JPH06116783A - Chrome plating method - Google Patents

Abstract

PURPOSE:To provide the method capable of executing the activation treatment and chrome plating of a material to be plated without polarizing one sheet of electrode to both positive and negative poles in a single plating bath. CONSTITUTION:At least a part of anodes and cathodes 4 and 5 are housed in addition to a material 3 to be plated into the single plating bath 2. The above-mentioned cathode 5 and the material 3 to be plated are energized therebetween in the activation treatment to polarize the material 3 to be plated to the positive pole. The above-mentioned anode 4 and the material 3 to be plated are energized therebetween, by which the above-mentioned anode 4 is polarized only to the positive pole and the above-mentioned cathode 5 is polarized only to the negative pole in the chrome plating to polarize the material 3 to be plated to the negative pole. The polarization of one sheet of the electrode to the positive and negative poles by the kinds of the treatment is eliminated, by which the deterioration of the electrodes is efficiently prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chrome plating method in which activation of the surface of a material to be plated and chrome plating are performed in the same plating bath.

[0002]

2. Description of the Related Art In the chrome plating method, not only the appearance of the formed surface is good, but also the coating layer formed is sufficiently hard and has sufficient corrosion resistance. , Engine parts for automobiles,
Widely used for plating various cylinders, tableware and cans for canning. The chrome plating method is roughly classified into a method using a silicofluoride bath in which silicofluoric acid is added to the plating bath and a method in which a sergeant bath to which sulfuric acid is added is used. In addition to this, an additive is added on the basis of the 2 methods. Various plating baths have been devised that change the liquid concentration.

Although the latter type of sergent bath has a problem that the current efficiency is slightly low in general, it is widely used because it is easy to handle and stable. Lead or lead alloys are generally used as the anode in this Sargent bath. In the usual chrome electroplating method, the material to be plated with chromium is once positively polarized to activate the surface, and then the material to be plated is negatively polarized so that chromium is electrodeposited. There is. In such an operation, the electrode facing the material to be plated and used to polarize the material to be plated is negatively polarized during the activation treatment of the material to be plated, while being positively polarized during chrome plating. In the case of a lead or lead alloy electrode usually used as the electrode, comparing the case where it is used only with positive polarization and the case where it is used so as to be polarized to both positive and negative polarities, the latter lead elution cannot be conducted in a remarkably short time. Often reaches a state. Lead eluted in the chrome plating bath accumulates in the plating bath as insoluble lead chromate and lead sulfate sludge, and the operation must be stopped to remove the sludge. Is big.

Recently, an insoluble anode, which is a platinum-plated electrode in which platinum is coated on a valve metal substrate such as titanium by electroplating, is becoming widespread. However, the platinum-plated electrode uses a noble metal as compared with an inexpensive lead or lead alloy electrode. Since the electrode is expensive and has insufficient durability when repeatedly used while changing the polarity, the economical merit of using the platinum-plated electrode by the chromium plating method was extremely small.

[0005]

SUMMARY OF THE INVENTION The inventors of the present invention have made various studies to solve the above-mentioned problems when performing chrome plating using a lead electrode, and are capable of minimizing the deterioration of the lead electrode while plating the lead electrode. We have reached a method that enables chrome plating of wood. That is, an object of the present invention is to provide a method for performing activation treatment of a material to be plated and chromium plating while sufficiently suppressing deterioration of the counter electrode in a single plating bath.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a chrome plating method for activating a material to be plated and chrome plating in a single plating bath. A cathode is installed, when the material to be plated is activated, an electric current is applied between the material to be plated and the cathode to positively polarize the material to be plated, and the material to be plated and the material to be plated are chromium-plated. It is a chrome plating method characterized in that the material to be plated is polarized negatively by passing current between the anodes.

The present invention will be described in detail below. The inventors of the present invention need to change the polarity of the material to be plated when activating the material to be plated and performing chrome plating using a single electrode, and accordingly, the polarity of the electrode is also changed. Change,
It is assumed that the change in polarity accelerates the deterioration of the electrode. Therefore, it is considered that even if the polarity of the material to be plated changes, the polarity of the electrode does not change. Therefore, it is necessary to use a plurality of electrodes, that is, at least one anode and cathode. The anode is always used in the state of being positively polarized without changing the polarity, and the cathode is always used in the state of being negatively polarized, and materials having high resistance to positive polarization and negative polarization are selected as the anode and the cathode, respectively. This enables stable chrome plating operation for a long period of time. In the method of the present invention, it is necessary to positively polarize the material to be plated during the activation treatment of the material to be plated, so that electricity is applied between the cathode of the plurality of electrodes in the plating bath and the material to be plated, while Since it is necessary to negatively polarize the material to be plated during chrome plating, electricity is applied between the anode of the plurality of electrodes in the plating bath and the material to be plated. According to this method, the anode in the plating bath is polarized only positively and never negatively polarized, and the cathode is polarized only negatively and never positively polarized. It is possible to perform stable chrome plating for a long period of time without causing any deterioration.

The means for energizing between the anode and the material to be plated and between the cathode and the material to be plated is not particularly limited, but two types of wirings in which current from one power source device flows are formed by using a relay, In the case of the activation process of the plated material using the control device, one wire is wired so that the current flows between the anode and the plated material, and the other wire connects between the cathode and the plated material. The current can flow in the latter connection, and the current can flow in the former connection when the material to be plated is chromium plated. Also using two power supplies,
One power supply is connected to the anode and the material to be plated, the other power supply is connected to the cathode and the material to be plated, and in the case of activation of the material to be plated, the latter power supply is closed and the material to be plated is In the case of chrome plating, the former power supply device may be closed to perform the required processing.

As the anode and cathode materials used in the method of the present invention, conventionally used electrode materials can be used as they are. That is, as the anode, lead, a lead alloy, platinum-plated titanium, a so-called insoluble electrode obtained by coating a platinum group metal or an oxide thereof on a valve metal or containing another metal oxide, a valve metal oxide sintered body, A ferrite electrode, a lead dioxide electrode, etc. can be mentioned, and these 1 type (s) or 2 or more types are used. Also, as the cathode, it is possible to use a metal or alloy having corrosion resistance to the chromium plating bath, a material such as carbon, organic matter, etc. as the electrode, and it is suitable for each plating bath in consideration of electrical conductivity, corrosion resistance, price, etc. It is possible to arbitrarily select and use different electrodes. As the plating solution constituting the plating bath, a Sargent bath (for example, a mixed bath of chromic acid and sulfuric acid) or a silicofluoride bath (for example, a bath containing silicofluoric acid) can be used.

Next, an embodiment of the method of the present invention will be illustrated with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing a chrome plating apparatus that can be used in the method of the present invention. In the illustrated chrome plating apparatus, one power supply device is used, and a current flow is controlled by a relay to activate a material to be plated. And chrome plating is performed using a pair of positive and negative electrodes. A plating bath 2 in a box-type electrolytic plating tank 1 contains a material to be plated 3, an anode 4 and a cathode 5 in order from the right side.
A pair of first relay 6 and second relay 7 is installed outside. The positive terminal of the first relay 6 is connected to the material to be plated 3 and the negative terminal is connected to the cathode 5, while the second relay 7 is connected.
Is connected to the material to be plated 3 and the positive terminal is connected to the anode 4. The first relay 6 and the second relay 7 are connected to each other, and the sequence control device 8 is connected to both the relays 6 and 7, and the first control device 8 controls the first relay 6 and the second relay 7.
The relay 6 and the second relay 7 are opened and closed. The positive and negative input terminals of the first relay 6 are respectively connected to the output terminals of the DC power supply device 9, and the current from the power supply device 9 is connected by opening and closing both relays 6 and 7 by the control device 8. The current is adjusted so that current is applied between the anode 4 and the material 3 to be plated or between the cathode 5 and the material 3 to be plated.

In other words, when the material 3 to be plated is polarized positively to activate the material 3 to be plated, the sequence control device 8 closes the first relay 6 as shown in FIG. When the positive terminal of 9 is connected to the material to be plated 3 and the negative terminal of the device 9 is connected to the cathode 5,
Is polarized positively and the cathode 5 is polarized negatively. When electricity is applied in this state, the material to be plated 3 is activated without electricity to the anode 4. Next, when the plated material 3 is negatively polarized and the plated material 3 is plated with chromium,
The sequence controller 8 opens the first relay 6 to connect the positive terminal of the power supply device 9 to the positive terminal of the second relay 7 whose other end is connected to the anode 4, as shown in FIG. The negative terminal of 9 is connected to the negative terminal of the second relay 7 whose other end is connected to the material 3 to be plated. When electricity is applied in this state, the material to be plated 3 is chromium-plated without electricity being applied to the cathode 5. In addition, the time to output from the sequence control device 8 to the first relay 6 and the second relay 7, the output order, control of repeated operation and individual operation can be arbitrarily set, but if the above operation is performed continuously, both relays 6 , 7 may start simultaneously at the same time, which is not preferable. Therefore, it is desirable to switch each relay at an appropriate interval.

As described above, when the plating apparatus shown in the figure is used, only the cathode 5 of the pair of anode 4 and cathode 5 is energized during the activation treatment of the plating material in FIG. The cathode 5 functions as a counter electrode of the positively polarized material 3 to be plated, while the negatively polarized material to be plated in FIG. The anode 4 functions as a counter electrode of the material 3 to be plated, which is negatively polarized by energizing only the electrode 4. Therefore, the anode 4 is polarized only positively and the cathode 5 is polarized only negatively, and a single electrode is not polarized positively or negatively depending on the kind of treatment as in the conventional case, so that deterioration of the electrode is prevented. The chrome plating process can be continued for a long time.

[0013]

EXAMPLES Examples of chromium plating according to the method of the present invention will be described below, but the examples do not limit the method of the present invention.

Example 1 The chrome plating apparatus shown in FIG. 1 was used to activate the material to be plated and perform chrome plating. Chromic acid 250 g / l and sulfuric acid 2.5 for chrome plating bath
A Sargent bath containing g / l and having a bath temperature of 60 ° C. was used, a lead-silver alloy electrode was used as the anode, and a copper plate was used as the cathode (areas were each 0.1 dm ² ). A copper plate was prepared separately from the cathode, and the copper plate was plated with chromium of about 3 μm by the plating bath to obtain a plated material (area: 0.1 dm).
² ). The material to be plated, the anode and the cathode are arranged in the Sargent bath as shown in FIG. 1, the current density is set to 30 A / dm ^2, and the activation treatment of FIG. 2 is performed using the sequence controller (the material to be plated is positively polarized). ) Is repeated for 10 seconds, and the chrome plating of FIG. 3 (the material to be plated undergoes negative polarization) is repeated for 1 hour each to perform continuous operation. As shown in Table 1, in this example, the value was 1 even after 5000 hours.
No increase in V potential was observed.

[0014]

Comparative Example 1 The lead-silver alloy electrode alone was used as the electrode without using the cathode made of the copper plate of Example 1, and the polarity of the lead-silver alloy electrode was reversed at the same time as the polarity of the material to be plated was changed. The same activation treatment and chrome plating of the material to be plated as in Example 1 were performed while controlling the change using a timer and a relay. The life of the electrode in this comparative example was 1800 hours as shown in Table 1.

[0015]

[Example 2] Activation of a material to be plated and chrome plating were performed in the same manner as in Example 1 except that a platinum-coated (3 µm) titanium electrode was used as an anode, and 5000 hours passed as shown in Table 1. Even after that, the potential increase of 1 V was not observed.

Comparative Example 2 The material to be plated was activated and chromium-plated in the same manner as in Comparative Example 1 except that a platinum-coated (3 μm) titanium electrode was used as the anode. As shown in Table 1, this Comparative Example The life of the electrode at 2500 was 2500 hours. It can be seen from Table 1 that the method of the example was capable of stable operation for 5000 hours or more, whereas the method of the comparative example was unable to continue the operation because the anode potential increased after 2500 hours.

[0016]

[Table 1]

[0017]

INDUSTRIAL APPLICABILITY The present invention provides a chrome plating method in which activation of a material to be plated and chrome plating are performed in a single plating bath, and one or more anodes and cathodes are installed in the plating bath. When the material to be plated is activated, current is applied between the material to be plated and the cathode to positively polarize the material to be plated, and when the material to be plated is chromium-plated, current is applied between the material to be plated and the anode. The method is a chromium plating method characterized in that the material to be plated is polarized negatively. In the method of the present invention, unlike the conventional chrome plating method, which differs from the method of activating the plated material and chrome plating while changing the polarities of one electrode and one plated material, respectively, at least In the activation treatment in which a pair of positive and negative electrodes are used and the material to be plated is positively polarized, chrome plating in which electricity is applied between the cathode of the positive and negative electrodes and the material to be plated and the material to be plated is negatively polarized. Then, the anode is polarized only positively and the cathode is polarized only negatively by energizing between the anode of the positive cathode and the material to be plated. Therefore, unlike the conventional case, one electrode is not polarized positively and negatively depending on the type of treatment, and deterioration caused by the electrode being polarized positively and negatively can be efficiently prevented, and stable for a long period of time. It is possible to continue the chrome plating operation.

In order to carry out the energization, a relay is used to form two types of connections in which a current from one power supply device flows, and one connection causes a current to flow between the anode and the material to be plated. It is desirable to wire the other wire so that a current flows between the cathode and the material to be plated. According to this method, only one power supply device is required, and the size of the device is reduced, which contributes to reduction of the installation area and economy.

[Brief description of drawings]

FIG. 1 is a schematic view showing a chrome plating apparatus that can be used in the method of the present invention.

FIG. 2 is a schematic diagram showing connection when the apparatus of FIG. 1 is used for activation treatment of a material to be plated.

FIG. 3 is a schematic diagram showing connection when the apparatus of FIG. 1 is used for chrome plating of a material to be plated.

[Explanation of symbols]

1 ... Plating bath 2 ... Plating bath 3 ... Plated material 4 ... Anode 5 ... Cathode 6 ... First relay 7 ... Second relay 8 ... Sequence control device 9 ... Power supply

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[Procedure amendment]

[Submission date] September 9, 1993

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

[Figure 3]

Claims (2)

[Claims] 1. A chrome plating method for activating a material to be plated and chrome plating in a single plating bath,
Installing one or more anodes and cathodes in the plating bath;
When the material to be plated is activated, current is applied between the material to be plated and the cathode to positively polarize the material to be plated, and when the material to be plated is chromium-plated, current is applied between the material to be plated and the anode. A method for chrome plating, characterized in that the material to be plated is polarized negatively. 2. A relay is used to form two types of connections in which a current from one power supply device flows, one connection carrying a current between the anode and the material to be plated, and the other connection forming a cathode and the target. The method according to claim 1, wherein wiring is performed so that a current flows between the plated materials.