EP0700452A1

EP0700452A1 - Chromium-free conversion-coating treatment of aluminium

Info

Publication number: EP0700452A1
Application number: EP94916970A
Authority: EP
Inventors: Uwe Karmaschek; Achim Roland; Hubert Vennschott; Harald Wennemann
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 1993-05-24
Filing date: 1994-05-17
Publication date: 1996-03-13
Anticipated expiration: 2014-05-17
Also published as: KR960702539A; US5584946A; AU6844294A; JP3476824B2; EP0700452B1; CA2163621A1; WO1994028193A1; DE4317217A1; JPH08510505A; KR100326612B1; ES2104390T3; DE59403473D1; CA2163621C; AU675328B2

Abstract

The invention concerns a method of pretreating aluminium or aluminium-alloy surfaces before permanent corrosion-protection conversion-coating treatment, in particular before phosphatization in acid phosphatization baths containing zinc, chromate treatment or a chromium-free treatment. The method is characterized in that the surfaces are brought into contact with acid aqueous treatment solutions containing complex fluorides of the elements boron, silicon, titanium, zirconium or hafnium alone or in mixtures with each other at total concentrations of between 100 and 4000 mg/l and at a pH between 0.3 and 3.5. Following the pretreatment, the aluminium or aluminium-alloy parts may, after shaping if necessary, be joined, by adhesive bonding and/or welding, to each other or to parts made of steel and/or zinc-plated and/or zinc-alloy-plated steel and/or aluminium-plated and/or aluminium-alloy-plated steel.

Description

Chromium-free aluminum conversion treatment

The invention is in the field of chemical surface treatment of aluminum for the purpose of corrosion protection, the so-called passivation. It describes chromium-free treatment processes for aluminum strips and aluminum molded parts in order to achieve temporary corrosion protection while maintaining the ability to be welded and glued, and the suitability of the material for a further conversion step, for example phosphating, chromating or chromium-free conversion treatment.

For the purposes of the invention, “aluminum” means not only pure aluminum, but also alloys whose main component is aluminum. Examples of frequently used alloy elements are silicon, magnesium, copper, manganese, chromium and nickel, the total weight fraction of these alloy elements in the alloy usually not exceeding 10%.

Aluminum is increasingly used in vehicle construction for a variety of reasons, such as weight, rigidity or recyclability. While engine and transmission parts, wheels, seat frames etc. are already made to a large extent from aluminum, the use in body construction is currently still on parts such as the radiator hood, trunk lid, interior door parts and various small parts as well as on truck cabins, side walls of transporters or bodies of Caravans limited. Overall, less than 5% of the metal surface of automobile bodies is made of aluminum worldwide. The increased use of aluminum in this area is being intensively examined by the aluminum and automotive industries. The joining of individual aluminum parts for vehicle construction is usually carried out by electrical resistance welding. According to data sheet DVS 2929 "Resistance welding. Measurement of the contact resistance on AluBiniiw materials", German Welding Association, August 1985, the following problems arise: "The affinity of aluminum to oxygen always leads to the formation of an oxide layer. Structure and thickness of this oxide layer Therefore, the surface treatment and the resulting electrical contact resistance of the sheet metal parts are of great importance for the reproducibility of the welding result and for the electrode position. In the spot welding of untreated aluminum sheets, the non-uniform and relatively large contact resistances are one The main causes of non-uniformity of the welds and for the small electrode numbers. The surface resistance is limited by surface treatments and largely uniform over the entire surface of the parts to be joined ig designed. "

For this reason, the material is pickled in order to remove the oxide layers formed during transport and storage and to reduce and even out the electrical surface resistance to the low values required for welding. This pickling, for which acidic or alkaline aqueous solutions are used, has hitherto mainly occurred in parts plants at short notice before the welding process. The close coordination of time is intended to suppress the build-up of disruptive layers of corrosion and dirt. In contrast, a chemical pretreatment of the aluminum in strip systems (coil systems), possibly with subsequent protective coating, is currently only carried out for parts that are no longer to be welded.

However, for an increased use of aluminum in large-volume vehicle production, it is preferable to carry out the pickling process at the manufacturer or supplier of the aluminum strip. This makes it possible to make the chemical operations of cleaning, pickling, rinsing, drying and oiling as well as the associated operations of wastewater treatment and disposal more rational, economical and environmentally compatible. So-called disposal technology is particularly cheap "No-rinse" processes in which the treatment solutions are applied, for example by roller application ("chemcoater"), and dried without rinsing. These processes significantly reduce the consumption of chemicals and the effort required to process the rinse water. However, they are only suitable for substrates with smooth surfaces, for example metal strips.

However, such a chemical pretreatment on the supplier side has the problem that the pickled aluminum surfaces, depending on the storage conditions (temperature, humidity, air pollution, time), are again covered with new, less specific, uneven and inorganic or organic contaminated oxide / hydroxide layers . As a result of this uncontrolled change in the surface condition and the associated electrical surface resistance, it is not possible to maintain constant working conditions in the welding and adhesive bonding techniques.

According to the prior art, this problem could be solved by applying conversion layers containing chromate directly after the pickling process. In conjunction with anti-corrosion oiling, they can withstand long storage times (up to 6 months) without corrosion and without loss of adhesive power. However, chromate-containing conversion layers have the following serious disadvantages with regard to the areas of application considered, which make it difficult to use such conversion layers for the intended area of use:

1. The aluminum parts are often ground after forming in order to improve the fit. Toxic and carcinogenic chromium (VI) -containing compounds can occur in the grinding dust. Therefore, increased requirements must be placed on measures to maintain occupational safety on site.

2. In automobile construction, the aluminum parts pretreated with chromate are joined together with parts made of steel and / or galvanized steel to form a so-called multi-metal body and driven through the body pre-treatment system. Soluble ones can be used in the usual alkaline cleaning step Chromium (VI) compounds are removed from the layer. On the one hand, this reduces the corrosion protection function of the layer and, on the other hand, the chromate-containing cleaning solution has to be subjected to a special detoxification step during disposal.

The chromium-free conversion treatment of aluminum surfaces with fluorides of boron, silicon, titanium or zirconium, alone or in combination with organic polymers, is known in principle in order to achieve permanent corrosion protection and to create a basis for subsequent painting:

US-A-5129967 discloses treatment baths for a no-rinse treatment (referred to there as "dried in place conversion coating") containing aluminum

a) 10 to 16 g / 1 polyacrylic acid or its homopolymers, b) 12 to 19 g / 1 hexafluorozirconic acid, c) 0.17 to 0.3 g / 1 hydrofluoric acid and d) up to 0.6 g / 1 hexafluorotitanic acid.

EP-B-8942 discloses treatment solutions, preferably containing aluminum cans

a) 0.5 to 10 g / 1 polyacrylic acid or an ester thereof and b) 0.2 to 8 g / l of at least one of the compounds H2ZrFö, H2TiFö and H2S1 5, the pH of the solution below 3.5 lies,

and containing an aqueous concentrate for replenishing the treatment solution

a) 25 to 100 g / 1 polyacrylic acid or an ester thereof, b) 25 to 100 g / 1 of at least one of the compounds H2ZrFö, H2T1 6 and H2SiFö, and c) a source of free fluoride ions that contain 17 to 120 g / 1 free Fluoride supplies. DE-C-1933013 discloses treatment baths with a pH value above 3.5 which, in addition to complex fluorides of boron, titanium or zirconium in amounts of 0.1 to 15 g / 1, based on the metals, additionally 0.5 to 30 g / 1 oxidizing agent, especially sodium metanitrobenzenesulfonate.

DE-C-24 33 704 describes treatment baths to increase paint adhesion and permanent corrosion protection to, among other things. Aluminum, which can contain 0.1 to 5 g / 1 polyacrylic acid or its salts or esters and 0.1 to 3.5 g / 1 ammonium fluorozirconate, calculated as Zrθ2. The pH values of these baths can fluctuate over a wide range. The best results are generally obtained when the pH is 6-8.

US-A-4 992 116 describes treatment baths for the conversion treatment of aluminum with pH values between about 2.5 and 5, which contain at least three components:

a) phosphate ions in the concentration range between l, lxl0 "5 to 5.3xl0 ~ 3 mol / 1 corresponding to 1 to 500 mg / 1, b) 1.1x10-5 to l, 3xl0" 3 mol / 1 of a fluoric acid of an element of the group Zr, Ti, Hf and Si (corresponding to 1.6 to 380 mg / 1 depending on the element) and c) 0.26 to 20 g / 1 of a polyphenol compound, obtainable by reacting poly (vinylphenol) with aldehydes and organic amines.

A molar ratio between the fluoric acid and phosphate of about 2.5: 1 to about 1:10 must be observed.

DE-A-2715292 discloses treatment baths for the chromium-free pretreatment of aluminum cans, the at least 10 pp titanium and / or zirconium, between 10 and 1000 ppm phosphate and a sufficient amount of fluoride to form complex fluorides of the existing titanium and / or zirconium, at least however, contain 13 ppm and have pH values between 1.5 and 4.

WO 92/07973 teaches a chromium-free treatment process for aluminum, the essential components in acidic aqueous solution being 0.01 to about 18% by weight of H2ZrFs and 0.01 to about 10% by weight of one 3- (N-Cι_4alkyl-N-2-hydroxyethylaminomethyl) -4-hydroxystyrene polymer ver¬ used. Optional components are 0.05-10% by weight of dispersed SiO 2, 0.06-0.6% by weight of a solubilizer for the polymer and surfactant. The polymer mentioned falls under the group of the "reaction products of poly (vinylphenol) with aldehydes and organic hydroxyl group-containing amines" which can be used in the context of the present invention.

These treatment baths according to the prior art were developed to achieve permanent corrosion protection, possibly in conjunction with good paint adhesion. The criteria of phosphatability and the required low welding resistance were not taken into account.

In contrast, the invention is based on the object not previously made in the art of providing a chromium-free process for pretreating surfaces made of aluminum or its alloys, which makes it possible to finish these surfaces after any intermediate mechanical processing steps, such as, for example, shaping or joining and / or physico-chemical steps such as cleaning and rinsing can then be further processed using conversion processes known in the prior art in order to achieve permanent corrosion protection. The conversion methods used to achieve permanent corrosion protection are, in particular, phosphating with acidic zinc-containing phosphating baths, chromating or chromium-free conversion treatment in accordance with the literature mentioned above, for example with reactive organic polymers and / or with compounds, in particular fluorocomplexes, of the elements titanium, Zircon and / or hafnium. The pretreatment according to the task must ensure temporary corrosion protection for a longer storage period, for example two to three months, without the material being bondable or weldable being adversely affected, for example by electrical resistance welding. For the weldability by means of resistance welding, it is particularly necessary that the electrical surface resistance is as uniform as possible, does not exceed a value of approximately 400 μOh and is preferably below approximately 100 μOhm. After alkaline pickling and subsequent storage for 4 weeks, on the other hand, sprinkle the electrical surface resistances locally very strong and cover a range from 100 to 1500 μOhm. The surface resistance is measured in accordance with the DVS 2929 data sheet in the form of a single sheet measurement with iron electrodes with a diameter of 20 mm.

Furthermore, the coating must be subject to the condition that the parts coated with it after assembly to form a multimetal body in the currently customary Multimeta11 pretreatment of the finished body in the automotive industry, consisting at least of the process steps of cleaning, rinsing, zinc phosphating, rinsing , Demineralized water rinsing, are covered with a permanently corrosion-protective zinc phosphate layer. A multimetal body is a body which is made from at least two of the materials: aluminum, steel, galvanized, alloy-galvanized, aluminized or alloy-aluminized steel. Suitable multi-metal phosphating processes are known to the person skilled in the field of conversion treatment, for example from DE-A-39 18 136 and EP-A-106 459, and are not the subject of this invention. Alternatively, in the case of all-aluminum -Body further corrosion-resistant conversion treatments in question, which must not be hindered by the first conversion step according to the invention. Examples include chromating with treatment baths containing Cr (VI) and / or Cr (III) or the above-mentioned chromium-free conversion processes.

This object is achieved in that surfaces made of aluminum or its alloys are first cleaned and rinsed with acid or alkali according to the prior art. According to the invention, a thin conversion coating is then applied, which consists of (mixed) oxides, (mixed) fluorides and / or oxyfluorides of aluminum and at least one of the elements boron, silicon, titanium, zirconium or hafnium and which includes organic polymers of the polyacrylate type Acrylate-containing copolymers or reaction products of poly (vinylphenol) with aldehydes and organic hydroxyl-containing amines can be modified. The feature "thin" is to be understood so that the concentration of the layer-forming elements boron, silicon, titanium, zirconium and / or hafnium on the aluminum surface together in the range 1-80 mg / πr, in particular is in the range 2 - 20 mg / m ² . The polymer content of the conversion coating must not exceed 5 mg / m ² and should preferably be in the range 0 to 3 mg / m ' ^** .

The invention accordingly describes a

Process for the pretreatment of surfaces made of aluminum or its alloys before a second, permanently corrosion-protective conversion treatment, preferably chromating, a chromium-free conversion treatment with reactive organic polymers and / or with compounds of the elements titanium, zirconium and / or hafnium, or a phosphating process acidic zinc-containing phosphating baths, characterized in that the surfaces are brought into contact with acidic aqueous treatment solutions, the complex fluorides of the elements boron, silicon, titanium, zirconium or hafnium individually or in a mixture with one another in concentrations of the total fluoro anions contain between 100 and 4000, preferably 200 to 2000, mg / 1 and have a pH between 0.3 and 3.5, preferably between 1 and 3.

The treatment solutions can additionally contain polymers of the type of the polyacrylates and / or the reaction products of poly (vinylphenol) with aldehydes and organic hydroxyl-containing amines in concentrations below 500 mg / 1, preferably below 200 mg / 1. If the treatment solution contains Zr, the concentration of the reaction products of poly (vinylphenol) with aldehydes and organic hydroxyl-containing amines should be less than 100 mg / 1.

Other potential components of the treatment baths are: free fluoride ions in concentrations up to 500 mg / 1 and polyhydroxycarboxylic acids or their anions, especially gluconate ions, in concentrations up to 500 mg / 1.

The complex fluorides of the elements boron, silicon, titanium, zircon or hafnium, ie the anions BF4-, SiF ² -, TiF ² , ZrF ² - or HfF ^{2 *} ", can be introduced in the form of the free acids or as salts. As Counterions are in particular alkali metal and ammonium ions. This also applies to the optional components free fluoride and polyhydroxycarboxylic acids. If these components are not used or are not used exclusively in the form of the acids, the pH of the treatment baths may need to be adjusted to the range from 0.3 to 3.5 according to the invention. Phosphoric acid, nitric acid and sulfuric acid are particularly suitable for this. An adjustment of the pH of the treatment solution to the range 1 to 3 is preferred. Depending on the substrate, the presence of sulfate ions in the treatment bath can be in concentrations of up to 5% by weight, in particular between 0.1 and 3% by weight. -%, be advantageous.

As optional additives in concentrations below 500 mg / l, suitable polymers of the acrylate type including acrylate-containing copolymers are known as commercial products in the prior art. Water-soluble polyacrylic acids in the molecular weight range between 20,000 and 100,000 daltons are particularly suitable, in particular those with an average molecular weight of about 50,000 to 60,000 daltons, the 5% by weight aqueous solution of which has a pH of about 2.

Suitable polymers of the type of the reaction products of polyvinylphenol with aldehydes and organic amines are known as agents for the surface treatment of metals and in particular for a passivating rinse of conversion-treated metal surfaces, for example from EP-A-319 016 and EP-A-319 017. These are polymers with molecular weights up to 2,000,000 daltons with a preferred molecular weight range between 7,000 and 70,000 daltons. The optionally substituted phenol rings in the chains can be linked via one or two carbon atoms, it being possible for the chains to have been subjected to a post-crosslinking process. A nitrogen atom is characteristically bound to at least some of the phenol rings via a carbon atom, which carries a further alkyl substituent which has at least one hydroxy function. This structure gives the polymer chelating properties against metal ions. In the technique of conversion treatment, it is customary not to produce the treatment baths by mixing the individual components together on site in the desired concentrations, but to use prefabricated concentrates for the preparation of the baths by dilution with water. Accordingly, the invention also includes aqueous concentrates which, when diluted to 0.5 to 10% by volume with water, give the treatment solutions described above.

The treatment solutions should have temperatures between 15 and 60 ° C and can be applied to the aluminum surfaces by spraying, dipping or in the no-rinse process. In the case of spray or immersion applications, the required treatment times are between 5 and 90 seconds. In the no-rinse process, which can be carried out, for example, by roller application (so-called chemcoater), the setting of a specific wet film thickness by squeezing rolls is a process-relevant step. The wet film thickness should be between 2 and 10 ml / m ² , preferably between 4 and 6 ml / m ² .

While by definition the treatment in the no-rinse process is not followed by a rinsing step, subsequent to the immersion or spray treatment, water rinsing with deionized water can optionally take place, the temperature of the rinsing water being between 10 and 40 ° C.

Regardless of the application method, it is advantageous to dry the aluminum surfaces after the treatment at temperatures between 40 and 85 ° C.

Since the described pretreatment method according to the invention is at the beginning of the processing chain pretreatment - possibly forming - joining (= gluing or welding) - conversion treatment - painting, it is to be seen in the functional context of the following steps. Accordingly, it is within the scope of the invention that

a) between the pretreatment of the surfaces made of aluminum or its alloys and the permanent corrosion-protecting conversion treatment - in particular phosphating with acidic zinc-containing Phosphating baths, chromating or a chromium-free conversion treatment - the parts made of aluminum or its alloys are subjected to a non-cutting and / or machining process and / or

b) between the pretreatment of the surfaces made of aluminum or its alloys and the permanent corrosion-protecting conversion treatment - in particular phosphating with acidic zinc-containing phosphating baths, chromating or chrome-free conversion treatment - the parts made of aluminum or its alloys with one another or with parts made of steel and / or galvanized and / or alloy-galvanized steel and / or aluminized and / or alloy-alloyed steel by bonding and / or by welding, in particular by electrical resistance welding and / or

c) between the pretreatment of the surfaces made of aluminum or its alloys and the permanent corrosion-protecting conversion treatment - in particular phosphating with acidic zinc-containing phosphating baths, chromating or chrome-free conversion treatment - cleaning and / or pickling steps, intermediate rinsing with water and / or with activating rinsing baths.

Examples

Execution examples

Aluminum sheets of size 100 x 200 mm and thickness 1.1 mm of different alloys from the group AA 6000 of different manufacturers and different ages (see Table 2) were washed with a 1% aqueous alkaline cleaning solution (Ridoline ^R C 72 , Henkel) freed from corrosion protection greasing at 65 ° C. for 10-12 s, rinsed in operating water for 5 s at room temperature and then rinsed in demineralized (DI) water for 5 s at room temperature. The conversion treatment was then carried out using treatment solutions according to the invention and comparative solutions according to Table 1 and the process according to Table 2. This was carried out either by immersion, spraying or spin coating (simulation of the application in the chemcoater = no rinse). After spinning in a paint spinner at 550 revolutions per minute, which results in a wet film of 5 to 6 μm after a spin duration of 5 seconds, the samples were immediately dried at 70 ° C. in a drying cabinet for 10 minutes. The sample panels treated by spraying or dipping were then rinsed in demineralized water for 5 s with gentle agitation and then dried. The conductivity of the draining water after the VE final rinse should not exceed 20 μS. The surface resistance is an indication of good spot weldability. It is determined in accordance with DVS leaflet 2929 (German Association for Welding Technology, status August 85). The single-sheet method shown in leaflet 2929 was used (electrode force: 75 KN, current: 20 A). The zero value (electrodes sit on top of one another) has already been subtracted from the resistance values given in Table 2. Tab. 2 contains the resistance values according to different storage times (1 day, 30 days, 60 days).

As an example of a permanent corrosion protection conversion treatment, the overphosphatization of the treated samples was checked as follows: With comparison processes, temporarily corrosion-protected sheets were treated with the following process: 1.Clean: Ridoline ^R C 1250 I alkaline cleaner (from Henkel)

2%, 55 ° C, 3 min

2. Rinse in Cologne tap water

3. Activation: Titanium phosphate-containing activating agent Fixodine ^R L (Fa.

Handle)

1% in demineralized water

RT, 45 s

4. Phosphating: Trication-phosphating process Granodine ^R 958 F (Fa.

Henkel) according to EP-A-106459 with the operating parameters according to the operating instructions

Free acid 1.0 - 1.1

Total acid 20.4

Zn 1.11 g / 1

Toner (Nθ2 ~) 1.8 - 2.0 pts.Free fluoride 600 ppm

52 ° C, 3 min

5. Rinse in tap water, RT, 20 s

6. Rinse in demineralized water, RT, 20 s

7. Dry by blowing with compressed air

The visual assessment of all phosphated surfaces after passivation according to the invention revealed a light gray, uniform, solid phosphate layer. This was confirmed by taking enlargements in the X-ray electron microscope.

As the exemplary embodiments show, the results obtained depend on the alloy selected and on the history of the material (storage time). The better results are generally obtained with the AC120 alloy. In all cases, conversion treatment according to the invention however, the findings regarding surface resistance and phosphatability are within the technically required framework.

In contrast, the samples treated with comparative solutions show clear deviations: An increase in the polymer concentration (see FIG. 1) leads to high surface resistances and a loss of phosphatability. If the concentration of the complex fluorides is reduced below the minimum concentration according to the invention (cf. 2 and 3), the phosphatability is retained, but the surface resistances increase sharply with the storage time and scatter considerably. An increase in the concentration of the complex fluorides beyond the range according to the invention (see FIG. 4) leads to surface resistances which increase only slightly with the storage time, but generally lead to high surface resistances. Furthermore, the phosphatability is negatively influenced. Comparative example 5 shows the negative influence of an excessively high phosphate concentration on the surface resistance.

The test for bondability was carried out with tensile shear tests in accordance with DIN 53283 using a commercially available two-component epoxy adhesive in accordance with the instructions for use (Terokal ^R 5045, Teroson, Heidelberg). The alloy AC 120 was used as the substrate, which was treated according to the method in Table 2 and then left open for 30 days. There was no further pretreatment before the adhesive strength was determined. For comparison, the values for an only degreased and for a green chromated sample were measured after the same storage time. The results are shown in Table 3.

Table 1: Conversion process; Bath concentrations in mg / 1

Experiment No. TiF ₆ 2- ZrF ₆ ² "BF4-SiF ₆ 2- HF polymer- H3PO4 HNO3 H2SO4 gluconate pH

Ex. 1 (Bl) 780 - - - 135 - 675 - - 450 3.0

Ex. 2 (B2) 780 - 100 - 50 - 650 - - 500 2.7

Example 3 (B3) - 1000 - - - A, 100 - - - - ² , 5

Ex. 4 (B4) - 1000 - - - B, 80 - - - - 2.5

JO CΛ Ex. 5 (B5) - 2000 - - 280 - - - - - 2.0

Ex. 6 (B6) - 800 - 200 - - - - - - 2.5 π

Example 7 (B7) 2700 - - - 140 - - - - - 2.0 zτ> m Example 8 (B8) - 600 - - 70 - - 1600 - 300 1.7 CD m Example 9 (B9) 1000 - - - - - - - - - 2.6 ro σ ^* > Ex. 10 (BIO) 1000 - - - - - - - 5000 - 1.3

Example 11 (B1) 1000 - - - - - - - 10000 - 1.0

Example 12 (B12) 1000 - - - - - - - 30000 - 0.5

Ex. 13 (B13) - 1000 - - - - - - - - 2.6

Ex. 14 (B14) 1000 - - - - A, 100 - - - - 2.5

Ex. 15 (B15) 1000 - - - - B, 100 - - - - 2.5

Continued Table 1: Conversion process; Bath concentrations in mg / 1

Experiment No. TiF ₆ 2- ZrF ₆ ² "BF" SiF ₆ 2- HF PolymerU H3PO4 HNO3 H2SO4 Gluconate PH

Cf. 1 (VI) - 1000 - - - A, 1000 - - - - 2.5

Cf. 2 (V2) 50 - - - - - - 100 - - 2.8

Cf. 3 (V3) - - - - - A, 100 - 200 - - 2.5 m cf. 4 (V4) - 6000 - - 280 - - - - - 2.0 rx> co

3? Cf. 5 (V5) - 2000 - - - - 800 - - - 2.3

Cf. 6 (V6) - - - - - - - - 10000 - 1.0

3D m

CD ro

-0 Polymers: A: water-soluble polyacrylic acid, average molecular weight 50000

B: reaction product of poly (4-vinylphenol) with formaldehyde and N-methylglucamine according to EP-A-319016; average molecular weight 40,000

Table 2: Type of application, electrical surface resistance - ¹ ) (μ-Ohm) and phosphatability after 30 days

Sample application temperature resistance after phosphating

(Time) 1 day 30 days 60 days availability-3)

Bl, a ² ) 60 ° C 115-140 100-200 400-500 o

Bl, b ² ) Diving 100-300 130-350 400-500 0

Bl, c ² ) (8 sec.) 30-50 90-180 400-500 +

B2, a 60 ° C 100-150 150-200 300-400 0

B2, b diving 90-250 100-300 300-400 0

B2, c (8 sec.) 30-50 80-150 250-400 +

B3, a No- 30- 45 50- 80 80-100 0

B3, b Rinse 20 ° C 40- 80 40- 60 80-160 +

B3, c 10- 15 30- 35 70-110 +

B4, a No- 30- 40 50- 80 90-120 +

B4, b Rinse 20 ° C 30- 60 40- 70 80-150 +

B4, c 10- 15 20- 30 70-120 +

B5, a No- 40- 50 45- 85 100-160 +

B5, b Rinse 20 ° C 20- 25 40- 80 75- 90 +

B5, c 4-7 15-20 20-70 +

B6, a No- 30- 45 50- 85 80-150 +

B6, b Rinse 20 ° C 20- 50 35- 60 70-130 +

B6, c 10- 15 20- 30 50- 80 +

B7, a 45 ° C 120-200 150-250 200-300 0

B7, b spray 120-180 160-240 200-300 0

B7, c (60 sec.) 100-150 150-200 200-250 + Continuation of table 2: type of application, electrical surface resistance ¹ ) (μ-ohm) and phosphatability after 30 days

Sample application temperature resistance according to phospha-

(Time) 1 day 30 days 60 days animal ability3)

B8, a 45 ° C 60-100 80-120 250-500 +

B8, b diving 50-100 130-180 200-500 +

B8, c (5 sec.) 10- 25 20- 55 75-100 +

B9, c syringes 40-45 ° C 15- 25 20-30 30-30 +

B9, b (25 sec.) 20-30 30-40 30-40 +

ORGANIC, c syringes 40-45 ° C 10- 20 10- 20 10- 20 +

ORGANIC, b (25 sec.) 15-20 15-25 15-25 +

Bll, c syringes 40-45 ° C 5- 10 5- 10 3- 10 +

Bll, b (25 sec.) 10- 15 10- 20 10- 20 +

B12, c syringes 40-45 ° C 3- 10 3- 10 3- 10 +

B12, b (25 sec.) 10- 15 15- 25 15- 25 +

B13, a No- 24-30 40-55 70-80 +

B13, b rinse 20 ° C 25-40 50-80 55-80 +

B13, c 4-7 20-30 30-85 +

B14, c No- 20 ° C 20- 25 30- 40 70-100 +

B14, b Rinse 40- 70 40- 80 80-160 +

B15, c No- 20 ° C 15- 25 25- 40 60-100 +

B15, b Rinse 30- 50 35- 70 70-140 + Continuation of table 2: type of application, electrical surface resistance ¹ ) (μ-ohm) and phosphatability after 30 days

Sample application temperature resistance na <: h phospha- (time) 1 day 30 days 60 days animal ability3)

VI, a No- 500-800 600- 800 700-1000 VI, b Rinse 20 ° C 400-700 500- 800 600- 900 VI, c 400-600 500- 700500- 700 _

V2, a 60 ° C 100-300 500-1000 600-1000 + V2, b diving 80-200 200- 900400-1000 + V2, c (8 sec.) 40- 60 200-1000300-1000 +

V3, a 60 ° C 80-200 300-1200 400-1200 + V3, b diving 50-150 200-1000300-1100 + V3, c (8 sec.) 30- 70 100- 700300- 900 +

V4, a No- 500-700 600- 900 700-1000 V4, b Rinse 20 ° C 500-800 600- 950700-1000 0 V4, c 400-700 500- 900650- 900 0

V5, c No-Rinse 20 ° C 700-1000 700-1000 700-1000 +

V6, c spray 40-45 ° C 10- 20 100- 150 300- 700 + V6, b (25 sec.) 10- 15 90-130 300- 800 +

1) Measured according to DVS leaflet 2929, single sheet measurement, iron electrodes with a diameter of 20 mm. ) Alloys of group AA 6016 a used: T 6009, from Alcoa; > Stored for 12 months b: T 6009, Alcoa; Stored for 3 months c: AC 120, Alusuisse; Virgin material 3) Phosphatability (scanning electron microscope images) +: closed, finely crystalline phosphate layer o: closed, coarser phosphate layer -: phosphate layer not closed or not available

Table 3: Tensile shear strengths (overlap: 25 x 12 mm)

Sample tensile shear strength (MPa)

B2c 12.3

B3c 13.5

B6c 11.5

B7c 12.8

Bllc 13.2

B13c 14.2

B14c 12.0

degreased 15.5 green chromated 12.0

Claims

1. Process for the pretreatment of surfaces made of aluminum or its alloys before a second, permanently corrosion-protective conversion treatment, preferably chromating, a chromium-free conversion treatment with reactive organic polymers and / or with compounds of the elements titanium, zirconium and / or hafnium, or one Phosphating with acidic zinc-containing phosphating baths, characterized in that the surfaces are brought into contact with acidic aqueous treatment solutions, the complex fluorides of the elements boron, silicon, titanium, zirconium or hafnium individually or in a mixture with one another in concentrations of the fluoro anions from a total of between 100 and 4000, preferably 200 to 2000, mg / 1 and have a pH between 0.3 and 3.5, preferably between 1 and 3.

2. The method according to claim 1, characterized in that the treatment solutions additionally polymers of the type of polyacrylates and / or the reaction products of poly (vinylphenol) with aldehydes and organic hydroxyl-containing amines in concentrations below 500 mg / 1, preferably below 200 mg / 1, and that in the presence of zirconium in the treatment solution the concentration of the reaction products of poly (vinylphenol) with aldehydes and organic hydroxyl-containing amines is less than 100 mg / 1.

3. The method according to one or both of claims 1 and 2, characterized ge indicates that the treatment solutions additionally contain frόie fluoride ions in concentrations up to 500 mg / 1.

4. The method according to one or more of claims 1 to 3, characterized ge indicates that the treatment solutions additionally contain polyhydroxycarboxylic acids or their anions, in particular gluconate ions, in concentrations of up to 500 mg / l.

5. The method according to one or more of claims 1 to 4, characterized in that the treatment solutions additionally sulfate ions in Contain concentrations up to 50 g / 1, preferably between 1 and 30 g / 1.

6. The method according to one or more of claims 1 to 5, characterized ge indicates that the treatment solutions have temperatures between 15 and 60 ° C and are applied to the aluminum surfaces by spraying, dipping or in the no-rinse process.

7. The method according to claim 6, characterized in that the aluminum surfaces are dried after the treatment at temperatures between 40 and 85 ° C.

8. The method according to one or more of claims 1 to 7, characterized ge indicates that between the pretreatment of the surfaces of aluminum or its alloys and the permanent corrosion-protective conversion treatment, in particular phosphating with acidic zinc-containing phosphating baths, chromating or a chromium-free Conversion treatment, the parts made of aluminum or its alloys are subjected to a non-cutting and / or machining process.

9. The method according to one or more of claims 1 to 8, characterized ge indicates that between the pretreatment of the surfaces made of aluminum or its alloys and the permanent corrosion-protective conversion treatment, in particular phosphating with acidic zinc-containing phosphating baths, chromating or a chromium-free Conversion treatment, the parts of aluminum or its alloys with each other or with parts made of steel and / or galvanized and / or alloy galvanized steel and / or aluminized and / or alloy-alloyed steel by gluing and / or by welding, in particular by electrical resistance welding, are connected the.

10. The method according to one or more of claims 1 to 9, characterized ge indicates that between the pretreatment of the surfaces made of aluminum or its alloys and the permanent anti-corrosion Conversion treatment, in particular phosphating with acidic zinc-containing phosphating baths, chromating or chrome-free conversion treatment, cleaning steps and intermediate rinsing with water and / or with activating or passivating rinsing baths.

11. Aqueous concentrate for the preparation of the treatment solutions for the process according to one or more of claims 1 to 5 by dilution with water to 0.5 to 10% by volume.