KR100925618B1 - Electolyric tin plating process using insolulble anode - Google Patents

Abstract

The present invention relates to an electro tin plating process using an insoluble anode.

The present invention is to supply tin ions to the tin plating solution by supplying the tin plating solution with oxygen to the tin melting tank and oxidizing and reacting with the tin particles charged in the tin melting tank, and then providing the tin ions to the plating solution storage tank from the tin melting tank. Applying a predetermined DC voltage to the electrode means immersed in the tin plating solution, so that an electrolytic reduction reaction occurs in the tin plating solution, providing the tin plating solution to an electroplating bath and charging the cathode in the electroplating bath. Immersing the prepared steel sheet in the tin plating solution and depositing tin ions in the tin plating solution on the surface of the steel sheet using the insoluble anode. Here, the predetermined DC voltage applied to the tin plating solution is maintained within a range between the equilibrium potential of the negative electrode of the electrode means and the potential at which the tin electrodeposition reaction starts.

According to the electro-tin plating method of the present invention, not only can the oxygen which causes sludge generation from the tin plating solution can be removed quickly, but also the tin ions in the sludge generation process can be prevented from effectively inhibiting the sludge formation.

Insoluble electrode, electro tin plating process, sludge, electrolytic reduction reaction

Description

Electroplating method using insoluble anodes {ELECTOLYRIC TIN PLATING PROCESS USING INSOLULBLE ANODE}

1 is a schematic view showing one embodiment of an electro-tin plating apparatus using a conventional insoluble anode.

2A is a schematic view of a part of an electroplating apparatus according to an embodiment of the present invention.

Fig. 2B is a cross sectional view of the electrolytic reduction apparatus that can be employed in the present invention.

3 is a cathode polarization curve according to the plating solution temperature for the tin plating solution.

4 is a schematic diagram showing an electroplating apparatus according to an embodiment of the present invention.

<Code Description of Main Parts of Drawing>

121: electroplating bath 122: insoluble anode

123: steel sheet 124: plating liquid storage tank

127: tin melting tank 40, 140, 150: electrolytic reduction apparatus

The present invention relates to an electro tin plating process using an insoluble anode, and more particularly, electro tin that can prevent sludge generation by removing dissolved oxygen from a circulating plating solution and suppressing oxidation of tin ions using an electrolytic reduction reaction. It relates to a plating method.

In general, tin is a metal which is harmless to human body and has strong corrosion resistance against weak acid and alkali solution, and is widely used in the form of tin plated steel plate by being plated to a predetermined thickness on the surface of steel sheet such as low carbon steel using an electro tin plating process. .

The electro tin plating process used here can be broadly classified into an electro tin plating process using a soluble anode and an electroplating tin process using an insoluble anode according to the diffusion method of tin ions. An electro tin plating process using a soluble anode uses a cathode consisting of a tin rod or a tin plate to supply tin ions to be electrodeposited onto the plated steel plate connected to the cathode. Is consumed and hassle to change the anode continuously.

In contrast, an insoluble anode made of titanium (Ti) having a surface of platinum (Pt) and iridium oxide (IrO ₂ ) which is inert to the tin electroplating solution is prepared, and tin ions are added to the electroplating solution through a separate tin melting tank. There is a method of dissolving and replenishing. This method is commonly referred to as an electroplating process using an insoluble anode.

In the process of electro tin plating using insoluble anode, unlike the process using soluble anode, it is not required to replace the consumed tin anode, which ensures high productivity and realizes the actual electroplating equipment requiring high speed process. It has the advantage of being suitable for

The insoluble anode system for implementing such a process can be classified into a system using a fluidized bed reactor and a system using an ion exchange membrane according to a separate tin dissolving device for distributing tin ions. . A representative example of a system using a fluidized bed reactor is the system described in US Pat. No. 4,181,580. One type of insoluble anode electroplating system using such a fluidized bed reactor is shown in FIG.

Referring to Fig. 1, an insoluble anode electroplating system includes a plating reaction tank 1, a plating liquid storage tank 4, and a fluidized bed reaction tank 7.

The plating reaction tank 1 is filled with an electro tin plating solution in which tin ions are dissolved, and includes an insoluble anode 2 and a plated steel plate 3 connected to the cathode. Inside the fluidized bed reaction tank 7 is provided a porous plate 10a made of titanium and a fluidized bed 19 supported by the porous plate 10a.

The fluidized bed reaction tank 7 serves to replenish tin ions used in the tin plating process in the plating solution. Through the hopper 11 disposed above the fluidized bed reaction tank 7, metal tin particles are provided to the fluidized bed reaction tank 7, and the plating liquid 17 of the plating liquid storage tank 14 is provided with a pump 15 and a valve ( By the operation of 18), the fluidized bed reaction tank 7 is directed. In order to cause the dissolution reaction of tin in the plating solution, which is a normal acidic solution, the oxygen supply unit 8 and the valve 6 provided at the lower portion of the fluidized bed reaction tank 7 are supplied with an appropriate amount of oxygen to the concentration of dissolved oxygen. Increase. The plating liquid containing such dissolved oxygen may dissolve the metal tin particles in the fluidized bed reaction tank 7 as in the reaction of Formula 1 below.

2Sn + O ₂ + 4H ⁺ ---> 2Sn ²⁺ + 2H ₂ O

The plating liquid in which tin ions are supplied in this way is supplied to the plating liquid storage tank 4 through the settler 16 and the filter 12, and is circulated between the plating liquid storage tank 4 and the plating reaction tank 1 by the pump 5. do. Through the plating solution circulation process, the tin ions component dissolved in the tin plating solution in the plating reaction tank 1 is plated on the steel plate as the negative electrode, and only oxygen is generated at the positive electrode.

2Sn ²⁺ + 4e ---> 2Sn (cathode)

2H ₂ O ---> O ₂ + 4H ⁺ + 4e (anode)

In the tin plating process using the insoluble anode, the dissolution amount of tin ions can be controlled by adjusting the oxygen supply amount blown from the outside, as shown in the formula (1). However, the utilization efficiency of the oxygen blown under normal plating conditions, that is, the ratio of the amount of oxygen taking part in the reaction up to about 70%, can be caused by an additional reaction by oxygen not participating in the reaction. have.

Most not involved in the tin dissolved oxygen is a reaction does not dissolve in the plating solution again, but released to the atmosphere, some of which are 4 tin ion to the tin plating solution 2 in the oxidizing ion (Sn ²⁺⁾ (Sn ⁴⁺⁾ And finally form a sludge which is SnO ₂ tin oxide.

The sludge generation rate is about 3% in the electro tin plating process using a soluble anode, while it is known to be 6-8% (more than 10% in the actual process) in the electro tin plating process using an insoluble anode. have. This is because the oxidation reaction of tin divalent ions in the plating solution occurs due to the remaining dissolved oxygen which does not participate in the dissolution reaction of the tin particles in the oxygen blown as described above.

In addition to oxygen participating in the tin dissolution reaction, oxygen generated by the anodic reaction of Formula 2 may also cause oxidation of tin ions. Fine oxygen bubbles generated at the anode in the electroplating tank may be dissolved in the plating solution, and the dissolved oxygen may oxidize tin divalent ions like the dissolved oxygen described above to form sludge.

Sludge in the plating liquid generated in this process not only consumes relatively expensive tin, but also increases the viscosity of the plating liquid, which may cause damage to friction of various rolls or supply pipes for transferring steel strips. In addition, there is a serious problem that the sludge component may be compressed between the roll and the steel sheet to cause surface defects, and wear of the coating layer of the insoluble anode may reduce the life of the expensive insoluble anode.

As a conventional technique for solving the sludge generation problem, US Patent No. 5,296,128 proposes a method of adding gallic acid to prevent the oxidation of tin divalent ions in a methanesulfonic acid-based plating solution, US Patent In No. 4,981,564, a method of adding an antioxidant such as hardokinine sulfonate, 1-phenyl-3-pyrrolidinone, and 4-alkylated 1-phenyl-3-pyrrolidinone to prevent oxidation of tin to the plating solution. Is proposing.

However, the chemical composition of the plating liquid is complicated, which makes it difficult to control the process, and there is a problem that the newly added material may adversely affect the plating reaction because the basic plating liquid is different.

In addition, US Pat. No. 4,432,844 proposes a method in which a tin plate or powder having a wide reaction surface area is placed in a plating solution and heated to 80 ° C. or higher using a separate heating device to remove tin tetravalent ions in the plating solution. The prior art proposes a method for suppressing sludge generation by using the above-described electrolytic equipment having an ion exchange membrane.

However, as additional heating facilities or ion exchange membranes for heating to a high temperature of 80 ° C. or higher, additional equipment is required, not only increase the cost, but also suppress the sludge generation since oxygen cannot be removed from the tin melting tank quickly. It has not been put into practical use as a fundamental solution.

Accordingly, in the art, sludge generation can be effectively suppressed by quickly removing dissolved oxygen generated in the tin melting tank and the anode and preventing oxidation of tin ions in a cheaper and simpler manner in an electro tin process using an insoluble anode. New plating methods have been strongly demanded.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to apply an electrolytic reduction reaction by applying a predetermined DC voltage to a plating solution in circulation in order to suppress oxidation reaction of tin ions. And a new electroplating method for quickly removing dissolved oxygen generated at the anode.

In order to achieve the above technical problem, the present invention, in the method of electroplating in an electroplating system having an insoluble anode, the tin plating solution is supplied together with oxygen to the tin melting tank and oxidized tin particles and charged in the tin melting tank The first step of supplying tin ions to the tin plating liquid by reacting with each other, and a predetermined direct current voltage on the electrode means immersed in the tin plating liquid so that an electrolytic reduction reaction occurs in the tin plating liquid provided from the tin melting tank to the plating liquid storage tank. In the second step of applying the tin plating solution to the electroplating tank, and the steel plate charged as a negative electrode in the electroplating tank is deposited in the tin plating solution and the tin ion in the tin plating solution using the insoluble anode And a third step of electrodepositing the surface of the steel sheet, wherein a predetermined DC voltage applied to the tin plating liquid is the number of electrodes. The present invention provides an electro-tin plating method which is maintained within a range between the equilibrium potential of the cathode and the potential at which the tin electrodeposition reaction starts.

In one embodiment of the present invention, by providing a separate electrolytic reduction apparatus at the tin melting tank discharge port it is possible to quickly remove oxygen that participated in the tin melting reaction.

In a preferred embodiment of the present invention, after the third step of electrodeposition on the surface of the steel sheet, a predetermined direct current voltage is applied to the electrode means immersed in the tin plating liquid to remove oxygen from the tin plating liquid discharged from the electroplating bath and circulated. The method may further include applying a fourth step. This provides a way to quickly remove the oxygen generated in the anode reaction of the electroplating tank.

In addition, one of the electrode means used for the electrolytic reduction reaction of oxygen may be mesh or porous to have a larger actual electrode area with respect to the same apparent area, thereby improving the electrolytic reduction reaction rate of oxygen.

Furthermore, the mesh means, the fabric structure or the porous electrode means may use a carbon fiber. In this case, it is preferable that the other electrode means uses an insoluble electrode such as titanium (Ti) electrode coated with platinum (Pt).

In the electro-tin plating method according to the present invention, it is preferable to control the temperature of the tin plating solution to 45 ° C. or less to control the voltage for the oxygen electrolytic reduction reaction. In consideration of the efficiency of the electrolytic reduction reaction for removing dissolved oxygen, it is preferable to maintain the concentration of iron trivalent ions below 3 g / L.

Hereinafter, the present invention will be described in detail with reference to the drawings.

Figure 2a is a schematic view of a part of an electro tin plating system using insoluble electrodes for implementing the method of the present invention.

Referring to FIG. 2A, there is shown a hopper 21 in which tin particles are stored, a tin dissolution tank 27 for ionizing the tin particles, and an oxygen supply device 28 for supplying oxygen for tin dissolution reaction.

The tin melting tank 27 shown in FIG. 2A supplies tin ions to the plating liquid used for electro tin plating. The tin melting tank 27 is a cylinder in which a porous plate 30 made of titanium and a fluidized bed 39 supported by the porous plate 30 are provided, as in the conventional electroplating system described in FIG. 1. Fluidized bed reactor in the bed.

The tin dissolving tank 27 receives tin particles through the hopper 21, and provides oxygen necessary for dissolution reaction of tin through the oxygen supply device 37 and the shielding valve 38 from the bottom thereof. The plating liquid passing through the shielding valve is supplied from a plating reservoir (not shown) as indicated in the A direction. The tin ions obtained in the tin dissolution reaction in the tin dissolution tank 27 are continuously replenished in the plating solution in circulation, and the plating solution in which tin ions are replenished is directed toward the C direction through the settling tank 36, and an electroplating tank (not shown) Strictly speaking, it is supplied to the plating liquid storage tank.

At this time, in the present invention, a part of the dissolved oxygen that participated in the dissolution reaction step remains in the plating solution and oxidizes the tin divalent ions (Sn ²⁺ ) to tin tetravalent ions (Sn ²⁺ ) in the plating solution circulating process to make sludge (SnO). _In order to prevent the occurrence of ₂ ), the process of removing dissolved oxygen using an electrolytic reduction reaction is added.

As shown in FIG. 2A, before the tin plating solution in which tin ions are replenished from the tin melting tank 27 is supplied to the precipitation tank 36, it passes through an electrolytic reduction apparatus 40 for inducing an electrolytic reduction reaction of oxygen. It is composed. The electrolytic reduction apparatus 40 may be provided as close to the outlet of the tin dissolution tank 27 as possible immediately after passing through the settling tank 36 as in the present embodiment.

The configuration of the electrolytic reduction apparatus 40 is shown in FIG. 2B. The electrolytic reduction device 40 includes an electrolytic cell 41 including a cathode 43 in which an electrolytic reduction reaction occurs, an anode 44 as a counter electrode thereof, and a reference electrode 45 for defining a cathode potential, and the cathode potential. It may include a separate DC power supply 49 connected to the cathode 43 and the anode 44 to maintain a constant range with respect to the reference electrode 45. The DC power supply 49 serves to apply a voltage for removing dissolved oxygen from the plating solution passing through the electrolytic cell 41 of the electrolytic reduction device 40. In addition, the electrolytic reduction apparatus 40 may add a separate separator 47 for separating the negative electrode 43 and the positive electrode 44. The anode 44 may be an insoluble anode, and the cathode 43 may use an electrode having a large surface area or a porous or woven fabric structure. Preferred conditions of the cathode structure will be described later.

In the electrolytic reduction apparatus 40 shown in FIG. 2B, the plating solution (denoted B) in which tin ions are supplied from the settling tank 36 (in the case of no settling tank 27), the positive electrode 44 and the negative electrode 43 Entering the space between the electrolytic cell 41 and passing through the cathode 43, which is a mesh or a porous or fabric structure, in the plating solution, an oxygen reduction reaction occurs as shown in Formula 3 below to remove dissolved oxygen and remove dissolved oxygen. The plating solution is directed to a plating reservoir (not shown) (indicated in the direction C).

4H ⁺ + O ₂ + 4e ^- ---> 2H ₂ O

In order to induce an electrolytic reduction reaction to remove such dissolved oxygen, an important condition is the applied voltage range. The voltage range applied at this time is larger than the equilibrium potential of the cathode and must be precisely controlled to the range of the potential at which tin electrodeposition reaction does not occur.

If the applied voltage does not reach the equilibrium potential of the cathode, an electrolytic reduction reaction for removing dissolved oxygen does not occur, and when the potential range in which the tin electrodeposition reaction occurs is reached, unwanted reaction occurs in the cathode of the electrolytic reduction apparatus 40. This is because tin electrodeposition reaction occurs.

This electrolytic reduction reaction process is preferably carried out before the plating solution provided from the tin melting tank 27 reaches the electroplating tank. In other words, in order to prevent the dissolved oxygen generated together with the tin ions from the tin melting tank 27 from participating in sludge generation, it is preferable to remove them as soon as possible. For this purpose, in the system shown in FIG. 2, it is preferable to arrange adjacent to the outlet of the settling tank 26. FIG.

In addition, the negative electrode in which the actual reaction occurs among the electrodes used in the electrolytic reduction apparatus for the electrolytic reduction reaction of oxygen employed in the present invention, the larger the area participating in the actual reaction is preferable. The reason for this is because the current density required for the electrolytic reduction reaction of oxygen is very low, and the removal rate of dissolved oxygen is very low. Therefore, in order to obtain a desired dissolved oxygen removal rate, the area of the cathode must be large, and thus there is a problem that the electrolytic reduction apparatus can be too large. To this end, it is desirable to implement a structure that can maximize the actual surface area to participate in the actual reaction in the same apparent electrode area. As the electrode having such a structure, there is an electrode having a mesh shape or a porous or woven fabric structure. As an electrode that can be actually applied, an electrode made of carbon fiber or metal syntepon is preferable. Since these electrodes have a large actual surface area for generating an electrolytic reduction reaction, there is an advantage that the apparent size of the electrodes can be reduced to obtain a desired dissolution rate.

3 is a cathode polarization curve for explaining the potential range required for dissolved oxygen removal in the present invention. Referring to FIG. 3, the polarization curve shows Ag / AgCl as the reference electrode, and is shown as four curves with different conditions depending on the temperature of the tin plating solution. That is, as the curve 1 progresses from the curve 4, the temperature of the tin temperature liquid increases. Since the tin electrodeposition reaction occurs approximately at -0.4 to -0.6V, it can be seen that if the cathode potential is maintained in the range of 0.1 to -0.4V, the oxygen reduction reaction occurs without the tin electrodeposition reaction.

As shown in FIG. 3, as the temperature of the tin plating solution increases, the potential at which tin electrodeposition reaction starts also increases. This is because the activation energy for tin electrodeposition decreases at higher temperatures. Therefore, the higher the plating liquid temperature is, the narrower the potential region for the electrolytic reduction reaction of oxygen becomes, and therefore, it becomes difficult to control the voltage applied to the cathode. In view of such a problem, it is preferable that the temperature of the tin plating liquid be maintained at 45 ° C. or lower at room temperature.

The electro tin plating method according to the present invention may be affected by the impurity concentration in the tin plating solution. In particular, the efficiency of the process may vary depending on the Fe ion (typically present up to 20 g / L), which is a representative component in the tin plating solution. Most of the iron ions in the plating solution are present in the divalent form (Fe ²⁺ ) and are not affected because they are reduced at lower potential than the electrodeposition reaction of tin, but some iron ions are present in the trivalent form (Fe ³⁺ ) to electrolyze oxygen. It may be reduced to Fe ^{+ 2} in the reduction reaction range. In this case, since the applied voltage is consumed in the reduction reaction of iron ions, the reduction reaction efficiency of dissolved oxygen may be lowered. As a result, the Fe ^{+ 3} concentration can be kept low to improve the efficiency of the reduction of dissolved oxygen. Therefore, in consideration of this, it is preferable to maintain the concentration of Fe ³⁺ ions at 3 g / L or less.

Figure 4 illustrates another embodiment of an electro tin plating system using insoluble electrodes for implementing the method of the present invention. This embodiment is an electro tin plating system implemented to remove not only oxygen remaining in the tin dissolving process but also oxygen generated in the anodic reaction of the plating reaction tank such as Chemical Formula 2.

The electro tin plating system shown in FIG. 4 includes an electroplating tank 121, a plating liquid storage tank 124, and a fluidized bed reaction tank 127 as shown in FIG. In addition, in the tin plating solution filled in the electroplating tank 121, the insoluble anode 122 and the plated steel sheet 123 charged with the cathode are used as in the conventional electroplating system shown in FIG. Electro tin plating is carried out. Tin ions in the tin plating solution used for the electro tin plating are provided by the tin melting tank 127. The tin melting tank 127 is a fluidized bed reaction tank having a cylindrical shape provided with a porous plate 130a and a fluidized bed 139 supported by the porous plate 130a. The plating liquid 137 of the plating liquid storage tank 134 is directed to the tin melting tank 127 by the operation of the pump 135 and the valve 138.

The tin melting tank 127 receives tin particles from the hopper 121, and oxygen necessary for dissolution reaction of tin is provided through the oxygen supply device 128 and the shielding valve 126 from the bottom thereof. Tin ions obtained in the tin dissolution reaction in the tin dissolution tank 127 are continuously supplied to the plating solution in circulation, and the plating solution in which tin ions are supplied is supplied to the plating liquid storage tank 124 through the precipitation tank 136 and the filter 132. , Circulated between the plating liquid storage tank 124 and the electroplating tank 121 by the pump 125.

In addition, the electro-tin plating system according to the present embodiment is a first electrolytic reduction device 140 for removing dissolved oxygen generated in the tin dissolution reaction process, and removes oxygen generated from the cathode 122 in the tin plating process It includes a second electrolytic reduction device 150 for.

The first electrolytic reduction device 140 and the second electrolytic reduction device 150, like the electrolytic reduction device 140 shown in FIG. Electrolyzer including a reference electrode for defining the potential of the, and may be made of a separate DC power supply for supplying a constant voltage connected to the positive electrode and the negative electrode.

Cathodes and anodes of the first and second electrolytic reduction devices 140 and 150 are immersed in the tin plating solution in the electrolytic reduction device, and a voltage for removing dissolved oxygen is applied, and oxygen remaining in the plating solution is removed by the electrolytic reduction reaction. Can be. At this time, the voltage supplied is controlled to be lower than the equilibrium potential of the cathode and higher than the potential at which tin electrodeposition reaction does not occur.

In particular, the second electrolytic reduction apparatus 150 added in the present embodiment, as described above, is similar to the first electrolytic reduction apparatus 140, but is generated at the anode during the plating process of the electroplating tank 122 It is a component for removing oxygen. The electrolytic reduction process for removing oxygen generated by the anodic reaction described in Chemical Formula 2 may be performed anywhere in the circulation path discharged from the electroplating tank 122, but after the electroplating process step, the electrolytic reduction process may be performed. It is preferable to carry out before. This is also to quickly remove the generated oxygen in order to minimize the effects of dissolved oxygen as much as possible.

Therefore, as shown in FIG. 4, the second electrolytic reduction device 150 is preferably disposed between the electroplating tank 122 and the plating liquid storage tank 124, particularly adjacent to the electroplating tank 122. .

As described above, the electrolytic reduction process for oxygen removal employed in the present embodiment rapidly removes not only dissolved oxygen generated in the tin dissolution reaction but also oxygen generated in the anode during the plating process, thereby preventing sludge generation due to oxidation of tin ions. It can be suppressed more effectively.

Hereinafter, the electro tin plating method according to the present invention will be described in detail through the embodiment.

(Example 1)

First, a tin electroplating system using an insoluble electrode capable of dissolution of tin and electroplating of tin was considered. The anode reaction tank of the tin electroplating system used in this experiment was to have a positive electrode and a negative electrode having a reaction area of 2 dm ² at 50 mm intervals, and the electrolysis was carried out for a long time while replacing the negative electrode every 10 minutes. In addition, the tin melting tank is a stainless steel tube structure having a diameter of 100mm and a height of 600mm was prepared so that up to 15kg of tin particles can be charged, the mesh is installed on the upper and lower sides to prevent the charged tin particles outflow.

Tin particles charged in a tin melting tank were spherical tin particles having a diameter of 15 mm. In addition, the amount of oxygen required for tin dissolution was controlled by a microvalve and a flow meter to the plating liquid pipe connected to the lower part of the tin dissolution tank. The oxygen solution was sprayed through a gas liquid ejector, which is an oxygen supply unit, to obtain the maximum oxygen solubility at atmospheric pressure.

In order to compensate for the acidity change of the solution by a long time experiment, phenolsulfonate (PSA) can be supplied using a metering pump. In addition, a bypass filter was installed between the tin melting tank and the plating liquid storage tank so that a cartridge filter could be used if necessary.

The flow rate of the tin plating liquid was adjusted by controlling the rotation speed of the pump by an inverter, and the flow rate was measured by a propeller type flow meter.

The temperature of the plating liquid was controlled in the range of ± 1 ^o C at the target temperature by a condenser-type cooler installed in the middle of the heater installed in the plating liquid storage tank and the connection pipe between the plating liquid storage tank and the tin melting tank.

In the present embodiment, the condition for the electrolytic reduction is to install a separate electrolytic reduction apparatus at the outlet of the tin melting tank located before the bypass line for the selective connection of the cartridge filter, the electrolytic reduction apparatus can be passed through the tin plating solution An electrolytic cell having an electrolytic cell, the electrolytic cell includes a cathode for defining an electrolytic reduction reaction as described above, a reference electrode for defining a potential of a counter electrode, a cathode, and a direct current for maintaining the potential of the cathode at a constant value. Prepared with power supply.

As the cathode means, a porous glass carbon fiber was used so that the reaction area involved in the actual electrolytic reduction reaction was wider than the apparent area, and its apparent area was 20 dm ² . In addition, an insoluble anode coated with platinum (Pt) of 5 to 6 m on titanium (Ti) was used as an anode, and Ag / AgCl was used as a reference electrode.

DC power supply used potentiostat with output voltage of 0-12V and maximum output current of 20A. As a result of the preliminary experiments, the equilibrium potential of the glass carbon electrode as the negative electrode in the conventional PSA-based tin plating solution was + 0.1V vs. Ag / AgCl and the electrode potential was -0.5V vs. In the region below Ag / AgCl, tin was deposited on the surface of the cathode.

In the electroplating system thus prepared, the tin plating process was carried out with the flow rate of the plating liquid being 86 L / min or 315 L / min, and the oxygen supply amount being 200 cc / min or 800 cc / min. In the plating process according to each condition, the operating conditions of the electrolytic reduction apparatus were different. That is, the tin plating process was performed even when the electrolytic reduction device was not operated, and even when the electrolytic reduction device was operated, the cathode potentials were changed to -0.2 V, -0.4 V, and -0.5 V, respectively.

In order to measure the amount of sludge generated according to each experimental result, the sludge was filtered through a glass fiber filter with a filter particle size of 1 μm and then completely dried at a predetermined time interval for each experiment according to each condition, and then the sludge weight was measured. In addition, the electrodeposition degree of the tin on the negative electrode was visually observed by the glass fiber electrode of the electrolytic reduction apparatus to grasp the electrodeposition state of the tin.

As such, the evaluation of the sludge generation amount and the degree of tin electrode deposition on the tin plating process performed under different conditions are shown in Table 1 below.

division Electrolytic Reduction Device Operation Cathode potential during electrolytic reduction (V vs. Ag / AgCl) Plating liquid flow rate (L / min) Oxygen supply (cc / min) Experiment time (hr) Sludge Generation (g / L) Cathode tin electrodeposition degree Example 1 behavior -0.2 V 86 200 8 <0.01 none Example 2 behavior -0.2 V 86 200 12 <0.01 none Example 3 behavior -0.4 V 315 200 4 <0.01 none Example 4 behavior -0.4 V 315 200 8 <0.01 none Example 5 behavior -0.4 V 315 800 6 <0.01 none Example 6 behavior -0.4 V 315 800 12 <0.01 none Example 7 behavior -0.4 V 315 800 18 <0.01 none Comparative Example 1 Non-operational - 86 200 8 0.12 none Comparative Example 2 Non-operational - 86 200 12 0.18 none Comparative Example 3 Non-operational - 315 200 4 0.46 none Comparative Example 4 Non-operational - 315 200 8 0.52 none Comparative Example 5 Non-operational - 315 800 6 1.10 none Comparative Example 6 Non-operational - 315 800 12 1.63 none Comparative Example 7 Non-operational - 315 800 18 2.61 none Comparative Example 8 behavior -0.5V 315 200 4 <0.01 Attach Comparative Example 9 behavior -0.5V 315 200 8 <0.01 Attach

Referring to Table 1, as in Examples 1 to 7, when the voltage was applied to be maintained within the negative electrode potential range of the present invention, the sludge generation rate appeared to be less than 0.01g / L level. As a result, it can be seen that the sludge generation effect is excellent compared to Comparative Examples 1 to 7 in which the electrolytic reduction apparatus is not operated. However, even when the electrolytic reduction apparatus is operated, when it is out of the negative electrode potential range according to the present invention, that is, when the tin electrodeposition reaction potential reaches -0.5V, as in Comparative Examples 8 and 9, the sludge generation rate also decreases, Tin was found to be electrodeposited at the cathode. Therefore, when inducing the electrolytic reduction reaction in the limit of the negative electrode potential range proposed in the present invention, it can be seen that it is possible to reduce the sludge generation by removing dissolved oxygen without tin electrodeposition reaction.

As a further effect of the present invention, the sludge generation rate shown in Examples 1 to 7 was found to appear less than the amount of sludge generated in the process from the tin ion to the electrolytic reduction device in the tin melting tank. This is because the potential region in which the reduction reaction of dissolved oxygen occurs due to the electrolytic reduction reaction is lower than the equilibrium potential of tin ions (Sn ⁴⁺ / Sn ²⁺ ), and thus, tin 4 ions (Sn ⁴⁺ ) to tin 2 ions (Sn). ²⁺ ) reduction can occur at the same time. That is, the sludge of SnO ₂ is not formed directly by tin divalent ions (Sn ²⁺ ) dissolved from tin particles in a tin melting tank, but is generated through tin tetravalent (Sn ⁴⁺ ) states, In the process, it is possible to expect the effect of suppressing sludge generation by reducing the oxidized tin tetravalent temperature together with the electrolytic reduction reaction for removing dissolved oxygen.

^{Sn +4 + 2e - ---> Sn} _2

Electrolytic reduction reaction employed in the present invention is accompanied by a reaction as shown in Formula 4, it can be seen that there is an additional action and effect in addition to the dissolved oxygen removal by the electrolytic reduction reaction.

Example 2

In this embodiment, as in Example 1, an insoluble electrode capable of performing electroplating reaction of tin, including a tin dissolving tank capable of carrying out the dissolution reaction of the prepared tin and an electrolytic reduction device provided at the outlet of the tin dissolving tank A tin electroplating system was used. The electroplating tank of the tin electroplating system used in this experiment was installed so that the insoluble anode and cathode having a reaction area of 2 dm ² were spaced at 50 mm intervals, and the electrolysis was performed for a long time while replacing the cathode every 10 minutes. At this time, the current density was 30 A / dm ² . The conditions of tin particles charged in the tin dissolution tank, oxygen blowing method, conditions for compensating for acidity change by long time experiment, flow rate control and measuring method of plating liquid, temperature condition of plating liquid, etc. were set to the same conditions as in Example 1. .

In addition, in order to confirm the effect of removing the sludge generated only by oxidation of the plating liquid by oxygen generated at the anode of the electroplating tank, the operating conditions of the electrolytic reduction apparatus installed at the outlet of the tin dissolution tank correspond to the ranges mentioned in Example 1. 0.4 V vs. Fixed with Ag / AgCl so that the amount of sludge generated from the dissolution tank was hardly generated.

In the present embodiment, the conditions for the electrolytic reduction of the plating liquid supplied from the electroplating tank to the plating liquid storage tank were performed by installing a separate electrolytic reduction apparatus at the outlet of the electroplating tank located in the electroplating tank and the plating liquid storage investigation. As described above, the electrolytic reduction apparatus includes a cathode including an anode in which an electrolytic reduction reaction occurs, an anode including a counter electrode, and a reference electrode for defining the potential of the cathode, and a direct current for maintaining a potential of the cathode at a constant value with respect to the reference electrode. It consisted of a power supply.

As the cathode means used in the electrolytic reduction apparatus, a porous metal syntepon was used so that the reaction area participating in the actual electrolytic reduction reaction was wider than the apparent area, and the apparent area was 20dm ² . In addition, an insoluble anode coated with platinum (Pt) of 5 to 6 mm on titanium (Ti) was used as an anode, and Ag / AgCl was used as a reference electrode.

The DC power supply device of the electrolytic reduction device provided in this embodiment is the same as that of the first embodiment. Based on the preliminary results, +0.1 V vs. Ag / AgCl and the electrode potential was -0.5 V vs. In the region below Ag / AgCl, tin was deposited on the surface of the cathode.

In the electroplating system prepared as described above, the tin plating process was performed with the flow rate of the plating liquid at 315 L / min and the oxygen supply amount at 200 cc / min. In the stone plating process according to each condition, only the operating conditions of the electrolytic reduction apparatus installed at the outlet of the electroplating tank were different. That is, the tin plating process was performed even when the electrolytic reduction device was not operated, and even when the electrolytic reduction device was operated, the cathode potentials were changed to -0.2 V, -0.4 V, and -0.5 V, respectively.

In order to measure the amount of sludge produced according to each experimental result, the sludge weight was measured after the sludge was filtered through a glass fiber filter with a filter particle size of 1 μm and then completely dried at a predetermined time interval for each experiment according to each condition. In addition, the electrodeposition degree of the tin on the negative electrode was observed by visually observing the metal synthephon electrode of the electrolytic reduction apparatus to determine the electrodeposition state of the tin.

Thus, the evaluation of the sludge generation amount and the degree of tin electrode deposition on the tin plating process performed under different conditions are shown in Table 2 below.

division Electrolytic Reduction Device Operation Cathode potential during electrolytic reduction (V vs. Ag / AgCl) Experiment time (hr) Sludge Generation (g / L) Electrodeposition of Sn on Cathode Example 1 behavior -0.2 V 12 <0.01 none Example 2 behavior -0.4 V 18 <0.01 none Comparative Example 1 Non-operational - 12 0.12 none Comparative Example 2 behavior -0.5 V 8 <0.01 Attach

Referring to Table 2, as in Examples 1 to 2, when a voltage was applied to be maintained within the cathode potential range of the present invention, the sludge generation rate appeared to be less than 0.01g / L. As a result, it can be seen that the sludge is effectively suppressed as compared with Comparative Example 1 in which the electrolytic reduction apparatus is not operated.                     

However, even when the electrolytic reduction apparatus is operated, when it is out of the negative electrode potential range according to the present invention, that is, when it reaches -0.5 V, which is the tin electrodeposition reaction potential, as in Comparative Example 2, the sludge generation rate decreases, but the tin in the negative electrode of the electrolytic reduction apparatus is reduced. It has been shown to be electrodeposited. Therefore, when inducing the electrolytic reduction reaction in the limit of the negative electrode potential range proposed in the present invention, it can be seen that it is possible to reduce the sludge generation by removing dissolved oxygen without tin electrodeposition reaction.

The present invention described above is not limited by the above-described embodiment and the accompanying drawings, but by the appended claims. Therefore, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible without departing from the technical spirit of the present invention described in the claims.

For example, the limit of the concentration range of iron trivalent ions or the temperature of the plating liquid is provided only in a preferable range in consideration of the efficiency of the present invention, and does not limit the scope of the present invention. In addition, the electrode structure used in the electrolytic reduction is also considered in order to improve the removal rate of dissolved oxygen, and if the electrode is made of a material that is permeable to the tin plating solution and has the conductivity required for the electrolytic reduction reaction, it is employed in the process of the present invention. It will be apparent to those skilled in the art that tin melting baths for distributing tin ions can be implemented in various forms. In addition, for quick removal of oxygen, it is preferable to provide at the outlet side of the tin melting tank and the electroplating tank where oxygen is generated. In any of the circulation paths of the plating liquid, it is possible to obtain the effect of removing oxygen through the electrolytic reduction reaction.

As described above, according to the electro-tin plating process of the present invention, in order to remove the oxygen causing the sludge from the plating liquid, by using a separate electrolytic reduction device by applying a voltage in the potential range that the tin electrodeposition reaction does not occur By carrying out the electrolytic reduction reaction, not only oxygen in the tin plating solution can be removed, but also sludge generation can be effectively prevented by suppressing oxidation reaction of tin ions in the sludge generation step.

Claims (9)

In the method of electroplating in an electroplating system having an insoluble anode, A first step of supplying tin ions to the tin plating solution by supplying the tin plating solution together with oxygen to a tin melting tank and oxidizing and reacting with the tin particles charged in the tin melting tank; A second step of applying a predetermined DC voltage to the electrode means immersed in the tin plating solution so that an electrolytic reduction reaction occurs in the tin plating solution provided from the tin melting tank to the plating solution storage tank; And, A third step of providing the tin plating solution to an electroplating bath and depositing a steel plate charged with a negative electrode in the electroplating bath to the tin plating solution and electrodepositing tin ions in the tin plating solution onto the surface of the steel plate using the insoluble anode. Steps, And a predetermined DC voltage applied to the tin plating solution is maintained within a range between an equilibrium potential of a negative electrode of the electrode means and a potential at which a tin electrodeposition reaction starts. The method of claim 1, After the third step of electrodeposition on the surface of the steel sheet, a fourth step of applying a predetermined DC voltage to the electrode means immersed in the tin plating solution to remove oxygen from the tin plating solution discharged from the electroplating bath and circulated. Electro tin plating method characterized in that it comprises a. The method of claim 2, In the fourth step of applying the DC voltage, an electrolytic cell including a reference electrode for defining a cathode, an anode, and a cathode potential is adjacent to the outlet side of the electroplating tank, and electrolytic reduction is performed in the tin plating solution provided to the electrolytic cell. And immersing the cathode and the anode in which the reaction occurs, applying a voltage maintained at the potential range with respect to the reference electrode. The method of claim 1, In the second step of applying the DC voltage, adjacent to the outlet side of the tin melting tank, by providing an electrolytic cell including a reference electrode for defining a negative electrode and a positive electrode and a negative electrode potential, the electrolytic reduction in the tin plating solution provided to the electrolytic cell And immersing the cathode and the anode in which the reaction occurs, applying a voltage maintained at the potential range with respect to the reference electrode. The method according to claim 1 or 2, Electrolytic tin plating method of the electrode means used in the second or fourth step, the cathode means for generating an electrolytic reduction reaction has a mesh shape, a fabric structure or a porous phase. The method of claim 5, The negative electrode means for generating the electrolytic reduction reaction is electro tin plating method characterized in that made of carbon fiber or metal synthephon. The method of claim 1, Electro tin plating method characterized in that the temperature of the tin plating solution is 45 ℃ or less. The method of claim 1, The electro tin plating method characterized in that the concentration of the iron trivalent ions (Fe ³⁺ ) in the tin plating solution is greater than 0 and less than 3g / L. In the electroplating method of electroplating with tin ions supplied while supplying tin ions while circulating a plating solution supplied with tin ions in an electroplating system, The electrode means is immersed in the plating solution being circulated, and a predetermined DC voltage is applied to the electrode means to generate an electrolytic reduction reaction, wherein the applied DC voltage is a potential at which the equilibrium potential of the negative electrode and the tin electrodeposition reaction of the electrode means start. Electroplating method characterized in that it is maintained within the range between.

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