DE19940619A1 - Zinc phosphating with epoxides - Google Patents

Abstract

The invention relates to a method for phosphatizing metal surfaces made of steel, galvanized or alloy-galvanized steel, aluminum and/or of aluminum alloys during which the metal surfaces are brought into contact with a phosphatizing solution that contains zinc by spraying or immersing the metal surfaces for a duration ranging from 3 seconds to 8 minutes. Said phosphatizing solution contains 0.2 to 3 g/l of zinc ions and 3 to 50 g/l of phosphate ions, whereby the weight ratio of phosphate ions to zinc ions is at least 3.7, and optionally contains one or more accelerators. In addition, the metal surfaces are brought into contact with an aqueous solution or suspension of an organic polymer during or after the phosphatizing. The inventive method is characterized in that the organic polymer is a polyepoxide selected from glycidyl ethers based on aliphatic polyols or based on bisphenol A or bisphenol F provided in a quantity ranging from 0.1 to 5 g/l in the aqueous solution or suspension.

Description

The invention relates to processes for phosphating metal surfaces aqueous, acid phosphating solutions containing zinc and phosphate ions. During the phosphating or afterwards the Metal surfaces in contact with organic polyepoxides (epoxy resins) brought that in the aqueous application medium in an amount up to 5 g / l as Solution or suspension. Such methods serve in particular as Pretreatment of the metal surfaces for subsequent painting, in particular an electro dip coating or a powder coating. The The method is applicable for the treatment of surfaces made of steel, galvanized or galvanized steel, aluminum, aluminum-magnesium alloys, aluminized or alloy aluminized steel.

The phosphating of metals pursues the goal on the metal surface to produce firmly grown metal phosphate layers, which are already the Improve corrosion resistance and in conjunction with paints or others organic coatings to significantly increase paint adhesion and resistance to infiltration when exposed to corrosion contribute. Such phosphating processes have long been known. For the Pretreatment before painting, especially electrocoating, The low-zinc phosphating processes, in which the Phosphating solutions comparatively low levels of zinc ions of z. B. 0.5  up to 2 g / l. An essential parameter in these low-zinc Phosphating baths is the weight ratio of phosphate ions to zinc ions is usually in the range greater than 8 and can assume values up to 30.

It has been shown that by using other polyvalent cations in the zinc phosphating baths phosphate layers with 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 Manganese ions and e.g. B. 0.3 to 2.0 g / l of nickel ions as a so-called trication Process for preparing metal surfaces for painting, for example for the cathodic electrocoating of car bodies, wide application.

Since nickel and the alternative cobalt are also made from toxicological and wastewater technology are classified as critical, there is a need for Phosphating processes that have a similar level of performance as the trication Have processes, but with much lower bath concentrations of Nickel and / or cobalt and preferably without these two metals get along.

EP-B-18 841 describes a chlorate-nitrite-accelerated zinc phosphate solution containing, among other things, 0.4 to 1 g / l zinc ions, 5 to 40 g / l Phosphate ions and optionally at least 0.2 g / l, preferably 0.2 to 2 g / l of one or more ions selected from nickel, cobalt, calcium and manganese. Accordingly, the optional manganese, nickel or cobalt content is at least 0.2 g / l.

EP-A-459 541 describes phosphating solutions which are essentially free of In addition to zinc and phosphate, nickel is 0.2 to 4 g / l manganese and 1 to 30 mg / l copper included. DE-A-42 10 513 are nickel-free Phosphating solutions known that, in addition to zinc and phosphate, 0.5 to 25 mg / l Contain copper ions and hydroxylamine as an accelerator. Optionally included these phosphating solutions additionally 0.15 to 5 g / l manganese.  

The German patent application DE-A-196 06 017 describes one heavy metal reduced phosphating solution containing 0.2 to 3 g / l zinc ions, 1 to 150 mg / l manganese ions and 1 to 30 mg / l copper ions. Optionally, this can Phosphating solution up to 50 mg / l nickel ions and up to 100 mg / l cobalt ions contain. Another optional component is lithium ions in quantities between 0.2 and 1.5 g / l.

The German patent application DE-A-195 38 778 describes the control of the Layer weight of phosphate layers through the use of hydroxylamine as an accelerator. The use of hydroxylamine and / or its Compounds for influencing the shape of the phosphate crystals is from one Series of published disclosures. EP-A-315 059 gives as special Effect of using hydroxylamine in phosphating baths the fact that on steel the phosphate crystals are still in a desired columnar or knot-like shape arise when the zinc concentration in the Phosphating bath exceeds the range customary for low-zinc processes. This makes it possible to use phosphating baths with zinc concentrations up to 2 g / l and operate with phosphate to zinc weight ratios down to 3.7. There are no advantageous cation combinations of these phosphating baths more detailed statements are made, however, in the patent examples in all cases Nickel used. The required hydroxylamine concentration is 0.5 to 50 g / l, preferably 1 to 10 g / l.

To improve the corrosion protection provided by the phosphate layer passivation rinsing usually takes place in technology, also called post-passivation. For this are chromic acid Treatment baths still widely used. For the sake of work and Environmental protection, however, tends to use these chromium-containing passivation baths to be replaced by chrome-free treatment baths. For this are, for example organic reactive bathroom solutions with complexing substitutes Poly (vinylphenols) known. For example, such connections are in the DE-C-31 46 265. WO 97/14822 describes a rinse solution for  phosphated metal surfaces known to be a reaction product of a epoxy functional material with at least 2 epoxy groups and alkanolamines and contains a material selected from Group IV-B metal ions. Diethanolamine is preferably used for crosslinking the epoxides Handle with care due to its tendency to form nitrosamines must become.

It is already known from the literature that phosphating solutions are polyacrylic acids to add. The article by J.I. Wragg, J.E. Chamberlain, L. Chann, H. W. White, T. Sugama, and S. Manalis: "Characterization of Polyacrylic Acid Modified Zinc Phosphate Crystal Conversion Coatings ", Journal of Applied Polymer Science, Vol. 50, 917-928 (1993) However, model-like zinc phosphating solutions were examined, which are clearly differ from those currently used in practice: they contain higher ones Contents in zinc, on the other hand the widely used manganese is missing as well as in the Rule the accelerators currently in use. They are therefore not a role model for them Low zinc used in the present invention Phosphating solutions.

WO 97/45568 discloses a method for phosphating metal surfaces made of steel, galvanized or alloy galvanized steel and / or aluminum, in which the metal surfaces are brought into contact with a zinc-containing phosphating solution by spraying or dipping for a time between 3 seconds and 8 minutes , characterized in that the phosphating solution
0.2 to 3 g / l zinc ions
3 to 50 g / l phosphate ions, calculated as PO ₄ ,
0.001 to 4 g / l manganese ions,
0.001 to 0.5 g / l of one or more polymers selected from polyethers, polycarboxylates, polymeric phosphonic acids, polymeric phosphinocarboxylic acids and nitrogen-containing organic polymers and
one or more accelerators selected
0.3 to 4 g / l chlorate ions,
0.01 to 0.2 g / l nitrite ions,
0.05 to 2 g / l m-nitrobenzenesulfonate ions,
0.05 to 2 g / l m-nitrobenzoate ions,
0.05 to 2 g / l p-nitrophenol,
0.005 to 0.15 g / l hydrogen peroxide in free or bound form,
0.1 to 10 g / l hydroxylamine in free or bound form,
0.1 to 10 g / l of a reducing sugar
contains.

The object of the present invention is a phosphating process to make available that with comparatively low levels of nickel and / or cobalt of a maximum of 200 mg / l and preferably without any addition of these metal ions gets along. Nevertheless, paint adhesion and Corrosion protection values can be achieved, as required for automotive engineering and how they are currently achieved with standard trication-phosphating processes become.

This object is achieved by a process for phosphating Metal surfaces made of steel, galvanized or alloy galvanized steel, Aluminum and / or aluminum alloys, in which one Metal surfaces by spraying or dipping for a time between 3 Seconds and 8 minutes in contact with a zinc-containing phosphating solution brings, the 0.2 to 3 g / l zinc ions and 3 to 50 g / l, phosphate ions, which Weight ratio of phosphate ions to zinc ions is at least 3.7, and optionally contains one or more accelerators, whereby the Metal surfaces during or after the phosphating with an aqueous solution or suspension of an organic polymer in Touches, characterized in that the organic polymer is a polyepoxide selected from glycidyl ethers based on aliphatic polyols or based on bisphenol A or bisphenol F,  that in an amount of 0.1 to 5 g / l in the aqueous solution or suspension is present.

The polyepoxides, i.e. the organic polymer, can be directly in the Phosphating solution are available. It is then used during the phosphating with the Contacted metal surface.

An alternative embodiment for this is that the metal surfaces are first brought into contact with the phosphating solution and then with the aqueous solution or suspension of the organic polymer, that is to say the polyepoxides. In this embodiment, the solution or suspension of the polyepoxides is used as a passivating rinse solution. It then serves to close pores in the phosphate layer and thereby improve the corrosion protection. Due to the low concentration of the polyepoxides in the aqueous solution or suspension of a maximum of 5 g / l, the organic film which is deposited is considerably thinner than a conventional coating and contains no more than 1 g of carbon per m ² . This post-passivation is therefore not to be confused with a classic paint job, which rather - preferably in the form of a cathodic electro-dip paint job - follows the passivating post-rinse as the next step.

In this embodiment, the solution or suspension of the organic Polymers as a passivating rinse after the actual phosphating is used, it is preferred that the aqueous solution or suspension of organic polymer additionally 10 to 1000, preferably 50 to 500 mg / l contains complex fluorides of titanium and / or zircon. Furthermore, this can passivating rinsing with an aqueous solution or suspension of organic polymers are made, regardless of a possible content complex fluorides of titanium and / or zirconium - 5 to 100 mg / l copper ions contains.

For use as a passivating rinse solution after phosphating adjust the pH of the aqueous solution or suspension of the organic  Polymers preferably to a value in the range of 3.8 to 5.5. The passivating rinse solution can with the phosphated metal surface by immersing the metal parts in the rinse solution or by spraying with the rinse solution are brought into contact. The duration of treatment is preferably in the range of 0.5 to 3 minutes. The temperature of the Rinse solution is preferably set to a range between 15 and 45 ° C on.

The zinc concentration is preferably in the range between about 0.3 and about 2 g / l and in particular between about 0.8 and about 1.6 g / l. Zinc levels above 1.6 g / l, for example between 2 and 3 g / l, are only sufficient for the process Little advantages, but on the other hand, the accumulation of sludge in the phosphating bath increase. Such zinc contents can be found in a working phosphating bath adjust if, when phosphating galvanized surfaces by the Pickling removal of additional zinc reaches the phosphating bath. Nickel and / or Cobalt ions in the concentration range from about 1 to about 200 mg / l each improve, preferably in conjunction with the lowest possible Nitrate content of no more than about 0.5 g / l, corrosion protection and paint adhesion compared to phosphating baths that do not contain nickel or cobalt. Depending on Low levels of nickel or cobalt may be sufficient for the substrate. for example levels between about 1 and about 50 mg / l for each of these Cations. For wastewater reasons, it is particularly preferable to No nickel or cobalt added to the phosphating bath at all. Still can in these cases too, the phosphating baths have low nickel contents, for example in the order of up to 10 mg / l. Such nickel contents can come out of nickel-containing substrate material Build up nickel-containing system parts.

Improved results compared to manganese-free phosphating baths one if the phosphating solution additionally about 0.001 to 3 g / l manganese ions contains. In the case of phosphate baths reduced in heavy metals, the manganese content can range from about 0.001 to about 0.2 g / l. Otherwise there are manganese contents from about 0.5 to about 1.5 g / l.  

Furthermore, the phosphating solution according to the invention can additionally about 1 to contain about 30 mg / l copper ions. This can be particularly advantageous if no nickel or cobalt ions are added. Depending on However, substrate material is also added without the addition of copper ions Sufficient corrosion protection and sufficient paint adhesion achieved.

There is a special embodiment of the method according to the invention in that the phosphating solution does not contain any deliberately added nickel, cobalt and contains copper ions. This means that one can do without the Phosphating solution to consciously add these three metal ions. However, how mentioned above, it cannot be excluded that small amounts of these Ions, especially nickel ions, via the container material or via the Get the substrate into the phosphating solution.

Furthermore, it can offer advantages in individual cases, the phosphating solution additionally add further divalent metal ions. For example, the Phosphating solution additionally each about 0.05 to about 3 g / l magnesium, Contain calcium, barium and / or iron (II) ions. Limited iron content preferably below 0.5 g / l.

In addition to the above cations, which are in the phosphate layer with be installed or at least the crystal growth of the phosphate layer the phosphating baths usually contain sodium, Potassium and / or ammonium ions to adjust the free acid. The term the free acid is familiar to the person skilled in the phosphating field. In the this method of determining the free acid and the Total acid is given in the example section. Free acid and total acid represent an important control parameter for phosphating baths because they have a great influence on the layer weight. Free acid values between 0 and 1.5 points for partial phosphating, for band phosphating up to to 2.5 points and the total acidity between about 15 and about 30 points  are in the usual technical range and are within the scope of this invention suitable.

In the case of phosphating baths which are said to be suitable for different substrates, it has become customary to calculate free and / or complex-bound fluoride in amounts of up to 2.5 g / l of total fluoride, of which up to 1 g / l of free fluoride, in each case as F ^- to 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. The use of fluoride-containing baths is therefore advantageous if the surfaces to be phosphated are at least partially made of aluminum or contain aluminum. In these cases, it is favorable not to use complex-bound, but only free fluoride, preferably in concentrations in the range from 0.5 to 1.0 g / l.

For the phosphating of zinc surfaces, it would not be absolutely necessary that the phosphating baths contain so-called accelerators. For the Phosphating of steel surfaces, however, requires that the Phosphating solution contains one or more accelerators. Such acceleration ger are in the prior art as components of zinc phosphating baths common. This is understood to mean substances that are caused by the pickling attack This chemically creates hydrogen on the acid on the metal surface bind that they themselves are reduced. Oxidizing accelerators continue to have the effect of pickling on steel surfaces released iron (II) ions to oxidize to the trivalent stage, so that they as Iron (III) phosphate can precipitate.

The phosphating baths according to the invention can contain one or more of the following components as accelerators:
0.3 to 4 g / l chlorate ions,
0.01 to 0.2 g / l nitrite ions,
0.05 to 2 g / l m-nitrobenzenesulfonate ions,
0.05 to 2 g / l m-nitrobenzoate ions,
0.05 to 2 g / l p-nitrophenol,
0.005 to 0.15 g / l hydrogen peroxide in free or bound form,
0.1 to 10 g / l hydroxylamine in free or bound form,
0.1 to 10 g / l of a reducing sugar
0.05 to 4 g / l of an organic N-oxide, preferably N-methymorpholine,
0.5 to 5 g / l of an organic nitro compound selected from nitroguanidine, nitroarginine and methyl, ethyl or propyl esters thereof and from nitrofurfurylidene diacetate.

When phosphating galvanized steel, it is advantageous if the Phosphating solution contains as little nitrate as possible. Nitrate concentrations of 0.5 g / l should not be exceeded, since at higher nitrate concentrations the Possibility of so-called "speck formation" exists. Hereby are white, kra ter-like defects in the phosphate layer meant. In addition, the Paint adhesion on galvanized surfaces impaired.

The use of nitrite as an accelerator leads in particular to steel surfaces for technically satisfactory results. For the sake of Ar occupational safety (danger of developing nitrous gases), however, it is em Recommended to avoid nitrite as an accelerator. For phosphating galvanized surfaces, this is advisable for technical reasons as well Nitrite can form nitrate, which, as explained above, is a problem of Speck formation and reduced paint adhesion to zinc can result.

For reasons of environmental friendliness, hydrogen peroxide, from the tech niche reasons of the simplified formulation options for Nachdo Sierlösungen hydroxylamine is particularly preferred as an accelerator. The however, sharing these two accelerators is not advisable because Hydroxylamine is decomposed by hydrogen peroxide. If you put hydrogen peroxide concentrations in free or bound form as accelerators from 0.005 to 0.02 g / l of hydrogen peroxide are particularly preferred. It can  Hydrogen peroxide can be added to the phosphating solution as such. It is however, it is also possible to use hydrogen peroxide in bound form as compounds use in the phosphating bath by hydrolysis reactions Deliver hydrogen peroxide. Examples of such compounds are persalts such as Perborates, percarbonates, peroxosulfates or. Peroxodisulfates. As further sources for hydrogen peroxide come ionic peroxides such as Alkali metal peroxides into consideration. A preferred embodiment of the invention is that in the phosphating in the immersion process a combination from chlorate ions and hydrogen peroxide is used. In this Embodiment can, for example, the concentration of chlorate in the range from 2 to 4 g / l, the concentration of hydrogen peroxide in the range from 10 to 50 ppm.

The use of reducing sugar as an accelerator is known from US-A-5 378 292 known. They can be used in quantities within the scope of the present invention between about 0.01 and about 10 g / l, preferably in amounts between about 0.5 and about 2.5 g / l can be used. Examples of such sugars are galactose, Mannose and especially glucose (dextrose).

Another preferred embodiment of the invention is as To use accelerator hydroxylamine. Hydroxylamine can be used as a free base, as Hydroxylamine complex, as an oxime, which is a condensation product of hydroxylamine represents with a ketone, or used in the form of hydroxylammonium salts become. Add free hydroxylamine to the phosphating bath or a Phosphate bath concentrate too, it becomes due to the acidic nature of this Solutions largely exist as a hydroxylammonium cation. In a ver The sulfates and the phosphates are used as the hydroxylammonium salt particularly suitable. In the case of phosphates, due to the better solubility preferred the acidic salts. Hydroxylamine or its compounds are added to the phosphating bath in such quantities that the calculated Concentration of free hydroxylamine between 0.1 and 10 g / l, preferably is between 0.3 and 5 g / l. It is preferred that the phosphating baths as only accelerator hydroxylamine, at most together with a maximum of 0.5 g / l  Nitrate. Accordingly, in a preferred embodiment Phosphating baths used that are not any of the other known accelerators such as nitrite, oxo anions of halogens, peroxides or Contain nitrobenzenesulfonate. As a positive side effect, hydroxylamine Concentrations above about 1.5 g / J increase the risk of rust formation insufficiently flooded areas of the components to be phosphated.

When the phosphating process is used on steel surfaces, iron goes in Form of iron (II) ions in solution. If the invention Phosphating baths contain no substances that oxidize against iron (II) act, the divalent iron only goes into the air as a result of air oxidation trivalent state so that it can precipitate as iron (III) phosphate. This is the case, for example, when using hydroxylamine. Therefore can iron (II) contents build up in the phosphating baths, which are significantly higher than the Laid down containing baths containing oxidizing agents. In this sense iron (II) concentrations of up to 50 ppm are normal, although in the short term in Production process values up to 500 ppm can occur.

The weight ratio of phosphate ions to zinc ions in the phosphating baths can vary within a wide range, provided that it is in the range between 3.7 and 30. A weight ratio between 10 and 20 is particularly preferred. For the indication of the phosphate concentration, the total phosphorus content of the phosphating bath is considered to be present in the form of phosphate ions PO ₄ ^3- . Accordingly, the known fact that the pH values of the phosphating baths, which are usually in the range from about 3 to about 3.6, only a very small part of the phosphate is actually in the form of the triple negative charged anions. At these pH values, it is rather to be expected that the phosphate is primarily present as a single negatively charged dihydrogen phosphate anion, together with smaller amounts of undissociated phosphoric acid and double negatively charged hydrogen phosphate anions.

The organic polyepoxides to be used according to the invention have preferably molecular weights (can be determined, for example, by Gel permeation chromatography) in the range from about 300 to about 3,000.

The phosphating baths or those for passivating preferably contain Rinsing used aqueous solutions or suspensions organic polyepoxides in a concentration between about 0.5 and about 1.5 g / l. The desired positive effect occurs at lower concentrations Paint adhesion and corrosion protection less and less. Higher Concentrations no longer significantly increase the effect and therefore become increasingly uneconomical.

Polyepoxides to be used preferably have an epoxy equivalent weight between about 150 and about 1,500.

The polyepoxides can be in various forms in the phosphating solution or in the aqueous solutions used for passivating rinsing or Suspensions are introduced. For example, it can be act water-emulsifiable liquid resins that can be reactively diluted. Or aqueous solid resin dispersions are used, which are also reactive diluted can. Combinations of these two types of use are also possible. As The following compounds can be present, for example, in reactive diluents: Alkyl monoglycidyl ether with a C chain between 4 and 18, preferably between 8 and 14 carbon atoms, cresyl glycidyl ether, neopentyl glycol diglycidyl ether or other commercially available connections.

Phosphating processes according to the invention are suitable for the phosphating of Surfaces made of steel, galvanized or alloy galvanized steel, aluminum, aluminized or alloy-aluminized steel as well as aluminum-magnesium Alloys. The term "aluminum" excludes the technically usual Aluminum alloys such as AlMg0.5Si1.4. The above Materials can - as is becoming increasingly common in automotive engineering coexist.  

Parts of the bodywork can also consist of material that has already been pretreated, such as is produced using the Bonazink ^R process. The base material is first chromated or phosphated and then coated with an organic resin. The phosphating process according to the invention then leads to phosphating on damaged areas of this pretreatment layer or on untreated rear sides.

The process is for use in immersion, spray or spray / immersion suitable method. It can be used in particular in automotive engineering where treatment times between 1 and 8 minutes, especially 2 to 5 minutes, are common. The use in band phosphating in the steel mill, whereby the Be action times are between 3 and 12 seconds, but is also possible Lich. When used in tape phosphating processes, it is recommended that Bath concentrations in each case in the upper half of the invention set preferred areas. For example, the zinc content in the range from 1.5 to 2.5 g / l and the free acid content in the range from 1.5 to 2.5 Points. It is particularly suitable as a substrate for tape phosphating galvanized steel, in particular electrolytically galvanized steel.

As is also common with other phosphating baths of the prior art, The suitable bath temperatures are independent of the area of application between 30 and 70 ° C, the temperature range between 45 and 60 ° C is preferred.

The phosphating process according to the invention is in particular for treatment of the metal surfaces mentioned before painting, for example before cathodic electrodeposition coating, as is common in automotive engineering. It is also suitable as a pre-treatment before a powder coating like this is used for example for household appliances. The phosphating process is to be seen as a sub-step of the technically usual pretreatment chain. In this Chain are the steps of cleaning / degreasing the phosphating,  Intermediate rinsing and activation upstream, the activation usually with activating agents containing titanium phosphate.

If the organic polyepoxides are located directly in the phosphating solution, a so-called post-passivation can take place on the phosphating. Depending on However, substrate material and corrosion protection requirements can be met also be dispensed with. Then you put in place of the post-passivation preferably a rinse with water, especially with deionized water on. Different post-passivation solutions can be used for post-passivation can be used as they are known in the prior art. For example Chromium (VI) -containing solutions can be used, but one is aimed at For reasons of environmental protection, occupational safety and disposal preferably waived. Instead, post-passivation solutions can be used Basis of reactive organic polymers such as amino-substituted Polyvinylphenol compounds are used. Furthermore, a Rinse solution based on complex fluorides of titanium or zircon used become. Furthermore, the rinsing can be carried out with an aqueous solution Contains 2 to 1,000 mg / l copper ions. This copper-containing post-passivation solution can also contain complex fluorides of titanium or zircon.

Embodiments

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, common in body production, was carried out as an immersion process:

• 1.Clean with an alkaline cleaner (Ridoline ^R 1559, Henkel KGaA), approach 2.5% in city water, 75 ° C, 5-10 minutes.
• 2. Rinse with city water, room temperature, 1 minute.  
• 3. Activation with an activating agent containing titanium phosphate (Fixodine ^R C 9112, Henkel KGaA), approach 0.2% in deionized water, room temperature, 1 minute.
• 4. Phosphating (3 minutes) with phosphating baths with a temperature of 50-54 ° C and with the following composition:
  1.4 g / l Zn ²⁺
  0.7 g / l Mn ²⁺
  11.5 g / l PO ₄ ^3-
  2.0 g / l (NH ₃ OH) ₂ SO ₄
  Polyepoxide according to the table.

In addition to the cations mentioned, the nitrate-free phosphating baths contained if necessary sodium ions to adjust the free acid.

The free acid score was 0.9-1.1, the total acid 20-22. Under the free acid score, consumption in ml becomes 0.1 normal Sodium hydroxide solution understood to make 10 ml bath solution up to a pH of 3.6 to titrate. Similarly, the total acid score gives the consumption in ml up to a pH of 8.2.

• 1. Rinse with water
• 2. Rinse with deionized water.
• 3. Blow dry with compressed air

The phosphated test panels were coated with a cathodic dip BASF coated (FT 85-7042). The corrosion protection effect was in an alternating climate test according to VDA 621-415 over 10 laps. As The result is the infiltration of paint on the Ritz (U / 2 = half the width of the scratch) in the Tables added.  

Table 1

Phosphating baths and phosphating results

In a further series of tests, test sheets were described as described above phosphated. There was an additional step between steps 6 and 7 passivating aftertreatment performed by the phosphated and rinsed sheets for 1 minute in an aqueous solution of room temperature immersed which had a pH in the range from 4.1 to 4.2 and 50 ppm contained copper ions. The polymer additive to the phosphating bath and the Corrosion protection results are shown in Table 2.  

Table 2

Phosphating baths and phosphating results

In a further series of experiments, the phosphating was carried out in one Spraying process. The substeps 1, 2 and 3 were as described above carried out. The phosphating was carried out by spraying with a for two minutes Phosphating solution of 50 ° C, the 1.2 g / l zinc, 0.9 g / l, manganese, 14.0 g / l, phosphate and contained 2.5 g / l hydroxylammonium sulfate. The following sub-steps 5 to 7 and the painting was done as above. Polymer additive for Phosphating bath and corrosion protection results are given in Table 3.  

Table 3

Phosphating baths and phosphating results

Analog experiments were carried out with polyepoxide contents of 0.1 g / l, 0.2 g / l, 0.3 g / l, 2 g / l and 5 g / l performed. The positive influence of the Polyepoxides on the anti-corrosion effect.

Another series of experiments concerned the use of aqueous suspensions or Solutions of the polyepoxides as a rinse solution after phosphating. there were test sheets according to the above-described operation, sub-steps 1 to 5 pretreated, however, the phosphating solution in sub-step 4 none Polyepoxide was added. Instead, a step 5 was carried out Treatment of the phosphated metal surfaces with a solution or Suspension of polyepoxides according to Table 4. The passivating rinse was done by immersion in a rinse solution with a polymer content according to Table 4, which has a pH of 4.2 and a temperature of 30 ° C had and which acted on the phosphated metal surfaces for 1 minute let. Process steps 6 and 7 and the painting were then carried out carried out according to the above procedure. The results of the Corrosion protection tests are contained in Table 4.  

TABLE 4

Use of the polyepoxides for rinsing after phosphating; Corrosion test results

Claims (13)

1. A process for phosphating metal surfaces made of steel, galvanized or alloy galvanized steel, aluminum and / or aluminum alloys, in which the metal surfaces are brought into contact with a zinc-containing phosphating solution by spraying or dipping for a time between 3 seconds and 8 minutes, the 0.2 to 3 g / l zinc ions and 3 to 50 g / l phosphate ions, the weight ratio of phosphate ions to zinc ions being at least 3.7, and optionally containing one or more accelerators, the metal surfaces being removed during or after the bringing the phosphating into contact with an aqueous solution or suspension of an organic polymer, characterized in that the organic polymer is a polyepoxide selected from glycidyl ethers based on aliphatic polyols or based on bisphenol A or bisphenol F, which in an amount of 0, 1 to 5 g / l is present in the aqueous solution or suspension. 2. The method according to claim 1, characterized in that the organic Polymer is present in the phosphating solution and during the phosphating is brought into contact with the metal surface. 3. The method according to claim 1, characterized in that the Metal surfaces first with the phosphating solution and then with the aqueous solution or suspension of the organic polymer in contact brings. 4. The method according to claim 3, characterized in that the aqueous Solution or suspension of the organic polymer an additional 10 to 1000 mg / l contains complex fluorides of titanium and / or zircon. 5. The method according to one or both of claims 3 and 4, characterized characterized in that the aqueous solution or suspension of the organic  Polymer additionally contains 5 to 100 mg / l copper ions. 6. The method according to one or more of claims 1 to 5, characterized characterized in that the phosphating solution additionally 0.001 to 3 g / l Contains manganese ions. 7. The method according to one or more of claims 1 to 6, characterized characterized in that the phosphating solution additionally 0.05 to 3 g / l Contains magnesium, calcium, barium and / or iron (II) ions. 8. The method according to one or more of claims 1 to 7, characterized characterized in that the phosphating solution in addition fluoride in amounts of up to 2.5 g / l total fluoride, of which up to 1 g / l free fluoride, each calculated as F contains. 9. The method according to one or more of claims 1 to 8, characterized in that the accelerator is selected from
0.3 to 4 g / l chlorate ions,
0.01 to 0.2 g / l nitrite ions,
0.05 to 2 g / l m-nitrobenzenesulfonate ions,
0.05 to 2 g / l m-nitrobenzoate ions,
0.05 to 2 g / l p-nitrophenol,
0.005 to 0.15 g / l, hydrogen peroxide in free or bound form,
0.1 to 10 g / l hydroxylamine in free or bound form,
0.1 to 10 g / l of a reducing sugar
0.05 to 4 g / l of an organic N-oxide, preferably N-methymorpholine,
0.5 to 5 g / l of an organic nitro compound selected from nitroguanidine, nitroarginine and methyl, ethyl or propyl esters thereof and from nitrofurfurylidene diacetate. 10. The method according to one or more of claims 1 to 9, characterized characterized in that the phosphating solution no intentionally added  Contains nickel, cobalt and copper ions. 11. The method according to one or more of claims 1 to 9, characterized characterized in that the phosphating solution additionally 1 to 200 mg / l, Contains nickel ions and / or 1 to 200 mg / l cobalt ions. 12. The method according to one or more of claims 1 to 9, characterized characterized in that the phosphating solution additionally 1 to 30 mg / l Contains copper ions. 13. The method according to one or more of claims 1 to 12, characterized characterized in that the aqueous solution or suspension of the organic Polymers contains these in a concentration between 0.5 and 1.5 g / l.