RU2293138C2 - Coating of polladium and its alloys applying method on metallic articles - Google Patents

Abstract

FIELD: application of coatings of palladium and its alloys with noble metals such as silver, gold, platinum, rhodium, ruthenium and with some non-noble metals such as copper, antimony, bismuth, tin, lead, nickel, possibly in microelectronics, electrical engineering, electrochemical systems.

SUBSTANCE: method comprises steps of degreasing, chemical etching and(or) activating, washing out and treating articles with plating solution of cyan free salts of applied metals such as nitrates, halides in organic solver selected from alkyl phosphates, sulfur-containing solvent, acidic acid and (or) propylene carbonate at temperature 20 - 150°C. Ammonium chloride, bromide or rhodanide and also monohydric or multihydric alcohol is added to plating solution.

EFFECT: possibility for applying thin-layer high adhesion strength coatings of palladium and its alloys upon metallic parts at controlling thickness of coating, its physical and chemical properties, increased wear resistance of parts in different conditions.

2 ex, 2 tbl

Description

The invention relates to the coating of palladium and its alloys with noble (silver, gold, platinum, rhodium, ruthenium) and some base metals (antimony, bismuth, lead, tin, nickel, copper) on parts made of copper and copper alloys, nickel and its alloys, ferrous, mild, alloyed and stainless steels. Such coatings are used in microelectronics (printed circuit boards), in electrical engineering (contacts, switching elements, wires), in electrochemical devices and devices (anodes, bipolar plates and separators of electrolyzers). A thin palladium coating is also used as an intermediate barrier layer, inhibiting the diffusion of the metals of the substrate and coating, for example copper from the substrate into a gold or silver coating. Thin-layer coatings of palladium and its alloys are of interest for the currently actively developed hydrogen energy devices, in particular thermal diffusion filters for hydrogen purification.

The most common method of coating palladium and its alloys on metal parts is electrodeposition (galvanic method) from aqueous solutions of electrolytes [N.F. Melashchenko. Galvanic coatings with noble metals. Directory. M., Engineering, 1993].

Water electrolytes have also been developed for the electrodeposition of palladium-nickel, palladium-cobalt, and palladium-indium alloys, which have found application in technology. The disadvantage of galvanic palladium from aqueous solutions is that, together with the electrodeposition of the coating, hydrogen is released at the cathode, while palladium is hydrogenated, which leads to internal stresses in the coating, cracking, porosity and deterioration of the physical and mechanical properties of the coating. In addition, the galvanic method is not applicable for coating parts of complex shape having internal surfaces where there is no electric field, as well as for local metallization, where it is difficult to supply electrical contact.

Known currentless chemical (autocatalytic) method of palladium from aqueous solutions using reducing agents (derivatives of borohydrides, hypophosphite). [N.F. Melashchenko. Galvanic coatings with noble metals. Directory. M., Engineering, 1993; S.Ya. Griliches, K.I. Tikhonov. Electrolytic and chemical coatings. Leningrad, Chemistry, 1990]. The disadvantage of this method is the low chemical stability of the chemical reduction solutions, which, along with the low application rate and hydrogenation of the coating, impedes its wide technological use. In addition, palladium coatings obtained by this method contain up to 15% impurities of boron or phosphorus, which reduces the ductility of the coatings and sharply narrows their scope.

A known method of coating of noble metals on metal parts [US Pat. RF №2112077]. According to the patent, the process is carried out in non-aqueous media, which allows to improve the adhesion of the coating to the substrate, as well as to avoid hydrogen disturbance and the associated deterioration of the physical and mechanical properties of the coating (stress in the coating, cracking). The method of applying a coating of noble metals includes degreasing, chemical etching and / or activation, washing and processing of parts with a metal solution. The essential features of the method are the treatment of prepared metal parts at 20-150 ° C with a metal solution of non-cyanide metal salts of nitrates, halides in an organic solvent from the group of alkyl phosphates, for example trimethyl phosphate, tributyl phosphate, sulfur-containing solvents, for example sulfolane, and / or acetic acid, and / or ethylene glycol and / or propylene carbonate.

In terms of the set of essential features, this technical solution is the closest to the claimed invention and is accepted by us as a prototype.

However, the prototype method does not allow you to adjust the thickness of the coating and apply coatings from alloys of palladium with other metals.

The objective of the invention is the creation of a new method that allows to apply thin-layer adhesive-resistant coatings of palladium and its alloys with noble and some base metals to metal parts, control the thickness of the coating, its physicochemical properties and increase resistance to wear under various types of exposure.

According to the invention, in order to solve this technical problem in the proposed method for coating palladium and its alloys with noble and base metals on metal parts, including the preparation of parts, for example, degreasing, chemical etching and / or activation, washing and processing of the prepared parts with a metalizing solution of non-cyanide salts precipitated metals, for example, nitrates, halides in an organic solvent from a number of alkyl phosphates, sulfur-containing solvents, as well as vinegar hydrochloric acid and / or propylene carbonate at a temperature of 20-150 ° C, a metallated solution is further added additive chloride, bromide or ammonium rhodanide and an additive of a monohydric or polyhydric alcohol, e.g., ethyl, isopropyl, glycerol. Distinctive features of the prototype method, ensuring the achievement of the objective of the invention, is the introduction of a metal solution of an additive of ammonium chloride, bromide or rhodanide and an additive of a monohydric or polyhydric alcohol, for example ethyl, isopropyl or glycerol. The method of processing metal parts with a metal solution of the specified composition is unknown in the scientific, technical and patent literature and is new.

The proposed method allows to realize the following advantages compared to the prototype method. Firstly, it allows one to purposefully obtain a number of palladium alloys with noble and base metals, specifically coatings from alloys Pd-Au, Pd-Ag, Pd-Ru, Pd-Pt, Pd-Sb, Pd-Bi, Pd-Pb, etc. e. alloys with different structure and properties. X-ray phase analysis showed that the Pd-Au alloy (example 8) has a solid solution structure, and the Pd-Bi alloys (examples 13, 14) and Pd-Pb (examples 15, 16) form intermetallic compounds. The melting temperature of Pd-Pb and Pd-Bi alloys is 300-600 ° C lower than the melting temperature of pure palladium, and this allows to achieve the effect of “tinning” the surface of the part with a palladium alloy during heat treatment of the coating and to obtain a continuous non-porous coating.

With the introduction of gold into the alloy with palladium, the plasticity of the coating increases by 25-30%, and with the introduction of ruthenium by 10-15% the resistance to electrical spark erosion of electrical contacts increases. The coating on a brass electrocontact from a silver alloy with 1-2% palladium with a thickness of 0.2-0.3 micrometers was tested at a specialized enterprise and passed the standard tests for contact resistance, moisture resistance, corrosion resistance in salt fog and service life with multiple short circuit- opening.

Secondly, the proposed method allows to obtain a palladium coating that does not contain impurities of boron and phosphorus, with a thickness of from 0.01 to 1 micrometer, which is necessary to solve a number of technical problems, for example, the creation of effective thermal diffusion hydrogen filters, protective coatings for parts of electrolyzers, etc. .

In general, the invention by introducing these additives of salts and alcohols expands the range of palladium coatings, allows you to adjust their thickness and other technical characteristics of the coatings, for example resistance to various types of wear, which is the technical result of the invention.

For each particular option, depending on the substrate metal, the required thickness and coating composition, the composition of the metal solution and the coating mode are selected. Table 2 shows the data of the prototype method and specific examples of the implementation of the proposed method.

Example 1

Metal parts are degreased using standard techniques [Electroplating. Handbook., M., "Metallurgy", 1987], either using an organic solvent or chemical or electrochemical degreasing, washed with water, then in alcohol and in an organic solvent, on the basis of which the metal solution is composed. After washing, the part is treated with a metal solution at a temperature of 20-150 ° C either by immersion in baskets, or in drums, or using other suitable technological methods. Both preparatory operations and treatment with a metal solution are carried out with mechanical stirring of the solution or under the influence of vibration or ultrasonic vibrations. The finished coating after washing and drying can be processed by known methods that improve the properties of the coating, namely mechanical processing, for example, tumbling with glass or steel balls, painting with brass or silver brushes, as well as thermal or chemical (e.g. chromating) treatments. Specific examples of the production of coatings from palladium and its alloys on various metal substrates are given in tables 1 and 2.

Example 2

Palladium-silver alloy coating on a curly copper disc with a diameter of 200 and a thickness of 2 mm. The technological process is described in table 1

Table 1 No. Operations Performance one Degreasing Rub with a coarse calico flap with moist Viennese lime 1-2 times until the surface of the part is completely wetted with water 2 Flushing Three times immersion in a container with distilled water 3 Activation Immersion in a 5-7% aqueous solution of hydrochloric acid (ChP), 30-60 s four Water flushing Three times immersion in a container with distilled water 5 Dehydration Immersion for 30 s in a container with highly purified alcohol 6 Coating Immersion in a metal solution: 17 g / l palladium chloride (ChP), 1 g / l silver nitrate and 10 g / l ammonium chloride (ChP) in trimethylphosphate at a temperature of 70-75 ° С with holding for 3 min while shaking the part 7 Flushing Washed sequentially in a solvent bath (about 1 min) and two baths with distilled water 8 Drying The washed part is air dried

Get a light uniform coating, adhesive strength of 101 kg / cm ² . The coating contains, according to x-ray analysis, 60 wt.% Palladium and 40% silver. Coating thickness 0.1-0.2 microns.

From table 2 it is seen (see examples 2-5) that by introducing additives of ammonium chloride, bromide or rhodanide, as well as additives of ethyl alcohol or glycerol, it is possible to adjust the thickness of the palladium coating from 0.1 to 1.0 micrometer. Examples 8, 12, 13, 15 show that the addition of glycerol to the metal solution also allows the coating thickness to be increased by palladium-ruthenium alloys to 0.4, palladium-bismuth to 0.8, and palladium-lead to 0.9-1.0 micrometer.

table 2 No. Substrate Coating The composition of the solution Coating mode Coating characteristics Metal salt, g / l Ammonium salt, g / l The solvent, vol.% Additive, vol.% Temperature ° C Time min Thickness, microns Adhesive strength, kg / cm ² Sod. Pd in the coating, wt.% one 2 3 four 5 6 7 8 9 10 eleven 12 Prototype method one Cu-Zn Pd PD-ats. - 2 - UK-5 - 80 2 0.09 54 one hundred PK-95 The proposed method 2 Cu-Zn Pd PdCl ₂ - 0.5 NH ₄ Cl - 0.5 TMF-80 Sp-20 75 10 0.1 one hundred one hundred 3 Cu-Zn Pd Pd (NO ₃ ) ₂ - 10 NH ₄ Br - 8 PK-75 Sp-25 75 10 0.2 101 one hundred four Cu Pd Pd (NO ₃ ) ₂ - 10 NH ₄ CNS - 8 PK-90 IS-10 90 10 0.4 109 one hundred 5 Cu-Zn Pd PdCl ₂ - 16.5 NH ₄ Cl - 10 TMF-40 Glitz.-20 90 10 1.9-2.0 105 one hundred DMSO-40 6 Cu-Zn Pd-au PdCl ₂ - 1.1 NH ₄ Cl - 2 TBF-98 SP-2 75 10 0.4 118 1,5 HAuCl ₄ - 10 7 Fe-Cr-Al Pd-au PdCl ₂ - 10 NH ₄ Cl - 6 Sul-98 SP-2 75 10 0.1 120 80 HAuCl ₄ - 1.2 8 Ni Pd-au PdCl ₂ - 2 NH ₄ Cl - 4 TMF-98 Glitz.-2 90 3 0.7-0.8 150 four HAuCl ₄ - 10 9 Cu Pd-ag Pd (NO ₃ ) ₂ - 10 NH ₄ Cl - 6 TMF-95 - 75 5 0.2-0.3 103 25 AgCl - 5 UK-5 10 Cu-Zn Pd-ag PdCl ₂ - 17 NH ₄ Cl - 10 TMF-100 - 75 5 0.2-0.3 101 60 AgNO ₃ - 1 eleven Cu Pd-ru PdCl ₂ - 10 NH ₄ Cl - 10 PK-95 Sp-5 80 fifteen 0.3 108 3 RuCl ₃ - 20.5 12 Fe-Ni Pd-ru PdCl ₂ - 10 NH ₄ Cl - 10 PK-98 Glitz.-2 90 10 0.4 102 1,5 RuCl ₃ - 12.5 13 Cu Pd-bi PdCl ₂ - 10 NH ₄ Cl - 10 PK-95 Glitz.-5 75 twenty 0.8 87 36 Bi (NO ₃ ) ₃ - 16 fourteen Ni Pd-bi PdCl ₂ - 6 NH ₄ Cl - 10 TMF-80 - fifty 10 0.5 110 44 Bi (NO ₃ ) ₃ - 12 PK-20 fifteen Ni Pd-pb Pd (NO ₃ ) ₂ - 10 NH ₄ Br - 8 PK-90 Glitz.-10 90 twenty 0.9-1.0 90 41 PbBr ₂ - 12 16 Cu Pd-pb PdCl ₂ - 12 NH ₄ Cl - 8 TMF-95 Glitz.-5 90 twenty 1,1 one hundred 36 PbCl ₂ - 12 17 Cu Pd-sb PdCl ₂ - 10 NH ₄ Cl - 6 TMF-90 - fifty 5 0.3 96 6 SbCl ₃ - 5 Sul-10 UK - acetic acid, PC - propylene carbonate, Sp - alcohol, TMF - trimethyl phosphate, DMSO - dimethyl sulfoxide, Glycine - glycerin, TBP - tributyl phosphate, IS - isopropyl alcohol, Sul - sulfolane

Claims (2)

1. The method of coating palladium and its alloys on metal parts, including degreasing, chemical etching and / or activation, washing and processing of parts with a metal solution of non-cyanide salts of the deposited metals - nitrates, halides in an organic solvent from the group of alkyl phosphates, sulfur-containing solvents, acetic acid and / or propylene carbonate at a temperature of 20-150 ° C, characterized in that an addition of ammonium chloride, bromide or rhodanide and an addition of one heavy or polyhydric alcohol. 2. The method according to claim 1, characterized in that ethanol, isopropyl alcohol or glycerol is introduced into the metal solution as an additive of a monohydric or polyhydric alcohol.