MX2010004134A - Continuous electrolytic chromium plating machine and process. - Google Patents

Abstract

The continuous electrolytic chromium plating machine and process has washing, rinsing, drying, primary current and chromium points, followed by further rinsing, compressed-air drying, secondary current and stripping points. The whole machine is communicated by a bar conveying line. The machine is based in that the process deposits the chromium at reduced pressure via chambers facilitating 1° that the hydrogen bubbles be detached from the metal substrate. 2° Facilitating the use of a closed circuit and 3° absorption of the electrolyte clouds.

Description

MACHINE AND PROCEDURE INTENDED TO PERFORM ELECTROLYTIC COATING OF CONTINUOUS CHROME DESCRIPTION Machine and procedure designed to perform electrolytic continuous chrome plating.

The present invention resides in a "Machine and method for making an electrolytic coating of continuous chrome plating".

Hard chrome plating is one of the most difficult electrolytic processes, capable of providing coated surfaces with the following properties: - hardness, - wear resistance, - low coefficient of friction, and - resistance to corrosion.

The phenomena that take place in the electrodes during the electrolysis process are basically the following: A - On the cathode: - Release of hydrogen from the electrolysis of water.

- Deposition of metallic chromium and - Reduction of hexavalent chromium to trivalent.

B - At the anode: - Oxidation of trivalent to hexavalent chromium and - Oxidation of other components.

The quality of the coating is always conditioned by the evolution of hydrogen on the cathodic surface, as well as by the deposition of metallic chromium. Hydrogen bubbles tend to remain on the surface, thus giving rise to porosity in the deposited chrome layer. When the coating behaves cathodally against the base metal, if there is a discontinuity, a corrosion pile will be formed, which will cause the oxidation of the base metal and subsequent coating cracking.

The assessment of this set of circumstances has led the technical team of the petitioner company to design a system for the manufacture of chromed bars different from those previously used and based on strictly conventional methods, all in order to offer a quality and service clearly improved and typical of a company with recognized and proven professional rigor.

In this way, a chrome-plating method has been developed, based on a continuous coating technique, totally different from other surface treatment techniques and specially designed for the chrome plating of long bars. steel of different diameters. This method is based on a machine linked to a method that is the object of this invention.

The basic idea of this method is constituted by the fact that the deposition of metallic chromium takes place under a reduced pressure, which is effected through one or several chromium chambers. The electrolyte circulates through all the chambers under a reduced pressure (about 450 ... 480 mm Hg) which: 1. It facilitates the release of hydrogen bubbles from the surface of the base metal. 2. It makes possible the use of a closed system, and 3 °. Absorbs the electrolyte mists.

The precise machine for this method of continuous chromating is a decisive step forward and a remarkable innovation in the technique of chroming, offering against conventional methods among others the following advantages; which we quote below with purely enunciative and non-limiting character: - The continuity guarantees a high quality constant surface coating (the deposited chrome layer remains constant and concentric both along and around the bars).

- The process can be controlled and adjusted in the desired way (current density, temperature, bar speed, thickness, electrolyte flow rate, characteristics and pulse wave duration, among others).

- There is the possibility of chromating long and thin bars without surface tension, which however does not occur in conventional chrome plating in an open bathroom.

- The system is completely sealed, so there is no danger of spillage, splashing in the bathroom or toxic fumes that contaminate the environment, improving working conditions equally remarkably.

- The chromium density increases due to the reduced pressure and the grain size becomes smaller. The adhesion between the base metal and the coating is improved because the electrolyte flow separates the hydrogen from the base metal, which in turn decreases the porosity.

- Improves the resistance to corrosion.

- Improves the roughness of the coating by 10-20% according to the working conditions developed.

- Increases the efficiency of the process, with which the deposit speed is higher (5-10% better efficiency than the system I conventional).

- Thanks to the fact that it is a closed system, it is not necessary to install suction systems, thus decreasing the economic costs.

Due to the uniformity of the coating the times of a later mechanized or rectified of the bars are also reduced or even annulled.

For a better understanding of this specification, the attached drawings that show an example of embodiment, not limitation, of the object of the invention and in which: The single sheet of designs presents a scheme of the machine object of this invention.

According to the attached designs the "machine and the procedure intended to perform electrolytic coating of continuous chrome plating" is articulated as follows: Firstly and as a prior operation, the bars (1) are placed on rollers (2) and are centered by means of a suitable device, the bars are joined with one another to achieve continuity. Then they run through a series of stations, which make up the machine.

A- Washing station consisting of a washing chamber (3) under pressure by closed circuit whose purpose is to eliminate any remaining dirt produced by the own handling of the bars prior to coating. With a proper degreasing chamber through which circulates the liquid from a closed container (4). B- Rinsing station consisting of a chamber lower than the previous one (5) with another closed circuit of pressurized water whose function is to eliminate the possible residues of degreasing housed in the surface of the bars, and this in order not to contaminate the subsequent processes. The waste goes to a water tank (6) equipped with a settling ramp (7).

C- Drying station, where drying is effected by compressed air issued by a tube (8).

D- Primary power and current station.

Beside this system there are brushes (13) through which the current takes place in the bars (a and c).

E- Chroming station, consisting of two or more chromium-plating chambers (9) equipped with covers made of iron material (10) divided in the form of a sandwich which are in the system and appear constituted by a tube (lead-tin) 93-7) of certain dimensions (11) that act as an anode in electrolysis. The cover in each chamber is held by flanges to ensure electrical contact to the camera.

For this purpose, a pulse wave rectifier transformer is available, adjustable according to the specific needs of each material and part to be coated (t), from which two anodic copper bars (a) and two copper cathode bars (c) emerge. The first ones are placed on the anodes (11) and the second ones end on the brushes (13).

The ends of the chamber are plastic caps in which there are specially designed seals through which the bars pass. These special design seals are present in all the chambers, both washing and rinsing and both before and after chromium plating.

Thanks to a suitable geometry and arrangement of the anodes, the electric and chrome attack of the bar surface in the chamber takes place as a continuous process.

To ensure the continuity of the electrolyte circulating through the intrinsic geometry of the chambers, transparent inlet and outlet pipes (27) are provided in each chamber, which allow the correct visualization of the flow of the liquid inside the chambers.

The aforementioned continuous process is based on a cathodic attack on one of the sides of the chamber, which performs the same function as a polarity inversion or an anode attack in a conventional system.

The same current with the same polarity, effects the attack and chrome at the same time. Chrome plating takes place on the other side of the camera. Our investigations have revealed that a cathodic attack done at about 15-29 V produces the same effect on the bar as an anode attack.

This method allows you to use more than one camera in series. The purpose of having several cameras in series is to create a multilayer coating or deposit that allows the possible cracks in the first deposit to be covered with the deposit produced in the second chamber and so on. An incomplete sealing of the chamber closures does not produce electrolyte losses in the working medium. The low pressure allows the passage of air bubbles through the seals, a circumstance that nevertheless does not affect chrome at all.

F- Rinsing station, which is another chamber (5a) equal to the other also of rinse described above, its purpose being to eliminate possible remains of the electrolyte that could be adhered to the surface of the bars. It is also a closed circuit under pressure, but independent of the other rinsing station and equipped with a water tank (6a) where the waste goes as well as a decantation ramp G- Drying station, also by compressed air, issued by a tube (8a).

H- Feeding and secondary current station, the movement of the bars is carried out by means of a system of rollers (12) driven by a reducer-variator to achieve an adjustable speed according to the specific needs of each bar.

Beside this system there are brushes (13) through which the current takes place in the bars (a and c). Other brushes are the same as the others, also for power supply and current described above, the purpose of which is exactly that of not losing at any moment the electrical continuity of the system and at the same time reducing the possible effects of decreasing the voltage of the system due to the distance or length of the bars. 1. Chromic circuit, composed of a container (14) of certain dimensions, which is covered with a "water bath" (15) in which the heating resistors (16), which are equipped with a dual-scale thermostat, are introduced. that are in contact with the electrolyte.

The composition of the electrolyte for optimal operation is as follows: - Chromic acid 200-300 g / 1 - Active catalyst 2-8 g / 1 - Temperature 50-65 ° C The suction of the electrolyte is carried out by a vacuum system consisting of a reserve chamber (17), two chambers for filling and emptying chromiums (18) linked together by an anti-return valve (19) and two probes (20) of minimum and the maximum level that makes a three-way solenoid valve (21) operate that connects or disconnects the vacuum system at the same time that it performs the same operation with atmospheric pressure.

All this is completed with an automatic purge decant trap (22) and with an adjustable vacuum pump according to each need (23) and an automatic purge solenoid valve (24).

This vacuum system circulates the suctioned chrome from the tank through the chrome chamber through a double filtration system of different micron (25) and by a refrigerator (26) piloted by a dual-scale thermostat that makes the electrolyte Keep at working temperature.

J. Disassembly and disconnection station composed of rollers (12a) for unloading bars.

Finally and after what has been described, it only remains to point out that in the present invention, as many variants of realization as possible will be possible, without altering the essence of the described, being able to manufacture its object in all kinds of shapes, sizes and materials, without limitation. .

Claims (6)

1. Machine designed to perform electrolytic continuous chrome plating, in which the bars (1) that must be chromed are placed on rollers (2) and are centered by a suitable device, the bars are joined with each other to achieve continuity. The machine is characterized by consisting of the following departments joined by a conveyor belt of the bars: 1 ° A washing station consisting of a washing chamber (3) under pressure by closed circuit and of a proper degreasing chamber through which the liquid from a closed container (4) circulates. 2nd A rinse station consisting of a smaller chamber than the previous one (5) with another closed circuit of pressurized water; the waste goes to a water tank (6) equipped with a decantation ramp (7) for its disposal. 3o A drying station, by means of compressed air issued by a tube (8). 4 ° A primary power and current station equipped with brushes (13) through which the current takes place in the anodic (a) and cathodic (c) bars. 5 ° A chrome-plating station, consisting of two or more chrome-plating chambers (9) equipped with iron material covers (10) sandwich-like pieces which are in the system and appear as a tube (lead- tin 93-7) of certain dimensions (11) that act as an anode in electrolysis. The cover in each chamber is held by flanges to ensure electrical contact to the camera. The machine has a pulse wave rectifier transformer, adjustable according to the specific needs of each material and piece to be coated (t) from which emerge two anodic copper bars (a) and two copper cathode (c). The first ones are placed on the anodes (11) and the second ones end on the brushes (13). The ends of the chamber are plastic caps in which there are specially designed seals through which the bars pass. These special design seals are present in all the chambers, both washing and rinsing and both before and after chromium plating. To ensure the continuity of the electrolyte circulating through the intrinsic geometry of the chromium chambers, transparent inlet and outlet pipes (27) have been provided in each chamber, allowing the correct visualization of the flow of liquid inside the chambers.

2. Machine designed to perform continuous chromium plating electrolytic coating, according to claim Ia, characterized in that the machine performs a cathode attack on one of the sides of the chamber, which obtains the same function as a reversal of polarity or an anode attack in a conventional system. The same current with the same polarity, effects the attack and the chromed at the same time making the chrome on the other side of the camera.

3. Machine designed to perform continuous chromium plating electrolytic coating, according to claim Ia and 2a, characterized in that the machine in another embodiment can also consist of a rinsing station, which is another chamber (5a) to the one described above with a closed circuit under pressure, but independent of the first rinse station and equipped with a water tank (6a), where the waste is collected as well as a decantation ramp (7a) for its elimination.

4. Machine designed to perform electrolytic continuous chrome plating, according to claim 3, characterized in that the machine below consists of a station of dried, also by compressed air, issued by a tube (8a) and a secondary power and feed station. The movement of the bars is carried out by means of a system of rollers (12) driven by a reducer-variator to achieve an adjustable speed according to the specific needs of each bar. Beside this system there are brushes (13a) through which the current takes place in the bars (a and c).

5. Method for making continuous chrome plating electrolytic, by means of the machine described according to previous claims, characterized in that the process has a chromium circuit, consisting of a container (14) of certain dimensions, which is covered with a "bath "Mary" (15) in which the heating resistors (16) are introduced, which are equipped with a double-scale thermostat that are in contact with the electrolyte. The composition of the electrolyte for optimal operation is as follows: - Chromic acid 200-300 g / 1 - Active catalyst 2-8 g / 1 - Temperature 50-65 ° C The suction of the electrolyte is carried out by a vacuum system consisting of a reserve chamber (17) two chambers for filling and emptying chromiums (18) linked together by an anti-return valve (19) and two probes (20) of minimum and maximum level that make pilot a three-way solenoid valve (21) that connects or disconnects the vacuum system at the same time that performs identical operation with atmospheric pressure. All this is completed with an automatic purge decant trap (22) and with an adjustable vacuum pump. function of each need (23) and an automatic purge solenoid valve (24). This vacuum system circulates the suctioned chrome from the tank through the chrome chamber through a double filtration system of different micron (25) and by a refrigerator (26) piloted by a dual-scale thermostat that makes the electrolyte Keep at working temperature.

6. Method for making continuous chromium plating electrolytic coating, according to claim 5, characterized in that the process ends in a dismantling and disconnection station composed of rollers (12a) for bar discharge.