FR2663045A1 - Device for metal deposition on uneven surfaces - Google Patents

Abstract

Device intended for metal deposition on a substrate (S) and more particularly on uneven surfaces, of the type which includes an electrolysis cell consisting of a vessel in which treatment solutions including the electrolyte circulate and where there emerge an anode (4) comprising a central feed channel (4b) and an ejection channel (5); the said vessel (2) being bounded by the nonuniform surface (1) forming a cathode, by components made of electrically insulating material (3a, 3c) forming means for leakproofing the said vessel (2) and by the anode (4), characterised in that the anode (4) has a geometry adapted to the profile of the uneven surface (1) forming a cathode, so that the distance between anode and cathode is substantially uniform throughout the cell.

Description

Device for metallic deposition on irregular surfaces.

 The present invention relates to a device intended for metallic deposition on a substrate and more particularly on irregular surfaces.

 Metallic deposition on substrates is generally carried out either by mechanical treatment or by electrolytic treatment.

 In practice, the electrolytic treatment can be done by immersion of the parts to be treated in electrolyte baths, or else by means of electrolysis cells consisting of an enclosure partially delimited by the surface to be coated forming the electrode.

 The devices comprising electrolysis cells of this type work in principle with an internal vacuum and are intended to produce very thin deposits in excess thickness.

 In addition, these devices are only suitable for carrying out the actual electrolysis and do not also make it possible to carry out the prior operations of pickling, degreasing, etc. which must therefore be done separately with another device.

 Furthermore, such devices are used to coat substantially flat or regular surfaces and are unsuitable for treating hollow or irregular surfaces such as cavities.

 The present invention aims to solve these technical problems satisfactorily.

 This object is achieved in accordance with the invention by means of a device intended for metallic deposition on a substrate and more particularly on irregular surfaces of the type which comprises an electrolysis cell consisting of an enclosure in which treatment solutions circulate. of which the electrolyte and to which an anode comprising a central supply channel and an ejection channel open; said enclosure being delimited by the irregular surface forming a cathode, by elements of electrically insulating material forming sealing means of said enclosure and by the anode, characterized in that the anode has a geometry adapted to the profile of the irregular surface forming cathode such that the distance between anode and cathode is substantially uniform throughout the cell.

 According to another characteristic of the invention, said anode is partially removable and interchangeable.

 According to a particularly advantageous characteristic, said sealing means also form means for positioning and fixing the cell on the substrate.

 According to yet another characteristic, said sealing and fixing means comprise a base surrounding the irregular surface to be coated and provided with a holding member by suction cup effect.

 The device of the invention is very reliable and allows the automation of the electrolysis process while considerably increasing the kinetics of the deposit.

 The invention also makes it possible to obtain, due to the regularity of the electrolysis parameters (agitation, temperature, current density, etc.), physico-mechanical characteristics of the very precise and perfectly reproducible deposits or alloys.

 In addition, it makes it possible to obtain certain mechanical characteristics which it is impossible to obtain in the traditional way by immersion in simple salt baths. (Ex: hardness, structure, porosity, etc.).

The invention will be better understood on reading the description which follows, accompanied by the appended drawings in which
Figure 1 shows a sectional view of the device of the invention.

 In this figure, the substrate S has an irregular surface materialized by a cavity 1.

 The device of the invention overcomes the technical problem which consists in coating the wall of this cavity 1 with a metallic deposit, the characteristics of which are imposed strictly and independently of the rest of the substrate.

 The device shown in Figure 1 comprises an electrolysis cell consisting of an enclosure 2 intended to contain the various treatment solutions including the electrolyte.

The enclosure 2 has a small volume and is delimited in the lower part by the wall of the cavity 1 forming a cathode, laterally by the sealing means 3 of the cell and in the upper part by the anode surface 4a of the anode 4.

 The sealing means 3 consist of elements made of insulating material from an electrical point of view and also have the function of positioning and fixing the cell on the substrate.

The fixing is carried out by clamping on the substrate, or by means of suction cup or magnets or even by means of mechanical means external to the cell (for example manipulator ...)
They include a base 3a which rests on the substrate surrounding the cavity to be treated, cooperating with a holding member 3b of said base on the substrate operating by suction or suction effect.

 Said base 3a is advantageously made of polypropylene and its thickness is optimally determined to laterally isolate the anode surface 4 from the cathode surface 1 while minimizing the volume of the enclosure 2.

 The sealing means 3 also comprise a support element 3c of the anode surface 4a connected to the base 3a and ensuring the sealing of the enclosure in the upper part jointly and peripherally with the anode surface 4a. This support element 3c is also made of an electrical insulating material and preferably of polypropylene.

 The anode surface 4a has a geometry adapted to the profile of the wall of the cavity 1 forming a cathode surface so that the air gap in which the electrolyte circulates has a substantially uniform width in the enclosure 2.

 The anode 4 also includes a central channel 4b opening into the enclosure 2 and intended for supplying said enclosure 2 with treatment solutions including the electrolyte.

 The anode may consist of a soluble material (nickel, copper, cadmium, zinc, etc.) or preferably of a material insoluble in the electrolytic solutions considered (lead, lead alloy, platinum, platinum or rhodium titanium, etc.).

 The anode surface 4a is removable and can be replaced totally or partially by another anode surface of different profile advantageously adapted to the shape of the cavity to be treated.

 The enclosure 2 is provided with an ejection channel 5 opening into said enclosure 2 and produced or mounted through the support element 3c. The ejection channel 5 is optionally connected to a pumping device for recirculation or evacuation.

 Of course, the anode 4 and the cathode surface of the cavity 1 are connected to electrical supply means so that the phenomenon of electrolysis can occur.

Example
Hardness obtained from a Watt nickel bath of conventional formulation without organic additive.

0 520C Stirring speed: 0.5 m / s
DDC 5A / dm2 10A / dm2 30A / dm2
Hardness 240 250 360
(HV / 100g)
DDC = current density
HV / 100 g = Vickers hardness under a load of 100 g.

 Conventionally, it is practically impossible to exceed a DDC of 8A / dm2, the rate of renewal of the ions in the cathode film being too low and therefore such high hardnesses cannot be reached.

 For hard chrome plating baths, the deposition speeds varying in a ratio of 5 to 10 compared to traditional devices are obtained using the same method with the device of the invention.

Claims (7)

1. Device intended for metallic deposition on a substrate (S) and more particularly on irregular surfaces of the type which comprises an electrolysis cell consisting of an enclosure in which circulate treatment solutions including the electrolyte and where an anode opens (4) comprising a central supply channel (4b) and an ejection channel (5); said enclosure (2) being delimited by the irregular surface (1) forming a cathode, by elements of electrically insulating material (3a, 3c) forming sealing means of said enclosure (2) and by the anode (4), characterized in that the anode (4) has a geometry adapted to the profile of the irregular surface (1) forming a cathode so that the distance between anode and cathode is substantially uniform throughout the cell. 2. Device according to claim 1, characterized in that said anode (4) is partially removable and interchangeable. 3. Device according to claim 1 or 2, characterized in that said sealing means also form means for positioning and fixing the cell on the substrate. 4. Device according to claim 3, characterized in that said sealing and fixing means comprise a base (3a) surrounding the irregular surface (1) to be coated and provided with a holding member (3b) by suction effect or sucking. 5. Device according to claim 4, characterized in that said base (3a) is made of polypropylene. 6. Device according to claim 1 or 2, characterized in that said anode 4 is made of a material insoluble in the electrolytic solution. 7. Device according to claim 1 or 2, characterized in that said anode 4 is made of Pb or a Pb alloy.