CN106574372B

CN106574372B - Method for coating metal surfaces, substrates coated thereby and use thereof

Info

Publication number: CN106574372B
Application number: CN201580015618.8A
Authority: CN
Inventors: K.德迈耶雷; T.维卢迈特; M.瓦尔特
Original assignee: Chemetall GmbH
Current assignee: Chemetall GmbH
Priority date: 2014-01-23
Filing date: 2015-01-22
Publication date: 2020-11-24
Anticipated expiration: 2035-01-22
Also published as: RU2016134227A3; KR20160111989A; PL3097221T3; RU2691149C2; BR112016017018A2; AU2015208176A1; EP3097221B1; BR112016017018B1; JP6622206B2; HUE059458T2; US20170009351A1; AU2015208176B2; RU2016134227A; CN106574372A; KR102416141B1; ES2921449T3; EP3097221A1; ZA201605375B; DE102015201090A1; WO2015110541A1

Abstract

The present invention relates to a process for coating a metal surface with an acidic aqueous conversion composition comprising: according to ZrF₆ ²⁺Calculating a total of 0.01 to 1g/L of TiF₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺0 or 0.01 to 1g/L each of Fe²⁺Mn and/or Zn ions, wherein at least one type of these ions is present in a content range of 0.01 to 1g/L, 0 or 0.01 to 2g/L of an organic polymer and/or copolymer, 0 or 0.01 to 2g/L of ultrafine particulate SiO₂About 0 or 0.01 to 10g/L of at least one surfactant, about 0 or 0.05 to 10g/L of an anion selected from the group consisting of carbonate, nitrate and sulfate, and 0 or 0.001 to 2g/L of a carboxylate and/or sulfonate anion, wherein the content of molybdate and/or P-containing oxyanion is each<0.1g/L or about 0g/L and wherein the composition has a pH of 2.5 to 6.5. The invention also relates to the use of the corresponding coating and of the substrate coated therewith.

Description

Method for coating metal surfaces, substrates coated thereby and use thereof

The invention relates to a method for coating metal surfaces with an optionally colored conversion layer, in particular for replacing alkaline phosphating, such as iron-based phosphating, to correspondingly coated substrates having metal surfaces, and to the use of these coated substrates.

In the examples, a process for producing alkali metal phosphate coatings, in particular such coatings as pretreatment layers before painting, has been described. Fresh unused alkali metal phosphate solutions usually contain little or only small amounts of aluminum, iron and zinc. The acidic aqueous alkali metal phosphate solutions contain, in addition to the ions of at least one alkali metal and/or ammonium, phosphate ions and, due to the pickling effect of these solutions on the metal surface, they also contain ions of metals such as aluminum, iron and/or zinc dissolved from the metal surface and trace alloy constituents of the pickled metal material. The phase formed predominantly in the alkali metal phosphate layer during alkali metal phosphating is the corresponding phosphate, oxide and/or hydroxide of the metal from the surface of the base substrate to be treated.

Alkali metal phosphate solutions and/or coatings when used on iron and steel materials are also referred to as iron phosphate solutions and/or coatings. Alkali metal phosphate coatings are also commonly referred to as so-called "non-stratified phosphating" layers according to Werner Rausch: Die Phosphotiering von Metallen, Saulgau 1988 (see especially pages 109-118). This term is misleading because layers are also formed here, but they are much thinner than other phosphate layers, such as various types of zinc-based phosphating. The alkali metal phosphate solution always contains an increased content of at least one alkali metal, such as sodium and/or ammonium.

The alkali metal phosphating is generally carried out in a simple and economical manner. However, high-quality alkali metal phosphate coatings, although they also offer only limited corrosion protection after a second subsequent corrosion protection treatment, are generally a) not better than, i.e. not less than, 3 mm subsurface corrosion (unterwardrun) for powder-lacquer coatings based on epoxy-polyester powder lacquers having a thickness of 60 to 80 μm on cold-rolled steel sheets tested in the salt-fog test according to DIN 50021 NSS for 500 hours, and/or are generally b) not better than, i.e. not less than, 4 mm subsurface corrosion for wet-lacquer coatings based on polyurethane-isocyanate lacquers having a thickness of 60 to 80 μm on cold-rolled steel sheets tested in the salt-fog test according to DIN 50021 NSS for 500 hours, and are generally c) not better than, i.e. not less than, 240 hours for powder-lacquer coatings based on epoxy-polyester powder lacquers having a thickness of 60 to 80 μm on cold-rolled steel sheets tested in the condensate climate (KK) test according to DIN EN ISO 2409, paint adhesion was not better than, i.e., not less than, GT 3 in the cross-cut test.

In the case of alkali metal phosphating, it is therefore generally necessary to apply an additionally applied second conversion layer, in most cases also at least one further subsequently applied lacquer layer. Such multi-step processes are not only particularly complex, but also require additional baths and/or treatment zones and optionally also additional rinsing steps and/or drying steps, and are also cost-intensive and time-consuming. The lacquer adhesion to alkali metal phosphate coatings is also often insufficient, so that an additional conversion coating, for example based on zirconium hexafluoride and/or silane, must be applied before lacquering. The coating process thereby becomes particularly complex and expensive. The high phosphate content in the phosphating of alkali metals is also disadvantageous, since the phosphate in the waste water has to be disposed of in a complicated manner.

Alkali metal phosphating is generally applied in multiple steps, where first only cleaning is performed in a first step and layering is performed in a second step. Followed by rinsing and/or re-rinsing.

The object of the present invention was to find aqueous compositions which can be applied easily and have a composition which is as environmentally friendly as possible and which yield a higher corrosion protection than high-quality alkali metal phosphate coatings.

This object is achieved by a process for coating a metal surface with an acidic aqueous conversion composition, said conversion composition being a solution or dispersion, characterized in that it contains:

in total 0.01 to 1g/L of TiF in ionic form₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺According to ZrF₆ ²⁺The calculation is carried out according to the calculation,

0 or 0.01 to 1g/L each of Fe²⁺Mn and/or Zn ions, wherein at least one type is present in a concentration range of 0.01 to 1g/L, wherein Mn and/or Zn ions are preferably present,

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

average particle diameter of 0 or 0.01 to 2g/L as measured on a scanning electron microscope and based on the solid content<Fine SiO particles of 0.3 micron₂，

About 0 or 0.01 to 10g/L of at least one surfactant,

about 0 or 0.05 to 10g/L of a carbonate, nitrateAnd sulfate ions, even when CO is present₃ ²⁺Or SO₄ ²⁺Time conversion to NO₃ ⁺And are and

from 0 or from 0.001 to 2g/L, calculated as the corresponding anion, of carboxylate and/or sulfonate anions which do not or hardly impair the layering,

wherein according to MoO₄ ²⁺Calculated molybdate content and/or as PO₄ ³⁺The calculated content of the P-containing Oxyanion (Oxyanion) is each<0.1g/L or about 0g/L

And wherein the acidic aqueous composition has a pH value of from 2.5 to 6.5, preferably from 3.0 to 5.5.

TiF₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺Is substantially equivalent and interchangeable in the acidic aqueous conversion composition, but ZrF₆ ²⁺Ions generally bring about the best properties of the conversion coatings made therewith. Preferably, the TiF of the acidic aqueous composition₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺The content is 0.05 to<1g/L, 0.1 to 0.8g/L, 0.15 to 0.50 g/L, or 0.20 to 0.33 g/L.

It is preferred here for the acidic aqueous conversion composition to be Fe only²⁺Cationic content of ions, based on Fe²⁺Mn and Zn ions, this content being derived at least in part from intentional additives. Manganese and zinc ions and, to a limited extent, Fe²⁺The ions are substantially equivalent and interchangeable in the acidic aqueous conversion composition, but the manganese and/or zinc ions generally give the best properties of the conversion coating made therewith. If manganese and zinc are added to the acidic aqueous conversion composition, it is particularly preferred to achieve a higher manganese content than zinc. They preferably contain 0 or 0.01 to 0.3g/L or 0.02 to 0.15 g/L Fe²⁺Ions and 0.01 to 1g/L of Mn ions and/or 0.01 to 1g/L or 0.1 to 0.6 g/L of Zn ions. It particularly preferably contains 0.1 to 0.6 g/L or 0.2 to 0.4 g/L of Mn ions and/or 0.1 to 0.6 g/L or 0.2 to 0.4 g/L of Zn ions.

Preferably, substantially no phosphate is present (A), (B), (C), (D), (< 0.1 g/L PO₄) Or completely free of phosphate (about 0 or exactly 0g/L PO)₄) And (5) carrying out operation. In the individual process variants, in particular owing to entrainment and impurities, the PO as a rule cannot be ruled out₄ ³⁺Calculate 0.001 and<a phosphate content of between 0.1 g/L. It is furthermore preferred that even substantially no phosphates (A), (B), (C), (D< 0.1 g/L P_xO_y) Or completely free of phosphates (about 0 or exactly 0g/L P)_xO_y) The operation was carried out without phosphate.

The addition of organic polymers and/or organic copolymers can contribute to further improvement of the properties of conversion coatings made therefrom and optionally subsequent lacquering can be omitted. Preferably, the acidic aqueous conversion composition has a content of organic polymer and/or organic copolymer of 0.01 to 3g/L, 0.1 to 2.5 g/L, 0.2 to 2g/L, 0.4 to 1.5 g/L or 0.6 to 1.2 g/L. The organic polymer and/or copolymer is preferably based on a (meth) acrylate/(meth) acrylic acid and/or vinyl acetate-acrylic copolymer.

If painting is omitted, in the case of the passivation layer coating produced and in the case of corrosion protection, this can be referred to as blank corrosion protection.

Adding very fine SiO particles₂(in particular<0.3 micron) such as SiO₂Nanoparticles may have a similar positive effect as the addition of organic polymers and/or organic copolymers, but the difference is usually in layering, and thus in SiO₂The coating in this case is more uniform.

Essentially at least one nonionic, anionic, cationic and/or zwitterionic surfactant can be added. The addition of at least one nonionic surfactant is particularly preferred here.

The anion selected from carbonate, nitrate and sulfate is typically added by adding the cation through a water soluble salt. Nitrate is particularly preferred here.

Instead of or in addition to these anions, carboxylate anions can be added essentially, for example by acetic acid and/or manganese carboxylates, and are generally suitable for preventing or reducing anions of mineral acids. Essentially all types of carboxylic acids and their derivatives, such as salts and esters, which are water-soluble and stable in this pH range, have no complex substance composition, form anions in water, do not impair the layering depending on the type and amount of anions and optionally form complexes with alkali metal and/or alkaline earth metal ions which do not participate in the layering, can be added.

These include in particular aliphatic carboxylic acids and mono-, di-and/or polycarboxylic acids, for example hydroxycarboxylic acids. When carboxylate anions are added, care should be taken that they do not impair layering, since, for example, citrate and certain other independent complexing agents may optionally impair layering depending on the type and amount of anion.

The addition of at least one sulfonic acid, for example methanesulfonic acid, amidosulfonic acid and/or one of its derivatives, is advantageous here to act as an accelerator and/or as an additional counter ion.

Essentially, according to MoO₄Calculating 0 or 0.01 to<A molybdate content of 0.5g/L, in particular from 0.02 to 0.3g/L, from 0.01 to 0.1g/L, is preferred. The addition of molybdate has proven advantageous only when very small amounts of addition are added.

Especially due to possible contamination of the wastewater and optionally also due to more severe sludge formation, which may lead to complicated wastewater and/or sludge disposal, the addition of P-containing oxoanions, such as orthophosphate, condensed phosphate and phosphonate, should be avoided. In particular in the case of P-containing oxyanions, it is preferred not to add P-containing oxyanions for reasons of environmental compatibility and avoidance of expensive disposal, and care should preferably be taken that as little P-containing oxyanions as possible are entrained.

In the case of the process of the present invention, the acidic aqueous composition preferably additionally contains, essentially consists of or consists of:

a total of from 0.03 to 5g/L of ions of lithium, sodium and/or potassium,

0 or 0.05 to 5g/L of ammonium ions,

about 0 or 0.05 to 0.3g/L total of Co and/or Ni ions,

0 or 0.01 to 0.8g/L each as ClO₃ ^-Calculated chlorate, according to NO₂Calculated nitrite and/or as H₂O₂CalculatedA peroxide compound, a metal salt, a metal oxide,

0 or 0.01 to 0.5g/L of a compound according to F^-Calculated free fluoride ion, and

0 or 0.01 to 0.2g/L as VO₄ ^3-Calculated vanadate ions.

In general, the lithium, sodium, potassium and/or ammonium content is not substantially avoided to achieve charge balance and not only to add multivalent cations, such as heavy metal ions. Among the monovalent cations, sodium ion is particularly preferred. They are essentially equivalent and interchangeable in the acidic aqueous conversion composition and are generally necessary for adjusting the pH.

As in many coating processes, the addition of cobalt and/or nickel is still advantageous here for achieving better corrosion protection, even if these elements are problematic with regard to environmental compatibility and working hygiene.

It is sometimes necessary to add at least one accelerator, in particular chlorate, nitrite and/or peroxide. However, it is noted herein that suitable amounts, e.g., much less than 1g/L of NO₂And (4) content. When at least one accelerator is added, layering can be accelerated and the properties of the coatings produced therefrom can be improved. Excessive addition of accelerator should be avoided here in order not to impair layering as in the case of example B40. The addition of nitroguanidine has not proved advantageous.

The content of complex fluoride(s) (komplexfluored) alone generally results in a low free fluoride ion content. The content and/or addition of the at least one fluoride may result in a slightly higher free fluoride ion content. Free fluoride content in F, particularly advantageous for aluminium-containing substrate surfaces^-The calculation is usually 0.01 to 0.5 g/L.

The addition of at least one vanadium compound can significantly improve the corrosion protection.

It cannot be ruled out here that additional element contents of the metal surfaces of the substrate and of the installation, due to the pickling action of the acidic aqueous conversion composition, enter the bath and optionally even accumulate in the bath composition, in particular Fe²⁺Ions and alloying elements and their ions.

On the other hand, it is also generally not excluded in the case of coating methods and apparatuses of today that small amounts of ions and substance contents from other apparatus regions, for example from previously used cleaning steps, are entrained, optionally despite the use of water rinsing. In particular, certain amounts of alkali metals, ammonium, complexing agents, surfactants, anionic impurities of the cleaning bath and/or additional impurities and/or ions thereof may be entrained thereby into the bath composition of the present invention. However, it is not absolutely necessary to provide a separate pre-cleaning step to enable substantial exclusion of extraneous ion input by the chemical treatment solution. At best, the cleaning step can be carried out with water containing surfactant but no builder (Reinigerer cream).

In one aspect, cleaning can be performed prior to conversion coating to clean the substrate prior to contacting the substrate with the aqueous composition, particularly by alkaline cleaning. On the other hand, in addition to or instead of this cleaning step, the aqueous composition may also contain at least one surfactant, so that cleaning and conversion coating (also) take place in the same process step.

Preferably, the following are not or only intentionally added to the aqueous conversion composition: for example up to 0.1g/L each of carboxylic acids, phosphates, phosphonates and/or compounds and/or ions of calcium, chromium, chromate, cobalt, copper, magnesium, molybdenum, nickel, vanadium and/or tin and/or silanes/silanols/siloxanes/polysiloxanes. Silane/silanol/siloxane and polysiloxane mean silane, silanol, siloxane and/or polysiloxane, since silanols and/or siloxanes, and sometimes also polysiloxanes (depending on the respective chemical definition) can be produced very rapidly in water and in coatings starting from, for example, silane.

The alkaline earth metal, such as calcium and/or magnesium, content of the acidic aqueous conversion composition is preferably no more than 0.2g/L in total to prevent precipitation in the presence of fluoride as much as possible.

The following variants are particularly preferred:

the acidic aqueous conversion composition has a pH of from 2.5 to 6.5 and contains, consists of, or consists essentially of a total of:

variant A:

According to ZrF₆ ²⁺Calculation, 0.01 to 1g/L of TiF in ionic form₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺And are and

0 or 0.01 to 1g/L each of Fe²⁺Mn and/or Zn ions, wherein at least one type of these ions is present in a content range of 0.01 to 1g/L,

and optionally an average particle diameter of 0.01 to 2g/L based on the solid content<Fine SiO particles of 0.3 micron₂And/or

Optionally 0.01 to 10g/L of at least one surfactant, and

<0.1 g/L PO₄phosphate content of (a).

Variant B:

According to ZrF₆ ²⁺Calculation, 0.01 to 1g/L of TiF in ionic form₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺，

0 or 0.01 to 1g/L each of Fe²⁺Mn and/or Zn ions, wherein at least one type of these ions is present in a content range of 0.01 to 1g/L, and

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

and optionally an average particle diameter of 0.01 to 2g/L based on the solid content<Fine SiO particles of 0.3 micron₂，

And optionally 0.01 to 10g/L of at least one surfactant,

and optionally 0.05 to 10g/L of an anion selected from carbonate, nitrate and sulfate, even when CO is present₃ ²⁺Or SO₄ ²⁺Time conversion to NO₃ ⁺And are and

optionally from 0.001 to 2g/L, calculated as the corresponding anion, of carboxylate and/or sulfonate anions which do not or hardly impair the layering,

wherein according to MoO₄ ²⁺Calculated molybdate content and/or as PO₄ ³⁺The calculated content of P-containing oxyanion is respectively<0.1g/L or about 0 g/L.

Variant C:

according to MoO₄ ²⁺Calculated from 0.01 to<A molybdate content of 0.5g/L,

and optionally 0.01 to 2g/L, based on the solids content, of an organic polymer and/or copolymer which is stable at a pH value of <6.5,

And optionally 0.01 to 10g/L of at least one surfactant,

wherein according to MoO₄ ²⁺The calculated molybdate content is 0.01 to<0.5g/L and as PO₄ ³⁺Calculated oxyanion content containing P of<0.1g/L or about 0 g/L.

For all three variants, it is preferred to add M and/or Zn ions, while Fe²⁺The ion content is preferably only washed out of the iron-rich metal substrate by the acid washing action of the acidic conversion composition. The coating is optionally subsequently painted at least once.

Particularly preferred are acidic aqueous conversion compositions which are solutions or suspensions and contain, consist essentially of, or consist of:

according to ZrF₆ ²⁺Calculated, 0.01 to 1g/L in total in the form of ionsTiF₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺，

0 or 0.01 to 1g/L of Mn and/or Zn ions, wherein at least one type of these ions is present in a concentration range of 0.01 to 1g/L,

0 or 0.01 to 0.3g/L Fe²⁺The ions are selected from the group consisting of,

of which Mn and/or Zn ions are preferably present,

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

average particle diameter of 0 or 0.01 to 1g/L as measured by scanning electron microscope and based on solid content<Fine SiO particles of 0.3 micron₂，

About 0 or 0.01 to 6 g/L of at least one surfactant,

about 0 or 0.05 to 6 g/L of an anion selected from the group consisting of carbonate, nitrate and sulfate, even when CO is present₃ ²⁺Or SO₄ ²⁺Time conversion to NO₃ ⁺And are and

from 0 or from 0.001 to 1g/L, calculated as the corresponding anion, of carboxylate and/or sulfonate anions which do not or hardly impair the layering,

wherein according to MoO₄ ²⁺Calculated molybdate content and/or as PO₄ ³⁺The calculated content of P-containing oxyanion is respectively<0.1g/L or about 0g/L, and

wherein the aqueous composition has a pH of 2.5 to 6.5, preferably 3.0 to 5.5.

The acidic aqueous composition particularly preferably also comprises, consists essentially of or consists of:

a total of from 0.01 to 5g/L of lithium, sodium and/or potassium ions,

0 or 0.05 to 5g/L of ammonium ions,

about 0 or 0.05 to 0.2g/L total of Co and/or Ni ions,

0 or 0.01 to 0.4 g/L each as ClO₃ ^-Calculated chlorate, according to NO₂Calculated nitrite and/or as H₂O₂The calculated amount of peroxide is calculated as the amount of peroxide,

0 or 0.01 to 0.1g/L as VO₄ ^3-Calculated vanadate ions.

The bath compositions of the invention can here preferably be prepared by diluting one or both concentrates with water at a dilution factor of 5:1 to 40: 1. The second concentrate may contain, for example, at least one surfactant and may also be aqueous. The fluoride ions can also be added here as monofluorides, fluorohydrides (bifluorides) and/or in the form of the corresponding acids. The free fluoride ion content is usually 0.01 to 0.2 g/L.

For the acidic aqueous conversion composition, preferably tap water or deionized water having a conductivity of, for example, about 200 to 600 μ S/cm is used for the batch and for replenishing the liquid level in the bath and for the first rinse after conversion coating.

After this first rinsing step, only as a final rinse according to the standard, a deionization rinse with deionized water is necessary to prevent drying of the salt component (salzfract), which would result in poor corrosion protection.

Paint adhesion and corrosion protection on Hot Dip Galvanized (HDG) steel tend to be slightly worse than Cold Rolled Steel (CRS) sheet. If the zinc content in the acidic aqueous conversion composition is reduced or even completely omitted, the coating properties on hot-dip galvanized steel sheets are generally improved.

Fe²⁺The ion content does not generally deteriorate the coating properties, but it has been shown that Fe²⁺Gradual oxidation of ions to Fe³⁺And settled as bath sludge. Here, the acidic aqueous conversion composition preferably has a manganese and/or zinc ion content.

The aqueous surfactant-containing composition may contribute to further improved degreasing and/or cleaning after pickling or at least to the omission of degreasing before conversion coating, and may thus be cleaned in a one-pot process and the omission of a cleaning step and in conversion coating.

In the process of the invention, it is preferred to bring at least one substrate having a metal surface into contact with the aqueous composition during the treatment of the component for a period of from 1 second to 10 minutes, in particular from 0.5 to 10 minutes. Particular preference is given to contact for a period of from 1 to 10 minutes, in particular in immersion, or preferably from 0.5 to 6 minutes, in particular in spraying. Thus even for these compositions, the same processing time as in alkali metal phosphating can be used, which is easy to convert from an alkali metal phosphating plant to the conversion coating of the invention. Since in alkali metal phosphating it is generally also used for 3 to 5 minutes. Alternatively, the composition of the invention can also be applied to the strip if the strip is also rinsed with water after coating (rinsing process). In strip coating, the metal strip is preferably contacted with the aqueous composition for a period of from 1 second to 2 minutes.

In the process of the invention, the substrate having a metal surface preferably has a temperature of from 5 to 90 ℃, preferably from 15 to 70 ℃ or from 30 to 60 ℃ when contacted with the aqueous composition. On the other hand, the aqueous composition also preferably has a temperature of 35 to 70 ℃ or 45 to 60 ℃ when in contact with a substrate having a metal surface. The temperature of these compositions can thus be the same as in alkali metal phosphating, where temperatures of from 50 to 55 ℃ are generally used. At temperatures of 50 to 55 ℃, the most uniform conversion coating and, after painting, the most uniform paint layer are obtained.

This object is also achieved with a coated substrate having a metal surface which is coated according to the invention.

It is preferred here that the coating produced in this way has a layer thickness of 0.3 to 3 μm and/or that the total applied amount of zirconium and/or titanium, measured as the element, in the conversion coating, measured by an X-Ray Fluorescence Analyzer (RFA), is 1 to 300 mg/m or preferably 15 to 150 mg/m.

The coatings produced in this way are also preferably colored, iridescent or grey. In the coating layer thus produced, it is preferable that a first order or higher order interference color or a color when the interference color is superimposed on an ion color occurs. These colors are the same as or similar to those in the alkali metal phosphate coating. These colors generally help to approximate the thickness of the coating and to some extent the uniformity and/or quality of the coating. This is particularly advantageous for the coating process if this is possible even at larger viewing distances.

For particularly high-quality use applications, the conversion coatings according to the invention produced therefrom are preferably subsequently rinsed with water or with aqueous post-rinsing solutions, in particular those containing silanes, organic polymers and/or organic copolymers, and optionally also painted. Aqueous post-rinse solutions may be used, for example Gardolene containing phenolic resins^®D95 or silane-based Gardolene^®D6890 post-flush.

The aqueous post-rinse solution particularly preferably contains at least one each of a) cations selected from the group consisting of alkaline earth metal cations, aluminum cations, titanium cations, yttrium cations and heavy metal cations, b) organic polymers and/or copolymers, c) silanes, silanols, siloxanes and/or polysiloxanes, and/or d) complex fluorides, wherein complex fluorides also represent the corresponding fluorine-containing acids. In particular, aminosilanes and/or bis-silyl silanes having one, two or even more amino groups are preferred silanes herein.

In a particularly preferred process according to the invention, a coating is applied with the acidic aqueous composition according to the invention, optionally followed by rinsing with water and/or optionally followed by rinsing again with the aqueous composition, and at least one coating layer thus produced is subsequently lacquered at least once.

In a particularly preferred process according to the invention, use is made of a catalyst based on ZrF₆ ²⁺Calculation of TiF in ionic form from 0.01 to 1g/L₆ ²⁺、ZrF₆ ²⁺And/or HfF₆ ²⁺Or ZrF only₅ ²⁺And 0 or 0.01 to 1g/L Fe²⁺Mn and/or Zn ions, wherein at least one type of these ions is present in a content range of 0.01 to 1g/L, and optionally an average particle diameter of 0.01 to 2g/L based on a solid content<Fine SiO particles of 0.3 micron₂And/or optionally 0.01 to 10g/L of at least one surfactant and substantially phosphate-free and substantially phosphonate-free acidic aqueous compositions according to the invention, followed by optional rinsing with water and/or optional subsequent treatment with zirconium-based complex fluorides, silanes and/or at pH<Aqueous combinations of organic polymers/copolymers which are stable at 6.5The object is rinsed again and at least one coating layer produced therefrom can then be lacquered at least once. Due to the surfactant content in the acidic aqueous composition of the present invention, the pre-cleaning step may optionally be omitted.

The conversion coating according to the invention thus produced can be dried and optionally also lacquered when it is free of organic polymers and free of organic copolymers, preferably without subsequent rinsing with water or preferably without aqueous post-rinsing solutions, in particular those containing silanes, organic polymers and/or organic copolymers.

Alternatively, if the conversion coating of the present invention thus produced contains an organic polymer and/or copolymer, it is preferably used without coating it with a primer, lacquer or adhesive.

The conversion coatings of the invention thus produced may also be coated, preferably at least once, with a primer, lacquer or adhesive, optionally after at least one rinsing with water and/or with an aqueous post-rinse solution. Thus, even in the case of these compositions, the same processing steps, order and method as in the alkali metal phosphating can be successfully employed as necessary.

The coatings thus produced may represent in an excellent manner an alternative to alkali metal phosphate coatings, for example iron-based phosphate coatings.

The at least one substrate with a metal surface coated according to the invention is preferably used as a construction element, as a container, as a structural or connecting element, as a profile element, as a heating element, as a complex shaped body and/or as a component in the construction industry, in energy technology, in automobile construction, in appliance construction, in household appliance construction or in machine construction.

Surprisingly, excellent coatings with excellent corrosion resistance, excellent paint adhesion and often noticeable color are obtained with the aqueous conversion compositions of the present invention. Without the subsequent use of a post-rinse solution to improve the coating properties, the corrosion resistance on the steel surface is almost as good as high quality zinc-based phosphating and is therefore significantly better than that of high quality alkali metal phosphating. Even the corrosion resistance of high quality zinc based phosphating can be achieved when using an additional post-rinse solution.

It is also surprising that an excellent alternative to alkali metal phosphating can be obtained in a relatively simple manner, which functions excellently and can be produced in a simple, environmentally friendly and optionally identical process.

The composition of the invention and the method of the invention are particularly advantageous in the chemical pretreatment of the surface of various steel substrates used in the metal working industry. It is even possible here to carry out the cleaning in one step and simultaneously apply the lacquerable conversion layer, for which purpose the three-step treatment with conversion coating cleaning, rinsing with tap water and rinsing with deionized water is entirely sufficient. In particular, bath analysis is very simple to operate, since there is little need to accurately determine anions and cations, since pH and conductivity generally provide sufficient information about the chemical condition of the bath.

The method of the invention can be used to produce a coloured, iridescent, grey or colourless (as in the case of B40) passivation layer (without painting) or a coloured, iridescent, grey or colourless (as in the case of B40) conversion coating (with painting). The passivation layer itself is also a coating made by conversion. The term "conversion coating" therefore also includes the term "passivation layer" in the sense of the present application, as long as or if for example painting is not carried out in the claims.

The process of the present invention can be used as an alternative to alkali metal phosphating or in one case even to zinc based phosphating. The products produced by the process according to the invention can be used in various ways, in particular as building elements, as containers, as structural elements or connecting elements, as profile elements, as heating body elements, as complex-shaped bodies and/or as components in the building industry, in energy technology, in automobile construction, in equipment construction, in household appliance construction or in machine construction, and for example as heating bodies, as frames, as sheets, as linings, as angle irons (winkels) or as components in the interior of automobiles or aircraft.

Examples and comparative examples

The subject matter of the invention is explained in more detail by means of examples. The examples were carried out using the substrates, process steps, materials and mixtures described below.

The following standard plates were used for coating: gardobond made of cold-rolled steel CRS from St14 DC05^®C. Gardobond made of corresponding hot-dip galvanized steel^®HDG/5 or Gardobond made from AA 5005 of AlMg1^®F, from Chemetall GmbH. Unless otherwise specified, a standard panel Gardobond was used^® C。

Aqueous conversion compositions according to table 1 were prepared. Using Gardobond^®The nonionic surfactant of additive H7438 acts as a surfactant, which ensures additional cleaning of the metal surface. Basic SiO stabilized with potassium hydroxide from Chemetall GmbH₂Dispersion Gardobond^®Additive H7157 had a solids content of 20% and an average particle size of 0.2 microns. Acrylate-based polymer dispersion 1 AC 2773 from Alberdingk has a solids content of 53%. Acrylate-containing copolymer dispersion 2 VA 294 VP from Alberdingk has a solids content of 47%. Acrylate-containing copolymer dispersion 3 AS 2084 VP from Alberdingk has a solids content of 53%. At the end of the mixing process, the polymer, copolymer, SiO₂The particles and/or surfactant are added separately to the aqueous conversion composition previously prepared. In individual experiments, ammonium molybdate was added.

In examples B45 to B48, approximately 0.02 g/L of Fe had been absorbed in the bath as a result of the pickling effect of the acidic conversion composition²⁺And (4) content. This iron content of the acid wash is thus higher than that of the other samples, Fe²⁺The content in the other samples is in the bath<0.001 to 0.01 g/L. In compositions B41 and B42, the iron contents mentioned in the table were intentionally added.

The panels were spin coated at 55 ℃ for 3 minutes, which simultaneously had a cleaning action when surfactant was present. The coated panels were then rinsed once with industrial water and then with deionized water and then dried in a drying oven at 120 ℃ for at least 10 minutes. No significant quality differences were observed when different temperatures were used.

Next, one paint layer each is applied on the conversion-coated panels: 60 toInterpon from Akzo Nobel Power Coatings GmbH at 80 micron layer thickness^®700 epoxy-polyester powder paint, 60 to 80 μm layer thickness of Alexit based on polyurethane and isocyanate from Mankiewicz^®Monolayer wet paint or Cataloguard from BASF in example B3 in a layer thickness of 15 to 20 microns^®350 Black cathodic dip-coating or Catheguard from BASF in thickness of 15 to 20 microns in examples B45 to B48^®800 cathode dip lacquers (KTL) and subsequently one layer each made of 25-30 micron fillers, 11-15 micron base lacquers and 40-50 micron clear lacquers according to Daimler Benz automotive manufacture.

The paint adhesion of the painted samples was determined in a cross-cut method according to DIN EN ISO 2409 before and after the alternating climate test for 240 hours. The corrosion resistance of the painted samples was determined in the salt spray test according to DIN 50021 in the neutral salt spray test NSS for 500 hours. Only one paint layer is applied here-unlike conventional practice in the asian and north american markets.

Surprisingly, a very high corrosion resistance of 0 mm was obtained in B44 after 1000 h in the salt spray test.

The layer weight was measured in milligrams per square meter for the applied elemental zirconium using an X-ray fluorescence analyzer. Elemental zirconium is generally an indicator of coating quality, with different amounts of zirconium metal applied being deposited using the same aqueous composition depending on the metal substrate.

In comparative examples VB1 and VB2, examples of the invention were compared internationally with Gardobond made from cold rolled steel^®The high-quality alkali metal phosphating widely used on the C plate is compared: a typical procedure in alkali metal phosphating (also known as iron-based phosphating when used on iron and steel materials) uses Gardobond^®WH performed operation = Gardobond^®A4976 is carried out on steel surfaces at 55 ℃ for 3 minutes, rinsed with deionized water and optionally subsequently with ZrF-based₆Gardolene (R) of^®D6800 washing the mixture for 5 minutes; and then dried in a drying oven at 120 c for at least 10 minutes. Alternatively, Gardolene, a post-rinse solution based on aminosilane and surfactant, is used^®D6890, makingWith a base based on two different aminosilanes and ZrF₆Of (3) a post-rinse solution Oxsilan^®9810/3 or was operated using an acrylate based organic dispersion 1 AC 2773 post-rinse solution and then dried in a drying oven at 120 ℃ for at least 10 minutes.

TABLE 1. composition of aqueous baths and general overview of the properties of the coated samples and coatings

These examples show that excellent corrosion resistance, excellent paint adhesion and often noticeable color under these conditions are obtained using the aqueous conversion compositions of the present invention despite the generally very simple composition and small content. With these compositions, both heavily pigmented and colorless coatings can be obtained. The corrosion resistance on the steel surface is almost as good as that of high quality zinc-based phosphating and is therefore far superior to that of high quality alkali metal phosphating (e.g. B3 vs VB 1).

In comparative example VB2, the coating properties were determined only after an additional second conversion treatment-this is different from the examples of the invention. The paint adhesion on the steel surface is almost as good as that of high-quality zinc-based phosphating and is therefore very significantly better than that of high-quality alkali metal phosphating. Furthermore, the aqueous conversion composition of the present invention has a rather environmentally friendly composition, is advantageous from the viewpoint of occupational hygiene and is phosphate-free.

If a post-rinse solution, such as those containing silanes, organic polymers and/or organic copolymers, is used after conversion coating according to the invention and after rinsing at least once with water, the paint adhesion achieved on the steel surface is at least as good as that of high-quality zinc-based phosphating and also the corrosion resistance is at least as good as that of high-quality zinc-based phosphating.

It has been demonstrated overall that the acidic aqueous conversion compositions of the present invention are excellent replacements for alkali metal phosphating on various types of metal substrate surfaces, and are not merely suitable replacements for iron-based phosphating on iron and steel surfaces. It has even been found that the polymetallic capacity in this treatment is such that mixtures of different types of metal surfaces can be treated simultaneously or successively in the same bath.

If ZrF₆Quilt TiF₆Alternatively, the corrosion protection may optionally be slightly impaired when used in particular on steel, compared to the measured layer properties.

When only zinc is used as the added heavy metal cation, a high quality coating is obtained even when the zinc content of the coating remains unexpectedly low and when no phosphate is added. When using only manganese as heavy metal cation, a high quality coating is obtained even when the manganese content of the coating is also unexpectedly very low and when no phosphate is added. If both manganese and zinc are used, a slight impairment is observed in some cases when no phosphate is added, compared to when only one of these heavy metal cations is used.

When using only Fe²⁺High quality coatings are also obtained when used as heavy metal cations or together with Mn and/or Zn ions. Fe from the substrate²⁺Can be resupplied from the bath of the iron-containing substrate surface by a reaction-induced pickling process. However, usually due to the circulation of the bath, it is subsequently usually oxidized to Fe³⁺And removed from the bath as a reactive component. Despite the addition of Fe²⁺But, however, doAs also in examples B41 and B42, 0.025 to 0.1g/L Fe is generally established²⁺Steady state Fe of²⁺And (4) concentration.

In the case of more permanent coatings, for example using multiple substrates, pickling in an acidic aqueous conversion composition removes the main constituents and a part of the alloying elements and can accumulate to some extent in the bath composition, then there are usually multiple cations present simultaneously in the bath, which can act in particular on the composition of the coating and can act secondarily on its properties.

If no heavy metal cations were added at all in comparative examples VB3 and VB4, in most cases poor coatings were obtained. Based on measurements by X-ray fluorescence analysis, Zn and Mn were only deposited in insignificant unmeasurable amounts compared to Zr. However, Zr is the main component of the layer and can be taken as, for example, Zr (OH)_xF_yAre present. Zn generally acts as a fluoride scavenger in the interface of the metal and the coating to incorporate less fluoride into the layer, which, according to the applicant's understanding, will lead to better results. Zn and Mn are only relatively small components of the layer and can therefore only be detected more accurately by means of photoelectron spectroscopy XPS/ESCA.

In comparable tests, when the Zr applied layer is thickest, the properties of the resulting coating are usually best. However, the Zr applied layer varies with different surface properties in the case of different grades of steel and in the case of the same grade of steel.

In these experiments, the addition of nonionic surfactant further improved the CRS Gardobond used^®And C, the cleanliness of the metal surface of the standard plate. The preliminary cleaning step can be omitted. If the addition of the surfactant is omitted compared to this, the coating properties are essentially the same, but the risk of insufficiently cleaning the metal surface is increased, which may also have a negative effect on the layer properties.

In the case of the addition of larger amounts of molybdenum, care must be taken as to the possibility of slight separation of the coating.

Organic polymer, organic copolymer and SiO₂The addition of nanoparticles has proven particularly advantageous. It should be noted herein that when the amount exceeds 0.5g/L, no foaming occursAnd there is no encrustation on the injection nozzle and the walls to cause interference.

Claims

1. Process for coating metal surfaces with an acidic aqueous conversion composition, said acidic aqueous conversion composition being a solution or dispersion, characterized in that it contains

According to ZrF₆ ^2-Calculated, total of 0.01 to 1g/L of TiF in ionic form₆ ^2-、ZrF₆ ^2-And/or HfF₆ ^2-，

0 to 1g/L Fe²⁺0.01 to 1g/L of Mn ions and/or 0.01 to 1g/L of Zn ions,

0.01 to 2g/L, based on solids content, of an organic polymer based on a (meth) acrylate/(meth) acrylic acid and/or vinyl acetate-acrylic copolymer which is stable at a pH value of <6.5,

an average particle diameter of 0 to 2g/L based on the solid content<Fine SiO particles of 0.3 micron₂，

0 to 10g/L of at least one surfactant,

0 to 10g/L of an anion selected from the group consisting of carbonate, nitrate and sulfate, when CO is present₃ ^2-Or SO₄ ^2-Time conversion to NO₃ ^-And are and

from 0 to 2g/L, calculated as the corresponding anion, of carboxylate and/or sulfonate anions which do not or hardly impair the layering,

and according to MoO₄ ^2-Calculated molybdate content and/or as PO₄ ^3-The calculated content of P-containing oxyanion is respectively<0.1g/L or 0g/L, and

the acidic aqueous conversion composition has a pH of from 2.5 to 6.5,

wherein no silanes, silanols, siloxanes and polysiloxanes are intentionally added to the acidic aqueous conversion composition and the conversion coating made therefrom is used without coating it with a primer, enamel or adhesive.

2. A process according to claim 1, characterized in that Fe²⁺The amount of (B) is 0.01 to 1 g/L.

3. The process according to claim 1, characterized in that the average particle size<Fine SiO particles of 0.3 micron₂The amount of (B) is 0.01 to 2 g/L.

4. The process according to claim 1, characterized in that the amount of the at least one surfactant is from 0.01 to 10 g/L.

5. Process according to claim 1, characterized in that the amount of anions selected from the group consisting of carbonate, nitrate and sulfate is from 0.05 to 10 g/L.

6. A process according to claim 1, characterized in that the amount of carboxylate and/or sulfonate anions is from 0.001 to 2 g/L.

7. The process according to claim 1, characterized in that the acidic aqueous conversion composition additionally contains:

a total of from 0.03 to 5g/L of ions of lithium, sodium and/or potassium,

0 to 5g/L of ammonium ions,

a total of 0 to 0.3g/L of Co and/or Ni ions,

0 to 0.8g/L each as ClO₃ ^-Calculated chlorate, according to NO₂ ^-Calculated nitrite and/or as H₂O₂The calculated amount of peroxide is calculated as the amount of peroxide,

0 to 0.5g/L of a compound according to F^-Calculated free fluoride ion, and

0 to 0.2g/L as VO₄ ^3-Calculated vanadate ions.

8. A process according to claim 7, characterized in that the amount of ammonium ions is from 0.05 to 5 g/L.

9. A method according to claim 7, characterized in that the amount of Co and/or Ni ions is 0.05 to 0.3g/L in total.

10. Process according to claim 7, characterized in that the amount of chlorate, nitrite and/or peroxide is in each case 0.01 to 0.8 g/L.

11. Process according to claim 7, characterized in that the amount of free fluoride is between 0.01 and 0.5 g/L.

12. A method according to claim 7, characterized in that the amount of vanadate ions is between 0.01 and 0.2 g/L.

13. A method according to claim 1, characterized in that the coating thus produced has a layer thickness of 0.3 to 3 μm.

14. A method according to claim 7, characterized in that the coating thus produced has a layer thickness of 0.3 to 3 μm.

15. The method according to any of the preceding claims 1 to 14, characterized in that the total applied amount of zirconium and/or titanium, measured as the element, measured with an X-ray fluorescence analyzer is between 1 and 300 mg/m.

16. A method according to any of the preceding claims 1-14, characterized in that the coating thus produced is coloured.

17. A method according to claim 16, characterized in that the coating thus produced is iridescent or grey.

18. A method according to any of the preceding claims 1-14, characterized in that the coating thus produced is a substitute for an alkali metal phosphate coating.

19. The process according to any of the preceding claims 1 to 14, characterized in that the acidic aqueous conversion composition is prepared by diluting one or both concentrates with water at a dilution factor of 5:1 to 40: 1.

20. The process according to any of the preceding claims 1 to 14, characterized in that at least one substrate having a metal surface is contacted with the acidic aqueous conversion composition for a time of from 1 second to 10 minutes.

21. The process according to any of the preceding claims 1 to 14, characterized in that the substrate having a metal surface has a temperature of 5 to 90 ℃ when contacted with the acidic aqueous conversion composition.

22. The process according to any one of the preceding claims 1 to 14, characterized in that the acidic aqueous conversion composition has a temperature of 35 to 70 ℃ when in contact with a substrate having a metal surface.

23. The process according to any of the preceding claims 1 to 14, characterized in that cleaning is carried out before the metal surface is contacted with the acidic aqueous conversion composition.

24. Process according to claim 23, characterized in that the acidic aqueous conversion composition further comprises at least one surfactant and the cleaning and conversion coating are carried out in the same process step.

25. The method according to any of the preceding claims 1 to 14, characterized in that the conversion coating thus produced is subsequently rinsed with water or with an aqueous post-rinse solution and optionally also painted.

26. A method according to any of the preceding claims 1 to 14, characterized in that the conversion coating thus produced is subsequently rinsed with an aqueous post-rinse solution containing silane, organic polymer and optionally also lacquered.

27. A method according to any one of claims 1 to 14, characterized in that the conversion coating thus produced is coated at least once with a primer, enamel or adhesive after rinsing at least once with water and/or with an aqueous post-rinse solution.

28. The method according to claim 27, characterized in that the aqueous post-rinse solution contains at least one each of a) cations selected from the group of alkaline earth metal, aluminium, titanium, yttrium and heavy metal cations, b) organic polymers, c) silanes, silanols, siloxanes and/or polysiloxanes and/or d) complex fluorides.

29. Process according to any one of the preceding claims 1 to 14, a coating is applied with an acidic aqueous conversion composition according to any one of claims 1 to 12, then optionally rinsed with water and/or optionally re-rinsed with an aqueous composition, and at least one coating thus produced is subsequently lacquered at least once.

30. The process according to any one of the preceding claims 1 to 14, the coating being applied with an acidic aqueous conversion composition based on

According to ZrF₆ ^2-Calculation of TiF in ionic form from 0.01 to 1g/L₆ ^2-、ZrF₆ ^2-And/or HfF₆ ^2-Or ZrF only₆ ^2-And 0 to 1g/L of Fe²⁺0.01 to 1g/L of Mn ions and/or 0.01 to 1g/L of Zn ions,

0.01 to 2g/L, based on solids content, of an organic polymer based on a (meth) acrylate/(meth) acrylic acid and/or vinyl acetate-acrylic copolymer which is stable at a pH value of <6.5, and

optionally an average particle diameter of 0.01 to 2g/L based on the solid content<Fine SiO particles of 0.3 micron₂And/or

Optionally 0.01 to 10g/L of at least one surfactant,

and the composition is substantially free of phosphates and substantially free of phosphonates,

optionally followed by rinsing with water and/or

Optionally followed by a rinsing with an aqueous composition based on an organic polymer, zirconium complex fluoride and/or silane stable at a pH <6.5, and

at least one coating layer thus produced is subsequently lacquered at least once.

31. The method according to claim 30, wherein Fe²⁺The amount of (B) is 0.01 to 1 g/L.

32. The method of any of the preceding claims 1-14, 17, 24, and 28, wherein the organic polymer is a copolymer.

33. The method according to claim 15, wherein the organic polymer is a copolymer.

34. The method according to claim 19, wherein the organic polymer is a copolymer.

35. The method according to claim 20, wherein the organic polymer is a copolymer.

36. The method according to claim 21, wherein the organic polymer is a copolymer.

37. The method according to claim 22, wherein the organic polymer is a copolymer.

38. The method according to claim 30, wherein the organic polymer is a copolymer.

39. A coated substrate having a metal surface coated according to the method of any one of claims 1 to 38.

40. Use of the substrates with metal surfaces coated by the process according to any of claims 1 to 38 as construction elements, as containers, as structural elements or connecting elements, as profile elements, as heating body elements, as complex shaped bodies and/or as components in the construction industry, energy technology, automobile construction, appliance construction, household appliance construction or machine construction.

41. Use of a process according to any one of claims 1 to 38 as an alternative to an alkali metal phosphating process or a zinc phosphating process.