EP1005578B1 - Phosphating method accelerated by n-oxides - Google Patents

Description

The invention relates to a phosphating solution, a phosphating concentrate and a method for phosphating metal surfaces with aqueous, acid phosphating solutions, the zinc and phosphate ions and contain at least one organic N-oxide, and their Application as pretreatment of the metal surfaces for a subsequent Painting, especially an electro dip painting. The The method can be used to treat steel surfaces, galvanized or alloy galvanized steel, aluminum, aluminized or alloy aluminum steel.

The phosphating of metals pursues the goal on the metal surface to produce firmly grown metal phosphate layers that are in themselves Improve corrosion resistance and in connection with paints and other organic coatings to a significant increase in Liability and resistance to infiltration Corrosion stress contribute. Such phosphating processes are has long been known in the art. For pre-treatment before The low-zinc phosphating processes are particularly suitable for painting, where the phosphating solutions are comparatively low levels of zinc ions of e.g. B. 0.5 to 2 g / l. On This is an essential parameter in these low-zinc phosphating baths Weight ratio of phosphate ions to zinc ions, which is usually in the Range is> 12 and can take values up to 30.

It has been shown that by using others more valuable Cations as zinc in the phosphating baths with phosphate layers significantly improved corrosion protection and paint adhesion properties can be trained. For example, find low zinc processes with the addition of z. B. 0.5 to 1.5 g / l of manganese ions and z. B. 0.3 to 2.0 g / l Nickel ions as a so-called trication process for the preparation of Metal surfaces for painting, for example for cathodic ones Electrocoating of car bodies, wide application.

DE-A-40 13 483 discloses phosphating processes with which similar good corrosion protection properties as achieved with the trication process can be. These processes do without and use nickel instead copper in low concentrations, 0.001 to 0.03 g / l. to Oxidation of the formed in the pickling reaction of steel surfaces divalent iron in the trivalent stage serves oxygen and / or other oxidizing agents with the same effect. Nitrite, chlorate, Bromate, peroxy compounds and organic nitro compounds, such as Nitrobenzenesulfonate. The German patent application DE 42 10 513 modifies this process in that as a modifying one Agent for the morphology of the formed phosphate crystals hydroxylamine, its salts or complexes in an amount of 0.5 to 5 g / l Hydroxylamine can be added.

The use of hydroxylamine and / or its compounds for Influencing the shape of the phosphate crystals is from a number of Disclosure known. EP-A-315 059 gives as special Effect of using hydroxylamine in phosphating baths The fact that on steel the phosphate crystals in one desired columnar or knot-like shape arise when the Zinc concentration in the phosphating bath for the low-zinc process exceeds the usual range.

Hydroxylamine has the great procedural advantage that it generally in the phosphating bath and in phosphating concentrates not decomposed by itself. This makes phosphating bath concentrates and Supplementary solutions for phosphating baths can be produced that the required accelerator quantities included directly. An expensive one separate replenishment, such as when using Nitrite or hydrogen peroxide may be required as an accelerator thus eliminated. However, the phosphating solution contains copper ions, for what there is currently a technical trend, hydroxylamine decomposes gradually under the catalytic influence of these ions. In this case the accelerator must separate the phosphating bath and increase it Amounts are added. Therefore, there is a need for new ones Accelerators, which are similar to hydroxylamine in phosphating baths, have their concentrates and supplementary solutions incorporated without they decompose in a short time. They should also have this property still have when copper ions are present.

GB-A-510 684 describes a method for phosphating metal surfaces Iron or steel is described, whereby as an accelerator in addition to organic nitro compounds, Nitroso compounds, trichloromethyl compounds and aldehydes also organic amine oxides can be used. Hydroxylamine is used as the amine oxide called. These accelerators are used in phosphating baths based on zinc dihydrogen phosphate or used manganese dihydrogen phosphate, which also May contain copper compounds.

The object of the invention is to provide a phosphating process make the benefits of hydroxylamine accelerated processes, but not which has disadvantages with regard to decomposition in the presence of copper ions. The phosphating process is said to be by spraying, spray-immersion or immersion be applicable.

The invention accordingly relates to an acidic, aqueous phosphating solution containing zinc ions, phosphate ions and an organic N-oxide as an accelerator,
characterized in that the solution
0.2 to 3 g / l zinc ions
3 to 50 g / l phosphate ions, calculated as PO ₄ ^3-
Contains 0.05 to 4 g / l of an organic N-oxide which has a saturated, unsaturated or aromatic five- or six-membered ring system, the N atom of the N-oxide being part of this ring system, and the weight ratio of phosphate ions to zinc ions is between 3.7 and 30.

Examples of such compounds are the N-oxides substituted or unsubstituted pyrroles, imidazoles, oxazoles, pyridines, Pyrimidines, pyrazines, oxazines or their hydrogenation products, the have saturated or partially unsaturated rings. Especially preferred is the use of N-oxides substituted or unsubstituted pyridines and morpholines such as in particular pyridine N-oxide, 2-methylpyridine-N-oxide, 4-methylpyridine-N-oxide, morpholine-N-oxide and N-methylmorpholine-N-oxide. The latter is particularly preferred.

The phosphating solution can contain one or more of these N-oxides contain. The total concentration of N-oxides in the phosphating solution is preferably in the range from 0.1 to 3 g / l and in particular in Range from 0.3 to 2 g / l. At lower concentrations, the accelerating effect after, higher concentrations do no harm, However, they have no technical advantage and are therefore economical disadvantageous.

In addition to zinc ions, phosphating baths generally contain sodium, potassium and / or ammonium ions to adjust the free acid.
The term free acid is familiar to the person skilled in the phosphating field. The method of determining free acid and total acid chosen in this document is given in the example section. Values of the free acid between 0 and 1.5 points and the total acid between about 15 and about 35 points are within the technically customary range and are suitable for the purposes of this invention.

The zinc contents are preferably in the range from 0.4 to 2 g / l and in particular from 0.5 to 1.5 g / l, as is customary for low-zinc processes are. The weight ratio of phosphate ions to zinc ions in the phosphating baths can vary widely, provided it is in the range is between 3.7 and 30. A weight ratio between 10 and 20 is particularly preferred

In practice, it has been shown that the inventive Using an organic N-oxide as an accelerator is recommended for those of phosphating usually upstream activation of relatively highly concentrated activation solutions use. However, if you supplement the organic N-oxide with a suitable co-accelerator, the activation can be operated as usual become.

0,003 bis 0,03, vorzugsweise 0,005 bis 0,015 g/l Wasserstoffperoxid in freier oder gebundener Form,

0,2 bis 1, vorzugsweise 0,25 bis 0,5 g/l Nitroguanidin,

0,15 bis 0,8, vorzugsweise 0,2 bis 0,5 g/l m-Nitrobenzolsulfonationen.

It is therefore preferable to use a phosphating solution according to the invention which additionally contains 0.3 to 4 g / l of chlorate ions. The chlorate concentration is preferably in the range between 1 and 3 g / l. Instead of or together with the chlorate ions, the phosphating solution can contain one or more of the following accelerators in addition to the organic N-oxide:

0.003 to 0.03, preferably 0.005 to 0.015 g / l hydrogen peroxide in free or bound form,

0.2 to 1, preferably 0.25 to 0.5 g / l nitroguanidine,

0.15 to 0.8, preferably 0.2 to 0.5 g / l m-nitrobenzenesulfonate ions.

Hydrogen peroxide can be added to the phosphating solution as such become. However, it can also be in bound form in the form of Compounds are used which are hydrogen peroxide in the phosphating bath form or split off. Examples of such compounds are Perborates, percarbonates, salts of peroxy acids such as, for example Peroxodisulfate or peroxides such as sodium or Potassium peroxide.

Chlorate ions and / or m-nitrobenzenesulfonate ions are preferably used in the form of their water-soluble salts, for example their alkali metal salts on.

0,1 bis 4 g/l Mangan(II),

0,2 bis 2,5 g/l Magnesium(II),

0,2 bis 2,5 g/l Calcium(II),

0,002 bis 0,2 g/l Kupfer(II),

0,1 bis 2 g/l Cobalt(II).

In the phosphating process according to the invention, phosphating solutions are preferably used which contain further mono- or divalent metal ions, which experience has shown to have a favorable effect on the paint adhesion and the corrosion protection of the phosphate layers produced thereby. Accordingly, the phosphating solution according to the invention preferably additionally contains one or more of the following cations:

0.1 to 4 g / l manganese (II),

0.2 to 2.5 g / l magnesium (II),

0.2 to 2.5 g / l calcium (II),

0.002 to 0.2 g / l copper (II),

0.1 to 2 g / l cobalt (II).

If desired, the phosphating solutions can additionally contain nickel ions contain. For health and environmental reasons, however Phosphating baths preferred, the lowest possible levels of nickel ions have or, if desired, can also be nickel-free.

For example, the phosphating solution according to the invention contains in one preferred embodiment except zinc ions as additional cations 0.1 to 4 g / l manganese ions and 0.002 to 0.2 g / l copper ions and no more than 0.05 g / l, in particular not more than 0.001 g / l nickel ions. wishes to stick to traditional trication technology, can be used phosphating baths according to the invention, which except Zinc ions, 0.1 to 4 g / l manganese ions and additionally 0.1 to 2.5 g / l Contain nickel ions. In what form the cations in the In principle, phosphating baths are irrelevant. It offers in particular to oxides and / or carbonates as a cation source use.

It has proven to be advantageous when phosphating surfaces containing zinc proven to increase the nitrate content of the phosphating bath to a maximum of 0.5 g / l limit. This causes the problem of so-called speck formation suppressed and corrosion protection especially when used Nickel-free phosphating baths improved. Phosphating baths are particularly preferred, that do not contain nitrate.

In the case of phosphating baths which are said to be suitable for different substrates, it has become common to use free and / or complex-bound fluoride in amounts of up to 2.5 g / l of total fluoride, of which up to 750 mg / l of free fluoride, each calculated as F ^- , add. The presence of such amounts of fluoride is also advantageous for the phosphating baths according to the invention. In the absence of fluoride, the aluminum content of the bath should not exceed 3 mg / l. In the presence of fluoride, higher Al contents are tolerated as a result of the complex formation, provided the concentration of the non-complexed Al does not exceed 3 mg / l.

In principle, phosphating baths can be made by dissolving the individual Components in the water in the desired concentration range directly in front Location. In practice, however, it is common to use concentrates use the individual components in the desired Quantity ratio included and from those on site by diluting with Water the operational phosphating bath is produced or as Supplement solution are added to a working phosphating bath, to balance the consumption of the active components. such However, phosphating concentrates are strongly acidic for stabilization set. After dilution with water, the pH value must be checked frequently and / or the free acid blunted to the desired range become. For this purpose, alkaline substances such as Sodium hydroxide solution or sodium carbonate or basic salts or hydroxides of Ca, Mg, Zn added.

Accordingly, the invention also relates to an aqueous concentrate which after dilution with water by a factor between 10 and 100 and if necessary, adjust the pH to a working range between 2.5 and 3.6 a phosphating solution according to one or more of the Claims 1 to 12 results.

The invention further comprises a method for phosphating Metal surfaces made of steel, galvanized or alloy galvanized steel and / or aluminum. The materials mentioned can, as in Automobile manufacturing is becoming increasingly common, also side by side. you brings the metal surfaces by spraying or dipping or by a Combination thereof with the phosphating solution according to the invention in Contact. The temperature of the phosphating solution is preferably in the Range between about 40 and about 60 ° C.

The phosphating process can be used to phosphate tapes Steel or galvanized steel can be used in conveyor systems. The Phosphating times are in the range from about 3 to about 20 Seconds. However, the method can be used in particular in automotive engineering are used where treatment times are between 1 and 8 minutes are common. It is especially used to treat the above Metal surfaces before painting, especially before cathodic electrocoating. The phosphating process is to be seen as a sub-step of the technically usual pretreatment chain. In This chain of phosphating is usually the steps Cleaning / degreasing, intermediate rinsing and activation upstream, whereby the activation usually with titanium phosphate-containing activating agents he follows. The phosphating according to the invention can, if appropriate after an intermediate rinse, follow a passivating after-treatment. Chromic acid-containing ones are used for such a passivating aftertreatment Treatment baths widely used. For reasons of work and environmental protection however, and for reasons of disposal, there is a tendency these chrome-containing passivation baths through chrome-free treatment baths to replace. Purely inorganic baths are used for this, especially on the Basis of zirconium compounds, or also organic baths, for example based on poly (vinylphenols). When using Phosphating solutions that contain neither nickel nor copper ions can a significant improvement in corrosion protection can be achieved if the baths for passivating post-treatment copper or Adds silver ions. For example, passivating Rinse solutions are used that contain 0.001 to 10 g / l copper ions included and, if desired, can be free from others passivating components. Between this post-passivation and the usually subsequent electrocoating is in usually performed an intermediate rinse with deionized water.

embodiments Examples 1-7, Comparative Examples 1 and 2

1. Reinigen mit einem alkalischen Reiniger (Ridoline^R 1559, Henkel KGaA), Ansatz 4 % in Stadtwasser, 60 °C, 4 Minuten.

2. Spülen mit Stadtwasser, Raumtemperatur, 1 Minute.

3. Aktivieren mit einem Titanphosphat-haltigen Aktiviermittel (Fixodine^R 9112, Henkel KGaA), Ansatz 0,2 % in vollentsalztem Wasser, Raumtemperatur, 1 Minute.

4. Phosphatieren mit Phosphatbädern folgender Zusammensetzung:

1,0 g/l Zn²⁺

0,8 g/l Mn²⁺

0,5 g/l Ni²⁺

0,05 g/l Fe²⁺

14 g/l Phosphat, berechnet als PO₄ ^3-

Beschleuniger laut Tabelle 1

pH: 3,3; Freie Säure: 0,9; Gesamtsäure: 23

Temperatur: 55 °C; Behandlungszeit: 3 Minuten Spritzen

Unter Punktzahl der freien Säure wird für alle Beispiele und Vergleichsbeispiele der Verbrauch in ml an 0,1-normaler Natronlauge verstanden, um 10 ml Badlösung bis zu einem pH-Wert von 3,6 zu titrieren. Analog gibt die Punktzahl der Gesamtsäure den Verbrauch in ml bis zu einem pH-Wert von 8,2 an. Ausnahmen von dieser Definition (Beispiele 19 - 31, Vergleichsbeispiele 6 - 11) sind dort angegeben.

5. Spülen mit Stadtwasser, Raumtemperatur, 1 Minute.

6. Trockenblasen mit Preßluft

The phosphating processes and comparative processes according to the invention were checked on steel sheets (St 1405), as are used in automobile construction. The following process step, common in body production, was carried out as a spray process:

1.Clean with an alkaline cleaner (Ridoline ^R 1559, Henkel KGaA), approach 4% in city water, 60 ° C, 4 minutes.

2. Rinse with city water, room temperature, 1 minute.

3. Activation with an activating agent containing titanium phosphate (Fixodine ^R 9112, Henkel KGaA), approach 0.2% in deionized water, room temperature, 1 minute.

4. Phosphating with phosphate baths of the following composition:

1.0 g / l Zn ²⁺

0.8 g / l Mn ²⁺

0.5 g / l Ni ²⁺

0.05 g / l Fe ²⁺

14 g / l phosphate, calculated as PO ₄ ^3-

Accelerator according to table 1

pH: 3.3; Free acid: 0.9; Total acidity: 23

Temperature: 55 ° C; Treatment time: 3 minutes of spraying

The free acid score for all examples and comparative examples means the consumption in ml of 0.1 normal sodium hydroxide solution in order to titrate 10 ml of bath solution up to a pH of 3.6. Similarly, the total acid score indicates consumption in ml up to a pH of 8.2. Exceptions to this definition (Examples 19-31, Comparative Examples 6-11) are given there.

5. Rinse with city water, room temperature, 1 minute.

6. Blow dry with compressed air

The mass per unit area ("layer weight") was determined by dissolving in 5% chromic acid solution in accordance with DIN 50942. Accelerators and phosphating results Example No. accelerator Concentration (g / l) Layer weight (g / m ² ) optical slice pattern Vergl.1 without 1.5 - COMP.2 hydroxylammonium 2.0 3.3 ++ Beisp.1 N-methylmorpholine-N-oxide 0.5 4.9 + Beisp.2 N-methylmorpholine-N-oxide 1 3.1 ++ Beisp.3 4-picoline-N-oxide 0.5 4.4 + Beisp.4 4-picoline-N-oxide 1 3.5 ++ Beisp.5 Pyridine-N-oxide 0.5 4.5 + Beisp.6 Pyridine-N-oxide 1 3.8 + Beisp.7 Pyridine-N-oxide 1.5 2.9 ++

Examples 8 to 14, Comparative Examples 3 and 4

1,0 g/l Zn²⁺

0,8 g/l Mn²⁺

0,007 g/l Cu²⁺

0,01 g/l Fe²⁺

15 g/l Phosphat, berechnet als PO₄ ^3-

Beschleuniger laut Tabelle 2

pH: 3,3 Freie Säure: 0,9 Gesamtsäure: 25

Temperatur: 55 °C Behandlungszeit: 3 Minuten Spritzen

The acceleration effect and the durability of the accelerators according to the invention were tested in nickel-free, copper-containing phosphating baths. The general procedure corresponded to Examples 1 to 7. Baths of the following composition were used for phosphating:

1.0 g / l Zn ²⁺

0.8 g / l Mn ²⁺

0.007 g / l Cu ²⁺

0.01 g / l Fe ²⁺

15 g / l phosphate, calculated as PO ₄ ^3-

Accelerator according to table 2

pH: 3.3 Free acid: 0.9 Total acid: 25

Temperature: 55 ° C Treatment time: 3 minutes spraying

Compared to the stability of the accelerator according to the invention To test copper ions was the concentration of the accelerator measured immediately after preparation of the phosphating bath. Immediately then 3 steel sheets were phosphated. The phosphating results are entered in Table 2. After phosphating the The phosphating bath was 3 test trays at a temperature of 55 ° C so strong for a period of 24 hours with a magnetic stirrer stirred that air was drawn into the phosphating bath through the stirring funnel has been. After that, the concentration of the accelerator was again certainly.

Hydroxylamine was determined in accordance with the prior art usual acetone method: (1) the 1:20 diluted bath solution with 0.1 N NaOH to a pH of 3.76, 10 ml of acetone and again (2) to pH 3.76 with 0.1 N NaOH. Consumption (2) in ml x 0.033 = % Hydroxylamine in the bathroom. In table 2 the content is up Converted hydroxylammonium sulfate.

The N-oxides were determined by high pressure liquid chromatography (HPLC). Accelerator, accelerator stability, phosphating results Example No. accelerator Initial concentration (g / l) Concentration after aging (g / l) optical slice pattern Layer weight (g / l) Vergl.3 Hydroxylamine 2 g / l - ++ 3.7 Vergl.4 Hydroxylamine 1.5 - ++ 4.0 Beisp.8 N-methyl-N-oxide 2.0 1.9 ++ 3.1 Beisp.9 N-methyl-N-oxide 1.5 1.45 ++ 3.2 Ex. 10 N-methyl-N-oxide 1.0 0.9 ++ 3.0 Beisp.11 4-picoline-N-oxide 2.5 2.4 ++ 2.9 Beisp.12 4-picoline-N-oxide 1.5 1.4 ++ 3.4 Beisp.13 4-picoline-N-oxide 0.75 0.7 ++ 4.1 Beisp.14 4-picoline-N-oxide 0.4 0.4 + 4.5

Example 15, Comparative Example 5

1) Reinigen mit einem alkalischen Reiniger (Ridoline^R 1401, Henkel KGaA), Ansatz 5 % in Stadtwasser, 75 °C, 5 Minuten Tauchen.

2) Spülen mit Stadtwasser, Raumtemperatur, 1 Minute.

3) Aktivieren mit einem flüssigen Titanphosphat-haltigen Aktiviermittel (Fixodine^R 50 CF, Henkel KGaA), Ansatz 0,05 % in vollentsalztem Wasser, Raumtemperatur, 1 Minute tauchen.

4) Phosphatieren mit einem Phosphatierbad folgender Zusammensetzung:

1,2 g/l Zn²⁺,

0,76 g/l Mn²⁺,

0,007 g/l Cu²⁺,

12,5 g/l PO₄ ^3-,

2,7 g/l 25-gew.-%ige Lösung von H₂SiF₆,

2 g/l N-Methylmorpholin-N-Oxid,

Freie Säure: 0,9; Gesamtsäure: 23

Temperatur 54 °C, 3 Minuten tauchen

5) Spülen mit vollentsalztem Wasser, Raumtemperatur, 1 Minute.

6) Trockenblasen mit Preßluft.

7) Lackierung: katodischer Elektrotauchlack Cathoguard 400 und Aufbau DB silbermetallik.

The automotive-typical substrates cold-rolled steel St 1405 (CRS), electrolytically galvanized steel (EG) on both sides and hot-dip galvanized steel (HDG) were used for this exemplary embodiment. The following procedure was carried out:

1) Clean with an alkaline cleaner (Ridoline ^R 1401, Henkel KGaA), batch 5% in city water, 75 ° C, 5 minutes of immersion.

2) Rinse with city water, room temperature, 1 minute.

3) Activate with a liquid titanium phosphate-containing activating agent (Fixodine ^R 50 CF, Henkel KGaA), mix 0.05% in deionized water, room temperature, immerse for 1 minute.

4) Phosphating with a phosphating bath of the following composition:

1.2 g / l Zn ²⁺ ,

0.76 g / l Mn ²⁺ ,

0.007 g / l Cu ²⁺ ,

12.5 g / l PO ₄ ^3- ,

2.7 g / l 25% by weight solution of H ₂ SiF ₆ ,

2 g / l N-methylmorpholine-N-oxide,

Free acid: 0.9; Total acidity: 23

Temperature 54 ° C, dive for 3 minutes

5) Rinse with deionized water, room temperature, 1 minute.

6) Blow dry with compressed air.

7) Painting: Cathoduard 400 cathodic electro-dip coating and DB silver metallic structure.

The layer composition was repeated on cold-rolled steel Detachment determined with atomic absorption spectroscopy. In doing so the following weight ratios of the metals were found: Zn: Mn: Cu = 160: 25: 1.

A typical automotive alternating climate test was carried out with painted metal sheets (VDA 621-415). For evaluation, the Measure undermining of paint on a scratch (half the scratch width) and the Degree of corrosion determined after a stone chip test according to the VW standard (Scale values from 1 to 10 after increasing corrosion).

Comparative example 5 differs from embodiment 15 in that that instead of N-morpholine-N-oxide as accelerator 2 g / l hydroxylammonium sulfate were used.

After the phosphating of cold rolled steel, the following became Metal ratio in the phosphate layer determines: Zn: Mn: Cu = 140: 22: 1.

The results are summarized in Table 3. The two experiments make it clear that the phosphating results when using N-morpholine-N-oxide as an accelerator according to the invention are not significantly different from those with the known accelerator hydroxylammonium sulfate. phosphating Example 15 substratum Layer weight (g / m ² ) Crystal size (µm) Paint infiltration (U / 2, mm) Stone chip test (K value) CRS 3.3 3 to 7 0.95 1 EC 4.6 3 to 5 2.45 1.5 HDG 4.2 2 to 6 2.95 2 Comparison 5 substratum Layer weight (g / m ² ) Crystal size (µm) Paint infiltration (U / 2, mm) Stone chip test (K value) CRS 2.6 3 to 5 0.85 1 EC 4.1 3 to 7 2.5 1 HDG 4.5 5 to 9 2.85 2.5

Examples 16, 17, 18

1) Reinigen mit einem alkalischen Reiniger (Ridoline^R 1559, Henkel KGaA) Ansatz 2,5 % in Stadtwasser, 75 °C, 5 Minuten tauchen.

2) Spülen mit Stadtwasser, Raumtemperatur, 1 Minute.

3) Aktivieren mit einem flüssigen Titanphosphat-haltigen Aktiviermittel (Fixodine^R 50 CF, Henkel KGaA), Ansatz 0,05 % in vollentsalztem Wasser, Raumtemperatur, 30 Sekunden spritzen, Spritzdruck 1 bar.

4) Phosphatieren mit Phosphatierbädern gemäß Tabelle 4, 52 °C, 30 Sekunden spritzen, Spritzdruck 1 bar. Zusätzlich zu den in Tabelle 4 angegebenen Komponenten enthielten die Phosphatierbäder unterschiedliche Mengen an komplexgebundenem Fluorid (H₂SiF₆) und wiesen unterschiedliche Werte der freien Säure und der Gesamtsäure auf. Diese sind in Tabelle 5 zusammen mit den erhaltenen Schichtgewichten und der Optik der Phosphatschichten (untersucht mit Rasterelektronenmikroskopie) enthalten.

5) Spülen mit Stadtwasser, Raumtemperatur, 1 Minute.

6) Trockenblasen mit Preßluft.

Phosphatierlösungen (Zusammensetzung in g/l) Komponente (g/l) Beisp.16 Beisp.17 Beisp.18 H₃PO₄ 85%ig 18,15 18,15 18,15 Zn²⁺ 1,3 1,3 0,85 Mn²⁺ 1,05 1,05 0,8 Fe²⁺ 0,03 0,03 0,03 Ni²⁺ - 0,4 - N-Methylmorpholin-N-oxid 2 2 2 Phosphatierparameter und Ergebnisse Phosphatierlösung F^- (frei) F^- (komplex) (ppm) Freie Säure (Punkte) Gesamtsäure (Punkte) Schichtgewicht (g/m²) Optik Beisp. 16 -
1500 0,7 20,3 1,22 fast geschlossen Beisp. 16 -
1500 0,35 19,8 1,38 geschlossen,
Kristalle 5 - 10 µm Beisp. 16 -
1500 0,15 18,4 1,82 geschlossen Beisp. 16 -
2500 0,38 21,2 1,22 geschlossen,
Kristalle 4-8 µm Beisp. 16 -
2500 0,2 20,9 1,53 geschlossen Beisp. 16 -
2500 0,15 20,8 1,84 geschlossen Beisp. 16 150
2500 0,3 21,5 1,22 geschlossen,
Kristalle 4-8 µm Beisp. 16 150
2500 0,15 20,8 1,84 geschlossen Beisp. 17 -
1500 0,5 22,2 1,95 geschlossen Beisp. 17 -
1500 0,3 21,7 3,34 geschlossen,
Kristalle 4-8 µm Beisp. 17 -
1500 0,36 21,8 1,85 geschlossen,
Kristalle 4-8 µm The following process was carried out for the phosphating of cold-rolled steel:

1) Clean with an alkaline cleaner (Ridoline ^R 1559, Henkel KGaA) Approach 2.5% in city water, 75 ° C, immerse for 5 minutes.

2) Rinse with city water, room temperature, 1 minute.

3) Activate with a liquid titanium phosphate-containing activating agent (Fixodine ^R 50 CF, Henkel KGaA), mix 0.05% in deionized water, spray at room temperature, 30 seconds, spray pressure 1 bar.

4) Phosphate with phosphate baths according to Table 4, spray at 52 ° C, 30 seconds, spray pressure 1 bar. In addition to the components listed in Table 4, the phosphating baths contained different amounts of complex-bound fluoride (H ₂ SiF ₆ ) and had different values of free acid and total acid. These are shown in Table 5 together with the layer weights obtained and the optics of the phosphate layers (examined with scanning electron microscopy).

5) Rinse with city water, room temperature, 1 minute.

6) Blow dry with compressed air.

Phosphating solutions (composition in g / l) Component (g / l) Beisp.16 Beisp.17 Beisp.18 H ₃ PO ₄ 85% 18.15 18.15 18.15 Zn ²⁺ 1.3 1.3 0.85 Mn ²⁺ 1.05 1.05 0.8 Fe ²⁺ 0.03 0.03 0.03 Ni ²⁺ - 0.4 - N-methyl-N-oxide 2 2 2 Phosphating parameters and results phosphating F ^- (free) F ^- (complex) (ppm) Free acidity (points) Total acidity (points) Layer weight (g / m ² ) optics Ex. 16 -
1500 0.7 20.3 1.22 almost closed Ex. 16 -
1500 0.35 19.8 1.38 closed,
Crystals 5 - 10 µm Ex. 16 -
1500 0.15 18.4 1.82 closed Ex. 16 -
2500 0.38 21.2 1.22 closed,
Crystals 4-8 µm Ex. 16 -
2500 0.2 20.9 1.53 closed Ex. 16 -
2500 0.15 20.8 1.84 closed Ex. 16 150
2500 0.3 21.5 1.22 closed,
Crystals 4-8 µm Ex. 16 150
2500 0.15 20.8 1.84 closed Ex. 17 -
1500 0.5 22.2 1.95 closed Ex. 17 -
1500 0.3 21.7 3.34 closed,
Crystals 4-8 µm Ex. 17 -
1500 0.36 21.8 1.85 closed,
Crystals 4-8 µm

The phosphating solution for Example 18 is included in Table 4. It also contained 1750 ppm of complex-bound fluoride (H ₂ SiF ₆ ). In this way, the substrates CRS, EG and HDG were phosphated at temperatures of 45 ° C. and 50 ° C. in the aforementioned process. The layer weights are shown in Table 6. In all cases, optically perfect layers were obtained. Phosphating parameters and results of phosphating solution according to Example 18 Temperature (° C) Free acidity (points) Total acidity (points) substratum Layer weight (g / m ² ) 45 0.2 19.3 CRS 2.60 EC 1.81 HDG 2.71 50 0.5 19.6 CRS 1.55 EC 1.53 HDG 2.07

Examples 19-31, Comparative Examples 6-11

1. Reinigen mit einem alkalischen Reiniger (Ridoline^R 1559, Henkel KGaA), Ansatz 2 % in Stadtwasser, 58 °C, 5 Minuten.

2. Spülen mit Stadtwasser, Raumtemperatur, 1 Minute.

3. Aktivieren mit einem Titanphosphat-haltigen Aktiviermittel (Fixodine^R 9112, Henkel KGaA), Ansatz 0,1 oder 0,5 % in vollentsalztem Wasser, Raumtemperatur, 1 Minute.

4. Phosphatieren mit Phosphatierbädern folgender Zusammensetzung:

1,2 g/l Zn²⁺

0,8 g/l Mn²⁺

0,007 g/l Cu²⁺

0,68 g/l SiF₆ ^2-

0,8 g/l F^-

14 g/l Phosphat, berechnet als PO₄ ^3-

Beschleuniger laut Tabellen 7 bis 10

pH: 3,3; Freie Säure: Tabellen 7 bis 10; Gesamtsäure: 21

Temperatur: 50 °C; Behandlungszeit: 4 Minuten Tauchen

Unter Punktzahl der freien Säure wird der Verbrauch in ml an 0,1-normaler Natronlauge verstanden, um 10 ml Badlösung bis zu einem pH-Wert von 3,6 zu titrieren. Analog gibt die Punktzahl der Gesamtsäure den Verbrauch in ml bis zu einem pH-Wert von 8,5 an.

5. Spülen mit Stadtwasser, Raumtemperatur, 1 Minute.

6. Trockenblasen mit Preßluft

The phosphating processes and comparative processes according to the invention were checked on steel sheets (St 1405), as are used in automobile construction. The following process step, common in body production, was carried out as a spray process:

1.Clean with an alkaline cleaner (Ridoline ^R 1559, Henkel KGaA), mix 2% in city water, 58 ° C, 5 minutes.

2. Rinse with city water, room temperature, 1 minute.

3. Activation with an activating agent containing titanium phosphate (Fixodine ^R 9112, Henkel KGaA), batch 0.1 or 0.5% in deionized water, room temperature, 1 minute.

4. Phosphating with phosphating baths of the following composition:

1.2 g / l Zn ²⁺

0.8 g / l Mn ²⁺

0.007 g / l Cu ²⁺

0.68 g / l SiF ₆ ^2-

0.8 g / l F ^-

14 g / l phosphate, calculated as PO ₄ ^3-

Accelerators according to tables 7 to 10

pH: 3.3; Free acid: Tables 7 to 10; Total acidity: 21

Temperature: 50 ° C; Treatment time: 4 minutes of diving

The free acid score is understood to mean the consumption in ml of 0.1 normal sodium hydroxide solution in order to titrate 10 ml of bath solution up to a pH of 3.6. Similarly, the total acid score indicates consumption in ml up to a pH of 8.5.

5. Rinse with city water, room temperature, 1 minute.

6. Blow dry with compressed air

The mass per unit area ("layer weight") was determined by dissolving in 5% chromic acid solution in accordance with DIN 50942. Variable bath parameters and layer weights Example No. Activating solution concentration (% by weight) N-methylmorpholine-N-oxide (g / l) Chlorate (g / l) Free acidity (points) Layer weight (g / m ² ) Vergl.6 0.1 0 3 0.7 ng Beisp.19 0.1 2 3 0.7 2.8 Beisp.20 0.1 2 3 1.2 3.2 Vergl.7 0.5 0 3 0.7 ng Beisp.21 0.5 2 3 0.7 2.3 Beisp.22 0.5 2 3 1.2 2.5 Variable bath parameters and layer weights Example No. Activating solution concentration (% by weight) N-methylmorpholine-N-oxide (g / l) H202 (ppm) Free acidity (points) Layer weight (g / m ² ) Comp. 8th 0.1 - 15 0.6 ng Ex. 23 0.1 2 5 0.6 3.2 Ex. 24 0.1 2 10 0.6 2.8 Ex. 25 0.1 2 15 0.6 2.0 Ex. 26 0.1 2 20 0.6 1.5 Variable bath parameters and layer weights Example No. Activating solution concentration (% by weight) N-methylmorpholine-N-oxide (g / l) Chlorate (g / l) Free acidity (points) Layer weight (g / m ² ) Comp. 9 0.1 - 400 0.8 ng Comp. 10 0.1 - 500 0.8 3.0 Ex. 27 0.1 2 300 0.8 2.6 Ex. 28 0.1 2 400 0.8 2.3 Variable bath parameters and layer weights Example No. Activating solution concentration (% by weight) N-methylmorpholine-N-oxide (g / l) m-nitrobenzenesulfonate (ppm) Free acidity (points) Layer weight (g / m ² ) Comp. 11 0.1 - 450 0.8 ng Ex. 29 0.1 2 150 0.8 2.4 Ex. 30 0.1 2 300 0.8 2.2 Ex. 31 0.1 2 450 0.8 2.0

Claims (14)

1. An acidic aqueous phosphating solution containing zinc ions, phosphate ions and an organic N oxide as accelerator, characterized in that the solution contains
   0.2 to 3 g/l zinc ions,
   3 to 50 g/l phosphate ions expressed as PO₄ ^-3 and
   0.05 to 4 g/l of an organic N oxide having a saturated, unsaturated or aromatic five- or six-membered ring system, the N atom of the N oxide being part of this ring system and the ratio by weight of phosphate ions to zinc ions being between 3.7 and 30:1.
2. A phosphating solution as claimed in claim 1, characterized in that the organic N oxide is selected from N oxides of substituted or unsubstituted pyrroles, imidazoles, oxazoles, pyridines, pyrimidines, pyrazines, oxazines or hydrogenation products thereof.
3. A phosphating solution as claimed in claim 1 or 2, characterized in that the N oxide is selected from N oxides of substituted or unsubstituted pyridines and morpholines, more particularly from pyridine-N-oxide, 2-methylpyridine-N-oxide, 4-methylpyridine-N-oxide, morpholine-N-oxide and N-methylmorpholine-N-oxide.
4. A phosphating solution as claimed in one or more of claims 1 to 3, characterized in that it contains 0.1 to 3 g/l of the organic N oxide.
5. A phosphating solution as claimed in one or more of claims 1 to 4, characterized in that it additionally contains
   0.3 to 4 g/l chlorate ions.
6. A phosphating solution as claimed in one or more of claims 1 to 5, characterized in that it additionally contains one or more of the following accelerators:

   0.003 to 0.03 g/l hydrogen peroxide in free or bound form,

   0.2 to 1 g/l nitroguanidine,

   0.15 to 0.8 g/l m-nitrobenzenesulfonate ions.
7. A phosphating solution as claimed in one or more of claims 1 to 6, characterized in that it additionally contains one or more of the following cations:

   0.1 to 4 g/l manganese(II),

   0.2 to 2.5 g/l magnesium(II),

   0.2 to 2.5 g/l calcium(II),

   0.002 to 0.2 g/l copper(II),

   0.1 to 2 g/l cobalt(II).
8. A phosphating solution as claimed in claim 7, characterized in that it contains 0.1 to 4 g/l manganese ions and 0.002 to 0.2 g/l copper ions and no more than 0.05 g/l nickel ions.
9. A phosphating solution as claimed in claim 7, characterized in that it contains 0.1 to 4 g/l manganese ions and in addition 0.1 to 2.5 g/l nickel ions.
10. A phosphating solution as claimed in one or more of claims 1 to 9, characterized in that it contains 0.4 to 2 g/l zinc ions.
11. A phosphating solution as claimed in one or more of claims 1 to 10, characterized in that it contains no more than 0.5 g/l nitrate ions.
12. A phosphating solution as claimed in one or more of claims 1 to 11, characterized in that it additionally contains free and/or complex fluoride in quantities of up to 2.5 g/l total fluoride, of which up to 750 mg/l is free fluoride, expressed as F^-.
13. A water-containing concentrate which gives the phosphating solution claimed in one or more of claims 1 to 12 after dilution with water by a factor of 10 to 100 and optionally pH adjustment to a working range of 2.5 to 3.6.
14. A process for phosphating metal surfaces of steel, galvanized steel or alloy-galvanized steel and/or of aluminium, in which the metal surfaces are contacted with the phosphating solution claimed in one or more of claims 1 to 12 for 3 seconds to 8 minutes by spraying or dipping or by a combination thereof.