LU88726A1 - Method for treating the metal surface of a material composed or coated with copper and / or zinc - Google Patents

Description

METHOD FOR TREATING A METAL SURFACE OF A MATERIAL COMPOSED OR COATED WITH COPPER AND / OR ZINC

The invention relates to a method for treating a metal surface of a material composed or coated with copper and / or zinc to obtain an iridescent surface state, and also to the products obtained by the method.

The term “iridescent surface state” is understood to mean a modification of the surface state by chemical or physical means, characterized by the appearance of heterogeneous coloring shades on the metal surface. This surface condition will be called iridescence below.

The object of the present invention is to provide a simple method for improving the appearance of the metal surface and thereby making the metal surface more attractive by giving it a significant iridescence. The metallic surfaces of material composed or coated with copper and / or zinc find, for example, their application in the manufacture of claddings for doors, fireplaces, etc.

Another object of the present invention is to provide a simple method for obtaining an iridescent metallic surface of a material composed or coated with copper and / or zinc comprising a pattern (image part) not iridescent on the metallic surface in question. This process turns out to be perfectly applicable to the production of signs, paintings and, in general, decorative objects composed or coated with copper and / or zinc.

The method of the invention consists in successively treating, and in any order, the metal surface with the following three chemical reagents: sodium hyposulfite, lead (II) acetate and copper sulfate. The three chemical reagents mentioned above produce the desired iridescence by successive reactions on the metal surface.

The invention will be described in more detail in the following description.

Before implementing the process of the present invention, the metal surface of a material composed or coated with copper and / or zinc is first carefully polished and degreased, to allow proper application of the iridescence treatment. Indeed, it is fundamental for the precision of the work to have a perfectly polished metal surface and free from any trace of dirt, and grease in particular. The conventional methods of polishing and degreasing metal surfaces are perfectly suited to the present invention.

The metal surface to be treated is then immersed in a soaking container containing hot water at a temperature between 50 ° and 100 ° C, preferably between 70 ° and 90 ° C. The metal surface must be completely covered with a few centimeters of water, preferably 3 to 10 cm.

The amount of water used depends on the shape and size of the metal surface to be treated, the size and shape of the soaking container, and the desired iridescence.

While keeping the metal surface entirely under water, the various chemical reagents are then added one after the other above the surface of the bath. It is important to add the chemical reagents successively and not jointly to obtain the desired iridescence and to control the influence of each of the reactants on the final iridescence.

The chemical reagents are added in a relatively short period of time, advantageously from 3 to 15 minutes. This relatively short period of time is important in order to maintain a non-uniform concentration gradient for the various chemical reagents. In fact, a longer treatment time results in diffusion of the various chemical reagents and results in homogenization of the concentration gradient in the aqueous solution. As the iridescence is obtained by successive non-uniform reactions, the homogenization of the concentration gradient in the soaking solution is not desirable.

The different chemical reagents used in the process of the invention are sodium hyposulfite, lead (II) acetate and copper sulfate, the three reagents are necessary to obtain the desired iridescent surface state. Each chemical reagent exhibits a characteristic reaction with the metallic surface of the material composed or coated with copper and / or zinc.

Said chemical reagents are used in the form of granules or powder. The amounts of reagents used vary of course depending on the size of the metal surface to be treated and the iridescent surface state that it is desired to obtain. In general, sodium hyposulfite is used in amounts ranging from 50 to 150 g / m2 of surface to be treated, preferably from 80 to 120 g / m2 of surface to be treated, lead acetate ( II) in the range from 50 to 150 g / m2 of surface to be treated, preferably from 80 to 120 g / m2 of surface to be treated, and copper sulphate in the range from 50 to 150 g / m2 of surface to be treated, preferably from 80 to 120 g / m2 of surface to be treated. The order of addition of the various compounds depends on the coloration which it is desired to obtain and is in no way a limiting factor of the present invention.

The color or coloration obtained at a specific location on the metal surface depends above all on the local concentration of the chemical reagent used, on the temperature of the bath and naturally on the soaking time. As each reagent provides a specific coloring varying with its local concentration and its application time, the number of shades that can be obtained on the metal surface of a material composed or coated with copper and / or zinc is very high. ^

By varying the different parameters such as the concentration of said reagents, the temperature of the soaking bath and the soaking time, it is possible to vary the iridescent surface state by giving the metal surface different coloring colors.

The metal surface of a material composed or coated with copper and / or zinc is then rinsed in a second container containing clean water at room temperature, to remove all the residues of the chemical reagents remaining on the metal surface.

When the iridescence of the metal surface is not as desired, the metal surface can be reprocessed, by immersing it in the bath containing the chemical reagents in solution and drying it under an ultraviolet lamp or in the open air. without prior rinsing. This post-treatment makes it possible to obtain a more uniform and darker coloring.

Another method for obtaining a more homogeneous and darker coloration is to leave the metal surface in the soaking bath for a period of time greater than 15 minutes. In this case, however, the amounts of chemical reagents used should be slightly reduced to avoid too dark (black) coloring. It is advantageous to allow the soaking bath to cool to room temperature before removing the metal surface from the soaking bath.

The iridescent metallic surface is then dried and completely covered with a finishing varnish, for example based on polyurethane, to protect the metallic surface. In addition, this top coat gives a shiny and smooth appearance to the metal surface and allows easier handling of the product.

If desired, a "orange peel" finish varnish is applied by applying a second layer of finish varnish after the application of the first layer. This second layer forming an even more effective protective barrier against various stains such as finger stains and scratches, and allows even easier handling of said product.

According to a preferred embodiment, the metal surface of a material composed or coated with copper and / or zinc comprises a pattern (image part) which is not subjected to an iridescence treatment. This pattern or design is applied before the iridescence treatment and acts as a mask against the attack of chemical reagents. As a result, an uniridescent pattern (image part) is thus obtained on an iridescent metallic surface (non-image part).

The method of the preferred embodiment will be explained in more detail below.

As described above, the metal surface of a material composed or coated with copper and / or zinc must first be carefully polished and degreased, to allow a clean and precise application of the pattern acting as a mask. Indeed, any imperfection of the metal surface will prevent the clean and precise application of the desired pattern. The conventional methods of polishing and degreasing of metal surfaces are perfectly suitable for the present invention.

The methods of applying patterns or designs to metal surfaces are very widely known and the methods described below are given only by way of illustrative examples. Conventional methods of applying drawings, such as freehand drawing, projection drawing, drawing by sticker cut by computer or manually are commonly used and are perfectly suited to the present invention. The paints used are generally paints for metals resistant to chemical reagents and to high temperatures (above 100 ° C.), while the stickers used are generally polymer films such as polyvinyls, polyesters and the like. These polymer films are necessarily products resistant to chemical reagents and to high temperatures (above 100 ° C).

The advantage of polymer stickers is that they can be removed easily after the metal surface has been treated. In fact, the solvents generally used to remove said stickers based on polymer films do not react with metallic surfaces and they have no effect on the metallic surface both on the iridescent parts and on the non-iridescent parts.

Of course, the above methods can be used alone or together, depending on the desired effect.

Then, the metal surface comprising the pattern is treated according to the iridescence method described above.

After the iridescent treatment, the mask consisting of the metal paint and / or the sticker will be removed by conventional methods, generally using polar or non-polar hydrocarbon solvents, which do not react with the surface. metallic both on the iridescent parts and on the non-iridescent parts.

The metal surface is then completely covered with a finishing varnish as described above. This varnishing is carried out immediately after removing the mask to avoid oxidation of the non-iridescent metal surface.

According to another aspect of the present invention, it is possible to increase the impression of depth of the pattern on the metal surface of a material composed or coated with copper and / or zinc. To this end, the iridescence treatment will be preceded by a treatment of the metal surface with a strong acid, such as nitric acid, picric acid or the like. These acids by attacking the non-image parts will give a certain relief to the final motif. It is obviously important in this case to use a mask which does not react with strong acids and which can be easily removed afterwards. Once the chemical attack has ended, the strong acid residues are removed by several successive rinses with water, to avoid any contamination during the iridescence treatment which follows. Said iridescence treatment is carried out according to the method of the present invention.

If desired, this relief effect can be further increased by working the pattern with a very fine iron wool after the iridescence treatment and after removing the mask.

Claims (16)

1. A method of treating the metal surface of a material composed or coated with copper and / or zinc to obtain an iridescent surface state, characterized in that the metal surface is treated by successive reactions in an aqueous medium with 1 sodium hyposulfite, lead acetate (II) and copper sulfate, these reactions being carried out in any order. 2. Method according to claim 1, characterized in that the surface to be treated is immersed by placing it horizontally in an aqueous bath and in that one sodium hyposulfite, lead acetate (II) and copper sulfate are added non-uniformly to the surface of the bath. 3. Method according to claim 2, characterized in that sodium hyposulfite, lead acetate (II) and copper sulfate are added to the surface of the bath in the form of powder or granules. 4. Method according to claim 2 or 3, characterized in that the surface to be treated is immersed at a distance of 3 to 10 cm below the surface of the bath. 5. Method according to any one of the preceding claims, characterized in that the sodium hyposulphite, lead acetate (II) and copper sulphate are added successively, in any order, in a time interval ranging from 3 to 15 minutes. 6. Method according to any one of claims 1 to 5, characterized in that the concentration of said sodium hyposulfite varies from 50 to 150 g / m2 of surface to be treated, preferably from 80 to 120 g / m2 of surface to be treated . 7. Method according to any one of claims 1 to 5, characterized in that the concentration of said lead acetate (II) varies from 50 to 150 g / m2 of surface to be treated, preferably from 80 to 120 g / m2 of surface to be treated. 8. Method according to any one of claims 1 to 5, characterized in that the concentration of said copper sulfate varies from 50 to 150 g / m2 of surface to be treated, preferably from 80 to 120 g / m2 of surface to be treated . 9. Method according to any one of the preceding claims, characterized in that the metal surface treatment is carried out in an aqueous solution at a temperature between 50 ° and 100 ° C, preferably between 70 ° and 90 ° C. 10. A method of metal surface treatment according to any one of the preceding claims, characterized in that the metal surface comprises a pattern (image part) and in that the surface treatment is carried out only on the surface parts which do not constitute the motif (non-image part). 11. A metal surface treatment method according to claim 10 characterized in that the pattern (image part) is a mask made of a material which does not react with sodium hyposulfite, lead acetate ( II) and copper sulphate. 12. A metal surface treatment method according to claim 11 characterized in that the mask consists of vinyl. 13. A metal surface treatment method according to claim 11 characterized in that the mask consists of a paint for metals. 14. Method according to claim 10, characterized in that the metal surface treatment is preceded by a treatment with nitric acid or picric acid. 15. Product composed or coated with copper and / or zinc, characterized in that it is obtained by the process as claimed in any one of the preceding claims. 16. Product according to claim 15, characterized in that it is covered with a finishing varnish.