EP2215285A1

EP2215285A1 - Zirconium phosphating of metal components, in particular iron

Info

Publication number: EP2215285A1
Application number: EP08853163A
Authority: EP
Inventors: Maximilian SCHÖNHERR; Jerzy-Tadeusz Wawrzyniak; Eva Wiedemann
Original assignee: Henkel AG and Co KGaA
Current assignee: Henkel AG and Co KGaA
Priority date: 2007-11-26
Filing date: 2008-11-25
Publication date: 2010-08-11
Anticipated expiration: 2028-11-25
Also published as: JP2011504550A; KR20100102619A; WO2009068523A1; DE102007057185A1; EP2215285B1; ES2584937T3; US20100293788A1; US8663443B2

Abstract

The present invention relates to a method for the corrosion-protective pretreatment of metal components, which at least partially comprise metal surfaces made of iron, using a chromium-free aqueous treatment solution, which contains fluoro-complexes of zirconium and/or titanium and phosphate ions in a specific ratio range to one another, and a metal component which is pretreated accordingly, and the use thereof for the application of further corrosion-protective coatings and/or lacquer systems (Figure 1). The method is suitable in particular as a pretreatment for electrophoretic painting of metal components, which are provided in the form of non-closed hollow bodies. The object of the present invention is therefore also a method for coating a non-closed metal hollow body, which comprises both the pretreatment using the chromium-free aqueous treatment solution and also subsequent electrophoretic painting, and a metal hollow body which is coated according to the method according to the invention, and the use thereof for the production of radiators.

Description

"Zirconium phosphating of metallic components, in particular iron"

The present invention relates to a process for the corrosion-protective pretreatment of metallic components which at least partially comprise metallic iron surfaces, with a chromium-free aqueous treatment solution containing fluorocomplexes of zirconium and / or titanium and phosphate ions in a specific ratio range to each other, and a metallic component, which has been pretreated accordingly, and its use for the application of further anti-corrosive coatings and / or paint systems. The method is particularly suitable as a pretreatment for an electrodeposition coating of metallic components, which are in the form of non-closed hollow bodies. The present invention therefore also relates to a process for coating a non-closed metallic hollow body, which comprises both the pretreatment with the chromium-free aqueous treatment solution and a subsequent electrodeposition coating, and a metallic hollow body which is coated according to the inventive method, and its use for the production of radiators.

The passivation of metallic materials, in particular of iron and iron steels, is ensured primarily by the zinc or iron phosphating. Thus, in the case of zinc or iron phosphating, mostly crystalline inorganic coatings are produced on the metallic base material, which have a layer thickness of several micrometers and, due to their surface topography, have excellent adhesion to organic cover layers, especially to coating systems applied in the electrocoating process. In non-film-forming iron phosphating, the conversion becomes the metal surface is typically made in a phosphoric acid medium also in the presence of accelerators and wetting agents at elevated bath temperature. Such iron phosphate layers rarely have layer weights of more than 1 g / m ² and, in contrast to phosphations with high layer weights, are amorphous. Typically, the classical phosphating is a multi-step process consisting of a cleaning step to degrease the component, an activation process and ultimately the actual phosphating, wherein for decoupling the process baths in continuous operation rinsing steps are installed. Such a rinsing process is obligatory, at least after the cleaning step, so that the phosphating is composed of at least four individual processes which have to be monitored and controlled in terms of process technology in individual baths. These high procedural requirements and the associated complexity of a Phosphatierbethebes sometimes present an obstacle to the introduction of such a passivation of the components in low-cost applications beyond the automotive manufacturing. Another disadvantage of a technical nature is the processing of residues, such as heavy metals loaded phosphate sludge, which are unavoidable at the high phosphate levels in the passivating dip and can be worked up only with renewed energy and mass transfer. Not least, the increased bath temperatures make the classic phosphating a process with a high energy consumption and an enormous need for recovery measures.

Additional alternative methods of standard phosphating, which provide coating weights of significantly more than 1 g / m ² , are, in addition to the non-layering iron phosphating, conversion treatments of the metallic surfaces to form purely amorphous, inorganic passive layers with much lower coating weights of the order of magnitude less as 200 mg / m ² .

Any pretreatment processes that produce such "non-film-forming" (non-crystalline) phosphating and / or metal surface conversion have the advantage of rendering surface activation unnecessary and can thus be saved in the process chain of pretreatment. Another advantage over the layer-forming zinc phosphating is the reduction of phosphate sludge in the phosphating baths.

For example, US Pat. No. 5,356,490 and WO 04/063414 teach phosphate-free and chromium-free aqueous treatment solutions containing zirconium and / or titanium compounds which are deposited on the metallic component in the acidic medium as a so-called passivating conversion layer due to the pickling attack of the treated metallic surfaces. Both documents teach that dispersed water-insoluble inorganic compounds must additionally be present in order to achieve the desired effect with regard to corrosion protection and paint adhesion, WO 04/063414 explicitly requiring the presence of acid-stable, nanodispersed compounds based on silica and, in contrast to US Pat 5,356,490 works without the addition of organic polymers.

DE 1933013 also discloses phosphate-free treatment baths having a pH above 3.5, in addition to complex fluorides of boron, titanium or zirconium in amounts of 0.1 to 15 g / l, based on the metals, in addition 0.5 to 30 g / l oxidizing agent, in particular sodium m-nitrobenzenesulfonate included. According to the teaching of DE 1933013, the function of the oxidizing agent sodium m-nitrobenzenesulfonate is to vary the treatment duration of the metal surfaces to a particularly large extent.

In contrast, WO 03/002781 discloses pretreatment solutions comprising not only phosphoric acid but also fluorocomplexes of zirconium and / or titanium and a homo- or copolymer of vinylpyrrolidone. Such a pretreatment solution provides low mass mixed amorphous mixed organic / inorganic passivations which may be provided with an electrodeposition paint. DE 2715292 discloses treatment baths for chromium-free pretreatment of aluminum cans containing at least 10 ppm of titanium and / or zirconium, between 10 and 1000 ppm of phosphate and a sufficient amount of fluoride to form complex fluorides of the existing titanium and / or zirconium, but at least 13 ppm and pH values between 1, 5 and 4.

The publication US 2007/0068602 discloses a passivating pretreatment solution which, in addition to fluorocomplexes of zirconium and phosphate anions, also contains oxoanions of vanadium, the respective contents of which must be within a predetermined ratio range in order to achieve effective corrosion protection.

However, the prior art for passivating pretreatment with compositions comprising compounds of zirconium and / or titanium and phosphate can not be taught which specific compositions of such pretreatment solutions ensure optimum corrosion protection with optimum electrocoatability of the amorphous passivation layers. In particular, for the original manufacturer, a comparatively low paint consumption with good paint coverage and the same corrosion resistance of the coated metallic component is of economic importance.

The object of the present invention is therefore to provide a conversion treatment of metallic components consisting at least partially of iron, which provides at least comparable or improved results in terms of corrosion protection and electrodeposition paint consumption over the non-layer-forming treatment methods known in the prior art, but without the to have to resort to complex and energy-intensive process steps of the layer-forming phosphating. On the one hand, the alternative process is intended to provide a corrosion-protected metallic process in as few process steps as possible that are easy to control Provide surface, especially iron surface, and on the other hand, as possible to save resources while avoiding difficult to work up residues, such as phosphate sludge, be feasible. In addition, such an alternative method must ensure the subsequent electrocoating of the treated metallic component, preferably in the form of a non-closed hollow body, with optimum lacquer coverage always aiming at the lowest possible paint consumption.

This object is first achieved by a method for corrosion-protective pretreatment, wherein the component to be treated, which at least partially has metallic surfaces of iron, with a chromium-free aqueous treatment solution containing (i) not less than 50 ppm and not more than 1000 ppm zirconium and / or titanium in the form of their fluoro complexes, as well

(ii) not less than 10 ppm and not more than 1000 ppm of phosphate ions, wherein the molar ratio of zirconium and / or titanium to phosphate ions is not greater than 10: 1 and not less than 1:10, at a pH of not less than 3.5 and not greater than 6.0 is brought into contact.

The metallic component preferably consists entirely of iron and / or an iron alloy with a content of more than 50 At. -% of iron or of surfaces whose iron content is greater than 50 at.%.

The treatment solution does not require any additions of chromium compounds and is therefore chromium-free for ecological reasons and to ensure a high level of occupational safety. However, it can not be ruled out that ions of chromium in a low concentration enter the pretreatment solution from the container material or from the surfaces to be treated, for example steel alloys. However, in practice, it is expected that the concentration of chromium in the ready-to-use processing solution is not higher than about 10 ppm, preferably not higher than 1 ppm. The pH of the treatment solution can be arbitrarily adjusted by adding dilute nitric acid or ammoniacal solution in the specified range. However, the pH of the treatment solution is particularly preferably below 5.5, in particular below 5.0.

By means of the molar ratio of zirconium and / or titanium to the phosphate present in the treatment solution, the performance of the pretreatment with regard to corrosion resistance of the treated components and the throw-over behavior in a subsequent electrodeposition coating can be adjusted. Surprisingly, it has been found that excessively high ratios of zirconium and / or titanium to the phosphate present in the treatment solution as well as excessively low relative zirconium and / or titanium contents have a significantly negative influence on the picking behavior. An optimum result, that is to say maximum permeation in the paint deposition, is achieved in particular if the molar ratio of zirconium and / or titanium to phosphate ions is not set to be smaller than 1: 1. With an increase in the ratio in favor of zirconium and / or titanium to values greater than 10: 1, a zirconium- and / or titanium-based phosphate passivation can obviously no longer be effectively carried out, since the entrainment in the subsequent paint deposit decreases markedly. The same applies to the corrosion-protecting properties of the pretreatment, which are particularly pronounced in the specified preferred ranges for the molar ratios of zirconium and / or titanium to phosphate ions.

The use of zirconium compounds in the different embodiments of the present invention gives technically better results than the use of titanium compounds and is therefore preferred. For example, complex fluoro acids or their salts can be used.

Furthermore, in the process according to the invention, those treatment solutions which are preferred as component (i) are at least 150 ppm, preferably at least 200 ppm, but not more than 350 ppm, preferably not more than 300 ppm zirconium in the form of a fluorocomplex.

The phosphate content of the treatment solution according to the invention is extremely low in comparison with zinc or iron phosphating baths described in the prior art. Already a low concentration of phosphate ions of at least 10 ppm in combination with the fluorocomplexes of zirconium and or titanium leads to the formation of a thin amorphous zirconium and / or titanium phosphate layer and thus to the desired passivation of the metal surface, in particular the iron surface. Thus, a homogeneous passivation takes place already at phosphate contents of preferably 30 ppm, more preferably at least 60 ppm. For reasons of process economy and to avoid phosphate sludge in the treatment bath, however, the phosphate content should not exceed 1000 ppm and preferably not more than 180 ppm, more preferably not more than 120 ppm phosphate ions.

Surprisingly, it has been found that accelerators known from zinc and iron phosphating promote the formation of a homogeneous passivation. Such accelerators are oxidizing agents which perform the task of a "hydrogen scavenger" in phosphating, by directly oxidizing and thereby reducing the hydrogen produced by the acid attack on the metallic surface The same is true for the presence of the accelerators in the non-film-forming iron phosphating, in which layer thicknesses of not significantly more than one micrometer are produced Homogeneous formation of an amorphous, only a few nanometers passive layer based on zirconium and / or titanium phosphate support, however, the activity of the accelerators in the treatment bath is wet lower than is the case, for example, in zinc phosphating, so that typical oxidizing agents should be used at levels not greater than 1000 ppm, but at least 10 ppm must be present in the treating solution to promote zirconium- and / or titanium-based passivation of the ferrous metal surface. Typical representatives of the oxidizing agents are chlorate ions, nitrite ions, nitroguanidine, N-methylmorpholine-N-oxide, m-nitrobenzoate-ions, p-nitrophenol, m-nitrobenzenesulfonate ions, hydrogen peroxide in free or bound form, hydroxylamine in free or bound form, reducing Sugar. In particular, with the m-nitrobenzenesulfonate as accelerator at levels of not less than 20 ppm, preferably not less than 50 ppm and not more than 500 ppm, preferably not more than 300 ppm, significantly improved passivation properties of the treatment solution are achieved.

A further improvement of the passive layer properties and the adhesion to subsequently applied lacquer layers results when adding particulate inorganic, water-insoluble compounds of the elements silicon, aluminum, zinc, titanium, zirconium, iron, calcium and / or magnesium, the content of these compounds in the treatment solution based on the element is at least 10 ppm, but should not exceed 200 ppm in order not to destabilize the treatment solution by agglomeration and sedimentation of the particulate components. Preferably, the oxidic compounds of said elements are used in nanoparticulate form.

The German patent application DE 100 05 113 is based on the finding that homo- or copolymers of vinylpyrrolidone have an excellent corrosion protection effect. The chromium-free treatment solution may therefore additionally preferably contain at least 50 ppm, more preferably 200 ppm, but not more than 1000 ppm of homopolymers or copolymers of vinylpyrrolidone in the process according to the invention.

A further feature of the present invention is that the process preferably without the addition of other organic polymers as such, which are polymers based on homopolymers or copolymers of vinylpyrrolidone, is feasible. Thus, polymers having hydroxyl and / or carboxyl functionalities are often added in substantial amounts (> 1 g / l) to the passivation baths in order to act as binders in the inorganic passive layer to act as further binders to subsequently applied organic coatings. However, the addition of further polymers considerably increases the process outlay, since the stability of the dip bath or the quality of the coating itself can be negatively influenced depending on the transfer of the polymeric constituents from the pretreatment solution into the dip bath on polymers which are not homopolymers or copolymers of vinylpyrrolidone, in a treatment solution of the process according to the invention not greater than 1 ppm.

Since any addition of polymer in the treatment solution thus enforces at least one intensive rinse step immediately after the pretreatment according to the invention in a subsequent electrocoating process, the process of the present invention should be adjusted to phosphate ion ratios with respect to molar ratios of zirconium and / or titanium to reduce the rinse time and rinse water level be that of a polymer addition can be waived entirely. Therefore, the present invention also includes those methods in which the molar ratio of zirconium and / or titanium to phosphate ions is not less than 1: 1 and the amount of organic polymers in the treating solution is not more than 1 ppm.

Moreover, the inventive method requires no further inorganic additives selected from oxo anions of vanadium, tungsten and / or molybdenum, in order to produce a sufficient passivation of the metal surface, in particular iron surface. In a particular embodiment, therefore, the treatment solution explicitly contains no oxo anions of the type described above, so that the content of these compounds is by definition in particular not greater than 1 ppm. In the treatment of special metal surfaces, in particular special iron alloys, small amounts of these oxoanions, in particular vanadates and molybdates, may be present as an additional constituent in the treatment solution in the process according to the invention in order to detect defects in the zirconium- and / or titanium-based phosphate layer already during the passivation heal. For reasons of process economy, however, the proportion of these compounds in the treatment solution of the process according to the invention relative to the respective element is preferably less than 50 ppm, more preferably less than 10 ppm.

In the process according to the invention, the treatment solution may additionally contain chelating substances. Surprisingly, it has been found that the presence of chelating substances, in particular those based on α-hydroxycarboxylic acids, stabilizes the pickling rate in the treatment bath for a longer service life of a bath, so that largely independent of the content of the metal ions, the by pickling the metal surface into the Bad, constant coating conditions of the zirconium and / or titanium-based phosphate layer result. Furthermore, by adding the chelating substances, the sludge formation consisting of sparingly soluble metal hydroxides can be significantly minimized. Preferably, the chelating substances are added as an additive to the treatment solution in the process according to the invention selected from α-hydroxycarboxylic acids, more preferably selected from polyhydroxy acids having not more than 8 carbon atoms, in particular gluconic acid is preferred. The content of chelating substances in the treatment solution of the process according to the invention is preferably at least 0.01% by weight, more preferably at least 0.05% by weight, but preferably not more than 2% by weight, more preferably not more than 1 wt .-%.

The metallic component to be treated in the method according to the invention is optionally previously removed in a cleaning step from superficial impurities, in particular from lubricating and / or corrosion protection oils freed. If such a cleaning is omitted, it is not possible to achieve a passivation homogeneously formed over the entire metal surface of the component in the method according to the invention. In order to save the cleaning step upstream of the pretreatment according to the invention, the acidic treatment solution of the process according to the invention may additionally comprise at least one surface-active substance, so that the effective cleaning of the metal surfaces of the component and their passivation are associated with one another. The use of surface-active substances in passivating pretreatment solutions is not self-evident and thus surprising in the process according to the invention. So 1933013 (Bonderite NT ^®) takes place for example in the presence of nonionic surfactants in phosphate-free treatment baths according to DE insufficient passivation of the metal surface. Suitable surface-active substances all common surfactants, preferably nonionic surfactants can be used in principle, which are stable in the treating solution of the present process and a low critical micelle concentration of less than 10 ^-3 mol / l, preferably at below 10 ^{^"4} mol / l.

The passivating pretreatment process according to the invention is preferably carried out at bath temperatures of the treatment solution of not more than 40 ^° C. If the pretreatment solution additionally contains surface-active substances, then the bath temperature for adequate cleaning of the metal surfaces of the component to be treated is preferably at least 30 ^° C., where higher bath temperatures than 80 ^° C. are not required and have a negative effect on the energy efficiency of the method.

In the treatment method of the present invention, the metal surfaces may be brought into contact with the pretreatment solution by either dipping or spraying.

In a further aspect, the present invention also includes a method of anti-corrosive coating of non-closed metallic Hollow bodies which have at least partially metallic surfaces of iron, wherein the previously described inventive method for anticorrosive pretreatment followed by an electrodeposition coating with or without intermediate rinsing step. Surprisingly, after the pretreatment according to the invention resulting amorphous and extremely thin zirconium and / or titanium-based phosphate passivation after electrocoating shows a compared to electrocoated crystalline phosphate coatings acceptable corrosion resistance and paint adhesion. To alternative methods, which are also, however, develop in a pretreatment stage amorphous passive layers based on oxide zirconium-containing conversion coatings (Bonderite NT ^®) coating process of the invention the corrosion resistance and paint adhesion on iron or steel is relative, however, at least equivalent. A decisive advantage of the pretreatment according to the invention for such alternative processes, however, is the lower paint consumption resulting in the electrocoating with identical wraparound behavior.

Preferably, according to the invention, such non-closed metallic hollow bodies are to be at least partially coated with iron surfaces in which the ratio of the inner surface area of the non-closed hollow body to the opening area of the same is not less than 5, that is, for example, at least cube-shaped.

The Umgriffverhalten so the deposition of the dip paint on the opposite sides of the counter electrode electrode or on the inner regions of the metallic hollow body, which are almost field-free due to their Faraday shielding at the beginning of the deposition and therefore only accessible via the resistance structure of the depositing paint layer for film formation is determined decisively by the passivating pretreatment according to the invention and can therefore also be used as a characterizing feature of the pretreatment according to the invention or of the coating according to the invention. Thus, the process-specific limitation of the layer thickness of the electro-dip is decisive for the encirclement of the paint, as with the same amount of charge, but lesser limited or maximum coating thickness, inevitably a better throwing takes place.

In this sense, as a feature of the method according to the invention, a specific layer thickness limit as the ratio of the layer thickness of the electrodeposition paint on the outer surface of a coated according to the invention hollow body to the thickness of the electrodeposition paint after identical, but only electrocoating without prior pre-treatment on the identical outer surface of an identical untreated, but be specified purified and degreased hollow body. This should not be greater than 0.95, preferably not greater than 0.9, and more preferably not greater than 0.8 according to the present invention.

The method according to the invention for coating a metallic hollow body can be carried out in such a way that a rinsing step takes place between the method steps of the pretreatment according to the invention and the electrocoating step, preferably with deionized water or city water.

In a further preferred embodiment of the coating method according to the invention, no drying of the metallic hollow body takes place after the pretreatment according to the invention and before the electrocoating process step.

The present invention likewise relates to the metallic components and non-closed metallic hollow bodies treated directly with the method according to the invention for the pretreatment and coating, wherein the metallic components and hollow bodies to be treated at least partially have metallic iron surfaces. Furthermore, the present invention encompasses the use of a metallic component whose entire surface, which consists at least partly of metallic iron surfaces, has been pretreated with the chromium-free aqueous treatment solution in accordance with the method according to the invention for the application of further corrosion-protective coatings and / or organic coating systems.

Likewise, the present invention comprises the use of a non-closed metallic hollow body whose entire surface, which consists at least partially of metallic iron surfaces, according to the inventive method first pretreated with the chromium-free aqueous treatment solution and then electrocoated with or without intervening rinsing step, for the production of radiators.

EXAMPLES

Embodiments of the invention and comparative examples for the pretreatment of steel sheets (CRS: CoId Rolled Steel) including their subsequent electrodeposition coating are mentioned below.

Comparative example "alkaline cleaning":

CRS sheets are treated by immersion for 5 min at 50 ⁰ C in an aqueous solution composed of 3 wt .-% Ridoline 1562 ^® and 0.3 wt .-% Ridosol 1270 ^® while stirring the cleaning solution.

Comparative Example "Bonderite NT-1 ^®":

CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet is rinsed for 1 min under running demineralised water (k <1 μScm ^-1 ). Treatment with Bonderite NT-1 ^® (Messrs. Henkel KGaA) a zirconium-containing, but phosphate-free aqueous solution is then carried out by immersion for 1 min at 20 ⁰ C. The thus pretreated sheet is then rinsed for 1 min under running demineralised water (k <1 μScm ^-1 ).

Comparative Example "Zn-phosphated":

CRS sheets are first cleaned in the immersion process according to the comparative example "alkaline cleaning", after which the cleaned sheet is rinsed for 1 min under running demineralised water (k <1 μScm ^-1 ). The treatment with the commercial product Granodine 958 ^® (Messrs. Henkel KGaA) according to the instructions Subsequently, the dipping method. This treatment includes an activation step before the actual phosphating. The thus pretreated sheet is then rinsed for 1 min under running deionized water (K <1 μScm ^-1 ).

Inventive example "Zr-phosphated":

CRS sheets are first in the dipping process according to the comparative example

Cleaned "alkaline cleaning", after which the cleaned sheet for 1 min rinsing with demineralized water (k <1 μS cm ^-1 ), followed by treatment with an aqueous solution according to the invention by spraying

Solution composed of

300 ppm Zr as H ₂ ZrF ₆ ,

100 ppm PO ₄ as H ₃ PO ₄ ,

100 ppm of sodium m-nitrobenzenesulfonate (m-NBS) and

3000 ppm Ridosol 2000 ^® (cleaner from. Henkel KGaA) for 2 min at 50 ⁰ C, wherein the pH is adjusted with ammoniacal solution to pH 4.5. The thus pretreated sheet is then rinsed for 1 min under running demineralized water (k <1 μScm ^"1 ).

All pretreated sheets are then coated with a cathodic immersion paint Cathogard 500 Fa. BASF and baked at 180 ⁰ C for 30 min.

The average coating thickness is determined by means of the Coating Thickness Gauge PosiTector 6000 (DeFelsko Ltd., Canada) by multiple measurements at different points on the anode-facing side of the sheet. For the determination of the lacquer layer thickness of the "Zn-phosphated" steel sheet, the layer thickness of the zinc phosphate layer is first determined by multiple measurement before the electrodeposition coating and subtracted from the determined layer thickness after painting.

It can be seen from Table 1 that the pretreatment according to the invention has the lowest layer thickness in comparison with the "non-layer-forming" pretreatments with identical electrodeposition coating time, with only the layer-forming phosphated CRS sheet having an even lower paint layer thickness after the electrodeposition coating.

These experimental data make it clear that the pretreatment according to the invention achieves a lower paint consumption and thus automatically also an improved throw-over compared to the prior art non-film-forming passivation process. Table 1

Layer thickness of the electrodeposition paint and charge efficiency of the electrodeposition coating depending on the type of

preparation

Charge quantity after an electrocoating time of 2 minutes with an applied DC voltage of 240 V.

Determining the layer thickness of the electrodeposition coating of the Zn-phosphated sheet by subtraction of the layer thicknesses measured after the pretreatment and after the electrodeposition coating.

The corrosion resistance of the sheets pretreated according to a formulation according to the previous example ("Zr-phosphated") but varying proportions of zirconium, phosphate and sodium m-nitrobenzenesulfonate and electrocoated according to the previous examples is reproduced in Figure 1. The corrosive infiltration measured after a removal of the thus coated CRS sheets over a period of 504 hours according to the salt spray test (DIN 50021 SS), that for those pretreatment solutions for which there is a molar ratio of zirconium to phosphate of 1:10 to 10: 1, The undercounter values are comparable to and even better than those found in corrosive infiltration after iron phosphating after 504 hours, which are typically 1.5 mm, and insignificantly larger than after pretreatment with Bonderite NT -1 ^® , provides the submarine values of 0.9 mm.

In an analogous manner, it can be stated that the whipping behavior is also optimal for CRS sheets which have been pretreated with compositions having the corresponding molar ratios according to the invention (FIG. 2). The wraparound is measured and averaged at different points on the side facing away from the anode side of the sheet at different points.

Claims

claims

1. A method for corrosion-protective pretreatment of metallic components, which at least partially have metallic surfaces of iron, characterized in that the component with a chromium-free aqueous treatment solution containing

(i) not less than 50 ppm and not more than 1000 ppm zirconium and / or titanium in the form of their fluorocomplexes;

(ii) not less than 10 ppm and not more than 1000 ppm of phosphate ions, wherein the molar ratio of zirconium and / or titanium to phosphate ions is not greater than 10: 1 and not less than 1:10, at a pH of not less than 3.5 and no larger than 6.0 in

Contact is brought.

2. The method according to claim 1, characterized in that the molar ratio of zirconium and / or titanium to phosphate ions is not less than 1: 1.

3. The method according to one or both of the preceding claims, characterized in that the treatment solution as accelerator (iii) nitrobenzenesulfonic acid with a content of not less than 20 ppm, preferably not less than 50 ppm and not more than 500 ppm, preferably not more than Contains 300 ppm.

4. The method according to one or more of the preceding claims, characterized in that the treatment solution as component (i) preferably at least 150 ppm, more preferably at least

200 ppm, but preferably not more than 350 ppm, more preferably not more than 300 ppm of zirconium in the form of a fluorocomplex.

5. The method according to one or more of the preceding claims, characterized in that the treatment solution preferably contains at least 30 ppm, more preferably at least 60 ppm, but preferably not more than 180 ppm, more preferably not more than 120 ppm phosphate ions.

6. The method according to one or more of the preceding claims, characterized in that the treatment solution additionally contains nanoparticulate inorganic compounds of the elements silicon, aluminum, zinc, titanium, zirconium, iron, calcium and / or magnesium, wherein the content of these compounds in the treatment solution based on the element is at least 10 ppm, but does not exceed 200 ppm.

7. The method according to one or more of claims 2 to 7, characterized in that the treatment solution additionally contains chelating substances selected from α-hydroxycarboxylic acids, preferably selected from polyhydroxy acids having not more than 8 carbon atoms and more preferably gluconic acid.

8. The method according to claim 7, characterized in that the content of chelating substances selected from α-hydroxycarboxylic acids in the treatment solution at least 0.01 wt .-%, preferably at least 0.05 wt .-%, but not more than 2 wt. -%, preferably not more than 1 wt .-% is.

9. The method according to one or more of the preceding claims, characterized in that the treatment solution additionally contains at least one surface-active substance.

10. A method for corrosion-protective coating of non-closed metallic hollow body having at least partially metallic surfaces of iron, characterized in that the hollow body first (A) pretreated according to the method according to one or more of the preceding claims and then

(B) is electrocoated with or without intermediate rinse step.

11. The method according to claim 10, characterized in that the ratio of the inner circumferential surface of the non-closed hollow body to the opening surface thereof is not less than 5.

12. The method according to one or more of claims 10 and 11, characterized in that after the pretreatment (A) and before the process step (B) of the electrocoating no drying of the metallic hollow body takes place.

13. The method according to one or more of claims 10 to 12, characterized in that the ratio of the layer thickness of the electrodeposition paint on the outer surface of a according to the method steps (A) and (B) coated hollow body to the layer thickness of the electrodeposition paint for identical, but only electrocoating according to process step (B) on the identical outer surface area of an identical untreated, but cleaned and degreased hollow body is not greater than 0.95, preferably not greater than 0.9 and particularly preferably not greater than 0.8.

14. Non-closed metallic hollow body having at least partially metallic surfaces of iron, characterized in that it has been coated according to a method according to one or more of claims 10 to 13.

15. Use of a non-closed metallic hollow body according to claim 14 for the production of radiators.