JP2018527467A - Method for pretreating an aluminum surface with a composition containing zirconium and molybdenum - Google Patents

Abstract

The present invention relates to non-cut forming of workpieces having an aluminum or aluminum alloy surface and / or to workpieces that have also been pretreated or optionally otherwise precoated, or steel and / or The following permanent for welding or adhesive bonding to galvanized and / or alloy galvanized steel precoated parts and also by phosphating, chrome-free treatment, primer coating or surface coating Related to pretreatment methods for corrosion protection treatment, where the workpiece is a) pickled with an aqueous acidic solution containing mineral acid by dipping or spraying, b) rinsed with water, and c ) The mass ratio of Zr: Wo (Zr / Mo metal conversion) is 15: 1 to 3.5: 1, does not contain chromium, and contains Zr as a composite fluoride and Mo as a molybdate. Sexual acidic solution, by a dip or coating by spraying, are contacted, after the subsequent resulting drying process, in each case, to give a layer weight of Zr and Mo of 2 to 15 mg / m ^2, the solution, It has a Zr of 100 to 800 mg / l, a Mo of 30 to 100 mg / l (in terms of Zr / Mo metal) and a pH of 2.5 to 4.5.

Description

  The present invention relates to a pretreatment method for a workpiece having a surface of aluminum or aluminum alloy. This method can be used for non-cut forming and / or on workpieces that have also been pretreated or optionally otherwise precoated, or steel and / or galvanized and / or alloy galvanized steel. To welded or adhesively bonded to pre-coated parts and also for subsequent corrosion protection treatment by phosphating, chromium-free treatment, primer application or surface coating.

  In preparation for the chemical surface treatment of metals, eg surface coatings, adhesives and polymers, the metal surface is cleaned in the first step, rinsed with water in the second step, and finally moistened with an aqueous solution. It is known that a chemical film is formed in three steps and the liquid film is dried. In this way, a thin non-metallic coating can be formed on the metal that can significantly improve the surface quality if the composition of the treatment liquid and the reaction conditions are properly selected. Thus, for example, a coating consisting of a surface coating composition, an adhesive and a polymer, when applied to such a pretreated metal, optionally in the form of a film, has significantly better adhesion and significantly increased corrosion protection. Can show gender.

  The method of the above type uses, for example, an aqueous solution containing hexavalent chromium, trivalent chromium, alkali metal ions and silicon dioxide in a specific ratio, and is coated as an adhesive base for electrical insulation, anticorrosion, surface coating, etc. Is generated (Patent Document 1).

  Due to the presence of hexavalent chromium, all these methods have the disadvantage that precautionary measures are required, in particular for the application of the coating composition and the handling of the coated metal.

  In order to avoid the disadvantages associated with the use of solutions containing hexavalent chromium, different types of methods are applied by application of conversion coatings, in particular for compositions based on zirconium and / or titanium fluoroanions on aluminum surfaces. Processing is provided (Patent Document 2, Patent Document 3, Patent Document 4, and Patent Document 5).

  In recent years, the use of workpieces having aluminum or aluminum alloy surfaces in vehicle structures has become increasingly important. Significant reasons for this are the reduction in vehicle weight and the advantageous recyclability of such workpieces. Here, generally a plurality of workpieces which have been formed previously without machining and which have a surface of aluminum or aluminum alloy or which have a surface of steel and / or galvanized steel and / or a surface of alloy galvanized steel It is common to manufacture a vehicle by joining together these parts. A much more important form of joining or assembly is welding or adhesive joining.

  After joining the parts, a corrosion protection treatment consisting of phosphating, chromium-free treatment, primer or surface coating is usually performed depending on the properties of the joined parts.

  In order to ensure defect-free joining of parts having an aluminum or aluminum alloy surface to each other or to parts made of steel and / or galvanized or galvanized steel, the surface of the aluminum or aluminum alloy is made of aluminum oxide or It must be ensured that it does not contain oxides of possible alloying components of aluminum. The pickling process, which appears to be attractive for this purpose, does not serve the purpose because after a very short time the aluminum surface is coated with a fresh oxide layer.

In order to solve the above problems, the method of US Pat. No. 6,057,059 provides a surface of aluminum or an alloy thereof to be contacted with an aqueous solution containing a complex fluoride of boron, silicon, titanium, zirconium or hafnium elements. A pre-treatment prior to the second permanent corrosion protection treatment is applied individually or mixed with each other at a total concentration of 100-4000 mg / l of fluoroanion and at a pH of 0.3-3.5. Between the pretreatment and the permanent corrosion protection conversion treatment, the parts made of aluminum or its alloys are subjected to a non-cutting and / or cutting forming process and / or joined together, or steel and / or With parts made of galvanized and / or alloy galvanized steel. Joined by adhesive bonding and / or welding. The application of the solution optionally containing a polymer with specific properties can be carried out by spraying, dipping or non-rinsing methods, in which case the amount of wet film is 2-10 ml / m ² / m ^{2 of} metal surface. ² , preferably in the range of 4-6 ml / m ² . Regardless of the method in which the solution is applied, it is advantageous to perform the drying in the temperature range of 40-85 ° C. For cleaning purposes, parts made of aluminum or its alloys are cleaned under acidic or alkaline conditions prior to the first conversion treatment, preferably with further cleaning steps and water and / or activated rinse baths. The intermediate rinse used is performed before permanent corrosion protection treatment.

From the numerical values of the concentration of fluoroanion in the solution to be applied and the amount of wet film, in the case of applying a solution containing a fluorotitanate, 0.06 to 11.73 mg / m ² , preferably 0.12 to 7.04 mg / The coating amount of m ² (in each case reported as titanium metal) is 0.09 to 17.78 mg / m ² , preferably 0.18 to 7.04 mg in the case of coating with a fluorozirconate-containing solution. It is possible to calculate the coating amount of / m ² (in each case reported as titanium metal).

  Research prior to the concept of the present invention is important for the possibility of many methods described in US Pat. No. 6,099,056, particularly for temporary corrosion protection achieved by the first chemical conversion treatment, and for producing welded joints. With respect to a good volume resistance, it is shown to give less favorable results.

  A good adhesive bond can be achieved by the method disclosed in US Pat. No. 6,057,077, where an organophosphorus compound is used to pretreat the aluminum substrate. However, this method is susceptible to bath contamination with aluminum ions that must be removed by the ion exchange resin.

DE-B 17 69 582 US-A-41 48 670 FR-A-942 789 EP-A-106 389 EP-A-825 280 EP-B-700 452 US 6,020,030 A

  An object of the present invention is to provide a pretreatment method for a workpiece having an aluminum or aluminum alloy surface. This method can be used for non-cut forming and / or on workpieces that have also been pretreated or optionally otherwise precoated, or steel and / or galvanized and / or alloy galvanized steel. To welded parts, specially pre-treated workpieces, welded or glued joints, specially glued and also phosphating, chromium-free treatment, primer coating or surface coating, specially chromium It is a method for the next permanent corrosion prevention treatment by freezing treatment or surface coating. This method usually results in a workpiece having a sufficiently low volume resistance combined with good phosphorylation and adhesion.

  Furthermore, the method of the present invention is preferred and provides good temporary corrosion resistance values and is hardly affected by bath contamination with aluminum ions.

First, this object is achieved by a method of the type mentioned at the outset constructed in accordance with the invention, the workpiece being
a) Pickling with an aqueous acidic solution containing mineral acid by dipping or spraying,
b) Rinse with water and
c) Zr: Wo mass ratio (Zr / Mo metal conversion) is 15: 1 to 3.5: 1, does not contain chromium, and contains Zr as a composite fluoride and Mo as a molybdate. To the acidic solution by dipping or spraying, resulting in a Zr and Mo layer mass of ^{2 to} 15 mg / m ² in each case after the subsequent drying step. Here, the solution has 100 to 800 mg / l of Zr, 30 to 100 mg / l of Mo (in terms of Zr / Mo metal), and a pH of 2.5 to 4.5.

In application by dipping or spraying, even in the application of a solution containing only fluorozirconate or only molybdate, the mass ratio of zirconium: molybdenum (Zr / Mo metal conversion) is outside of 15: 1 to 3.5: 1. Satisfactory results have been achieved for the purposes of the present invention in the application of certain solutions and also in the application of solutions in which the layer mass of zirconium and molybdenum is outside of ² to 15 mg / m ² .

  In step c) for application by dipping or spraying, the aqueous acidic solution is preferably 15: 1 to 5: 1, particularly preferably 13: 1 to 7: 1, very particularly preferably 11: 1. It has a mass ratio of Zr to Mo of ˜9: 1.

The application by dipping or spraying, after drying, in each case is preferably ^{2 to} 12 mg / m ² , particularly preferably ^{2 to} 10 mg / m ² and very particularly preferably ^{2 to} 8 mg / m ² of Zr. This results in a layer mass of Mo.

  Aqueous solutions for application by immersion or spraying are preferably 250-700 mg / l Zr and 30-80 mg / l Mo, particularly preferably 400-600 mg / l Zr and 40-60 mg / l Mo. , And very particularly preferably, 475-525 mg / l Zr and 45-55 mg / l Mo.

  Furthermore, the aqueous solution for application by dipping or spraying is preferably 3.1 to 4.3, particularly preferably a pH of 3.6 to 4.0, preferably 20 to 50 ° C., particularly preferably 20 It has a temperature of ~ 30 ° C.

Secondly, this object is achieved by a method of the type mentioned at the outset constructed in accordance with the invention, the workpiece being
a) Pickling with an aqueous acidic solution containing mineral acid by dipping or spraying,
b) Rinse with water and
c) A mass ratio of Zr: Wo (Zr / Mo metal conversion) of 2: 1 to 1: 2, which does not contain chromium, and contains Zr as a composite fluoride and Mo as a molybdate. The solution is contacted by roller application, resulting in a Zr and Mo layer mass of ^{2 to} 15 mg / m ² in each case after the subsequent drying step. Here, the solution has 0.4 to 7.5 g / l of Zr, 0.4 to 7.5 g / l of Mo (in terms of Zr / Mo metal) and a pH of 1.0 to 3.0.

In the application by the roller application method, a solution in which the mass ratio of zirconium: molybdenum (Zr / Mo metal conversion) is outside of 2: 1 to 1: 2 even in the application of a solution containing only fluorozirconate or molybdate. Satisfactory results were achieved for the purposes of the present invention both in the application of the solution and in the application of solutions with a layer mass of zirconium and molybdenum outside of 2-15 mg / m ² .

  The aqueous acidic solution in step c) for application by roller application is preferably 1.7: 1 to 1: 1.7, particularly preferably 1.4: 1 to 1: 1.4, Very particular preference is given to a mass ratio of Zr to Mo of 1.1: 1 to 1: 1.1.

The application by the roller application method is preferably ^{2 to} 12 mg / m ² , particularly preferably ^{2 to} 10 mg / m ² and very particularly preferably ^{2 to} 8 mg / m ² of Zr in each case after drying. This results in a layer mass of Mo.

  The aqueous solution for application by roller application is preferably 1.0 to 6.0 g / l Zr and 1.0 to 6.0 g / l Mo, particularly preferably 2.0 to 4.0 g. / L Zr and 2.0 to 4.0 g / l Mo, and very particularly preferably 2.8 to 3.2 g / l Zr and 2.8 to 3.2 g / l Mo .

  Furthermore, the aqueous solution for coating by the roller coating method preferably has a pH of 1.4 to 2.7, particularly preferably 1.8 to 2.5.

With respect to setting the defined layer weights (2-15 mg / m ² ) of zirconium and molybdenum in each case, depending on the manner of application, ie application by spraying or dipping or application by roller application, fluorozirco It is very important that different aqueous acidic solutions with respect to the concentration and ratio of the nate and molybdate anions and the pH are used in step c).

  The aqueous acidic solution in step c) is preferably prepared by predilution with a suitable concentration in water and optionally by setting the pH at a magnification of 1:30 to 1: 100, more preferably about 1:50. be able to.

  In order to achieve the objectives sought by the present invention, it is also important that the workpiece be pickled with an aqueous acidic solution containing mineral acid by dipping or spraying. Alkali cleaning, for example, results in the formation of a zirconium / molybdenum layer with low volume resistance.

Workpiece joints pre-treated according to the present invention may be pre-treated as well, or optionally pre-coated in other ways. That is, for phosphating, aluminum or its alloy surface. If joining to parts made of steel and / or galvanized and / or alloy galvanized steel is intended, these parts can have bare or precoated surfaces. One suitable precoat can be, for example, a phosphate layer or a layer of conductive primer having a layer mass of ² g / m ² or less.

  If the workpiece is oily, the washing / degreasing step should be performed before the pickling step, or the pickling step should be performed so that simultaneous washing / degreasing occurs. The latter can be achieved by adding a surfactant to the pickling solution.

  The process for phosphating is in the foreground with solutions based on zinc phosphate and in particular for low zinc technology or working with alkali metal phosphates. The solution can be modified by adding a smaller amount of a polyvalent cation such as calcium, magnesium, nickel, copper or manganese.

  For the chromization treatment, in particular an acidic solution containing a fluorocomplex of titanium, zirconium, hafnium or silicon, optionally an organic polymer is used.

  These acidic solutions can further comprise at least one organosilane and / or at least one hydrolysis product thereof and / or at least one condensation product thereof.

  The at least one organosilane preferably has at least one amino group. Particular preference is given to organosilanes which can be hydrolyzed to bis (trimethoxysilylpropyl) amine or aminopropylsilanol and / or 2-aminoethyl-3-aminopropylsilanol.

  As a primer, a reactive primer or a binder can be applied.

  The pre-treatment of the workpiece according to the invention ensures a satisfactory and temporary protection against relatively long storage times. During this time, there is no adverse effect on weldability, particularly electrical resistance welding or adhesion. Furthermore, with regard to weldability, it is ensured that the volume resistance is substantially the same in all surface areas of the workpiece.

  Workpieces for the purposes of the present invention are individual parts such as strips, sheets and profiles.

  The application of the solution in step c) can in each case be carried out by rinsing with water or by spraying or dipping without rinsing. When applying without rinsing with water, it is advantageous to remove excess treatment solution with a squeegee roller.

  In the treatment of sheets or strips, the application of treatment solutions by means of a roller coating method is particularly advantageous. A desired wet film thickness can be set in one operation.

  After application of the type of solution described above, the workpiece is dried or the solution is evaporated. A body temperature of 30 to 90 ° C. is particularly advantageous.

In order to make up the treatment liquid, usually a concentrated liquid diluted with low salt water, preferably deionized water, to a concentration set in each case is used. In order to avoid the introduction of alkali metal ions, it is particularly advantageous to introduce the necessary fluoroanion of zirconium with a free acid and to set the respective pH by adding ammonia as required. On the other hand, molybdate is introduced as ammonium heptamolybdate and / or sodium heptamolybdate, preferably as ammonium heptamolybdate, and particularly preferably as ammonium heptamolybdate × 7H ₂ O.

  For the purposes of the present invention, the term “molybdate” also includes protonated forms such as in particular molybdic acid.

  The pickling of the workpiece (processing step a)) is performed using an aqueous acidic solution containing a mineral acid. This can be done electrolytically or chemically. In the case of electrolytic pickling, phosphoric acid is particularly suitable as a mineral acid. Nitric acid or nitric acid / hydrofluoric acid can be used to perform pickling by a generally preferred chemical route for a simpler mode of operation for the apparatus. In a preferred embodiment of the invention, the workpiece comprises a surfactant, sulfuric acid, and a compound selected from the group consisting of hydrofluoric acid, phosphoric acid and iron (III) sulfate, preferably hydrofluoric acid. It is pickled by spraying or dipping with a solution. A solution containing 3-8 g / l sulfuric acid, 50-150 mg / l uncomplexed free fluoride and 1-3 g / l nonionic surfactant has been found to be particularly suitable. Ethylene oxide adducts with fatty alcohols, such as abietic acid, are particularly suitable as nonionic surfactants.

  Free fluoride measurements were made using a fluoride sensitive electrode and electrode calibration was done using a solution having the same pH as that of the solution being tested.

In order to obtain a layer having the optimum volume resistance in the next treatment as in step c), a pickling step is carried out so that removal of the metal of the workpiece of about 0.1 to 0.6 g / m ² is obtained. Should be implemented.

  Rinsing with water following the pickling of the workpiece corresponding to step b) is preferably carried out in a plurality of rinsing stages, and it is particularly advantageous to send the rinsing water countercurrently to the workpiece. Here, the final rinsing step should be performed using deionized water. The treatment of step c) following the pickling and rinsing step prevents new growth of the oxide layer occurring on workpieces having an aluminum or aluminum alloy surface.

  In an advantageous embodiment of the invention, the solution used in step c) is from the group consisting of poly (meth) acrylic acid, (meth) acrylic acid copolymer, polyvinylphosphonic acid, vinylphosphonic acid copolymer and maleic acid copolymer. It additionally has at least one polymer selected.

  It is preferred to use a (meth) acrylic acid-maleic acid copolymer as the (meth) acrylic acid copolymer and a vinylphosphonic acid-acrylic acid copolymer as the vinylphosphonic acid copolymer. Particularly preferred polymers are polyacrylic acid and acrylic acid copolymers, in the latter case specially acrylic acid-maleic acid copolymers.

  The poly (meth) acrylic acid used is preferably a number average molecular weight in the range from 4000 to 300000 g / mol, particularly preferably from 50000 to 250,000 g / mol, very particularly preferably from 100,000 to 250,000 g / mol. (MW).

  The (meth) acrylic acid copolymer used preferably has a number average molecular weight (MW) in the range of 4000-100000 g / mol, particularly preferably in the range 60000-80000 g / mol.

  The polyvinylphosphonic acid used or the vinylphosphonic acid copolymer used preferably has a number average molecular weight (MW) in the range from 4000 to 70000 g / mol, particularly preferably from 10,000 to 30000 g / mol.

The concentration of the at least one polymer is in the range from 100 to 600 mg / l, preferably from 100 to 400 mg / l, particularly preferably from 135 to 290 mg / l, very particularly preferably from 170 to 180 mg / l. is there. By using at least one polymer, in each case a layer mass of ^{2 to} 15 mg / m ² of Zr and Mo can be applied by spraying, relatively independently with respect to spraying time, preferably almost independently. It is possible to get. This is particularly advantageous because similar layer masses can be achieved at different strip speeds. On the other hand, no adverse effect on the volume resistance due to the polymer content is observed.

  In the case of subsequent processing by non-cutting after step c), a further advantageous embodiment of the invention provides for applying a lubricant to the workpiece. Such lubricants are in particular molding oils based on completely synthetic or naturally occurring mineral oils or dry lubricants based on polyethylene / polyacrylate.

  It is generally useful to insert a washing step and a water rinsing step prior to permanent anticorrosion treatment. For the intended application of primer or surface coating, prior drying is recommended. When a chromium-free treatment is performed, the application by dipping or spraying can also be carried out wet on wet, i.e. without prior drying. In the case of application by a roller coating method, intermediate drying is essential. Similarly, in the case of a subsequent phosphating treatment that can be carried out wet-on-wet, it is advantageous to carry out the activation treatment using, for example, titanium and a phosphoric acid containing activator.

  The method of the present invention typically provides a workpiece having a layer that allows defect-free shaping and / or adhesive bonding, or as a result of uniform low electrical volume resistance across the workpiece surface. It results in defects and no problem welding. Furthermore, the workpiece is very suitable for the subsequent permanent anticorrosion treatment.

  The present invention will be described in more detail using the following examples, which should not be construed as constituting a limitation.

  Except for metal sheets cleaned under alkaline conditions (Comparative Example CE2 in Table 1), sheets made of AA6111 and AA5754 grade aluminum alloys were first degreased and pickled at a temperature of 50 ° C. by dipping or spraying. I went to. The pickling solution consists of sulfuric acid (100% concentration) 6 g / l, hydrofluoric acid (100% concentration) 100 mg / l, and a non-ionic surfactant consisting of ethoxylated fatty alcohol and ethoxylated abietic acid in a mass ratio of 1: 1. 2 g / l of agent.

In the pickling process, the removal of substances during pickling is 0.05 to 0.2 g / m ² in the case of alloy AA5754 and 0.05 to 0.4 g / m ² in the case of alloy AA6111. there were. For this purpose, a processing time of 5 to 20 seconds was required.

  Subsequently, the workpiece was rinsed thoroughly with water and deionized water was used at the final stage. The volume resistance measured on a single sheet was about 60 μohm for alloy AA5754 and about 13 μohm for alloy AA6111.

  This is followed by treatment with a solution of hexafluorozirconic acid and / or molybdate, in each case optionally including a polymer or copolymer, and for 6 seconds spray application, zirconium and / or molybdenum and ( Table 1 shows the data regarding the co-polymer concentration, pH and coating temperature. If necessary, the pH was adjusted with an ammonia solution. Excess treatment solution was removed with a squeegee roller, followed by drying of the treated surface.

  Polymers A to D in Table 1 are as follows.

A: Polyacrylic acid, MW = about 60000 g / mol in colloidal solution
B: Acrylic acid-maleic acid copolymer, MW = about 70000 g / mol
C: polyacrylic acid, MW = about 250,000 g / mol
D: Vinylphosphonic acid-acrylic acid copolymer, MW = 4000-70000 g / mol

The second column of Table 2 shows the Zr and Mo layer masses thus obtained in mg / m ² . The measurement of the mass of the individual layers was performed by X-ray fluorescence (XRF) analysis.

  Furthermore, the volume resistance in μ ohms obtained from the individual measurements of the metal sheet is shown in the third column of Table 2. Volume resistance measurements were made immediately after drying / evaporation (in each case first row “0d”) and after 30 days storage (in each case second row “30d”). It was carried out according to the leaflet 2929 (September 2001 issue) of Deutscher Verbandes fuer Schweissen und Verwandte Verfahren e.V. (DSV) using a 20 mm diameter copper electrode.

  The results of the corresponding phosphate and modified APGE tests in the live cycle are shown in the second and third columns of Table 3.

  Adhesion was determined by a modified APGE (Arizona Proving Ground Equivalent) test. For this purpose, in each case two test plates (56.25 × 25 × 0.25 mm each) are coated with an industrial dry lubricant and glued with an appropriate industrial adhesive. It was. These six pairs of test plates were then screwed together at each end to form a chain subjected to 2400 N tensile stress. For each week of the study, a program with the following conditions was used:

1. Immerse in a 5% by weight solution of NaCl in distilled water for 15 minutes,
2. Dry in a dry environment for 105 minutes,
3. 22 hours at controlled temperature and atmospheric humidity: 50 ° C. and 90% relative humidity,
4). Repeat steps 1-3 four times
5. 48 hours at 50 ° C. and 90% relative humidity.

  One sequence of steps 1 to 3 by definition represents one cycle. The cycle is considered to survive when the adhesive bond between all test plates in the chain is fast. The entire test is counted as passed when at least 45 cycles survived.

  Phosphorylation was determined using scanning electron micrographs. Here, “+” in Table 3 means a closed microcrystalline phosphate layer, and “o” means a closed coarse phosphate layer (a crystal having a ridge length exceeding 20 μm). Meaning, “-” means a phosphate layer that is not closed throughout and is not present.

  From the measured values in Tables 2 and 3, the following can be concluded. The treatment of the aluminum sheet with an alkaline cleaner carried out to determine the need for an acid pickling treatment in step a) of comparative example CE2 has a low volume resistance (18 μohm for AA5754 and 26 μohm for AA6111) Resulting in a sheet having

Comparative Example CE1, the mass of Zr layer found to be excessively high in the layer obtained by the process according to step c) (the case of AA5754 37 mg / ^{m 2} and for AA6111 26mg / ^{m 2),} in particular storage of 30 days Later, very high volume resistance is obtained (100 μohm for AA5754 and 38 μohm for AA6111).

  In the case of comparative examples CE4 and CE5, the layer mass obtained is in the desired range, but the zirconium / molybdenum ratio in the treatment solution of treatment step c) is 20: 1 (see CE4) or 2: 1 (see CE5). The volume resistance obtained can be in particular not acceptable for AA6111 (26 and 44 μohms for CE4 and 19 and 22 μohms for CE5).

pH is too low, i.e. the comparative example CE3 with 2.1, undesirably high coating amount of Zr (18mg ^{/ m} 2 for 24 mg / ^{m 2} and AA6111 for AA5754), and very high too volume resistivity (40 and 79 μohm for AA5754 and 67 and 73 μohm for AA6111) are observed.

  On the other hand, Examples E1 to E7 attach the essential conditions of the present invention regarding the type of pickling treatment, the Zr / Mo ratio, the mass of the produced layer, the respective concentrations, and the pH range of the treatment solution. A layer with very good volume resistance combined with good adhesive properties is obtained.

  Also, as can be seen from Table 3, it is clear that all examples E1-E7 have passed the modified APGE test, ie at least 45 cycles are alive in both AA5745 and AA6111. . On the other hand, in the case of Comparative Example CE1, this was not adapted at all, and only 10 to 30 cycles survived in each case. Other Comparative Examples CE2-CE5 were no longer subjected to the modified APGE test (Table 2, see above) because the results already obtained for layer mass or volume resistance were poor.

  With respect to phosphorylation (see Table 3), all examples E1 to E7 (except E7 for AA5754) showed a closed microcrystalline phosphate layer ("+"), comparative example CE2 ~ CE5 has a phosphate layer that is not closed all the time ("-") in AA5754 and only has a significantly worse result in AA6111 (except CE2).

  The test plates of Examples E6 and E7 pretreated according to the present invention and the untreated bare test plate CE6 were also subjected to a multi-stage anticorrosion treatment consisting of the following steps.

i) Alkaline cleaning (60 ° C .; 180 seconds)
ii) Rinsing (main water; RT; 60 seconds)
iii) Activation (titanium phosphate; RT, 30 seconds)
iv) Phosphorylation (trications; 53 ° C., 180 seconds)
v) Rinse (main water; RT, 30 seconds)
vi) Passivation (zirconium fluoride; RT, 45 seconds) vii) Post-rinse (demineralized water; RT, 30 seconds)
viii) Drying (convection oven; 100 ° C .; 7 minutes)

  Subsequent electrophoretic coating and topcoat, then filiform corrosion test according to DIN EN 3665 (average value according to DIN EN ISO 4628-8) and cyclic corrosion test according to VDA 621-415 (DIN EN ISO 4628-8) was implemented. The smaller the measured migration under the coating, in mm, the better the corrosion resistance. The results are shown in the table below.

  The anticorrosion in the case of E6 and E7 is equivalent to the case of CE6 in any case. Therefore, the pretreatment according to the present invention does not adversely affect the anticorrosion subsequently achieved by the anticorrosion treatment.

Claims (15)

A pre-treatment method for a workpiece having an aluminum or aluminum alloy surface, for non-cut forming and / or to a workpiece that has been similarly pre-treated or optionally pre-coated, or For welding or adhesive bonding to steel and / or galvanized and / or alloy galvanized steel pre-coated parts and also by phosphating, chromium-free treatment, primer application or surface coating Is a pretreatment method for permanent corrosion prevention treatment of
The workpiece is a) pickled using an aqueous acidic solution containing mineral acid by dipping or spraying, b) rinsed with water, and c) a mass ratio of Zr: Wo (in terms of Zr / Mo metal). 15: 1 to 3.5: 1, which does not contain chromium, is contacted with an aqueous acidic solution containing Zr as a composite fluoride and Mo as a molybdate, by dipping or spraying, After the resulting drying step, in each case, a layer mass of 2-15 mg / m ² of Zr and Mo was obtained, the solution being 100-800 mg / l Zr and 30-100 mg / l Mo (Zr / Mo metal conversion) and a pH of 2.5 to 4.5.   The aqueous acidic solution in the step c) is composed of Zr as a composite fluoride and Mo as a molybdate in a mass ratio of Zr: Mo (in terms of Zr / Mo metal) of 13: 1 to 7: 1. The method according to 1. A pre-treatment method for a workpiece having an aluminum or aluminum alloy surface, for non-cut forming and / or to a workpiece that has been similarly pre-treated or optionally pre-coated, or For welding or adhesive bonding to steel and / or galvanized and / or alloy galvanized steel pre-coated parts and also by phosphating, chromium-free treatment, primer application or surface coating Is a pretreatment method for permanent corrosion prevention treatment of
The workpiece is a) pickled using an aqueous acidic solution containing mineral acid by dipping or spraying, b) rinsed with water, and c) a mass ratio of Zr: Wo (in terms of Zr / Mo metal). 2: 1 to 1: 2, free of chromium, contacted with an aqueous acidic solution containing Zr as a composite fluoride and Mo as a molybdate by roller coating, resulting in a subsequent drying step After that, in each case, a layer mass of 2-15 mg / m ² of Zr and Mo is obtained, the solution comprising 0.4-7.5 g / l of Zr and 0.4-7.5 g / l of A method having Mo (Zr / Mo metal conversion) and a pH of 1.0 to 3.0.   The aqueous acidic solution in the step c) contains Zr as a composite fluoride and Mo as a molybdate in a mass ratio of Zr: Mo (in terms of Zr / Mo metal) of 1.4: 1 to 1: 1.4. The method of claim 3, wherein   The aqueous acidic solution of step c) has at least one polymer selected from the group consisting of poly (meth) acrylic acid, (meth) acrylic acid copolymer, polyvinylphosphonic acid, vinylphosphonic acid copolymer and maleic acid copolymer. The method according to any one of claims 1 to 4.   The method of claim 5, wherein the at least one polymer is polyacrylic acid and / or an acrylic acid-maleic acid copolymer.   The method according to claim 1, wherein the workpiece is pickled with a solution containing a surfactant, hydrofluoric acid and sulfuric acid.   8. The workpiece according to claim 7, wherein the workpiece is pickled using a solution comprising 3-8 g / l sulfuric acid, 50-150 mg / l free fluoride and 1-3 g / l nonionic surfactant. Method.   9. A method according to any one of the preceding claims, wherein in the case of pre-treatment of the workpiece for non-cut forming, a lubricant is applied prior to the forming process.   The method according to any one of claims 1 to 8, wherein the cleaning, water rinsing and optionally activation treatment is performed before the permanent anticorrosion treatment.   An aqueous acidic solution for pretreatment of a workpiece having an aluminum or aluminum alloy surface, said solution being free of chromium and containing Zr as a composite fluoride and Mo as a molybdate in Zr: Mo The mass ratio (Zr / Mo metal equivalent) is 15: 1 to 3.5: 1, and the solution is 100 to 800 mg / l Zr, 30 to 100 mg / Mo (Zr / Mo metal equivalent) and 2.5 to A solution characterized by having a pH of 4.5.   A concentrate obtainable by diluting the solution according to claim 11 with water or an aqueous solution and optionally adjusting the pH.   An aqueous acidic solution for pretreatment of a workpiece having an aluminum or aluminum alloy surface, said solution being free of chromium and containing Zr as a composite fluoride and Mo as a molybdate in Zr: Mo It has a mass ratio (Zr / Mo metal conversion) of 2: 1 to 1: 2, and the solution is 0.4 to 7.5 g / l of Zr and 0.4 to 7.5 g / l of Mo (Zr / Mo metal). And a solution having a pH of 1.0 to 3.0.   A concentrate obtainable by diluting the solution according to claim 13 with water or an aqueous solution and optionally adjusting the pH.   11. A workpiece having a surface of aluminum or aluminum alloy, wherein the workpiece is pretreated by the method according to any one of claims 1-10.