RU2691149C2 - Method of coating metal surfaces, bases coated with such method, and their use - Google Patents

Abstract

FIELD: technological processes.

SUBSTANCE: invention relates to a method of producing a conversion coating on a metal surface. Method comprises treating a base with a metal surface with an acidic aqueous conversion composition which contains 0.01 to 1 g/l of TiF₆ ^2-, ZrF₆ ^2- and/or HfF₆ ^2- in form of ions calculated as ZrF₆ ^2-, from 0.01 to 1 g/l Fe²⁺-, Mn- and/or Zn-ions, of which at least one type of said ions is contained in range of 0.01 to 1 g/l, and content of molybdate, calculated as MoO₄ ^2-, and/or content of phosphorus-containing oxyanions, calculated as PO₄ ^3-, is correspondingly less than 0.1 g/l, wherein said acidic aqueous composition has a pH in range of 2.5 to 6.5, and the obtained coating has a layer thickness of 0.3 to 3 mcm.

EFFECT: inventions are excellent for replacement of alkaline phosphating on metal surfaces of bases of various types, and metal surfaces of various types can be processed simultaneously or successively in the same bath.

25 cl, 1 tbl

Description

The invention relates to a method of coating metal surfaces using, if necessary, a colored conversion layer, in particular, to replace alkaline phosphating, such as, for example, iron phosphating, bases with metal surfaces with a suitably applied coating, as well as the use of these coated bases.

Methods for producing coatings with alkaline phosphates, in particular, as preparatory layers before varnishing, have been described in some cases. Fresh, not yet used alkaline phosphate solutions usually have practically no or only very small amounts of aluminum, iron and zinc. Aqueous solutions of acidic phosphates of alkali metals, in addition to ions of at least one alkali metal or / and ammonium, also contain phosphate ions, and due to the effect of etching these solutions on metal surfaces, the concentration of ions extracted by dissolving metals, such as, for example, aluminum, iron or / and zinc, as well as traces of the alloying components of the etched metal material. The phases, predominantly formed during alkaline phosphating in the alkaline phosphate layer, are the corresponding phosphates, oxides and / or metal hydroxides from the surfaces of the substrate base to be treated.

Solutions or coatings of alkaline phosphates when used on iron and steel materials are also referred to as iron phosphate solutions or coatings. Alkaline phosphate coatings according to Werner Rausch: Die Phosphatierung von Metallen, Saulgau 1988 (see, in particular, pages 109-118) are also collectively referred to as layers of the so-called “phosphatization without layer formation”. This designation is misleading, since it also forms layers, which, however, are noticeably thinner than other phosphate layers, such as, for example, with different types of zinc phosphating. The alkaline phosphate solution always has a high content of at least one alkali metal, such as, for example, sodium, and / or ammonium.

Alkaline phosphating in most cases can be carried out in a simple and economical manner. However, high-quality alkaline phosphate coatings, despite the subsequent second conversion treatment, demonstrate only limited protection against corrosion, usually a) corrosion protection is no better than, that is, no less than 3 mm of penetration, when tested in a salt chamber in accordance with DIN 50021c neutral NSS test for 500 hours in the case of a powder lacquer coating based on a powder lacquer made from epoxides and polyesters with a thickness of 60 to 80 microns on a steel sheet of cold rolled steel, or, respectively b) anti-corrosion protection is no better than, that is, no less than 4 mm of penetration, when tested in a salt chamber in accordance with DIN 50021 in a neutral NSS test for 500 hours in the case of coating with a polyurethane-isocyanate varnish with a thickness of 60 or more up to 80 µm on cold-rolled steel sheet, and usually c) varnish adhesion is not better than, that is, not less than GT 3 when tested with a lattice cut at 240 hours of testing according to tests in a climate chamber in accordance with DIN EN ISO 2409 in case of powder lacquer a new coating based on epoxy and polyester powder lacquer from 60 to 80 microns thick on a cold-rolled steel sheet.

Therefore, during alkaline phosphating, it is usually necessary to apply another additionally applied second conversion layer, and in most cases also at least one other applied lacquer layer. Such multistage processes are not only particularly laborious, but also require additional baths and / or treatment areas and, if necessary, also additional washing stages and / or drying stages, and are also costly and time consuming. Often also the adhesion of varnish to the alkaline phosphate coating is insufficient, so that in this case an additional conversion coating should be applied, for example, based on zirconium hexafluoride or / and silane. As a result, the coating process becomes particularly laborious and expensive. The disadvantage is also a high phosphate content in alkaline phosphating processes, since phosphate in the case of wastewater must be subjected to expensive disposal.

Alkaline phosphating is often used in several stages, and in the first stage it is mainly only purified, and in the second stage the formation of a layer takes place. This is followed by rinsing or, respectively, additional rinsing.

The task was to find waterborne compositions that can be applied simply, are formulated as environmentally friendly as possible, and which result in higher corrosion protection than high-quality alkaline phosphate coatings.

The problem is solved using the method of coating metal surfaces with an acidic aqueous conversion composition, which is a solution or dispersion, which differs in that it contains:

a total of from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- in the form of ions, calculated as ZrF ₆ ^2- ,

0 or from 0.01 to 1 g / l, respectively, Fe ²⁺ -, Mn - or / and Zn-ions, of which at least one type of these ions is contained in the content range from 0.01 to 1 g / l,

and preferably contains ions of Mn or / and Zn,

0 or from 0.01 to 2 g / l of an organic polymer or / and copolymer that is stable at a pH value <6.5, based on the solids content,

0 or from 0.01 to 2 g / l of SiO ₂ in the form of particles with an average particle diameter of <0.3 μm, measured on a scanning electron microscope and based on the solids content,

about 0 or from 0.01 to 10 g / l of at least one surfactant,

about 0 or from 0.05 to 10 g / l of anions selected from the group consisting of carbonate, nitrate and sulfate, in terms of NO ₃ ^- , also if CO ₃ ^2- or SO ₄ ^2- are present, and

0 or from 0.001 to 2 g / l carboxylate or / and sulfonate anions, which do not interfere or hardly interfere with the formation of the layer, calculated as the corresponding anions,

moreover, the content of molybdate, calculated as MoO ₄ ^2- , or / and the content of phosphorus-containing oxyanions, calculated as PO ₄ ^3- , is respectively <0.1 g / l or about 0 g / l, and the specified acidic aqueous composition has a pH value in the range from 2.5 to 6.5, and preferably in the range from 3.0 to 5.5.

The TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- ions in this acidic aqueous conversion composition are substantially equivalent and interchangeable, however often the ZrF ₆ ^2- ions give the best properties of a conversion coating made with them. Preferably the content in the acidic aqueous conversion composition of TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- is from 0.05 to <1 g / l, from 0.1 to 0.8 g / l, from 0, 15 to 0.50 g / l or from 0.20 to 0.33 g / l.

While it is preferable that in the case of the content of cations in the acidic aqueous conversion composition only from ions of Fe ²⁺ , relative to the total content of ions Fe ²⁺ , Mn and Zn, this content is at least partially derived from the target addition. The ions of manganese and zinc, as well as to a limited extent also the ions of Fe ²⁺ , in the acidic aqueous conversion composition are largely equivalent and interchangeable, however often the ions of manganese or / and zinc give the best properties of the conversion coating produced with their help. If manganese and zinc are added to the acidic aqueous conversion composition, it is particularly preferable to achieve a manganese content that is greater than the zinc content. Preferably it contains 0 or from 0.01 to 0.3 g / l or from 0.02 to 0.15 g / l of Fe ^{2+ ions} , and also from 0.01 to 1 g / l of Mn ions or / and from 0.01 to 1 g / l or from 0.1 to 0.6 g / l Zn ions. Particularly preferably it contains from 0.1 to 0.6 g / l or from 0.2 to 0.4 g / l of Mn ions or / and from 0.1 to 0.6 g / l or from 0.2 to 0 , 4 g / l Zn ions.

It is preferable to operate mainly without phosphate content (<0.1 g / l PO ₄ ) or completely without phosphate content (approximately 0 or exactly 0 g / l PO ₄ ). In the case of individual variants of the method, the phosphate content, calculated as PO ₄ ^3- , between 0.001 and <0.1 g / l cannot be excluded, in particular, due to entrapment during entrainment and contaminants. In addition, it is also preferable to operate mainly without the content of phosphonates (<0.1 g / l P _x O _y ) or completely (approximately 0 or exactly 0 g / l P _x O _y ) without phosphonates.

The addition of an organic polymer and / or an organic copolymer can contribute to the fact that the properties of the conversion coating obtained with its help can be further improved and that, if necessary, the subsequent varnishing can be dispensed with.

Preferably the content in the acidic aqueous conversion composition of an organic polymer and / or organic copolymer is from 0.01 to 3 g / l, from 0.1 to 2.5 g / l, from 0.2 to 2 g / l, from 0, 4 to 1.5 g / l or from 0.6 to 1.2 g / l. This organic polymer and / or copolymer is preferably a compound based on (meth) acrylate / (meth) acrylic acid or / and vinyl acetate-acrylic copolymer.

In case of refusal from varnishing in the case of a made coating, one can speak of a passivating layer, and in the case of anticorrosive protection, anticorrosion protection without further coating ..

The addition of SiO ₂ , having the form of the smallest particles (in particular, <0.3 μm), such as, for example, SiO ₂ nanoparticles, can show a similar positive effect, like the addition of an organic polymer or / and an organic copolymer, however often with the the difference is that the formation of the layer, and, consequently, the coating, in the case of SiO ₂ is even more uniform.

In general, at least one non-ionic, anionic, cationic, and / or zwitterionic surfactant, respectively, may be added. Moreover, the addition of at least one non-ionic surfactant is particularly preferred.

The addition of anions selected from the group consisting of carbonate, nitrate and sulfate is often carried out by adding cations through water-soluble salts. In this case, nitrates are particularly preferred.

The addition of carboxylate anions, such as by means of acetic acid or / and by means of manganese carboxylate, is generally possible and often well suited as an alternative or supplement to these anions to prevent or reduce the content of anions of mineral acids. As a rule, all types of carboxylic acids and their derivatives can be added, such as salts and esters, which are water soluble and which are stable in the pH range, which do not have a complex composition of substances, which form anions in water, which, depending on the type and the amounts of these anions do not adversely affect the formation of the layer and which, if necessary, form complexes with alkali or / and alkaline earth metal ions, which do not participate in the formation of the layer. These are, in particular, aliphatic carboxylic acids and mono-, di- or / and polycarboxylic acids, such as, for example, hydroxycarboxylic acids. When adding carboxylate anions, you should pay attention to the fact that these anions do not have a negative effect on the formation of a layer, since, for example, citrate and some other complexing agents, if necessary, depending on the type and amount of these anions, can badly affect the formation of a layer .

Moreover, the addition of at least one sulfonic acid, such as, for example, methanesulfonic acid, amidosulfonic acid, and / or one of its derivatives may be favorable to act as an accelerator or / and as another counterion.

As a rule, the content of molybdate, calculated as MoO ₄ , 0 or in the range from 0.01 to <0.5 g / l, in particular, from 0.02 to 0.3 g / l, from 0.01 to <0.1 g / l. The addition of molybdate has proven itself well only with very small added amounts.

Additives of phosphorus-containing oxyanions, such as, for example, orthophosphate, condensed phosphates and phosphonates, should be avoided, in particular, because of the possible load on the wastewater, and if necessary also because of the higher formation of sludge, which can lead to more expensive disposal sewage or / and sludge. In particular, in the case of phosphorus-containing oxyanions, for reasons of environmental safety and prevention of disposal costs, it is preferable that no content of phosphorus-containing oxyanions is added, and it is preferable to pay attention to the possibility that no phosphorus-containing oxyanion content also appears due to ablation.

In the method according to the invention, it is preferable that the acidic aqueous composition optionally contains, in addition, mainly consisted of or consisted of:

from 0.03 to 5 g / l of the sum of lithium, sodium and / or potassium ions,

0 or from 0.05 to 5 g / l of ammonium ions,

about 0 or from 0.05 to 0.3 g / l of the sum of Co- or / and Ni-ions,

respectively, 0 or from 0.01 to 0.8 g / l of chlorate, calculated as ClO ₃ ^- , nitrite, calculated as NO ₂ , or / and peroxide, calculated as H ₂ O ₂ ,

0 or from 0.01 to 0.5 g / l of free fluoride, calculated as F ^- , and

0 or from 0.01 to 0.2 g / l of vanadate ions, calculated as VO ₄ ^3- .

As a rule, lithium, sodium, potassium or / and ammonium content cannot be avoided in order to achieve charge compensation and to add not only polyvalent cations, such as, for example, heavy metal ions. Among monovalent cations, sodium ions in particular are particularly preferred. In an acidic aqueous conversion composition, they are substantially equivalent and interchangeable and are often necessary for pH adjustment.

As in many coating methods, the addition of cobalt and / or nickel is also favorable in this case in order to achieve better corrosion protection, despite the fact that these elements are problematic in terms of environmental acceptability and industrial hygiene.

Sometimes it is useful to add at least one accelerator, in particular, the addition of chlorate, nitrite and / or peroxide. However, you should pay attention to suitable amounts, for example, the content of NO ₂ , which is significantly less than 1 g / l. With the addition of at least one accelerator, the formation of a layer can be accelerated and the properties of the coating obtained with it can be improved. In this case, you should avoid exceeding the accelerator dose in order not to impair the formation of a layer, as in the case of example B40. The addition of nitroguanidine was not helpful.

The content of only complex fluoride (fluorides) often leads to a low content of free fluoride. The content and / or addition of at least one fluoride can lead to a slightly higher content of free fluoride. Frequent is the content of free fluoride, which is favorable, in particular, for aluminum-containing steel surfaces, in the range from 0.01 to 0.5 g / l, calculated as F ^- .

Also, the addition of at least one vanadium compound can markedly increase corrosion protection.

This does not exclude the fact that the contents of elements from the metal surface of the base and the installation fall into the bath as a result of the pickling effect of the acidic aqueous conversion composition, and if necessary also accumulates in the bath composition, in particular, Fe ^{2+ ions} and alloying elements or ions.

On the other hand, in the case of modern methods of applying coatings and installations, it is also usually not excluded that the content of ions and substances from other parts of the installation is introduced in insignificant amounts, such as, for example, from the previously used purification stage, if necessary despite washing with water. As a result, the composition of the bath according to the invention can be introduced, in particular, the content of alkali metals, ammonium, complexing agents, surfactants, anionic contaminants from the cleaning bath or / and other contaminants or, respectively, their ions. However, a separate preliminary purification step is not necessarily provided for, so that the introduction of foreign ions through the treatment chemical solution can be excluded as much as possible. At best, the purification step can be carried out using water containing a surfactant and without the content of a cleansing base (detergent component).

On the one hand, the cleaning can be carried out before applying the conversion coating, so that it is cleaned before being brought into contact with the base of the aqueous composition, in particular using alkaline cleaning. On the other hand, the aqueous composition, in addition to or instead of this purification step, may also contain at least one surfactant, so that the cleaning and application of the conversion coating (also) is carried out at the same process step.

Preferably, no amount is added to the aqueous conversion composition, or only an insignificant amount is added, such as up to 0.1 g / l, respectively, of carboxylic acids, phosphates, phosphonates or / and compounds or / and calcium ions, chromium, chromate, cobalt, copper. , magnesium, molybdenum, nickel, vanadium or / and tin or / and silane / silanol / siloxane / polysiloxane. Silane / silanol / siloxane / polysiloxane means silane, silanol, siloxane or / and polysiloxane, since silanol or / and siloxanes can be obtained very quickly in water and in coating, for example, based on silane, which sometimes also, depending on chemical determination, polysiloxanes can produce.

The content in the aqueous conversion composition of alkaline earth metals, such as calcium or / and magnesium, preferably in the aggregate is not more than 0.2 g / l, in order, as far as possible, to prevent precipitation in the presence of fluorides.

Especially preferred are the following options

Acidic aqueous conversion composition has a pH value in the range from 2.5 to 6.5 and contains, mainly consists of or consists of a total of:

In the case of option A:

from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- in the form of ions, calculated as ZrF ₆ ^2- , and

0 or from 0.01 to 1 g / l, respectively, of ions of Fe ²⁺ -, Mn - or / and Zn-ions, of which at least one type of these ions is contained in the range of contents from 0.01 to 1 g / l;

and, if necessary, from 0.01 to 2 g / l of SiO ₂ in the form of particles with an average particle diameter of <0.3 μm, calculated on the solids content and / or

if necessary, from 0.01 to 10 g / l of at least one surfactant and with a phosphate content of <0.1 g / l PO ₄ .

In the case of option B:

from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- in the form of ions, calculated as ZrF ₆ ^2- , and

0 or from 0.01 to 1 g / l, respectively, Fe ²⁺ -, Mn - or / and Zn-ions, of which at least one type of these ions is contained in the content range from 0.01 to 1 g / l, and from 0.01 to 2 g / l of an organic polymer or / and copolymer that is stable at a pH value <6.5, in terms of solids content,

and, if necessary, from 0.01 to 2 g / l of SiO ₂ in the form of particles with an average particle diameter of <0.3 μm, calculated on the solids content,

and if necessary, from 0.01 to 10 g / l of at least one surfactant,

and, if necessary, from 0.05 to 10 g / l of anions selected from the group consisting of carbonate, nitrate and sulfate, in terms of NO ₃ ^- , also if CO ₃ ^2- or SO ₄ ^2- are present, and

and, if necessary, from 0.001 to 2 g / l of carboxylate or / and sulfonate anions, which do not interfere or hardly interfere with the formation of the layer, calculated as the corresponding anions,

moreover, the content of molybdate, calculated as MoO ₄ ^2- , or / and the content of phosphorus-containing oxyanions, calculated as PO ₄ ^3- , is respectively <0.1 g / l or about 0 g / l.

In the case of option C:

from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- in the form of ions, calculated as ZrF ₆ ^2- ,

0 or from 0.01 to 1 g / l, respectively, Fe ²⁺ -, Mn - or / and Zn-ions, of which at least one type of these ions is contained in the content range from 0.01 to 1 g / l, and the content of molybdate, calculated as MoO ₄ ^2- , in the range from 0.01 to <0.5 g / l, and also, if necessary, from 0.01 to 2 g / l of organic polymer or / and copolymer, which is stable when pH <6.5, based on the solids content,

and if necessary, from 0.01 to 2 g / l of SiO ₂ in the form of particles with an average particle diameter of <0.3 μm, calculated on the solids content,

and if necessary, from 0.01 to 10 g / l of at least one surfactant,

and, if necessary, from 0.05 to 10 g / l of anions selected from the group consisting of carbonate, nitrate and sulfate, in terms of NO ₃ ^- , also if CO ₃ ^2- or SO ₄ ^2- are present, and

and, if necessary, from 0.001 to 2 g / l of carboxylate or / and sulfonate anions, which do not interfere or hardly interfere with the formation of the layer, calculated as the corresponding anions,

moreover, the content of molybdate, calculated as MoO ₄ ^2- , is in the range from 0.01 to <0.5 g / l, and the content of phosphorus-containing oxyanions, calculated as PO ₄ ^3- , is respectively <0.1 g / l or approximately 0 g / l.

In all three options, it is preferable that Mn or / and Zn ions are added, while the content of Fe ^{2+ ions is} preferably extracted by etching as a result of the etching effect of an acidic conversion composition from an iron-rich metallic base. If necessary, the coating is then varnished at least once.

Especially preferred is an acidic aqueous conversion composition, which is a solution or dispersion, which contains, mainly consists of or consists of:

a total of from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- in the form of ions, calculated as ZrF ₆ ^2- ,

0 or from 0.01 to 1 g / l of Mn- or / and Zn-ions, of which at least one type of these ions is contained in the range of content from 0.01 to 1 g / l,

0 or from 0.01 to 0.3 g / l of ions of Fe ²⁺ ,

and preferably contains ions of Mn or / and Zn,

0 or from 0.01 to 1 g / l of an organic polymer or / and copolymer that is stable at a pH value <6.5, based on the solids content,

0 or from 0.01 to 1 g / l of SiO ₂ in the form of particles with an average particle diameter of <0.3 μm, measured on a scanning electron microscope, and in terms of the solids content,

about 0 or from 0.01 to 6 g / l of at least one surfactant,

about 0 or from 0.05 to 6 g / l of anions selected from the group consisting of carbonate, nitrate and sulfate, in terms of NO ₃ ^- , also if CO ₃ ^2- or SO ₄ ^2- are present, and

0 or from 0.001 to 1 g / l of carboxylate or / and sulfonate anions, which do not interfere or hardly interfere with the formation of the layer, calculated as the corresponding anions,

moreover, the content of molybdate, calculated as MoO ₄ ^2- , or / and the content of phosphorus-containing oxyanions, calculated as PO ₄ ^3- , is respectively <0.1 g / l or about 0 g / l, and moreover, this aqueous composition has a pH value of range from 2.5 to 6.5 and preferably in the range from 3.0 to 5.5.

Particularly preferably specified acidic aqueous composition contains, mainly consists of or consists of additionally:

from 0.1 to 5 g / l of the sum of lithium ions, sodium or / and potassium, 0 or from 0.05 to 5 g / l of ammonium ions, about 0 or from 0.05 to 0.2 g / l of the sum of Co ions or / and Ni, respectively, 0 or from 0.01 to 0.4 g / l of chlorate, calculated as ClO ₃ ^- , nitrite, calculated as NO ₂ , or / and peroxide, calculated as H ₂ O ₂ ,

0 or from 0.01 to 0.5 g / l of free fluoride, calculated as F ^- , and

0 or from 0.01 to 0.1 g / l of vanadate ions, calculated as VO ₄ ^3- .

While the composition of the bath according to the invention can preferably be obtained by diluting one or two concentrates with water, with a dilution ratio in the range from 5: 1 to 40: 1. The second concentrate could, for example, contain at least one surfactant and also be aqueous. At the same time, fluoride can also be added as monofluoride, as bifluoride or / and in the form of the corresponding acids. The content of free fluoride often lies in the range from 0.01 to 0.2 g / l.

Preferably, for an acidic aqueous conversion composition, they work with tap water with an electrical conductivity, for example, from about 200 to 600 µS / cm, or with completely demineralized water, both for the initial mixture and to replenish the liquid level in the bath, and for the first washing after conversion coverage.

After this first washing stage, a completely desalted washing with completely demineralized water is standardly necessary only as a final washing in order to avoid drying out the salt layer, which can lead to poorer anticorrosion protection.

Hot-dip galvanized steel sheets (short HDG - hot dip galvanized), lacquer adhesion and anti-corrosion protection are usually slightly less good than on cold-rolled steel sheets (short CRS - cold rolled steel). If the zinc content in the acidic aqueous conversion composition is reduced or completely prevented, the properties of the coating on hot-dip galvanized steel sheets are often improved.

The content of Fe ^{2+ ions} often does not degrade the properties of the coating, but it turns out that the Fe ^{2+ ion} gradually undergoes oxidation to Fe ³⁺ and precipitates as sludge in the bath. Therefore, it is preferable that the acidic aqueous conversion composition has a content of manganese ions and / or zinc.

The composition containing surfactants can, either after degreasing or / and after etching, help to further improve cleaning, or at least to refuse to degrease before applying a conversion coating, so that it can be cleaned in one vessel and so that the cleaning step is excluded and carried out within applying a conversion coating.

In the method according to the invention, it is preferable that at least one base with metal surfaces is brought into contact with the aqueous composition over a time ranging from 1 second to 10 minutes, in particular from 0.5 to 10 minutes, during the processing of the parts. Particularly preferably, it is then brought into contact over a time in the range from 1 to 10 minutes, in particular during dipping, or preferably from 0.5 to 6 minutes, in particular during spraying. Thus, in the case of these compositions, similar processing times can also be used, as in the case of alkaline phosphating, which facilitates the conversion of the installation from alkaline phosphating to the application of a conversion coating according to the invention. Since alkaline phosphating also uses the time from 3 to 5 minutes. Alternatively, the composition according to the invention can also be applied to the tape, if after this coating the tape is still washed with water (rinsing method). When coating the tape, the metal tape is brought into contact with the aqueous composition, preferably for a time ranging from 1 second to 2 minutes.

In the method according to the invention, it is preferable that the base with metal surfaces, when conducting contact with the aqueous composition, has a temperature in the range from 5 to 90 ° C, and preferably in the range from 15 to 70 ° C or from 30 to 60 ° C. On the other hand, it is also preferable that the aqueous composition, when conducting contact with the base with the metal surfaces, has a temperature in the range from 35 to 70 ° C or from 45 to 60 ° C. Thus, in the case of these compositions, the same temperatures can also be used as in the case of alkaline phosphating, at which temperatures from 50 to 55 ° C are often used. At a temperature in the range from 50 to 55 ° C, the smoothest conversion coatings were obtained, and after varnishing also the smoothest varnish layers.

The task is also solved with the help of a base having a metal surface, coated with a coating, which was coated according to the invention.

It is preferable that the coating obtained using this layer has a layer thickness of 0.3 to 3 microns or / and that the sum of zirconium or / and titanium deposits when measured as elements in the case of a conversion coating lies in the range from 1 to 300 mg / m ² or preferably in the range from 15 to 150 mg / m ² , when measured using a X-ray fluorescence analysis (XRF) unit.

In addition, it is preferable that the coating obtained by means of this coating be colored, iridescent or gray. Preferably, in the coatings obtained with this, interference colors of 1st or higher order or color are encountered, in which case the interference color is overlapped by the color of the ions. These colors are similar or similar when coated with alkaline phosphates. Colors often help to approximate the thickness and, in part, the uniformity or / and quality of the coating. If this is possible even at a greater visibility distance, then this is especially preferable with the coating method.

First of all, for uses that require particularly high quality, it is preferable that the conversion coating obtained according to the invention obtained by this is then washed with water or an aqueous solution for subsequent washing, in particular with the content of silane, organic polymer or / and organic copolymer, and necessities are also varnished. Subsequent rinsing can be carried out using aqueous solutions for subsequent rinsing, such as, for example, using Gardolene ^® D95 with a phenolic resin content or using Gardolene ^® D6890 based on silane.

Particularly preferably, the aqueous solution for subsequent washing has a content of at least one a) cation selected from alkaline earth metal cations, aluminum, titanium, yttrium and heavy metals, b) an organic polymer or / and copolymer, c) silane, silanol, siloxane or / and polysiloxane or / and d) complex fluoride, and the complex fluoride is also the corresponding fluorine-containing acid. In this case, aminosilanes having one, two, or even more amino groups, and / or bisylsilanes are preferred as silanes.

In a particularly preferred method according to the invention, the coating according to the invention is applied with an aqueous acidic composition, then, if necessary, washed with water and / and then, if necessary, washed with an aqueous composition, and the at least one coating thus obtained is then varnished at least once.

Moreover, in the case of a particularly preferred method according to the invention using an aqueous acidic composition according to the invention on the basis of from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- or / and HfF ₆ ^2- or only ZrF ₆ ^2- in form of ions, calculated as ZrF ₆ ^2- , and 0 or from 0.01 to 1 g / l, respectively, Fe ²⁺ , Mn, or / and Zn ions, of which at least one type of these ions is contained in the concentration range from 0.01 to 1 g / liter, and optionally 0.01 to 2 g / l of SiO ₂ in the form of particles having an average particle diameter of <0.3 microns, in terms of solid content, and / or at neobhodimos and from 0.01 to 10 g / l of at least one surfactant, which mainly contains no phosphates and does not contain phosphonates, can be coated, then, if necessary, washed with water or / and after that, if necessary, additionally washed with an aqueous composition based on a complex of zirconium fluoride, silane or / and an organic polymer / copolymer that is stable at a pH value <6.5 and the thus obtained at least one coating can then at least once varnishes ovatsya. Due to the content of the surfactant in the aqueous acidic composition according to the invention, if necessary, it is possible to refuse the preliminary purification stage.

The conversion coating according to the invention obtained with this, if it is free from an organic polymer and from an organic copolymer, preferably without subsequent washing with water or preferably an aqueous solution for subsequent washing, in particular with a content of silane, an organic polymer or / and an organic copolymer, can be dried and if necessary also varnished.

The conversion coating according to the invention obtained by this means, alternatively, if it contains an organic polymer or / and an organic copolymer, can preferably be used without coating with a primer coating, varnish or adhesive.

The resulting conversion coating according to the invention, if necessary, after at least one washing with water or / and an aqueous solution for subsequent washing, can preferably be coated with a primer coating, varnish or adhesive substance at least once. Thus, in the case of these compositions, if necessary, similar steps, sequences and processing methods can also be successfully used, as in the case of alkaline phosphating.

The coating obtained with this can in a remarkable manner be a replacement for an alkaline phosphate coating, such as, for example, an iron phosphate coating.

At least one base with metal surfaces, which was coated according to the invention, is preferably used as an architectural element, as a reservoir, as a construction or connecting element, as a profile element, as a heating element, as a molded part with complex profile and / or as a component in construction, energy, vehicle manufacturing, instrument making, home appliances or machine building .

Unexpectedly, using the aqueous conversion compositions according to the invention, excellent coatings are obtained which have excellent corrosion resistance, excellent varnish adhesion and in most cases also noticeable color. The corrosion resistance on steel surfaces is almost as good as the corrosion resistance of high-quality zinc phosphating, and, therefore, is significantly superior to the corrosion resistance of high-quality alkaline phosphating without using a solution for subsequent washing to improve the properties of the coating. With the use of an additional solution for subsequent washing, the corrosion resistance of high-quality zinc phosphating can even be achieved.

In addition, it was unexpected that in a relatively simple way they were able to find an exceptionally effective one, obtained in a simple, safe for the environment and, if necessary, completely similar replacement process for alkaline phosphating.

The composition according to the invention and the method according to the invention are particularly favorable for chemical pretreatment of surfaces from various steel bases, which are used in the metalworking industry. In this case, in one working operation, it is even possible to clean and simultaneously apply a conversion layer suitable for lacquering, for which this three-stage treatment method of cleaning with a conversion coating, washing with tap water and washing with completely desalinated water is completely sufficient. First of all, it is very simple to use a bath analysis, since accurate determination of anions and cations is required only occasionally, since the pH value and electrical conductivity give sufficient information about the chemical state of the bath.

The method according to the invention can be used to obtain a colored, nacreous, gray or colorless (as in the case of B40) passivation layer (without varnishing) or painted, nacreous, gray or colorless (as in the case of B40) conversion coating (with varnishing). The passivation layer itself is also a conversion-derived coating. Therefore, the term “conversion coating” according to this application also includes the concept of a “passivating layer” until or if no varnishing is applied, for example, also in the case of the claims.

The method according to the invention can be used as a replacement for the alkaline phosphating process or in some cases even as a replacement for the zinc phosphating process. Products obtained using the method according to the invention can be used in a variety of ways, in particular, as architectural elements, as reservoirs, as structural or connecting elements, as profile elements, as heating elements, as molded parts with a complex profile and / or as components in construction, energy, vehicle manufacturing, instrument making, home appliance manufacturing or mechanical engineering, and, for example, as heaters, as carcasses, as panels, as facings, as corner profiles or as components in the interior of vehicles or airplanes.

Examples and examples for comparison

The object of the invention is explained in more detail on the basis of examples of execution. These examples were conducted using the following bases, process steps, substances, and mixtures.

The coating used standard metal sheets Gardobond ^® C from cold rolled steel, CRS, from St14 DC05, Gardobond ^® HDG / 5 of the respective hot-dip galvanized or Gardobond ^® F from AIMg1 AA 5005 from the company Chemetall GmbH. Unless otherwise indicated, Gardobond ^® C standard metal sheets were used.

Conversion aqueous compositions were preconditioned in accordance with Table 1. As the surfactant used nonionic surfactant Gardobond ^® Additiv N7438, which facilitated further purified metal surface. The alkaline, potassium hydroxide-stabilized dispersion of SiO ₂ Gardobond ^® Additiv H 7157 from Chemetall GmbH had a solids content of 20%, as well as an average particle size of 0.2 microns. The dispersion of polymer 1 AC 2773 on the basis of the acrylate of the company Alberdingk had a solids content of 53%. The acrylate-containing dispersion of copolymer 2 VA 294 VP from Alberdingk had a solids content of 47%. The acrylate-containing dispersion of copolymer 3 AS 2084 VP from Alberdingk had a solids content of 53%. The polymer, copolymer, particles of SiO ₂ or / and surfactant were added to the pre-prepared water conversion composition separately, at the end of the blending process. In separate experiments, ammonium molybdate was added.

In the case of examples B45 to B48, the content of Fe ^{2+ of} approximately 0.02 g / L has already been established due to the etching effect of the acidic conversion composition. Consequently, this iron content, extracted by etching, is higher than in the case of other samples, which in the case of these other samples in the bath ranged from <0.001 to 0.01 g / l Fe ²⁺ . In the case of compositions B41 and B42, the iron content indicated in the table was added purposefully.

A conversion coating was applied to the metal sheets at 55 ° C for 3 minutes, with a cleansing effect when a surfactant was present. After that, they were washed once with technical water and then with completely desalted water before the coated metal sheets were dried in a drying cabinet at 120 ° C for at least 10 minutes. When using a different temperature, there was no noticeable difference in quality.

After that, the metal sheets with the conversion coating was applied in each case a layer of varnish: or powder coating of epoxy and polyester Interpon ^® 700 company Akzo Nobel Powder Coatings GmbH with a layer thickness of from 60 to 80 microns, the liquid lacquer Alexit ^® Monolayer on polyurethane basis and Mankiewicz firm isocyanate with a layer thickness of from 60 to 80 microns, or black cathode varnish dipping Cathoguard ^® 350 company BASF with a layer thickness of from 15 to 20 .mu.m in the case of B3 example, or in the case of examples B45 on B48 cathode varnish dipping Cathoguard ^® 800 (KTL) BASF company with a layer thickness of 15 to 20 microns, and then one layer a tomobilnogo composition according to Daimler Benz filler of 25-30 microns, 11-15 microns, and bases 40-50 .mu.m of varnish clearcoat.

The adhesion of varnish on varnished samples was determined in tests with a lattice notch according to DIN EN ISO 2409 before or after 240 hours of tests in a climatic chamber. The corrosion resistance of varnished samples was determined in tests in a salt chamber according to DIN 50021 for 500 hours in a neutral test in an NSS salt chamber. At the same time, in contrast to what is usually for the Asian and North American market, only one single layer of varnish was applied.

Surprisingly, when tested in a salt chamber after 1000 hours in the case of example B44, a very high corrosion resistance with a value of 0 mm was also obtained.

The mass of an elemental zirconium deposition layer was measured in mg / m ² using an X-ray fluorescence analysis setup. The element zirconium is often an indicator element for the quality of the coating, and depending on the metal base, with the same aqueous compositions, various metal deposits of zirconium are deposited.

The examples according to the invention in the case of examples for comparison VB1 and VB2 were compared with high-quality, often used in the world alkaline phosphating on metal sheets of Gardobond ^® C from cold-rolled steel: while working with the usual order of the process with alkaline phosphating, which in the case of iron and steel materials are also called iron phosphating with Gardobond ^® WH = Gardobond ^® a 4976 on steel surfaces at 55 ° C for 3 minutes while washing with demineralized water and optionally with the pos eduyuschey additional washing for 5 minutes with a solution afterflush Gardolene ^® D 6800/6 on SALT ZrF ₆ before dried at 120 ° C in an oven for at least 10 minutes. As an alternative, before being dried at 120 ° C in an oven for at least 10 minutes, worked with a solution for subsequent washing with aminosilan based Gardolene ^® D 6890 with a surfactant, with a solution for subsequent washing with Oxsilan ^® 9810 / 3 on the basis of two aminosilanes of different types and ZrF ₆ or with a solution for subsequent washing from the dispersion of the polymer 1 AC 2773 based on acrylate.

The examples explain that using the aqueous conversion compositions according to the invention, despite often very simple formulations and low concentrations, excellent coatings are obtained, which under these conditions have excellent corrosion resistance, excellent adhesion of varnish and in most cases also noticeable color. With these compositions, both intensely colored and colorless coatings can be obtained. Corrosion resistance on steel surfaces is almost as good as the corrosion resistance of high-quality zinc phosphating, and, therefore, is far superior to the corrosion resistance of high-quality alkaline phosphating (for example, B3 compared to VB1).

In the case of the example for comparing VB2, the coating properties were determined only after an additional second conversion treatment, in contrast to the examples according to the invention. The adhesion of varnish on steel surfaces is even as good as the adhesion of varnish in high-quality zinc phosphating, and, therefore, is very noticeably superior to the adhesion of varnish in high-quality alkaline phosphating. Additionally, the aqueous conversion compositions according to the invention are very environmentally friendly, hygienic and phosphate free.

If after applying the conversion coating according to the invention and after at least one washing with water, a solution was used for subsequent washing, for example, with a silane, organic polymer or organic copolymer content, lacquer adhesion was achieved on the steel surface, which is at least as good like the adhesion of varnish to high-quality zinc phosphating, and corrosion resistance has also been achieved, which is at least as good as corrosion resistance s zinc phosphate coating.

In general, it was found that the acidic aqueous conversion compositions according to the invention are excellent for replacing alkaline phosphating on metal surfaces of various types of bases, and not just iron phosphating on iron and steel surfaces. At the same time, the processing even turned out to be suitable for many metals, so that in the same bath simultaneously or sequentially a mixture of metal surfaces of various types can be processed.

When replacing ZrF ₆ with TiF ₆ , in particular with steel, if necessary, slight deterioration in the anticorrosion protection as compared with a certain layer thickness can be obtained.

When only zinc was used as the added metal cation, high-quality coatings were obtained, also when the zinc content in the coatings was unexpectedly extremely low and no phosphate was added. When only manganese was used as the added metal cation, high-quality coatings were obtained, also when the manganese content in the coatings also remained unexpectedly extremely low and when no phosphate was added. When manganese and zinc were used at the same time, in part, in comparison with only the use of one of these heavy metal cations, if no phosphate was added, insignificant deterioration was obtained.

When using only Fe ²⁺ as a heavy metal cation or in addition to Mn or / and Zn ions, high-quality coatings were also obtained. In this case, Fe ²⁺ can additionally be supplied from the base as a result of the pickling process caused by the reaction from a bath of base surfaces containing iron. However, then this cation is often oxidized as a result of circulation in the bath to Fe ³⁺ and is removed from the bath as a reactive component. Despite the addition of Fe ²⁺ , a constant concentration of Fe ²⁺ is often set in the range of 0.025 to 0.1 g / l Fe ²⁺ , as in the case of Examples B41 and B42.

Since in the case of long-term coating, for example, with many bases, the main elements and part of the alloying elements are extracted by etching into an acidic aqueous conversion composition and can partially accumulate in the bath composition, in this case several cations are often present in the bath, which can influence first of all, on the composition of the coating, and secondly on its properties.

If no heavy metal cation was added, as in the case of examples for comparing VB3 and VB4, then in most cases more poor coatings were obtained. Zn and Mn, as opposed to Zr, are deposited only in insignificant measurable amounts relative to measurements using X-ray fluorescence analysis. However, Zr is the main component of the layer and may be present, for example, as (Zr (OH) _x F _y ). Zn at the metal-coating interface often acts as a fluoride trap, so that less fluoride can be embedded in the layer, which, according to the applicant's understanding, leads to better results. Zn and Mn are components of the layer only in insignificant quantities and therefore can be more accurately detected analytically only by photoelectron spectroscopy of XPS / ESCA (XPS / ESCA).

The obtained properties of coatings are often the best in the case when the deposition of Zr in the case of comparable experiments is the highest. However, this Zr deposition is different in the case of different types of steel and also in the case of identical types of steel with different surface properties.

In the experiments, a non-ionic surfactant was also added, which further improved the purity of the metal surface of the standard CRS Gardobond ^® C metal sheet used. Therefore, we were able to abandon the preliminary cleaning stage. When, in comparison with this, the addition of a surfactant was abandoned, basically no other coating properties were obtained, unless there was an increased risk that the metal surfaces were not sufficiently cleaned, which, if necessary, could negatively affect the properties of the layer.

With higher molybdate additions, attention should be paid to the possibility of easy peeling of the coating.

Especially well proven additives organic polymer, organic copolymer and nanoparticles of SiO ₂ . It should pay attention to the fact that in the case of the added amount in excess of 0.5 g / l there is no interference from foaming and no interference from deposits from the spray nozzles and walls.

Claims (25)

1. A method of obtaining a conversion coating on a metal surface, comprising treating the base with a metal surface with an acidic aqueous conversion composition, characterized in that the acidic aqueous conversion composition contains from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- and / or HfF ₆ ^2- in the form of ions, calculated as ZrF ₆ ^2- , from 0.01 to 1 g / l Fe ²⁺ -, Mn - and / or Zn-ions, of which at least one type of these ions is contained in content ranging from 0.01 to 1 g / l, and molybdate content, calculated as MoO ₄ ^2- and / or phosphorus content oksia ions, calculated as PO ₄ ^3- is suitably <0.1 g / l or about 0 g / l, wherein said acidic aqueous composition has a pH value in the range from 2.5 to 6.5, and the resulting coating has a layer thickness from 0.3 to 3 microns. 2. The method according to p. 1, characterized in that the acidic aqueous composition further comprises from 0.01 to 2 g / l of an organic polymer and / or copolymer, which is stable at pH <6.5, in terms of solid content substances. 3. The method according to p. 1, characterized in that the acidic aqueous composition further comprises from 0.01 to 2 g / l of SiO ₂ in the form of particles with an average particle diameter of <0.3 microns, based on the solids content. 4. The method according to p. 1, characterized in that the acidic aqueous composition further comprises from 0.01 to 10 g / l of at least one surfactant. 5. The method according to p. 1, characterized in that the acidic aqueous composition further comprises from 0.05 to 10 g / l of anions selected from the group consisting of carbonate, nitrate and sulfate, in terms of NO ₃ ^- , also if there are CO ₃ ^2- or SO ₄ ^2- . 6. The method according to claim 1, characterized in that said acidic aqueous composition additionally contains from 0.001 to 2 g / l of carboxylate and / or sulfonate anions, which do not interfere or hardly interfere with the formation of the layer, calculated as the corresponding anions. 7. The method according to p. 1, characterized in that the acidic aqueous composition further comprises from 0.03 to 5 g / l of the sum of lithium, sodium and / or potassium ions, 0 or from 0.05 to 5 g / l of ammonium ions , about 0 or from 0.05 to 0.3 g / l of the sum of Co- and / or Ni-ions, 0 or from 0.01 to 0.8 g / l of chlorate, calculated as ClO ₃ ^- , nitrite, calculated as NO ₂ and / or peroxide, calculated as H ₂ O ₂ , 0 or from 0.01 to 0.5 g / l of free fluoride, calculated as F ^- , and 0 or from 0.01 to 0.2 g / l Vanadate ions, calculated as VO ₄ ^3- . 8. The method according to p. 1 or 7, characterized in that the sum of the deposits of zirconium and / or titanium when measured as elements lies in the range from 1 to 300 mg / m ² , when measured using the installation for X-ray fluorescence analysis. 9. The method according to p. 1 or 7, characterized in that the coating obtained with it is colored, iridescent or gray. 10. The method according to p. 1 or 7, characterized in that the coating obtained with it is a replacement of the coating based on alkaline phosphate. 11. The method according to p. 1 or 7, characterized in that the bath composition is obtained by diluting one or two concentrates with water, with a dilution ratio in the range from 5: 1 to 40: 1. 12. The method according to p. 1, characterized in that at least one base with metal surfaces is brought into contact with the aqueous composition over a period of time ranging from 1 second to 10 minutes. 13. The method according to p. 12, characterized in that the base with metal surfaces when brought into contact with the aqueous composition has a temperature in the range from 5 to 90 ° C. 14. The method according to p. 12 or 13, characterized in that the aqueous composition when brought into contact with the base with metal surfaces has a temperature in the range from 35 to 70 ° C. 15. The method according to p. 12, characterized in that before bringing the base into contact with the aqueous composition, it is cleaned. 16. The method according to p. 15, characterized in that the aqueous composition contains at least one surfactant, while cleaning and applying a conversion coating is carried out at the same stage of the process. 17. The method according to p. 1, characterized in that the conversion coating obtained using it is then washed with water or an aqueous solution for subsequent washing, in particular, with the content of silane, organic polymer and / or organic copolymer, and, if necessary, varnished. 18. The method according to p. 1, characterized in that the conversion coating obtained using it, if it is free from organic polymer and organic copolymer, without subsequent washing with water or an aqueous solution for subsequent washing, in particular, with the content of silane, organic polymer and / or an organic copolymer, dried and, if necessary, varnished. 19. The method according to p. 1, characterized in that the conversion coating obtained using it, if it contains an organic polymer and / or copolymer, is used without coating with a primer coating, varnish or adhesive substance. 20. The method according to p. 1, characterized in that the conversion coating obtained with it after at least one washing with water and / or an aqueous solution for subsequent washing is at least once coated with a primer coating, varnish or adhesive. 21. The method according to p. 20, characterized in that the aqueous solution for subsequent washing contains at least: a) a cation selected from alkaline earth metal cations, aluminum, titanium, yttrium and heavy metals, b) an organic polymer and / or a copolymer, c) silane, silanol, siloxane and / or polysiloxane and / or d) complex fluoride. 22. The method according to p. 1 or 7, characterized in that using an aqueous acidic composition is coated, after which it, if necessary, washed with water and / or if necessary, it is washed with an aqueous composition, and the thus obtained at least one coating is then at least once varnished. 23. The method according to p. 1, characterized in that using an aqueous acidic composition based on from 0.01 to 1 g / l TiF ₆ ^2- , ZrF ₆ ^2- and / or HfF ₆ ^2- or only ZrF ₆ ^2- in the form of ions, calculated as ZrF ₆ ^2- , and from 0.01 to 1 g / l of ions of Fe ²⁺ -, Mn - and / or Zn - ions, of which at least one type of these ions is contained in the range of contents from 0.01 to 1 g / l, and, if necessary, from 0.01 to 2 g / l of SiO ₂ in the form of particles with an average particle diameter of <0.3 μm, calculated on the solids content, and / or, if necessary, from 0 , 01 to 10 g / l of at least one surfactant, which mostly free of phosphates and mostly free of phosphonates, coated, if necessary, then washed with water and / or if necessary, then washed with an aqueous composition based on organic polymer / copolymer, which is stable at pH <6.5, complex zirconium fluoride and / or silane, and the thus obtained at least one coating is then at least once varnished. 24. The base with a metal surface having a conversion coating obtained by the method according to one of paragraphs. 1-23 25. The use of the base with a metal surface having a conversion coating applied by the method according to one of paragraphs. 1-23, as an architectural element, a reservoir, a structural or connecting element, a profile element, a heating element, a molded part with a complex profile and / or a component in construction, energy, vehicle manufacturing, instrument making, home appliances or mechanical engineering.