ES2742948T3 - Procedure for application with adhesive resistance of a sol-gel layer on a metal surface - Google Patents

Abstract

Procedure for the application with adhesive resistance of a layer of sol-gel on a metallic surface, comprising: - producing an oxide layer on a metallic surface by treating the metallic surface at a temperature of 600ºC to 1500ºC in an atmosphere with an oxygen content of 22-100% by volume or by oxygen plasma, - apply a liquid sol to the metal surface, the sol comprising a silane of the formula Si (OR ') 4-nR "n, where n = 0 , 1 or 2, dissolved in a solvent, where each OR 'independently represents a hydroxyl, alkoxy and / or cycloalkoxy moiety and each R ", if present, independently represents an alkyl and / or cycloalkyl moiety , - Let the sun react to give a gel by evaporating the solvent and curing the gel.

Description

DESCRIPTION

Method for the application with adhesive resistance of a sol-gel layer on a metal surface Background of the invention

The present invention relates to a method for applying adhesive strength of a solgel layer on a metal surface.

Sol-gel coatings are non-metallic hybrid inorganic or polymeric materials from colloidal dispersions, the so-called brine. Starting materials are also called precursors. From them finer particles are formed in the solution in the first basic reactions. The powders, fibers, layers or aerogels can be produced by a special post treatment of the brine. Hydrolysis of precursor molecules and condensation between the resulting reactive species are the main basic reactions of the sol-gel process. The processes and properties of the precursor molecules have a decisive influence on the resulting material properties.

The adhesive strength of sol-gel coatings on metal surfaces has a wide dispersion depending on the coated metal, depending on the metal to be coated and the pretreatment.

Extensive research has shown that good adhesion to metal surfaces is only achieved if the metal surface to be coated has a homogeneous layer of metal oxides. Sol-gel coatings of adhesive resistance cannot be obtained on metal surfaces without an oxide layer. Based on this experience, the state of the art prefers metals that already form oxide layers with environmental oxygen, such as aluminum, stainless steels and titanium.

State of the art

As a general rule, sol-gel coatings are applied to stainless steels, aluminum and titanium after a previous treatment by degreasing in the existing, naturally formed oxide layers. This generally results in good results with stainless steels and titanium, except on mechanically burnished surfaces. In the case of aluminum, a thin oxide layer is applied by electrochemical oxidation (anodization) of approx. 1 to 3 m thick before coating, generally before pretreatment. In carbon steels and Corten steel, an adhesive resistance coating is not possible because naturally formed oxide layers do not allow sufficient bonding of the coating and are not even resistant to corrosion. This leads to poor adhesion of the sol-gel layers and to the shedding of the layers by subsurface oxidation.

On mechanically burnished surfaces on stainless steel and aluminum, it is not possible, as a rule, to achieve sufficient adhesion strength. Obviously, the high mechanical load and deformation of the material combined with the action of the polishes leads to the formation of oxide layers with poor conditions for a high-quality, homogeneous and firmly bonded sol-gel coating.

The object of the invention is to provide a method for the application of adhesive strength of a sol-gel layer on a metal surface. This is achieved through the process according to the claims.

From EP 1816219 A1 a process for the heat treatment of steel strips by direct flame heating is known.

EP 1975 128 A1 discloses a process for the manufacture of titanium oxide coatings on various substrates.

Document PE 0 967 297 A1 refers to a process for the manufacture of articles provided with a silicone film coating.

Brief Description of the Invention

The present invention relates to a method for applying adhesive strength of a solgel layer on a metal surface, which comprises: producing an oxide layer on a metal surface by treating the metal surface at a temperature of 600 ° C at 1500 ° C in an atmosphere with an oxygen content of 22-100% by volume or by means of oxygen plasma, apply a liquid sun on the surface of the metal, the sun comprising silanes of the formula Si (OR ') 4- ⁿ R " ⁿ with n = 0, 1 or 2 dissolved in a solvent, each OR 'independently representing each other a hydroxyl, alkoxy and / or cycloalkoxyl moiety and each R' comprising, if present, independently of one another. alkyl and / or cycloalkyl moiety, allow the suns to react to form a gel by evaporating the solvent and curing the gel.

A metal surface can be a smooth surface of a metal. A metal surface can also be a previously treated metal surface such as a polished or granulated surface. A metal surface can also be a metal surface with a passivation layer, such as, for example, an oxide layer present on a metal surface. The oxide layer provided on this metal surface by the method according to the invention differs from any existing passivation layer in the form of an oxide layer on the metal surface.

The oxygen content in the atmosphere is 22-100% by volume, preferably 30-90% by volume, more preferably 40-80% by volume.

The treatment of metal surfaces is preferably carried out in a period of 1 to 20 seconds.

It is especially preferable that the atmosphere does not contain sulfur compounds. It is also preferable that the process does not include an additional organic waste disposal step of at least one metal surface.

The layer thickness of the oxide layer is preferably from 10 nm to 200 nm, more preferably from 20 nm to 100 nm.

The special results of the process according to the invention can probably be explained by the fact that during the short-term treatment of the metal surface at temperatures above 1000 ° C, iron and aluminum oxides are chemically formed very resistant by reaction. In this way, a-AhO ³ aluminum oxide can be formed above 1000 ° C and, therefore, above the melting temperature of aluminum. At temperatures above 1000 ° C, a-Fe ² O ³ can also be formed, which is also chemically very stable. Both forms of oxide are hardly corroded by hydrolysis or acids. The very short treatment time of the process according to the invention also prevents critical heating of the underlying lower metal surfaces (below).

A method for applying adhesive strength of a sol-gel layer on a metal surface comprises the manufacture of oxide layers on metal surfaces as described above. The application of the sol-gel layer is usually added directly, without additional steps of the process being provided. In addition, the process comprises, on the corresponding treated metal surface, the application of liquid soles on the at least one metal surface, preferably by immersion, flooding, spraying or propagation, and allowing the soles to react to give a gel, preferably by means of evaporation of the solvent.

Optionally, a gel curing step is performed, preferably from 160 ° C to 300 ° C for a period of 10 to 45 minutes.

The sol comprises a silane dissolved in a solvent of the formula Si (OR ') ^4-n R " ⁿ with n = 0, 1 or 2, each independently representing OR' each representing a hydroxyl, alkoxy and / or cycloalkoxyl moiety and each R ", if present, independently represents an alkyl and / or cycloalkyl residue.

The sun also preferably comprises one or more elements of the group consisting of Al, Ti, Zr, Mg, Ca and Zn. The thickness of the oxide layer is preferably from 100 nm to 2 | im, more preferable from 200 nm to 1.8 | im, more preferable from 300 nm to 1.7 | im, even more preferable from 500 nm to 1 , 5 | im and even more preferably from 800 nm to 1 | im.

Through the process according to the invention, a material comprising a metal with at least one oxidized metal surface and a sol gel layer thereon can be produced.

The layer thickness of the oxide layer is preferably from 100 nm to 2 µm, more preferably from 200 nm to 1.8 µm, more preferably from 300 nm to 1.7 µm, more preferably from 500 nm to 1.5 | im and even more preferably from 800 nm to 1 | im.

The layer thickness of the sol-gel layer is preferably about 6 | im, more preferably about 0.5 5.0 | im, more preferably 1.0-5.0 | im, or 0.5- 3.0 | im and more preferably 1.0-4.0 | im. Preferably, the sol-gel layer has a uniform thickness with variations of less than 10% of the thickness of the layer.

The metal is preferably selected from carbon steel, Corten steel, metal with chrome surfaces, metal with mechanically burnished surfaces, stainless steel and aluminum.

Detailed description of the invention

Within the framework of these investigations, it has been shown that the quality of the oxide layers may be different and dependent on the conditions in which they were created. Furthermore, it has been shown that the structure and properties of the oxide layers have a strong influence on the adhesion strength of the subsequent applied sol-gel layers. The chemical stability and corrosion resistance of the oxide layers is an essential factor for the permanent adhesion of the sol-gel layers to the oxide layers as an adhesive base. The sol-gel layers are generally not completely devoid of pores. Through these pores, corrosive media can penetrate and weaken the oxide layer. The degradation of the oxide layers with low corrosion resistance can lead to the subsequent dissolution of the sol-gel layers.

It has been shown that the conditions under which the oxide layers were created can lead to recognizable differences in their structure and properties. This has a direct influence on the adhesive strength of the sol-gel layers subsequently applied.

Extensive studies on the parameters of the formation of oxide layers on metal surfaces and the resulting properties and their influence on the adhesive strength of the sol-gel layers have shown that the temperature and oxygen content of the atmosphere during the formation of The oxide layers have a significant impact on the adhesive strength of the sol-gel layers subsequently applied. This new and surprising embodiment led to the development of the procedures that are based on the invention in question.

The procedures known and applied according to the state of the art for the pretreatment of metal surfaces before sol-gel coating are used at temperatures below 10 ° C and consist of wet chemical processes.

The process step for the production of an oxide layer on a metal surface comprises a treatment of metal surfaces with high temperatures in the range of preferably 800 ° C to 1200 ° C, especially preferably from 1000 ° C to 1200 ° C , in combination with a rich oxygen supply of more than 22% by volume, that is, an oxygen content greater than that of the Earth's atmosphere, preferably 22-100% by volume, more preferably 30-90% by volume. The appropriate temperature is chosen according to the metal to be coated and the quality of its surface.

Therefore, the oxygen content in the atmosphere is 22-100% by volume, preferably 30-90% by volume.

The treatment is preferably carried out either by treatment with a gas flame (subjected to flame), which has a significant excess of oxygen and, therefore, is very oxidized, or by treatment with an oxygen plasma. In the case of a gas flame, the remaining components that are used in the combustion of the flame and make up the atmosphere are fuels such as propane, butane, a mixture of propane / butane, hydrogen and methane.

As a general rule, the duration of treatment amounts to 1 to 10 seconds. In this regard, only a thin layer of surface material is heated without the underlying metal undergoing any significant change. The treatment of metal surfaces is preferably carried out in a period of 1 to 10 seconds.

It is particularly preferable that the atmosphere with an excess of oxygen does not contain sulfur compounds. Suitable gases for inflammation are gases that do not comprise sulfur components or sulfur compounds. These can lead to the formation of metal sulphides and affect the coating capacity.

Atmospheric plasma oxide layers, on the other hand, are not suitable for pretreatment, since the high nitrogen content of about 78% by volume in the natural atmosphere leads to the adhesion of metal surfaces. A sol-gel layer of adhesive resistance cannot be applied on these surfaces. The oxides produced at high temperature under excess acidity lead to significantly improved adhesive strength and homogeneity of the applied sol-gel layers. As a result, some metals may also be provided with sol-gel layers of high-quality adhesive strength, in which this was not previously possible, such as carbon steels, Corten steel and chrome surfaces, as well as on burnished surfaces. mechanically on stainless steel and aluminum.

Another advantage of the treatment according to the invention is that the organic residues on the surfaces to be coated, which can adversely affect the adhesive strength of the coatings, are also reliably removed. Therefore, in a single step, both the metal surface can be prepared with an oxide layer, and organic waste can be removed, providing a simplified procedure. Therefore, it is preferable that the process does not comprise any additional step of removing organic waste from the surface of at least one metal surface.

The process according to the invention preferably comprises the application of the liquid sun on at least one metal surface by immersion, flooding, spraying or propagation, and allowing the sun to react to give a gel by evaporating the solvent and curing the gel, preferably from 160 ° C to 300 ° C for a duration of 10 to 45 minutes.

The sol comprises, in dissolved silane, a solvent of the formula Si (OR ') ^4-n R " ⁿ with n = 0, 1 or 2, where each OR' independently represents the rest of a hydroxyl, alkoxy and / or moiety or cycloalkoxy and each R ", if present, represents an alkyl and / or cycloalkyl moiety.

The sun further preferably comprises one or more elements of the group consisting of Al, Ti, Zr, Mg, Ca and Zn. The sol-gel layers on treated surfaces according to the invention are characterized by significantly improved adhesive strength and homogeneity compared to the sol-gel layers on conventionally treated surfaces.

To determine the adhesive strength, test methods such as the Rockwell test, the cross-linking test, the scratch resistance test, the extraction test or the folding test were used.

In the Rockwell test (VDI guideline 3198), a diamond cone with defined force is pressed on the surface of the layer. In the environment of hardness printing, the layer is damaged, which in the microscope can be recognized as a network of cracks or as layer notches in the area of the edge of the print. The evaluation of flaking around printing can be carried out either according to VDI guideline 3198, classifying in adhesion classes 1-6, or by digitally evaluating images of flaked surface parts, which It results in a more objective and subdivided evaluation more precisely.

In the case of the crosslinking test, the adhesive strength is determined by continuous cuts at right angles to each other, resulting in a lattice. The scratch resistance test used to evaluate the adhesive strength of organic film systems such as varnishes and coating products used in flat and smooth sample plates, the sample material with a uniform layer thickness is applied on plates flat test with the same surface finish. After drying, the adhesive strength is determined by guiding the sheets against a lathe tool or rounded cylinder, which is loaded with weights until the varnish layer separates from the substrate. The extraction test determines the minimum tensile force necessary to extract or tear a single layer or multilayer paint perpendicular to the surface. Unlike the shear force load of the scratch resistance test, with this method the coating is loaded with maximum tensile force. For the test, a dolly is attached first to the coating perpendicularly. After the adhesive has cured, a test device is connected to the bearing and is aligned to create a tension perpendicular to the test surface. The force is gradually increased and monitored in a controlled manner until the coating surface detaches or a certain value is reached.

In the folding test, the sheets coated with a defined radius are folded 90 ° depending on the thickness of the sheet D (x times D) on a spike. It is determined from which radius the coating is detached in the folding area. The multiplier serves as a parameter. A second parameter is the value of how many degrees the sheet can be folded above 90 ° without the coating coming off.

Through the application of flame or oxygen plasma, solder-gel layers of adhesion resistance can be obtained on carbon steel, Corten steel and chromed surfaces, as well as on mechanically burnished surfaces on stainless steel and aluminum.

It is understandable to the person skilled in the art that a sol-gel layer is first applied in the form of a liquid sun with colloidal particles floating therein, which then becomes a gel and finally forms a layer of solid varnish and hard. If there is also talk of "the application of the sol-gel varnish" or about "the cure of the sol-gel varnish", the person skilled in the art knows in what state the sol-gel system is.

Sol-gel coatings generally consist of two reaction components, which are mixed in a fixed proportion to each other shortly before processing. To this mixture is finally added as a third component a dilution, usually an alcohol. By dilution, the concentration of the reaction mixture and the viscosity of the finished precipitate are adjusted. The sol-gel is preferably a silica sol based on silanes that are dissolved in solvents, further including the silica sol preferably one or more additional sun-forming elements, preferably one or more elements of the group formed by Al, Ti, Zr, Mg, Ca and Zn, substituting these elements to the atoms of Si in the colloidal structures. The preferable sol-gel coatings / sol-gel varnishes are described in EP 2145980. This refers in particular to the sol-gel coatings described in EP 2145980, as well as to the process for their application.

The starting compounds for the formation of the sun and, finally, the sol-gel varnish are hydrolysable silanes of formula SiR ⁴ , the 4 residues R comprising hydrolysable residues OR '2-4 and non-hydrolysable residues R "0-2. Therefore, these starting silanes can also be represented as Si (OR ') ^4-n R ” ⁿ with n = 0, 1 or 2. If used Additional sun-forming elements as described above, the appropriate compounds should be selected according to the values of the elements as starting compounds, such as AlR ³ , etc.

The OR 'hydrolyzable moieties are hydroxyl, alkoxy and / or cycloalkoxy moieties. Suitable examples include hydroxyl, methoxy, ethoxy, n-propoxy, isopropoxyl, n-butoxy, i-butoxy, t-butoxy, pentoxyl, hexoxyl, cyclopentyloxy, cyclohexyloxy residues, with ethoxy, n-propoxy residues being particularly preferable. isopropoxy. The OR 'hydrolyzable moieties may be the same or different from each other.

The non-hydrolysable moieties R ", as present, are alkyl and / or cycloalkyl moieties. Examples suitable for this include, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, i-butyl, t-butyl, pentyl, hexyl, cyclopentyl, cyclohexyl moieties, methyl, ethyl moieties being especially preferable , n-propyl and isopropyl. The non-hydrolysable moieties R "can also be the same or different from each other.

The starting compounds of the sun may consist of a single type of silane, but often comprise mixtures of several silanes (and, where appropriate, sun-forming starting compounds of other elements). It is preferable that at least one of the components of the starting compounds is a silane of the formula Si (OR ') ^4-n R " ⁿ with n = 0, that is, Si (OR') ⁴ . For example, a preferred sol-gel layer may comprise the starting materials TEOS (tetraethoxyortosilane) and mTe S (methyltriethoxysilane) and / or DMDES (dimethyldiethoxysilane).

In addition, other additives commonly used in the field of sol-gel systems can also be used, such as additional network formers, such as acryloxypropyltrimethoxysilane or methacryloxypropyltrimethoxysilane, which may allow for greater organic crosslinking, in particular if an insignificant part of the starting compounds are the so-called network converter compounds of the formula Si (OR ') ^4-n R " ⁿ with n = 1 or 2.

In the sun, the starting compounds are partially hydrolyzed to the corresponding hydroxyl compounds (for example, orthosilicic acid, trihydroxyalkylsilane, etc.), which can be facilitated by the addition of a catalyst, such as acid. Due to the high tendency to condensation of these hydroxyl compounds, these can now be condensed by dividing water into smaller siloxane networks. In the sun there are already colloidal particles that contain siloxane bonds. The siloxane bonds are bonds of the form = Si-OS¡e, where "=" symbolizes three arbitrary independent links with each other with other elements, especially with OH, OR 'and R ", resulting in a three-dimensional cross-linked structure in the particles colloidal In this respect, OR 'and R ”have the same meaning as before.

The application of the sol-gel varnish can be done in any way, for example, by immersion, flooding, spraying or spreading. However, it is preferably done by spraying, since this allows precise control of the amount applied per unit area.

In this regard, the quantity can be adjusted as necessary. For example, a sol-gel layer may have a layer thickness of about 6 | im, or about 0.5-5.0 | im, preferably 1.0 5.0 | im, or 0.5- 3.0 | im and more preferably 1.0-4.0 | im. Preferably, the sol-gel layer has a uniform thickness with variations of preferably less than 10% of the layer thickness.

The viscosity of the sol-gel varnish can be adjusted by the person skilled in the art. It is known that the sun, in a correspondingly high dilution, is very fluid enough in its solvent to penetrate the pores of a surface. It is known that the sun, in a correspondingly high dilution, is very fluid enough in its solvent to be applied by splashing, spraying, rolling or brushing.

Suitable solvents for the sun are water and especially alcohols such as methanol, ethanol, n-propanol or isopropanol, ethanol and isopropanol being especially preferred due to their physical properties and the low toxicity of their vapors.

Consequently, the applied sun is allowed to react to give a gel. This reaction transforms the liquid sun into a layer of solid gel in which the colloidal particles of the sun cross-link with each other through increased hydrolysis and condensation and with non-hydrolyzed and condensed starting compounds. This can happen, for example, by evaporation of the alcoholic solvent upon drying.

After drying the surfaces, the sol-gel coatings can be burned, forming a ceramic structure that adheres firmly, is resistant to aging and resistant to environmental influences. The burning of the coating can be carried out by the person skilled in the art according to the usual procedure. For example, surfaces coated with the gel are treated with a thermal cure, for example, at 250 ° C. This happens at elevated temperatures, in which the gel is transformed into a colorless, transparent layer, similar to glass. The silica sol components are transformed into an even more crosslinked silicon dioxide to, depending on the composition of the underlying sun, be able to contain other components such as aluminum oxide, titanium oxide or zirconium oxide. These layers are hard, closed and resistant to many of the chemicals with which A surface may come into contact under normal circumstances and temperatures of up to approximately 500 ° C.

According to a preferred embodiment, the coated surface is subjected to temperatures of 160 ° C to 300 ° C, especially preferably 160 ° C to 250 ° C and more preferably 160 ° C to 220 ° C during subsequent curing. of the gel. This curing should be performed for a period of at least 10 minutes, preferably 20 to 45 minutes, for example, 30 minutes. Curing is preferably carried out at temperatures between 180 ° C and 250 ° C, for example at 200 ° C, but temperatures below 180 ° C are also suitable. In doing so, the gel becomes a hard, colorless and transparent varnish, similar to glass, which seals the surface firmly, in turn, does not present cracks and gives the surface a high hardness and wear resistance.

The gel formation and curing processes can overlap, since, for example, gel formation by drying and evaporating the solvent can take place at least partially even at the beginning of the curing treatment. Also such a procedure, in which the gel formation and gel curing processes overlap, is encompassed by the invention.

However, other conventional curing procedures can also be carried out.

The invention also relates to a Corten steel with a treated surface, which contains a colorless, transparent coating, on a surface of the Corten steel, the surface treatment being carried out according to a method according to the present invention. Corten steel according to the invention differs structurally from known corten steels, recognizable by their color and properties, such as corrosion resistance.

As sol-gel coatings / sol-gel varnishes, for example, POLIANT or POLISEAL de POLIGRAT are used.

The object of the invention is also to produce a metal comprising an oxidized metal surface by a method described above.

The layer thickness of the oxide layer is preferably from 100 nm to 2 µm, much more preferably from 200 nm to 1.8 µm, much more preferably from 300 nm to 1.7 µm, even much more preferably from 500 nm to 1.5 | im and even more preferably from around 800 nm to 1 | im.

The object of the invention is also a material comprising a metal with at least one oxidized metal surface and a sol-gel layer thereon, the material being produced according to a procedure described above.

The layer thickness of the oxide layer is preferably from 100 nm to 2 µm, much more preferably from 200 nm to 1.8 µm, much more preferably from 300 nm to 1.7 µm, even much more preferably from 500 nm to 1.5 | im and even more preferably from around 800 nm to 1 | im.

The layer thickness of the sol-gel layer is preferably about 6 | im, much more preferably about 0.5-5.0 | im, much more preferably 1.0-5.0 | im, or 0.5 -3.0 | im and most preferably 1.0-4.0 | im. Preferably, the sol-gel layer has a uniform thickness with variations of less than 10% of the layer thickness.

The metal is preferably selected from carbon steel, Corten steel, metal with chrome surfaces, metal with mechanically burnished surfaces, stainless steel and aluminum.

Examples:

Example 1 (Comparison Example)

A 1 mm thick DIN A5 stainless steel sheet made of 1.4301 material with a mechanically polished specular gloss surface was cleaned with a dipping grease, rinsed with water, air dried and covered with a layer of sol-gel in a spray procedure. Subsequently, the surface was cured in air for 30 minutes at a temperature of 250 ° C.

After cooling, the coating could be rubbed in places with the thumb. In a 90 ° folding test with a curvature radius of 5 times the sheet thickness, the coating completely detached in the deformation zone.

Example 2:

A stainless steel sheet according to example 1 was degreased and dried in this way. Subsequently, the The surface was subjected to the flame with an oxygen-rich (blue) gas flame for 3 seconds and coated with a sol-gel layer after cooling in a spray procedure. Subsequently, the surface was cured for a period of 30 minutes at a temperature of 250 ° C.

After cooling, the coating adhered firmly and could not be rubbed with the thumb. In a 180 ° folding test with a curvature radius of 5 times the sheet thickness, the coating in the deformation area showed no shedding or cracking.

Example 3: (Comparison example)

A sheet of Corten steel of DIN A5 size with 1 mm thickness and with a slight oxide in some parts was cleaned in an immersion grease, rinsed with water and a sol-gel coating was applied without prior treatment in a procedure of spray. It was then air cured for a period of 30 minutes at 250 ° C.

After cooling, it was possible to clean the surface surface layer with your finger. In a 90 ° folding test with a 5 x D radius, the coating completely detached in the folding zone.

Example 4:

A Corten steel sheet as shown in the example was cleaned in an immersion grease, rinsed with water and dried. Subsequently, it was subjected to the flame with a gas flame (blue) rich in oxygen for 5 seconds. After cooling, the coating adhered firmly and could not be rubbed with the thumb. In a 180 ° folding test with a radius of 5 times the thickness of the sheet, the coating did not peel off and showed no cracks or detachment in the folding zone. In a subsequent salt spray test for 400 hours, the surface showed no corrosion.

Example 5: (Comparison example)

A sheet of Corten steel was oxidized by pretreatment in a solution with 15% hydrogen peroxide and then a sol-gel layer was applied in a spraying process and burned at 250 ° C for 30 minutes.

The layer could not be rubbed with the finger and passed the folding test with a radius of 5 times the thickness of the blade at 90 ° without detachment. In a subsequent saline spray test, the surface showed significant corrosion after 40 hours. The high corrosion resistance of the surface in example 4 compared to example 5 shows the influence of the quality of the oxide layer shown in example 4 by the process according to the invention based on the coating.

Claims (5)

1. Method for the application with adhesive resistance of a sol-gel layer on a metal surface, comprising: - produce an oxide layer on a metal surface by treating the metal surface at a temperature of 600 ° C to 1500 ° C in an atmosphere with an oxygen content of 22-100% by volume or by oxygen plasma, - applying a liquid sun to the metal surface, the sun comprising a silane of the formula Si (OR ') ^4-n R " ⁿ , where n = 0, 1 or 2, dissolved in a solvent, where each OR' represents independently of each other a hydroxyl, alkoxy and / or cycloalkoxyl moiety and each R ", if present, independently represents an alkyl and / or cycloalkyl moiety, - Let the sun react to give a gel by evaporating the solvent and curing the gel. 2. Procedure for the application with adhesive resistance of a sol-gel layer on a metal surface according to claim 1, the oxygen content in the atmosphere being 30-90% by volume. 3. Method for applying adhesive strength of a sol-gel layer on a metal surface according to claim 2, the oxygen content in the atmosphere being 40-80% by volume. 4. Method for the application with adhesive resistance of a sol-gel layer on a metal surface according to one of claims 1 to 3, the treatment of the metal surfaces being carried out in a period of 1 to 10 seconds. 5. Method for application with adhesive resistance of a sol-gel layer on a metal surface according to any of the preceding claims, wherein the metal is selected from carbon steel, Corten steel, metal with chrome surfaces, metal with mechanically burnished surfaces , stainless steel and aluminum.