RU1786185C - Method of protecting steel products against corrosion - Google Patents

Abstract

Summary of the invention: after surface preparation, the steel product is subjected to plasma nitriding in an external electric field, after which a layer of polycrystalline silicon is applied by vacuum deposition to obtain the desired decorative color by interference, and then oxidation is carried out in an oxygen-containing medium.

Description

The method of protecting steel products from corrosion refers to chemical-thermal methods of processing steel, is intended to increase the corrosion resistance of their surface and give it a decorative color in outdoor conditions (category I according to GOST 15150-69) and can be used in engineering construction of buildings and structures, as well as in artistic and decorative crafts,

Various methods are known for anticorrosive protection of steel and for the preparation of a decorative color for outdoor conditions, comprising the steps of preparing surfaces, applying a protective layer and fixing. These include the galvanic method of coating chromium, copper, nickel, and other corrosion-resistant metals. accepted as prototype. According to this method, surface preparation consists in mechanically cleaning the surface to be treated, then in cleaning it from organic compounds and oxides (degreasing, etching, washing, etc.). Application of protective layers

is carried out by electrolytic deposition of corrosion-resistant metals, and the fixing operation consists in cleaning the surface from process residues (washing, drying, etc.).

However, these processes give a small spectrum of colors (and are expensive due to the use of rare and expensive metals,

There are also known methods of multilayer surface protection, on which special layers are applied, for example, a paint layer, to previously applied anti-corrosion layers to obtain a decorative color.

But these processes are expensive and harmful to humans and the environment. In addition, the most common element in nature is silicon, which is much cheaper than materials such as chromium, nickel, and the like. Silicon is used in several methods for treating metal surfaces, for example siliconizing. plasma and chemical vapor deposition. When siliconizing protected surface C

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Silicon diffusion occurs, but the coating is uneven and does not have a decorative color. In known processes of plasma spraying and chemical deposition of silicon from the vapor-gas phase, a layer of 0.2 to 5 microns or more is deposited. In this case, the silicon layer on the metal becomes porous due to the different coefficient of thermal expansion of the metal and the silicon layer; therefore, such a layer is weak and does not have a decorative color. Thus, all known coating methods do not have a wide range of decorative colors and require an additional layer to produce them, which makes the process more expensive.

The purpose of the invention is to obtain a wide range of decorative colors for the protective layer and to reduce the cost of the process.

This goal is achieved by a method of protecting steel products from corrosion, including surface preparation, applying a protective layer and its subsequent processing, different from known methods in that after surface preparation, plasma nitriding is carried out in an external electric field, a layer is applied as a protective layer by vacuum deposition polycrystalline silicon with a thickness necessary to obtain the desired decorative color by interference, and oxidation into ki is carried out as a subsequent processing sulphurous environment. Thanks to that; When purified from organic compounds and oxides, the steel surface is saturated with nitrogen atoms, it is freed of a hundred oxygen atoms and passivated by the nitride layer of the starting metal. As a result of this, a polycrystalline structure of the deposited film is formed. In this case, the applied silicon layer is dense on the one hand and has high strength, which allows the stresses in the surface layer to withstand without breaking due to the difference in the thermal expansion of the silicon and metal layers, and, on the other hand, to obtain a thin uniform polycrystalline layer - silica with a thickness of 0.05-0.15 microns, which allows interference to obtain the specified decorative color a, depending on the thickness of the layer. Due to the high refractive index (, 7), which is close in magnitude to the refractive index of diamond, it is possible to obtain a color gamut containing about one hundred saturated decorative colors and shades of the full color spectrum. It should be noted that the intensity of decorative painting of steel surfaces depends on the degree of surface roughness. Passing the film with silicon oxide increases the chemical resistance of the polysilicon film.

The saturation of metal surfaces with nitrogen is known as nitriding, which is used to passivate the surface and increase wear resistance. However, in this case, the saturation with nitrogen of the surface to be protected has another meaning, namely, heating the steel surface to the required temperature due to the heat obtained by converting the kinetic energy of nitrogen ions dispersed in an external electric field into heat. The process is carried out in a vacuum oven. By mechanical cleaning, steel billets are degreased into

0 trichlorethylene or ethyl alcohol. Beyond the introduction of preforms in the furnace, an atmosphere of dissociated nitrogen is established with a pressure of 50-1000 Pa and, by accelerating nitrogen ions in an external electric field, the preforms are heated to 550-600 ° C and simultaneously plasma nitriding of the surface. In this case, additional cleaning of the surface from organic and other contaminants, displacement occurs.

With nitrogen (removal) of oxygen from the surface and at the same time a nitride layer forms. Then, monosilane (SIH4) with a partial pressure of 30-130 Pa is introduced into the vacuum furnace with the external electric field switched off. In this case, polycrystalline silicon with a thickness of 0.05-0.15 μm is deposited on the surface of the preforms, depending on the desired decorative color, which is controlled by the deposition time and

0 partial pressure of the reaction gas (monosilane).

Upon completion of the deposition and evacuation of the furnace, the surface of the polycrystalline silicon is passivated.

5 by introducing oxygen into the furnace to atmospheric pressure and maintaining an oxygen-containing medium until the workpieces are cooled. After cooling the blanks, they are removed from the vacuum oven.

Claims (1)

0 Thanks to the described method, it is possible to obtain a thin and strong layer on the surface of metals, which, depending on the thickness, gives the product not only protective properties, but also a decorative color. Thus, there is no need to apply an additional decorative layer, thereby achieving the object of the invention. SUMMARY OF THE INVENTION A method for protecting steel products from corrosion, comprising preparing over 51786185 6 In particular, the deposition of a protective layer and a post-shield layer is applied by a vacuum deposition process, which distinguishes the polycrystalline silicon layer in that, in order to obtain a wide sheath. necessary to obtain spectrum of decorative colors and cheaper-interference of a given decorative no process, after preparing the surface-5 color, but as a subsequent processing They conduct plasma nitriding, conduct oxidation in an oxygen-containing electric field, as a protecting medium.