SU910833A1 - Melt for applying magnesium coatings - Google Patents

Description

(B) MELT FOR APPLICATION OF MAGNESIUM COATINGS

The invention relates to the application of metallic coatings by immersion in molten salts and, in particular, to the deposition of coatings of magnesium and its alloys, and can be used in the engineering, metallurgical, chemical and other industries of the industry.

A powder composition for applying a magnesium coating on the surface of aluminum for its surface alloying is known. The coatings are applied in a mixture containing, in wt.%: Magnesium 70-85, ammonium chloride 2-5, magnesium oxide - the rest. Chemical and thermal treatment is carried out in a container with a fusible bolt for 2 hours.

The disadvantages of this composition are the laboriousness and duration of the preparatory operations for coating and the dustiness of the atmosphere in the process of preparing the saturation of the mixture.

The closest to the technical essence of the present invention is a melt for applying magnesium coatings containing magnesium chloride and alkali metal chlorides. The magnesium coating is applied at t10-50 ° C and a cathode current density of 0.006-0.012 A / cm.

However, the known melt does not allow to obtain on the cathode surface

10 solid coatings. Only individual magnesium dendrite crystals were obtained. Such coatings cannot be used to protect products against oxidation and corrosion, since they do not completely overlap the surface of the substrate and are poorly adhered to the substrate. Additional equipment (generators or rectifiers) is needed for electrolysis.

The aim of the invention is to improve the continuity of coatings and simplify the process technology.

Claims (2)

The goal is achieved by the fact that the melt, including magnesium chloride and alkali metal halides, additionally contains magnesium or magnesium alloy powder and alkaline earth metal chlorides selected from the group comprising calcium, strontium and barium chlorides, with the following ratio of components, weightD: Powder magnesium or magnesium alloy 2-10 alkaline-earth metal chlorides selected from the group consisting of calcium, strontium chloride, barium 2-32 magnesium chloride 5-50 alkali metal haloedins Else The melt is prepared by mixing the components ntovy in the set ratio. The formation of coatings consumes magnesium powder or its alloy, which makes it possible to obtain diffusion coatings without applying a current. The introduction of alkali metal chlorides allows the melting point of the molten salt to be reduced. Calcium, barium and strontium chlorides are used as alkali earth metal chlorides. If the melt contains less than 2% magnesium powder or its alloy, the coating thickness is small. If the powder is greater than Q%, the melt becomes very viscous, resulting in large melt losses with recoverable parts. If the melt contains less than 10% or more than 50% magnesium halide, the melting point of the salts increases and The salt process is in a frozen state. Chemical-thermal treatment of products with magnesium powder is carried out in an open bath at liOO-Si O C (below the melting point of magnesium, 650 ° C). For carrying out the process above 650 ° C, magnesium powder is replaced with magnesium alloy powder with silicon, nickel, cobalt, titanium and other metals and the treatment is carried out at 660-800 C. Chlorides and fluoride are used as alkali metal halides. Additives of fluoride increase the thickness of the diffusion 55 layer, the concentration of magnesium in the coating and reduce the volatility of the melt. The processing time is determined by the required coating thickness and varies from 2 to 10 hours. To obtain a uniform coating, the melt is stirred with a mechanical stirrer. Example 1. In the melt containing, wt.%: Magnesium chloride 50; calcium chloride 2; sodium chloride 40; sodium fluoride 3; magnesium powder 5; load parts from copper at 450C. With an exposure time of 2 hours, the thickness of the diffusion layer is 12 μm, and at 5 hours - 30 μm. Example 2. In the melt containing wt.%: Magnesium chloride 10; barium chloride 3 potassium chloride 5; lithium chloride kO; magnesium powder 2; (Samples of aluminum are loaded. After 2 hours, a coating of a thickness of CO microns is obtained, after 4 hours - 70 microns. Example 3. A melt containing, in wt.%: magnesium chloride 10, strontium chloride 2, potassium chloride, lithium chloride 36; fluoride sodium 5; magnesium alloy powder with titanium 2; samples of aluminum bronze are loaded at 5 hours, a coating is obtained with a thickness of 30 μm Example: For copper samples lowered into a melt containing, in wt%, magnesium chloride 10; calcium chloride 32; lithium chloride, kO; sodium fluoride; magnesium powder 10; for 3 hours, a coating is obtained 35 microns. Example 5. A melt containing, in wt.%: magnesium chloride 46, barium chloride 2, sodium chloride sodium fluoride 3, magnesium alloy powder with silicon Mg, jSi 5 is loaded with copper samples and for 3 hours a coating is obtained b5 μm Example 6. On copper samples dipped into a melt containing, weightD: magnesium chloride 5, barium chloride 5, lithium chloride 58, sodium chloride 20, sodium fluoride 2, magnesium alloy powder with nickel 10, for 2 hours a coating is obtained 45 microns thick. The magnesium coating layers are uniform, non-porous, well adhered to the substrate. The magnesium content in the coating varies from 3 to 60% by weight, depending on the process conditions. The coatings are distinguished by high heat resistance and low wettability by liquid molten steel. Their surface hardness increases by 10 times in comparison with the base. The proposed melt improves the quality of magnesium coatings, simplifies the technology for producing the coating, since the process is conducted without current overlap and, accordingly, eliminates the need for equipment for electrolysis and provides diffusion coatings doped with silicon, nickel, cobalt, titanium and other metals, thereby increasing their heat resistance . The improved properties of the obtained coatings provide an increase in the efficiency of products, in particular, those working in contact with the molten metal, which makes it possible to use this invention in the national economy. Claims A magnesium oxide coating melt containing magnesium chloride and alkali metal halides, characterized in that, in order to improve the continuity of coatings and to simplify the process technology, it additionally contains magnesium powder or magnesium alloy, alkaline earth metal chlorides, selected from the group - including calcium, strontium and barium chlorides, in the following ratio of components, weight: 2-10 magnesium or magnesium alloy powder Alkaline earth metal chlorides, selected from the group including calcium chloride and, strontium and barium 2-32 magnesium chloride Alkali metal halides References Sources of information taken into account during the examination 1. USSR author's certificate No. & 12376, cl. C 23 C 9/02, 1979. 2.J. ZIndau, FV Saherwaldf. Semi-heavy metal electrolysis of the melt. - Zeitschrift filr anopganische und allgenselne Chemie, 359, No. 1-2, c. 90-101, 1968. I