions, fluoride complexes or / and fluoride ions, in particular Na-ions or K-.
Ions or at least one readily dissociable fluoride, eg NaF, NH ₄ F
, Using the NaHF ₂ or KF, precipitating aluminum phosphating solution according to claim 1 or 2 wherein. 4. The method according to claim 1, wherein the content of alkali metal ions in the bath is maintained in a concentration range of 1 to 20 g / l. 5. The process according to claim 1, wherein the free fluoride concentration in the precipitation tank or in a separate zone of the bath tank is 5 to 500 mg / l free fluoride. 6. The process according to claim 1, wherein the residence time of the phosphating solution in the precipitation tank or in a separate precipitation zone is up to 1 h. 7. A component, profile, strip or / and wire to be treated or pretreated is cleaned, rinsed and optionally rinsed and cleaned prior to pickling / phosphate treatment. 7. A method according to any one of claims 1 to 6, which is separately contacted, for example, with an activating solution based on colloidally dispersed titanium phosphate. 8. Treated or pretreated components, profiles, strips and / or wires after pickling / phosphate treatment, in particular chromate-containing compounds, titanium fluoride, zirconium fluoride, Rinse with a passivating solution based on silanes, self-assembling molecules such as those based on phosphonates, polymers soluble or / and dispersible in solvents, soluble rare earth compounds-especially soluble cerium-containing compounds. The method according to any one of claims 1 to 7, wherein: or / and it is passivated, whereby the concept of rare earth elements should also include scandium, yttrium and lanthanum. 9. The treated, pretreated or / and passivated component, profile, strip or / and wire is dried after pickling / phosphating or after passivation. The method according to any one of claims 1 to 8, wherein the method is performed. 10. The method according to claim 1, wherein the precipitation of aluminum is carried out under normal pressure and at a temperature ranging from room temperature to 70 ° C. 11. The method according to claim 1, wherein the formation of the chemical conversion layer or the passivation layer is performed under normal pressure and at a temperature from room temperature to 70 ° C. 12. The treated or pretreated or / and passivated component, profile, strip or / and wire is coated with a paint, a different organic coating, a foil or / and an adhesive layer, Optionally printed and optionally deformed,
Any of the preceding claims, in which the metal parts so coated may additionally be glued, welded and / or otherwise joined together with other parts together. The method according to item 1. 13. Measuring equipment, control equipment, test equipment, structural elements, casings for household appliances, appliances in the automobile industry, in the aircraft industry, in equipment and machinery assembly, in the furniture industry, in the construction industry. For liners, shelves, racks, frames, dividers, partitions, veneers, lighting fixtures, guardrails, radiator elements or fence elements and small parts, in particular body parts or bodies, according to claims 1 to 12. Use of a product manufactured by the method according to any one of claims.