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INVENTION
Russian Federation Patent RU2118401
METHOD electrochemical deposition of metal coatings
ON NATURAL MATERIALS
Name of applicant: Institute of Chemistry, Far Eastern Branch of Russian Academy of Sciences
Name of the inventor: Tatiana Arzhanova
The name of the patentee: Arzhanova Tatiana
Address for correspondence:
Starting date of the patent: 1997.08.28
Usage: jewelry making, jewelry, souvenirs. The surface of the natural materials are pretreated with acetone and 3 - 5% solution of alkali metal hydroxide or aqueous ammonia, and then forming thereon electroconductive layers sulfide, aged in air required electrodeposited metal coatings. Galvanic coatings are 100% continuity, a strong bond with the surface uniform gloss and do not contain pitting. In addition, they reproduce in detail the thin micro-relief surface of natural materials.
DESCRIPTION OF THE INVENTION
The invention relates to electrochemical plating of dielectrics, in particular to electrochemical plating of natural materials, mainly plant, to give them a protective and decorative metallic coatings and may be used in the jewelry industry, for example for jewelery, costume jewelery, souvenirs, and in other industries.
Known plating method on dielectrics, such as plastic, ceramic, gypsum, glass and wood, which consists in the fact that their surface is previously applied special composition comprising an organic resin (such as ABS), an organic solvent (0.5-1. 5 parts by weight of resin) and finely divided carbon powder (40 - 45% by weight of the resin). After curing composition obtained electroconductive film subjected to a treatment to impart hydrophilic properties to it and then the metal coating deposited by electrochemical method (US Pat. Japan N 16437, cl. 25, 1971).
However, the known method does not allow to reproduce the thin micro-relief surface of natural objects and obtain smooth mirror-bright metal coating.
Known plating method for wood comprising applying to the surface of the conductive layer of the acrylic enamel AC-588 (WTU LF 1444-68) and nickel powder, and it elektoroosazhdenie metal coatings (SU, USSR N 329041, cl. B 44 C 1/04, 1972) /
However, this method and does not provide a display of the characteristic features of the microrelief surface of natural materials, as galvanic coatings deposited on layers of paint have shagreen texture.
Known plating method and a cellulosic product, preferably paper based on the surface treatment in a 10% solution of sodium periodate for 15 minutes at 17 o C, and washing the chemical deposition of silver (Japanese Patent Application N 01-294869 cl. C 23 C 18 / 20, 1989).
The obstacles metallization natural materials include that known method is intended primarily for etching the surface of the paper and is not suitable in particular for the efficient processing of plant leaves and cones conifers since not ensure 100% adhesion strength and continuity of the metal coatings with the above dielectrics. Furthermore, in the known method is applied chemical metal deposition step which requires stabilization, and purification correction constant used for this purpose electrolytes.
The closest to the technical nature of the proposed method is a method of applying metal coatings on electrically conductive materials: plastic, ceramic and cellulose (US patent N 3620834, C 23 B 5/02, C 23 F 17/00, 1971). This method consists in treating the surface first with an aqueous or non-aqueous solution, AsCl 3, SbCl 3 or PCl 3 and then the solution containing S-ions, in particular, H 2 S, Na 2 S or NaHS, after which the surface is covered with a metal by a chemical method or electrochemical method, or series of chemical and electrochemical methods.
According to the known method on the surface of dielectric layers formed of arsenic or antimony sulfides, electrical conductivity which is insufficient for obtaining a direct electrochemical method are continuous metal coating of uniform thickness. Furthermore, the absence of pre-treatment and adversely affects the strength of its adhesion to galvanized coatings.
Object of the invention is to improve the continuity and adhesion of metal coatings strength with natural materials.
The task is achieved by the fact that in the proposed method of electrochemical deposition of metal coatings on natural materials, natural materials, the surface is pretreated with acetone and 3 - 5% solution of alkali metal hydroxide or aqueous ammonia, and then electrically sulfide layers formed by surface treatment with a solution comprising zinc salt and excess complexing sorbing it water-soluble complex of zinc compounds which are converted into zinc hydroxide, and then in its sulphide, after which the surface of natural materials treated with a metal salt solution more electropositive than zinc, and kept in air for 1 - 15 h before electrodeposition of metallic coating on it.
The surface treatment is carried out in acetone for 0.5 - 300 minutes and a solution of alkali metal hydroxide or aqueous ammonia for 0.5 - 40 minutes. Moreover, surface treatment with a solution of alkali metal hydroxide or aqueous ammonia may be carried out at 30 - 55 o C. In addition, the sorption of water-soluble complex compounds on the surface of zinc is carried out for 10 - 20 and their conversion into zinc hydroxide - at 30 - 55 o C for 1 - 3 min.
Surface treatment Natural materials with acetone for a time of less than 0.5 m and 300 m high, in the first case it leads to a partial lyophilization due to incomplete dissolution of harmful pollutants in the surface itself, and working solutions, and in the second - to a deterioration of the surface properties dielectrics.
The lower limits of concentration of alkali metal hydroxide or aqueous ammonia, and the surface treatment time in these natural materials are determined starting solutions of their effective action on the surface.
When the concentration of alkali metal hydroxide or aqueous ammonia, and the surface treatment time in these natural materials above the upper limits of the solutions is the destruction of natural materials, in particular, on the surface of glossy green leaves of plants, there are many red spots.
Increasing the temperature of an alkali metal hydroxide solution or aqueous ammonia reduces the surface treatment of the natural materials. However, at a solution temperature above 55 o C to conduct this process environmentally unsafe because significant increases alkali concentration or the concentration of ammonia in the air.
Sorption of water-soluble zinc complex compounds on the surface of natural material surface depends on the processing time in a solution containing zinc salt and an excess of complexing agent. The time interval is 10 - 20, provides a fairly complete adsorption of these complexes, which leads eventually to the deformation on the surface of a solid uniform conductive sulfide layers. The conversion of water-soluble by hydrolysis of complex of zinc in zinc hydroxide compounds, having high adhesion to the surface of the natural material which is more fully at 30 - 55 o C for 1 - 3 min. The above hydrolysis time and temperature regimes and allow to obtain a sufficient amount of zinc hydroxide to convert it first into the zinc sulfide, and then the electroconductive layer sulfide.
To increase conductivity of the sulfide layer applied to a value suitable for its direct electrochemical metallization, the latter is kept in air for 1 - 15 hours depending on the kind of natural material.
The deposition of metallic coatings on natural materials with conductive sulfide layers is carried out by an electrochemical method of the electrolytes used in certain modes of electrolysis.
conifers cones, leaves of various plants, wood, cellulose, etc.: The natural materials can be used as a basis for electrochemical metallization.
When surface treated with acetone natural materials, especially the leaves, cones or coniferous trees dissolves natural waxes or resins composing them.
The processing plant leaves sodium hydroxide or aqueous ammonia dissolves cutin and wax, and wood treatment - dissolving the lignin and hemicellulose.
Thus, pretreatment of natural materials and the acetone solution of alkali metal hydroxide or aqueous ammonia results in a rough surface and freeze, and processes proposed modes sulfide forming conductive layers - to increase their conductivity, which ensures the continuity of 100% and a good adhesion strength galvanic metal coatings with dielectrics.
The advantage of the proposed method is that it allows you to efficiently and consistently applied by the electrochemical method of metal coating on a variety of natural materials, reproducing detail of thin micro-relief surface.
The process is as follows. Surface pre-treated natural material in acetone for 0.5 - 300 minutes and 3 - 5% solution of alkali metal hydroxide or aqueous ammonia at room temperature or a temperature of 30 - 55 o C for 0.5 - 40 minutes, after then forming thereon an electrically conductive layer of sulphide or lead sulphide copper as follows. Natural material is immersed in an aqueous zinc salt solution with an excess of complexant to 10 - 20 seconds, washing with water was subjected to hydrolysis at 30 - 55 o C for 1 - 3 min and treated with a solution of sodium sulfide for 3 - 5 min. Next, the natural material surface treated with a metal salt solution more electropositive than zinc, for 3 - 7 min and kept in air for 1 - 15 hours depending on the kind of natural material, whereupon it electrodeposited desired metal coating, for example matt and shiny nickel or brushed nickel and polished brass.
Example 1 The glossy sheet plants pretreated with acetone for 0.5 min, 5% sodium hydroxide solution for 4 minutes and washed with water. It was then immersed for 20 seconds in a solution (pH 8 - 10) containing zinc chloride (100 g / l) and aqueous ammonia (25%), conducts heat (at a temperature of 40-45 o C) and cold water hydrolysis washing for 2 minutes, treated with sodium sulfide (100 g / l) for 5 minutes and washed with water. Then the sheet was immersed in plants lead nitrate solution (100 g / l) for 7 min and washed with water, after which it was allowed to stand in air for one hour, and to it an electrochemically deposited thin underlayer of nickel electrolyte composition, g / l:
Ni (SO 3 NH 2)2 · 4H 2 O - 600,0
NiCl 2 · 6H 2 O - 10,0
H 3 BO 3 - 30.0
pH - 3,6 - 4,5
Electrolysis was carried out in a stirred solution at 50 - 60 o C and a cathodic current density of 3 - 4 A / dm 2. Then washed with water to the surface electrochemically precipitated bright nickel plated from the electrolyte composition, g / l:
NiSO 4 · 7H 2 O - 250,00
NiCl 2 · 6H 2 O - 30,00
H 3 BO 3 - 30,00
Chloramine - 2.00
1,4-butynediol (35%) - 1.00 ml / l
Formalin (20%) - 0.16 ml / l
pH - 4.50 - 5.50 The electrolysis is carried out in a stirred solution at 45 - 55 o C and a cathodic current density of 2.5 - 3.5 A / dm 2.
The resulting electroplated metal coating has a strong adhesion to the surface of a sheet of natural, uniform gloss and no pitting. The continuity of this coating is 100%.
Example 2 Cones were pretreated softwood acetone for 300 minutes, and a 5% solution of sodium hydroxide for 20 min. Formation of the electroconductive layer of lead sulfide on the surface bumps is carried out as in Example 1. Then, the bump layered lead sulfides kept in air for 15 hours, after which its surface is electrochemically deposited nickel of the above formulations in Example 2 solutions.
The resulting electroplated metal coating is 100% continuity, uniform gloss and a strong bond with the surface of the bumps.
Coating quality is assessed visually.
Thus, the claimed method allows to obtain not only high-quality electroplated metal coating on a variety of natural materials, but also play them thin micro-relief surface, and in the process to activate the surface not used expensive and scarce salts of precious metals, and does not apply "capricious" stage chemical metal deposition.
CLAIM
1. A method for electrochemical deposition of metal coatings on natural materials, comprising forming on the surface of the electrically conductive layers sulfide followed by application of electroplating metal coatings, characterized in that the surface of natural materials pretreated with acetone and 3 - 5% solution of alkali metal hydroxide or an aqueous solution ammonia, and forming conductive sulfide layers is carried out by treating the surface with a solution containing zinc salt and excess complexing sorption therein water-soluble complex of zinc compounds, which are converted to zinc hydroxide, and then into its sulphide, after which the surface of natural materials treated with a metal salt solution more electropositive than zinc, and kept in air for 1 - 15 h before electrodeposition metallic coating on it.
2. A method according to claim 1, characterized in that the surface treatment is carried out in acetone for 0.5 - 300 minutes.
3. The method of claim 1, wherein the surface treatment solution of an alkali metal hydroxide or aqueous ammonia is carried out for 0.5 - 40 minutes.
4. The method of claim. 1 and 3, characterized in that the surface treatment solution of an alkali metal hydroxide or aqueous ammonia is carried out at 30 - 55ºC.
5. The method according to claim 1, characterized in that the sorption of water-soluble complex compounds on the surface of zinc is carried out for 10 - 20 and their conversion into zinc hydroxide at 30 - 55ºC for 1 - 3 min.
print version
Publication date 03.01.2007gg
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