The method of applying a coating of noble metals as well as nickel, copper, mercury, indium, bismuth and antimony in metal parts

 

(57) Abstract:

The invention relates to the field of deposition of thin metal coatings on metal parts, specifically for the application of gold, silver, platinum, palladium, Nickel, mercury, indium, bismuth and antimony, and can be used in microelectronics, electrical and reflective devices, and also in the jewelry industry. The method of coating is that as metalliser solution for covered products take a solution nationistic metal salts, such as nitrates, halides, sulfates, acetates, Axalto in an organic solvent, chemically compatible with the metal salts and technologically secure. 2 C.p. f-crystals, 1 table.

The invention relates to the field of application of thin-layer metallic coatings for various applications, including protective and decorative metal parts and, particularly, to a coating of noble metals (silver, gold, platinum, palladium or their alloys with each other, and alloying additives, as well as Nickel, copper, mercury, indium, bismuth and antimony on parts of copper and copper alloys, Nickel and its alloys, black, kalogeridis, the electrical contacts, the switching elements, wires, cables, microwave equipment (waveguides, resonators), reflective devices (reflectors), as well as in the jewelry business [1].

Thin-layer Nickel and copper coatings are used as an intermediate sublayer when applying other coatings to ensure strong adhesion of the coating to the substrate, as well as for decorative articles, apparatus, devices in almost all industries.

Coating of indium and bismuth are used as anti-friction layer in the bearings, to increase the reflectivity of the mirrors and reflectors. These coatings, and layers of antimony and mercury are used in semiconductor technology [2].

Known methods of applying these coatings. Of these the most widespread and common electroplating method, in which the metal part after pre-treatment (degreasing, chemical etching or activation, rinsing) polarize cathode in the electrolyte solution, and the anodes are made of overlapping metal, with details is the electrodeposition of metallic coatings. Most high-quality coverage of the call, including potassium cyanide [1, 2, 3].

The disadvantages of electroplating method is the complexity of the coating process, due to the bulkiness of the equipment (power supply, measuring devices), the slowness of the process (hours, days), as well as the complexity of the recycling and disposal of waste. Known electroplating methods of coating of noble metals on metal parts using nationistic electrolytes (genesisintermedia, radamisty, pyrophosphates, iodide, bromide, sulphamate, ethanolamine), i.e., aqueous solutions nationistic compounds of noble metals. However, marianista electrolytes or does not provide coverage of the required quality (uneven floor, unsatisfactory adhesive strength), or ethnologica (prone to decomposition, low outputs metal precipitation current). In this regard, in industry, to cover the noble metals are widely used cyanide electrolytes [1, 2].

Also known chemical methods of applying metallic coatings without the use of electric current. An example would be the way gilding products of Nickel and its alloys [4]. According atomki pre-treatment with acid and washing with deionized water, immersed in the heated solution, containing dicyanoaurate potassium, cyanide of potassium, phosphate and water. This way, as the closest in technical essence to offer, we accepted for the prototype.

The disadvantages of the prototype method are unsatisfactory adhesive strength of the coating and environmental hazard. The main and fundamental drawback of the prototype method is unsatisfactory adhesive strength of the coating. It is associated with the chemical interaction between the surface of the metal substrate with water, thus inevitably formed or gas bubbles (hydrogen), or an oxide film, is both durable prevents the adhesion of the coating to the substrate. This leads to slezanie coating of parts (i.e., marriage) or in the process of obtaining coverage or in the operation of the products, for example, with the closure and opening of the electrical contact.

Environmental hazard way connected with the use of toxic aqueous solutions of cyanide, which leads to the need for disposal of hazardous waste, because the wastewater discharge of cyanide compounds without their prior disposal is prohibited. Thus, using the method-prototype cyanide inevitably requires utilis isih energy.

In the invention, the technical solution lies in the fact that in the known method of applying a thin metallic coating on metal parts, including degreasing, chemical etching or activation, washing and processing of the prepared parts metallorum solution, as metalliser solution a solution take nationistic metal salts, specifically, nitrates, halides, sulfates, acetates, oxalates, in an organic solvent, chemically compatible with the metal salts and technologically secure.

For each case, an organic solvent, selected from the following groups: trialkylphosphine, for example, triethylphosphate, tributyl phosphate, sulfur-containing solvents, for example, sulfolane, dimethylsulfoxide, acetic acid, ethylene glycol, propylene carbonate, or their solutions in each other. The metallation process is carried out at 20 - 150oC.

Significant difference between the proposed solution from the prototype method is, firstly, the inclusion in metallurgy solution nationistic metal salts, for example, specifically, nitrates, halides, sulfates, acetates, oxalates, instead of poisonous cyanide compounds that safely increases razlagaemogo method is the preparation metalliser solution-based organic solvent. The role of organic solvent is to dissolve compounds of metals of the coating and the substrate and to protect the surface of the metal substrate from corrosion, from the formation therein of gas bubbles and passive films, which leads to an increase in the adhesion strength of the coating. However, from the variety of organic solvents only provide some of the performance of the proposed technical solutions. The organic solvent must meet three characteristics specified in the claims. First, he must dissolve these marianista metal salts. So, for example, hydrocarbons (n-hexane, n-heptane, kerosene, diesel oil) are not dissolved metal salts and therefore unusable. Secondly, the organic solvent must be compatible with the specified asianstyle salts of metals, i.e. the solution during operation must be chemically resistant. And finally, thirdly, the organic solvent must be technologically safe from the point of view of pozarovzryvobezopasnost and physiological effect on a living organism. So, for example, acetonitrile and hexamethylphosphoramide satisfy the first and second characteristics and metallurgy solution based on each of microphase, because it applies to flammable liquids (because 81,6oC, high volatility), and hexamethylphosphoramide is a strong mutagen and refers to substances hazardous to health. All mentioned in the formula characteristics satisfies a narrow group of organic solvents, providing the efficiency of the proposed technical solutions.

The coating when heated from 20 to 150oC speeds up the process.

In addition to these metallurgy solution may contain various brightening agent additives.

Below is the data of the prototype method and specific examples of implementation of the proposed method.

Example. Metal parts degreasing standard techniques [2], washed with water, treated with one of the known solutions for chemical polishing [4], bringing the surface to a mirror finish, washed in water and then in an organic solvent, on the basis of which is composed metallurgy solution. Immediately after leaching detail process metallorum solution. Preparatory operations (degreasing, chemical polishing, cleaning and operation of the metallation is to be mechanical in the tvii vibration or ultrasonic vibrations. The finished coating after washing and drying can be processed by known methods of improving the properties of the coating, namely mechanical (surface finishing process, krzewina) thermal or chemical treatment. For example, the silver coating can be protected from tarnishing processing in chromate solutions (chromate) [1, 4].

Specific examples of the preparation of thin metal coatings on metal substrates listed in the table.

The proposed method of applying metal coatings on metal parts allows comparison with the method of the prototype:

a) increase the adhesive strength of the coating;

b) to improve process safety by eliminating from it the poisonous cyanide;

C) to protect the environment and to facilitate the disposal of waste.

So, for gold coating prepared according to the prototype method, the adhesion strength was 10 - 35 kg/cm2while the present method 63 - 90 kg/cm2. Increased adhesive strength is confirmed also in the operation of the coatings. For example, the contact device with a silver coating prepared on a copper substrate by the present method with the standard ispytaniyami coating obtained by a known method.

Determination of the adhesion strength of the coatings deposited on metal substrates was performed according to GOST 27890-88 by measuring the force required to tear the film in the direction perpendicular to its surface. Samples for testing were obtained by gluing with epoxy glue two steel bases rectangular in between flat metal plate of the same shape are printed on its surface coating.

Sources of information

1. P. M. Vyacheslavov and other electroplating of precious and rare metals. L.: Engineering, 1970.

2. Electroplating. /Directory. M.: Metallurgy, 1987.

3. Application 62-23996. Japan. class. C 25 D 3/46, publ. 31.01.87.

4. Galvanic coatings in engineering. /Directory. M.: Mashinostroenie, 1985, T. 1, S. 224.

1. Method of applying coatings of noble metals as well as Nickel, copper, mercury, indium, bismuth and antimony in metal parts, including degreasing, chemical etching and/or activation, washing and processing of prepared parts metallorum solution, characterized in that as metalliser solution a solution take nationistic metal salts, for example nitrates, Galya fact, what organic solvent taken from the group trialkylphosphates, for example trimethyl-, tributyl phosphate, or serosoderjaschei solvents, such as sulfolane, dimethyl sulfoxide, and/or acetic acid and/or ethylene glycol and/or propylene carbonate.

3. The method according to p. 1, characterized in that the processing of prepared parts metallorum solution is carried out at 20 - 150oC.

 

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