Method of electrolytic application of metal coatings. RU patent 2509832.

FIELD: metallurgy.

SUBSTANCE: metal coating is applied by electrochemical deposition from electrolyte whereto additive of polyphosphate or the mix of polyphosphates are added in amount of 0.1-450 g per one liter of electrolyte. Note here that the metal is selected from the group of noble metals including silver and metal of platinum group.

EFFECT: higher adhesion of coatings, wear resistance, antirust properties.

4 cl, 1 dwg, 3 tbl

The invention relates to the electrolytic processing of metals and can be used when applying metal electroplating, in particular, gold, silver, copper, platinum group metals and other

In practice widely used ways of drawing on the surface

details layers of metals from solutions of electrolytes, in particular, gold, silver, copper, platinum group metals and other

Known coating technology precious metals according to GOST 8.305-84 (Coating metallic and non-metallic inorganic. Operation of the technological processes of coating)

One of the biggest problems in coating technology noble metals is contact deposition of metals - the ability of most metals coated surface to restore, to oust chemically from solutions of the precious metals. While electrolytes are polluted base metals and easily damaged, and the surface appears loose, poorly connected with the surface layer of metal, dramatically worsening the quality of coverage.

To combat this phenomenon in the known methods of application of galvanic coatings noble metals, in particular, use immersion details in the electrolyte energized with advanced coating in dilute solutions of complex compounds of precious metals, changing the degree of dissociation of complex compounds, for example, by cyanide. The potential recovery of metals at low concentrations, has a strong focus on the negative side, that together with the external current inhibit contact deposition of precious metals. It is also used pre-machining of parts with mercury (Liner V.I. Modern electroplating. M., 1967). The disadvantage technologies include very harmful conditions of work with mercury; low quality of coatings due to the fact that mercury diffuses in the part materials and coatings, undermining their properties; the complexity of implementation and low productivity with immersion parts under voltage.

Known the electrolytic method of applying a protective layer of gold on the barrier sublayer laminated strips of integrated circuits of Nickel in phosphate gold-plating electrolyte to the anode of platinum-containing on 1 l of distilled water: potassium, Tiziano-I-Aurat, K[Au(CN) 2 ], - 8...12 g/l (in terms Au); ammonium phosphate one-deputizing, (NH 4 )3PO 4 3H 2 O - 8...12 g/litre; the ammonium phosphate disubstituted, (NH 4 ) 2 HPO 4 , - 40...80 g/l; thallium nitrate, TlNO 3 , -0,005...0,015 g/l, with acidity pH 5.2...5,6 at the current density D=0,4 0,3...A/DM 2 & t=68±2ºC. (Patent RF №2341048, IPC H05K 3/18, publ. 10.12.2008 year).

The disadvantage of this method is that the high toxicity of the salts of thallium harmful effects on the staff, without additives which electrolysis loses stability.

Known phosphate additives of potassium, sodium or ammonium (Na 2 HPO 4 , K 2 HPO 4 , (NH 4 )H 2 PO 4 ) in electrolytes for increased conductivity. Table 1 shows the composition of electrolytes 1, 2, 3 for the deposition of coatings on copper and Nickel. (Handbook of electroplating in mechanical engineering. - M: Engineering, 1979. - 296 C., Il. (table str)).

Table 1.

Composition

Concentration, g/l

Temperature With

Ik, A/DM 2

KAu(CN) 2

Up to 0.5

KAu(CN) 2

Up to 0.5

Na 2 4 HPO

KAu(CN) 2

Up to 0.5

(NH 4 )H 2 PO 4

K 2 4 HPO

The disadvantage of electrolyte 1 is high toxicity, and the impossibility of obtaining high-purity coating; they may be extended use. In addition, the use of toxic components of electrolytes 1 and 2 negative impact on the environment.

To increase the electrical conductivity of electrolyte, increased deposition rate and improve properties of coatings, made of precious metals used additives electrolytes.

Introduction to the electrolyte 1 phosphate salts reduces the concentration of free cyanide, without reducing the speed of the process and partly to deaccelerate anodes in conditions of shortage of complexing agents, to increase the conductivity (electrolyte 2). But the introduction of the electrolyte orthophosphate does not resolve issues with the cleanliness of surface and structure of the precipitation is typical of the electrolyte 1.

Introduction mixture orthophosphate allows to refuse completely from free cyanide (an electrolyte 3).

Known additives in electrolytes ortho and pyro phosphates with the purpose of influence on the structure of deposited coatings. Table 2 shows the composition of the electrolyte for deposition of thick copper molding coverings described in this source. (Technical electroplating. / O. Kudryavtsev. - SPb.: Polytechnic, 2010. - 148 S.: Il. (page 94, 101)).

Table 2.

Composition

Concentration, g/l

Temperature With

Ik, A/DM 2

Cu(NH 2 SO 3 ) 2

K 2 P 2 O 7

H 2 SO 4

But the introduction of orthophosphate not affect the adhesion of the coating, gilding in these formulations are recommended to guide the sublayer. In addition, known for its low stability, and in the open literature there are no data on the influence on mechanical properties of the coating orthophosphate entered in the electrolyte.

Technical problem which solution the aim of the proposed invention is to increase the quality of deposited coatings by improving the properties of electrolyte, in particular the scattering and opacity of the electrolyte.

The goal of the project is solved that in the way of galvanic coating on the base of noble metals by electrochemical deposition, the electrolyte, according to the proposed invention, in the electrolyte enter Supplement polyphosphates or mixture of polyphosphates in quantity from 0,1 up to 450 g per litre of electrolyte.

Technical the result, achieved in the implementation of all declare a set of essential features is to increase the adhesion strength of coatings obtained (adhesion), changing patterns of coverage and consequently the change of resistance to wear, corrosion or electrical properties of the coating by use method as an additive in the electrolyte polyphosphates or their mixtures, which improved the properties of electrolyte, in particular the scattering and opacity of the electrolyte.

The invention is illustrated by figure 1, which presents the dependence of micro electro-plating, caused by electrochemical deposition of electrolyte with addition and without it on current density, where

curve 1 - silver coating obtained by electrochemical deposition from without electrolyte additives

curve 2 - silver coating obtained by electrochemical deposition of electrolyte additive polyphosphate,

curve 3 - gold coating obtained by electrochemical deposition from without electrolyte additives

curve 4 - gold coating obtained by electrochemical deposition of electrolyte additive polyphosphate.

Precious metals - metals with low corrosion activity that distinguishes them from most metals. The main noble metals - gold, silver, platinum, metals of platinum group (ruthenium, rhodium, palladium, osmium, iridium), copper.

Polyphosphates can be described by the following chemical formula: Me n (RO 3 ) n Me n+2 P O n 3n+1 , Me n H 2 P O n 3n+1

Polyphosphates are used for water softening, degreasing fiber, as a component of detergents and Soaps, inhibitor (substance that slow reaction) corrosion, catalytic Converter, in the food industry. Polyphosphates low toxicity.

As an additive polyphosphates (polyphosphate sodium polyphosphate potassium polyphosphate sodium-calcium polyphosphate calcium) or their mixture is introduced into the electrolyte quantity from 0,1 up to 450 g per litre of electrolyte. Polyphosphates are entered into the electrolyte directly or after pre-dissolution.

The claimed interval ensures the achievement of a technical result. Introduction to the electrolyte polifosfatov in quantities of less than 0.1 g per litre, does not render appreciable influence on the properties of electrolyte. The increase in the concentration of more than 450 g per litre may lead to loss of salt crystals that affects the floor, and on the equipment of electrolysis baths. In particular, can clog the anode bags and filter pumping device that causes the loss of their health.

The optimal concentration range of polyphosphates, for electrolytes of gold plating 30-190 g per litre, electrolytes of silver plating - 30-250 gr. per litre, copper plating electrolytes - 75-250 g per litre.

In the result of the use of polyphosphate when precipitation increases durability of coupling with the basis of obtained coatings (adhesion) due to the inhibition of the process of chemical recovery of the deposited metal and improvement of mechanical and corrosive properties of coatings, as a result of changes in the structure of the coating. This allows you to get a tightly coupled, malabarista floor, which can be used as directly as cover, and for the subsequent build-up in the usual galvanic processes from the standard electrolyte. Additive protects electrolytes from contamination by metals basis, simplifies the process of covering and increase productivity.

Below in table 3 as examples shows the composition of the electrolyte used in the claimed method.

Table 3.

Composition

Concentration, g/l

Temperature With

Ik, A/DM 2

KAu(CN) 2

Up to 0.5

(NaPO 3 )n•nH 2 O

KAg(CN) 2

Up to 0.5

(NH4)H2P04

(NaPO3)n·nH 2 O

Up to 0.5

(Na) 2 HPO 4

(NH 4 )H 2 PO 4

(NaPO 3 )n•nH 2 O

H 2 PtCl 6* 6H 2 O

Up to 0.5

(NH 4 )H 2 PO 4

(NaPO 3 )n•nH 2 O

Adhesion with the increase polyphosphate improving linearly and already at achievement of concentration of polyphosphates 6 g/l coatings can withstand termoobrabotki and soldering. Additive polyphosphate in the standard electrolyte copper (part 2, table 1) to receive the silver clutch cover especially in brass with low copper content, which in the standard electrolyte to get a grip fails. Illustration 1.

The strength of adhesion of coatings obtained is determined by the method of repeated bending of the samples at a coating thickness of 30 microns, and according to GOST 9.302-88 p.3.

According to the changes of mechanical properties on the concentration of additives is not linear and have expressed maxima.

For example, the microhardness of electrolytes gilding and silvering grows with increase of the current density and reaches its maximum at current density of 0.3 and 0.37 A/DM 2, respectively. The value of the microhardness of this is within the range of values 60-105 kg/mm 2 silver and 87-97 kg/mm 2 the Golden covering. Example changes in the microhardness is shown in figure 1, where the curve 1 - silver coating without electrolyte additives, curve 2 - with the addition of polyphosphate, curve 3 - gold coating without electrolyte additives, curve 4 with the addition of polyphosphate. The microhardness was measured by hardness tester PMT-3 on the end cut diamond pyramid with a load of 20,

The proposed invention allows to receive electrolytes for galvanic coating with specified by functional properties in one galvanic bath in a single process and can be used with high technical and economic efficiency without the use of expensive and dangerous electrolytes in the coating;

to provide corrosion resistance and wear resistance of the coatings.

1. The way galvanic deposition of metal coatings by electrochemical deposition of electrolyte, characterized in that into the electrolyte enter Supplement polyphosphate or mixture of polyphosphates in quantity from 0,1 up to 450 g per litre of electrolyte, this metal is chosen from a group of noble metals, including silver and platinum group metals.

2. The method according to claim 1, characterized in that into the electrolyte copper enter Supplement polyphosphate or mixture of polyphosphates in the amount from 30 to 250 g per litre of electrolyte.

3. The way galvanic deposition of metal coatings by electrochemical deposition, the electrolyte, characterized in that into the electrolyte enter Supplement polyphosphate or mixture of polyphosphates in quantity from 0,1 up to 450 g per litre of the electrolyte, thus as metal choosing copper.

4. The method according to claim 3, wherein the electrolyte copper plating enter Supplement polyphosphate or mixture of polyphosphates in the amount of 75 to 250 g per litre of electrolyte.