DE1015298B - Process for the surface treatment of metals by applying layers of silicate - Google Patents

Description

GERMAN

The invention relates to the production of surface layers on metals by applying a coating of silicates from solutions. To change the surface of metals, especially to achieve a protective layer against mechanical and chemical effects, are generally applied to metals, especially those which are about in thin layers are vapor-deposited, outer layers of metal oxides, preferably silicon oxide or Titanium dioxide, applied by vaporizing the metallic substrates with such oxides. However, the production of such layers is relatively expensive and, on the other hand, the The thickness of the layers is limited in many cases, as they are no longer sufficiently transparent in greater thickness to keep the color of the metal to be coated unchanged.

On an industrial scale, enamelling is used as corrosion protection, a well-known process in which various oxides or compounds forming them are melted or unmelted in the form of powder or suspensions on metals or other heat-resistant surfaces applied and then heated above the softening point, creating a uniform smooth Surface is created. For such a process, relatively high temperatures are required, and most of the time colored, thick enamel layer tends to peel off and is so brittle that it can be deformed Document is no longer possible. The latter, felt as a deficiency, are more pronounced Measure also for coatings that are made of metal oxide mixtures with a little water glass as Binders are mixed, exist, which are burned on at a lower temperature. Such coatings have a relatively rough surface because of the oxide mixture does not melt and may have to be sanded. Finally is it also known the inner walls of metallic storage containers with a suspension of calcium oxide or to spray calcium carbonate under pressures of about 10 atmospheres and the adhering particles of the Calcium compound, if necessary with a dilute solution of water glass to a small extent to spray. Such a layer, however, has such a poor adhesive strength that it can be obtained by mere Splashing can be removed again, and in this form can hardly be described as a uniform silicate layer will.

The method of the invention now shows a simple way of producing smooth, firmly adhering protective layers To apply metal surfaces, which consists in the fact that a solution of alkali silicate, which contains at least one soluble metal salt,

for the surface treatment of metals by applying layers of silicate

Applicant:
German gold and silver separator

formerly Roessler,
Frankfurt / M., Weißfrauenstr. 9

Alois Seidl, Lam (Ndb.),
has been named as the inventor

applied and the layer is then dried in the air or by additional heat. The metal salts used are preferably heavy metal salts that are in the treatment solution are contained in the form of soluble compounds. It has surprisingly been found that such Layers that can be addressed as mixed silicate layers, similar to the vapor-deposited coatings Adhere perfectly to the metal base and also for thin metal layers, such as those in the vapor deposition, sufficient protection against mechanical damage and ensure chemical influences.

The application of the layers or the treatment with the corresponding solutions can be carried out in take place in a manner known per se by dipping, brushing on or spraying, whereupon with the solution coated surface in the air or by additional heat, e.g. B. at 50 to 250 °, dried will. The layer obtained in this way can be applied by soaking the coated object and subsequently repeated drying can be improved.

Particularly good adhesive strength is achieved when the base metals are those with a high affinity for oxygen, such as B. aluminum, iron or chromium can be used. So you want on other metals achieve particularly well-adhering coatings according to the method of the invention, one becomes the Metal base advantageously first by vapor deposition or in some other way with a thin one Coating layer of aluminum, iron or chromium and the thus prepared surface of the invention Subject to treatment.

70S ¹ fiiSO / 238

It has proven advantageous to stabilize the surface layers consisting of mixed silicates proven to carry out a subsequent treatment at elevated temperatures of up to 400 ° and more, which, if necessary, can be driven so far that a part of the base metal is underneath Formation of a mixed oxide is built into the silicate layer. This is also an extraordinary one high hardening of the surface layer connected, which has a particularly good mechanical resistance guaranteed.

Temperature post-treatment can be used, in particular when covering vapor-deposited metal layers regulate so that a given amount of the metal from the substrate under transition into the non-metallic state transferred into the silicate layer and thereby the light permeability of the Layer is changed at will. If the substrate is heated unevenly during this post-treatment, so the course of the light absorption within the layer can be continuous change so that effects are achieved that are desired, for example, in anti-glare glasses.

To ensure complete wetting of curved or otherwise profiled surfaces with the treatment solution To achieve this, it is advisable to close the pad before applying the silicate solution heat.

According to the invention, the wettability (behavior when wetting) the mixed silicate layers by modifying the starting solution to a large extent Limits are changed, so that in this way, low-fog or fog-free layers on metals can be generated. For this purpose it is advisable to add iodine, for example, to the treatment solution.

You can also obtain non-wettable surface layers by the fact that the finished formed Mixed silicate layers with suitable organic compounds, for example with organic silicon compounds of the silicone type or with isocyanates, their hydrophobic Properties are known per se.

Finally, the mixed silicate layers can also be colored by adding appropriate dyes will.

The process of filing is both for the surface protection of solid metals and for thin metallic vapor deposition layers are important. So the layers created with it serve as corrosion protection or as insulating layers on transformer cores or capacitor foils be used.

A solution of the following composition, for example, can be used to carry out the process Apply to the metal to be coated: ecm water, 10 ecm sodium silicate (commercially available Water glass), 7 ecm l% silver nitrate solution, 5 ecm ethyl alcohol (10%).

Claims (6)

Patent claims: 1. Process for the surface treatment of metals by applying layers of silicate from water glass solutions, characterized in that a solution of alkali silicate, the at least a soluble metal salt, in particular a heavy metal salt, contains, optionally on the to be coated Preheated metal surface is applied and the layer is then dried in the air or with additional heat will. 2. The method according to claim 1, characterized in that as a base for the silicate layer easily oxidizable metals, preferably aluminum, iron or chromium, are used, which may be subjected to pre-oxidation before the silicate layer is applied. 3. The method according to claims 1 and 2, characterized by a subsequent temperature treatment, where optionally a part of the underlying metal is converted into the non-metallic state by bond formation with the cover layer is convicted. 4. The method according to claim 3, characterized in that by uneven subsequent Heat treatment locally different proportions of the metal base in the Silicate layer are transferred. 5. Process according to Claims 1 to 4, characterized in that solutions are used which contain coloring additives or additives which cause water repellency. 6. The method according to claims 1 to 5, characterized in that the silicate layers one Subsequent treatment with silicones or other hydrophobic substances will. Considered publications:
German patent specifications No. 671 646, 854 455,
576. © 709 560/238 p.