DE2002599A1 - Process for applying organic coatings to metallic surfaces - Google Patents

Description

"2002599 Dipl.-lng. H. Sauenland · Dn.-lng. R. König Patent Attorneys ■ 4odd Düsseldorf · Cecilienallee 7B -Telefon 43Ξ7 3Ξ

Our file: 25,626 January 20, 1970

Fuji Iron & Steel Co., Ltd., No. 2-3, 3-chome, Marunouchi, Chiyoda-ku, Tokyo, Japan

"Process for applying organic coatings to metallic surfaces"

The invention relates to a method of application organic coatings on metallic surfaces, i.e. on the natural or coated with a metal layer Surface of a metal. -

One of the objects on which the invention is based is in creating a metallic material that remains completely free of corrosion during deformation and, as a final product, excellent paintability-> shows.

The invention is further concerned with the application of an oil film to the metal in order to wear it off in this way and prevent scratches without deteriorating the adhesiveness of the paint.

As metals for the base body and the coating layer all metals come into consideration that have a chromic acid level> -

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action are corrosion-resistant, such as Steel, zinc, tin, lead, chromium, aluminum, copper, magnesium, silver and their alloys.

The chromic acid treatment according to the invention includes dipping into a Chromatiösung and galvanizing in Chromatic "solution or a chromic acid, which are carried out in aqueous solutions, wherein the main component of chromic acid anhydride, dichromate or Chromät are ₀

When immersing, the metal to be treated is immersed in an aqueous solution, the main components of which are individually or to several sodium dichromate, potassium and sodium chromate as well as chromic anhydride with additions of sulfuric acid, sulfates, nitric acid and fluorine compounds contains.

During electroplating, the metal is cathodically immersed in an aqueous solution of chromic anhydride or sodium dichromate brought, which also contains additives such as sulfuric acid, sulfates, fluorine compounds, nitric acid, manganates, May contain tungstates and molybdates. The electroplating can also be used as electrolytic treatment and chrome plating of steel in an aqueous solution of chromic anhydride with additives such as phosphoric acid, sulfuric acid, boric acid, sulfonic acid, acetic acid, hydrochloric acid, bromic acid, Hydrofluoric acid and its salts as well as fluorine compounds take place.

The coating obtained by the chromic acid process is identified as hydroxide CxCr ₂ CK α yCrO-,. 8H ₂ O), which contains trivalent and hexavalent chromium. In contrast, the coating produced on steel by the electrolytic chromic acid process consists of an upper layer of trivalent chromium hydroxide and a lower layer of metallic chromium.

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The aqueous chromium hydroxide layer applied to the metallic base body or to a metallic coated body is corrosion-resistant, but extremely chemically active, so that organic, in particular Oily substances that come into contact with the layer immediately after being coated are very strongly adsorbed will"

Therefore they have a chromium hydroxide layer Materials. Immediately after the layer formation a very strong adhesion to applied organic coatings. However, if after the layer formation an oily Substance is adsorbed in a subsequent process step, the surface properties change, so that in particular the adhesion to a melamine alkyd coating is reduced. Furthermore, the adsorbed Layer very difficult to remove with the help of conventional degreasing, so that after degreasing poor adhesion of the layer results. ;

In order to overcome the difficulty caused by the good adsorption capacity of the chromium hydroxide layer, one would have to immediately after the formation of this layer a substance are adsorbed, which is compatible with paint and which Paint adhesion is not impaired in this way an adsorption of other substances during the subsequent Process steps that lead to poor adhesion should be avoided. For this reason, the Japanese patent application Sho 42-26 458 has already been proposed the chromium hydroxide is coated with oils from an allyl * to treat esters or allyl ethers. Since here before the Applying the oil if drying is necessary, it must be considered disadvantageously accepted that organic substances or dust contained in dry air during of drying are adsorbed and lead to a change in the surface properties, so that the out of use

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benefit resulting from allyl compounds will. In the case of the use of allyl compounds in electrostatic painting or spraying, the highly reactive, unsaturated bonds of the allyl compounds lead to polymerization by way of air oxidation and increase viscosity, resulting in incomplete atomization and clogging of the nozzle. On the other hand, the use of allyl compounds contributes the emulsion method in terms of adsorption surfactants and other additives have an adverse effect. Next leads the use before organic Solvents become significant because of the risk of ignition, explosion and human adverse effects Disadvantages.

The substances adsorbed by the chromium hydroxide layer, which are intended to prevent adsorption of other substances during further treatment must not only not affect the paint adhesion and polymerize itself into the paint layer, but must also be water-soluble so that they are adsorbed evenly while the chromium hydroxide layer is still after washing with water is wet and free of other contaminants. These substances are said to be essentially after ordinary drying be insoluble and resistant to vegetable oils, which are used in subsequent process steps to protect against Abrasion and scratches are used. In addition, the substances must not be used by lubricants when molding are used, result in limited paint adhesion and must ultimately allow easy removal of these oils, before the varnish is applied. With this in mind, water-soluble binders have been selected, to solve the problems raised above.

According to the present invention, a coating, the main component of which is chromium hydroxide, is applied to the metal surface

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_ ₅ _ 20Q2599

before brought, washed with water, for a short time immersed in an aqueous solution of the water-soluble binder or sprayed while the surface layer is still wet, whereupon the workpiece is finally squeezed between rollers in order to produce a thin one even layer of the water-soluble binder to reach the layer of chromium hydroxide «,

The water-soluble binders according to the invention, being resins and forming water-soluble paints, are compatible with the paints applied to the metal and polymerize themselves into a coating layer after painting, so that the paint has better adhesiveness. In addition, the thin layer of water-soluble binder formed on the surface of the chromium hydroxide layer not only adheres firmly, but becomes practically insoluble after drying, i.e. it is not attacked by substances containing oil such as lubricants, so that degreasing can also be carried out with ease without impairing the adhesion of the organic coating _e

The water-soluble binders according to the invention leave ^ can be divided into the following five groups,

1. Oleoresins. . . ~

These resins are created by mixing rosin, ester gum, alkylphenol resin, coumarone resin, cyclopentadiene resin, Petroleum resin and mahogany nut shell oil or epoxy resin with castor oil, wood oil, linseed oil or soybean oil. and, by subsequent reaction with maleic acid or instead with fumaric acid, Itaconic acid, acrylic acid or citraconic acid.

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2. Alkyd resins.

These polyesters are made from polyalcohols such as glycerine, Trimethylolethane, trimethylolpropane, pentaerythritol, Sorbitol, diglycerine, dipentaerythritol, epichlorohydrin, allyl glycerine ether, phenyl glycerine ether as well as epoxy resin and dibasic acids such as phthalic acid, maleic acid, fumaric acid, succinic acid, Adipic acid, itaconic acid, citraconic acid or instead of the above-mentioned dibasic acids polybasic acids such as benzene tricarboxylic acid, benzene tetracarboxylic acid, Phosphoric acid, additions of rosin and maleic anhydride and maleic oils. Polyesters with polyoxymethylene bonds are also suitable, by using polyether as polyalcohol, such as polyethylene glycol and propylene glycol develop.

3, phenolic alkyd resins.

These include resole with modified alkyd resins, whose Rohbestandteil cresol, xylenol or butylphenol; Remote Egg 'with a pentaerythritol ester of diphenolic acid modified alkyd resins and eventually with a water soluble resin, which was prepared by incorporating carboxyl and then methyl groups oil modified alkyd resins.

H. Aminoalkyd resins,

Hierbai is about with methoxymethylmelamine, beisp i elrjweiüö dimethoxymethyl trimethylolmelaniin and HexamethoxyinethyIo! Melamine Alkydhor ^ eii, also uia by partial / eratherfces Pol ymetltylolmelamiii or Polymt.'th, 7iolhar "i ..:; toff modified alkyd resins as well by Polyniethylolinelamin, Alkylenpolyamlne ^ Hydroxypolyiiinine and guanidine modified alkyd resins,

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5. Acrylic resins.

These are copolymers of the Acrylic or methacrylic acid with methyl acrylate, ethyl acrylate or methyl crotonate; also to mixed polymer "risate of the alkyl ester, acrylic or methacrylic acid with vinyl toluene; furthermore to hydroxymethylated copolymers of acrylamide or methacrylamide with N-vinyl lactam; and finally around Copolymers of N-methylolamide with ethyl acrylate «

The water-soluble binders listed above can either individually or in combination to be used.

Provided a water-soluble binder on its own is used, due to the low affinity of the binder used with the base resin, some paints may only produce poor adhesion »To avoid this, it is therefore desirable to have two or more water-soluble Use binders together. Good adhesion With all types of paints, results in the use of alkyd resin binders, in which epoxy resin as Polyalcohol is used.

The amount adsorbed can be varied as desired by adjusting the binder concentration in the aqueous solution. However, the preferred concentration is 0.1 to 8% or 3 to 100 mg / m 2 in the adsorbed amount of the binder. These amounts are small in comparison with those conventionally used for water-soluble paints, in which these values are, for example, 10 to 20% in the concentration of the binder or 50 to 500 mg / dm. The binders used according to the invention have neither the purpose of underprotection nor

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that of a pore filler in the traditional sense. The use

The amount of binder, namely 3 to 100 mg / m, is completely sufficient to form a thin layer; baking is not required, just a simple removal of the water by an ordinary drying process. The layer is extremely thin, ie less than 0.1 L., so it is colorless and transparent without affecting the appearance. It does not act as a protective film, but only acts as a barrier to the adsorption of oily substances.

The lower limit of the adsorbed layer, namely 3 mg / m 2, is to be regarded as the minimum amount that is necessary is to completely cover the entire surface; smaller amounts do not produce the desired effect. The adsorbed amount of 3 mg / m 2 of the water-soluble binder corresponds to a concentration of 0.1 - 6 in one Solution. Below this concentration, the paint adhesion is insufficient if, for example, a lubricant is brought to the metallic material. on the other hand

If the amount of binder exceeds the upper limit of 100 mg / m 2, the binder layer is so thick that uneven compression often occurs when rolling or squeezing, which has an adverse effect on the appearance. The adsorbed amount of 100 mg / m corresponds to a concentration of 8% in a solution. A higher concentration and thus a larger adsorbed amount does not produce the desired effect, but affects the appearance and leads to incomplete drying. For these reasons, the amount of water-soluble binder

limited to 3 to 100 mg / m.

The metals to be treated according to the invention can be bent or drawn using lubricants can; they were then degreased and finally covered with a varnish or paint. It is essential that

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the thin binder layer firmly on the chromium hydroxide layer adheres to the fact that it is practically insoluble and does not adsorb lubricant, so that complete degreasing is possible. The binder layer is covered with common stoving colors, such as alkyd, melamine alkyd, ■. · Compatible with epoxy, epoxy melamine alkyd, acrylic and vinyl paints «, This is due to the property of the binder in the applied organic lacquer layer polymerize and increase the adhesion of the paint.

The thin layer of binder on the metal comes in handy insoluble and can never be degreased with the usual solvent such as trichlene degreasing and emulsion degreasing. However is partial removal from the surface is possible when treated with a strong alkaline degreaser containing sodium hydroxide or sodium silicate. Even with the complete removal of the fats it remains part of the binder back and thus improves the adhesion of the colors.

Even when an oily substance is used in an amount of 3 to a 10 mg / m, in order to prevent abrasion and scratching of the metal- ^v metallic surface, a direct coating is possible, without further treatment is necessary in view of a good paint adhesion is. This is probably due to the fact that the oil-containing substance is not adsorbed by the thin layer of binder, but rather diffuses into the paint without any adverse effect. "

The oils used in accordance with the invention also include. D.O.S, (di-2-ethyl hexyl sebacate), cottonseed oil and Flaxseed oil.

A better understanding of the invention emerges from the

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Examples listed below in connection with the Drawing. It shows

1 shows a cross section of a metallic material according to the invention,

2 shows a corresponding cross section of a metallic material, but the metallic base body being provided with a coating layer,

3 shows a further cross section, with an oil layer being applied to the metallic material shown in FIG.

FIG. 4 shows a further cross section, an oil layer being applied to the metallic material according to FIG. 2.

In FIGS. 1 and 2, 1 is the metallic base body, 2 is the chromium hydroxide layer and 3 is the thin layer of the water-soluble binder. In Figs. 3 and 4, 4 is an intermediate layer of a coating metal between the metal base body 1 and the chromium hydroxide layer 2, while 5 is an oil film is.

Some examples based on the teaching according to the invention are shown below.

example 1

In an aqueous solution containing 60 g / l ChromiumLiurearihydrid and containing 0.55 g / l sulfuric acid, a cold-rolled steel strip was cathodically treated to on the steel strip a double layer of chromium hydroxide and metallic To form chromium. After that, the steel belt was covered with water washed and for two seconds in a 496-ige aqueous

BATH ORIGINAL

Solution of an oleoresin immersed as a binder, the by heating a mixture of 75 parts of castor oil or ricinoleic anhydride, 5 parts of an epoxy resin (Epikote ^ 812) and 20 parts of maleic anhydride was obtained. After a compression by means of rollers, to adjust the adsorbed amount of the binding agent

The steel strip was dried at room temperature to 30 mg / m 2. In this sample, spindle oil was used to protect the surface

(iff 60) used in an amount of 2 g / m »After degreasing with trichlene steam for two minutes, a white melamine alkyd varnish was applied in a pick of 25 µm and baked. The Erichsen test with an X marking gave a value of 0/100 for the flaked surface. In contrast, a similarly treated steel holds spindle oil to its surface without adsorbed binding agent; in this case the Erichseh test gave a value of 97/100.

■ Example 2

A cold-rolled steel strip was electrolytically treated in a chromic acid solution as in Example 1, washed with water and then sprayed for two seconds with a 0.596 strength aqueous solution based on the weight of the water-soluble alkyd resin binder, the binder being produced by heating a mixture which consisted of .40 parts of castor oil anhydride, 15 parts of trimethylolpropane and 45 parts of phthalic acid. Thereafter, the steel belt was squeezed between rollers to adjust the adsorbed amount of the binding agent to 10 mg / m ² , then dried with hot air at 50 ° C. and finally provided electrostatically with cottonseed oil in an amount of 8 mg / m. After a month an alkyd coating (hammer lacquer) was applied by baking in a thickness of 25. The X test according to Erichsen gave 0/100 of the flaked surface, while the same test at

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a sample without the use of a binder gave a value of 100/100. '

Example 5

After one month, the samples were pressed according to Example 2 using a # 620 press oil at a draw ratio of 2 to a cylinder with a diameter of 40 mm and a flat bottom. After one week, the samples were immersed in cold Trichlene for one minute P and degreased and then exposed to trichloro steam for two minutes. A melamine alkyd varnish was applied to a thickness of 30 yU and baked. In the X-shaped scribing according to Erichsen on the bottom and on the side wall of the cylinder, the sample with the resin binder gave a value of 0/100, while the test on the same cylinder of the other sample, in which no binder was used, gave a value of 96 / 100 and 50/100 on the side wall.

Example 4

An electrolytically tinned plate was treated as a cathode in a 3% solution of sodium dichromate to apply a chromium hydroxide coating. Thereafter, the plate was washed with water and one second in a 0.2 # aqueous solution of a binder immersed, which consisted of 80 parts of a water-soluble alkyd and 20 parts of hexamethoxymethylmelamine. The alkyd was through Heating a mixture of 60 parts of linseed oil, 10 parts of glycerine and 30 parts of maleic acid obtained. the wet plate was squeezed between rollers to adjust the adsorbed layer to 5 mg / m 2. After drying at room temperature, D.O.S. (Di-2-ethylhexyl sebacate) in an amount of 5 mg / m using turpentii Oil substitute applied as a solvent.

A white melamine alkyd varnish was applied to this sample.

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brought and burned in, in a thickness of whereupon the product with a draw ratio of 2 to one Cylinder with a diameter of 40 mm and a flat one Bottom was deep drawn. The Erichsen experiment yielded on the ground and on the side wall of the cylinder values of 0/100 and 1/100, while the same test on a cylinder, which was deep-drawn from a sample without a binding agent, Values of 43/100 and 82/100 resulted.

Example 5 "J

A cold-rolled steel strip was galvanically coated with a 0.01 ^ thick layer of chromium hydroxide and metallic chromium in an aqueous solution of 30 g / l chromic anhydride and 0.1 g / l chromium sulfate. Immediately after washing, an aqueous solution with 6% of a binder was sprayed on, which consisted of 40 parts of partially butoxylated methylolurea and 60 parts of a water-soluble alkyd resin according to Example 2. m set, and dried by blowing warm air at 6O ^{0 C.} Then cottonseed oil was electrostatically in | an amount of 3 mg / m and anti-rust oil (Valvoline 861 Q) in an amount of 5 g / m. After three months, the sample was deep-drawn with a draw ratio of 2 to a cylinder 40 mm in diameter with a flat bottom. The cylinder was subjected to two seconds of Sprühentfettung at 60 ⁰ C with a 3% solution of Parco Cleaner # 358th Then a melamine alkyd clear lacquer was applied in a thickness of 3Q ^ and baked. The Erichsen test was carried out on the bottom and on the side wall of the cylinder and gave a value of 0/100. The same treatment would be carried out with a comparative sample. But without a binder. This resulted in incomplete degreasing, so that

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the exfoliated area gave values of 100/100 and 93/100. Furthermore, a salt spray test of the sample ^{according to the invention without an organic coating at 35 °} C. after 20 hours immediately after the application of cottonseed oil showed no rust, while the same test on a binder-free sample showed a rust ratio of 2.5%.

Example 6

P A galvanized steel strip was electrolytically treated by the chromate process in an aqueous solution containing 30 g / l of chromic anhydride and 0.2 g / l of sulfuric acid in order to form a layer of chromium hydroxide on the steel strip. Immediately after washing with water, a 1% strength aqueous solution of Resydrol P411 and phenol-modified alkyd resin was sprayed on and then the tape was squeezed between rollers in order to adjust the adsorbed amount of the binder to 15 mg / m 2. After drying, machine oil # 120 was applied in an amount of 5 g / m 2. After three months, the sample was degreased by immersion in cold Trichlene for one minute and then in Trichlene steam for a further minute. Subsequently, a Melaminalkydharzlack in a thickness of 25 / *> was applied and baked. The Erichsen test gave a value of 0/100, while a comparison sample without a binder showed a value of 38/100.

Example 7

A cold-rolled steel strip was first coated with a chromium layer 0.025 ^ thick and then treated electrolytically in a solution using the chromate process 60 g / l chromic anhydride, 5 g / l acetic acid and 0.5 g / l sodium fluorosilicate. The layer mainly contained Chromium hydroxide. Immediately after washing with

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In water, the tape was immersed for one second in an aqueous solution which contained a 1% water-soluble acrylic resin made from a copolymer of N-methyloiamide and aorylacrylate. The tape was then squeezed between rollers in order to adjust the adsorbed amount of the binding agent to 15 mg / m 2. After dem.Trocknen at room temperature, the sample with # 640 press oil was deep-drawn into a cylinder of 80 mm diameter and 60 mm depth, was immersed for degreasing one minute each in cold trichlene and 2% sodium hydroxide solution at 60 ⁰ C. Then a phthalic acid alkyd varnish 15 Å thick was applied and baked. The Erichsen test gave values of 0/100 on the bottom and on the side wall of the cylinder, whereas in the same test on a cylinder made from a similar but binder-free sample The bottom gave a value of 100/100 and a value of 97/100 on the side wall.

Example 8

A cold-rolled steel strip was subjected to an electrolytic chromic acid treatment in an aqueous solution containing 50 g / l of chromic anhydride, 0.2 g / l of sulfuric acid, and 0.4 g / l of sodium fluorosilicate to form a double layer of chromium hydroxide and chromium-containing water to apply metallic chrome. Immediately after washing with water, the tape was placed in a 1.0% strength aqueous solution of a binder mixture of 50 parts of a water-soluble oleoresin according to Example 1 and 50 parts of a water-soluble alkyd resin according to Example 2 for one minute. The tape was then squeezed between rollers in order to adjust the adsorbed amount of the binder to .15 mg / m, and then dried at room temperature. A white melamine kyd varnish was applied to a thickness of 25JUs , and burned in. The Erichsen experiment gave 0/100. On dieyPrfbe ^ w ^^ thereafter a rust protection oil (Noxrust 53OF) in .einer. _r amount .of-

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5 g / m and the sample was stored for three months. Thereafter .wurde the sample by immersing it in cold Trichlene for one minute and then treating it with Trichlene steam degreased for two minutes and a white melamine alkyd varnish applied to a thickness of 25 ^ and baked. Of the Erichsen's test yielded a value of 0/100 of the flaked Surface.

The Erichsen experiment on a similar sample to which no binder was applied gave 23/100 when the same white lacquer was applied directly, and 100/100 when the above anti-rust oil has been applied for three months.

Example 9

A cold-rolled steel strip was coated with a 0.025 / ^ thick layer of chromium and subjected to the electrolytic chromate process in an aqueous solution containing 80 g / l sodium dichromate and 2 g / l ammonium sulfate to apply a chromium hydroxide layer. Immediately after washing with water, the tape was immersed for one second in a 496% strength aqueous binder solution which consisted of 70 parts of a water-soluble alkyd resin according to Example 2 and 30 parts of a water-soluble acrylic resin according to Example 7. The tape was then squeezed between rollers and in this way the adsorbed amount of the binding agent was adjusted to 45 mg / m 2. After drying. Then at 60 ^° C. DOS ₈ (di-2-ethylhexyl sebacate) was applied in an amount of 5 mg / m. Two samples prepared in this way were provided with an alkyd white varnish and an acrylic white varnish to a thickness of 30% and fired. The Erichsen test produced a value of 0/100 for the paint layer.

Two more samples to which the binder and D.O.S. were applied with a draw ratio of 2

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using a machine oil ■ # 120 to a cylinder Deep-drawn with a diameter of 40 mm and a flat bottom. Degreasing was done by immersion in for one minute cold trichlene and two minutes with trichlean steam, then a white alkyd varnish and a white acrylic varnish with a thickness of 30 / ^. applied and baked. Of the Erichsen's test on these two samples showed no peeling the cover on the bottom and the side wall,.

On the other hand, similar samples to which no binder, but directly D.O.S. and white Alkydlaek and | a white acrylic varnish was applied, values of 97/100 or 8/100. Further comparison samples on which no binder but D.O.S. applied directly, were after degreased by deep drawing into a cylinder with a flat bottom and covered. The Erichsen test on these two samples gave values of 83/100 for the soil and 45/100 for the side wall of the cylinder with the alkyd varnish and values from 17/100 and 10/100 in the case of acrylic varnish,

Example 10

A cold-rolled steel strip was coated with chromium in an aqueous solution containing 150 g / l of chromic anhydride and 1.5 g / l sulfuric acid, a metallic chromium layer of 0.32 g / m on the strip and an aqueous one Apply a chromium oxide layer of 8 mgCr / m on the chromium layer. Immediately after washing with water, that became Tape with a 1% aqueous solution of a binder sprayed, which consists of 5 parts of a half-ester of an epoxy resin (Epicote # 812) and trimellitic anhydride and 1 part polymethyiolmelamine (Smitex resin MW). That Tape was squeezed between rollers to remove the adsorbed Adjust the amount of binder to 9 mg / m, then dry and then provided with 3 mg / m linseed oil.

Samples of a tape treated in this way were treated with oil

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white alkyd varnish, a white melamine alkyd varnish, a white acrylic varnish or polyester coating in one thickness covered by 3O ^. The Erichsen trial yielded for these samples values of 0/100,

In contrast, similar samples to which no binder, but similar coatings were applied directly, resulted were, values of 20/100, 35/100, 9/100 and 13/100,

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Claims (1)

Claims; (M 7) Process for applying organic coatings to metallic surfaces, thereby g e k e η η ζ e i chn e t,. "· that on an essentially chromium hydroxide existing layer a water-soluble binder of i Oleoresin, alkyd resin, aminoalkyd resin, phenol alkyd resin and acrylic resin is applied individually or side by side. 2 »Method according to claim 1, characterized in that the binder layer in one - ■■■■ "· ρ ■ * - , .Thickness of 3 to 100 mg / m is applied * 3. The method according to claim 1 or 2, characterized g e k e η η ζ ei c h η e t that on the binder layer an oil film is applied. 4. The method as claimed in claim 3, since d u r c h 'g e k e η η draw t that on the binder layer D.O.S. " (Di-2-ethylhexyl sebacate), cottonseed oil or flaxseed oil be applied. 5. The method according to any one of claims 1 to 4 ₉ because you rc h characterized in that a double layer of metallic chromium and chromium hydroxide is applied to the metallic surface. · 009831/1560 do Blank page