TWI702313B - Chrome plating solution, electroplating method and manufacturing method of chrome plating solution - Google Patents

Abstract

The present invention provides a chromium plating solution and an electroplating method, as well as a method for manufacturing the aforementioned chromium plating solution. During the plating process, the increase of the concentration of hexavalent chromium in the anode can be suppressed, and good chromium plating can be performed for a long period of time.

The chromium plating solution of the present invention is characterized in that it contains trivalent chromium ions and at least one selected from the group consisting of palladium ions and gold ions. In addition, the chromium plating solution of the present invention is characterized in that it contains: trivalent chromium ions, hexavalent chromium ions, and at least one selected from the group consisting of palladium ions and gold ions. By containing palladium ions and/or gold ions in the chromium plating solution, the increase in the concentration of hexavalent chromium at the anode can be suppressed, and a good plating process can be performed for a long period of time.

Description

Chrome plating solution, electroplating method and manufacturing method of chrome plating solution

The present invention relates to a chromium plating solution, an electroplating method, and a manufacturing method of the chromium plating solution.

The plating technology that deposits the metal ions in the plating solution on the surface of the object by electrolysis or other methods can give the object decoration, abrasion resistance, and corrosion resistance, so the industrial use value is very high. As an example of such a plating technique, chromium electroplating is a well-known technique, which is used in various fields such as decorative applications and industrial applications.

In recent years, for the purpose of reducing the amount of harmful hexavalent chromium and improving the functionality of plating, it has been proposed to use trivalent chromium plating solutions, or so-called compromise plating solutions of hexavalent chromium and trivalent chromium (for example, Refer to Patent Documents 1 to 3 and Non-Patent Document 1, etc.). Due to the increase in the concentration of hexavalent chromium in these plating solutions, there is a problem of poor plating in a relatively short period of time. Therefore, methods to suppress the increase in the concentration of hexavalent chromium have been proposed (for example, refer to Patent Documents 4 to 6 Wait). Specifically, Patent Document 4 discloses a technique for suppressing the increase of the concentration of hexavalent chromium in the anode by adding a manganese salt to the electroplating solution; Patent Documents 5 and 6 disclose the use of coated iridium oxide catalysts in the chromium plating solution The anode is a technology that suppresses the increase in the concentration of hexavalent chromium in the anode.

【Prior Technical Literature】 【Patent Literature】

[Patent Document 1] JP 2009-545669 A

[Patent Document 2] JP 2010-540781 Publication

[Patent Document 3] JP 2011-099126 A

[Patent Document 4] JP 2012-511099 Publication

[Patent Document 5] Japanese Patent Application Laid-Open No. 8-13199

[Patent Document 6] JP 2011-140700 A

【Non-Patent Literature】

[Non-Patent Document 1] Metal Surface Technology Vol. 37, No. 7,341p (1986)

However, the allowable concentration of hexavalent chromium in a trivalent chromium plating bath that does not contain hexavalent chromium is about tens of mg/L, and the technology disclosed in Patent Document 4 above increases the hexavalent chromium concentration to about two hours 40mg/L, cannot effectively reduce the concentration of hexavalent chromium. In addition, as disclosed in Patent Documents 5 and 6, it is difficult to prevent the concentration of hexavalent chromium from increasing by using only anodes coated with iridium oxide-based catalysts. In addition, with such conventional techniques, if the concentration of hexavalent chromium in the plating solution is not controlled within a certain range, the plating solution will suffer from poor plating after a relatively short period of time. Therefore, it is necessary to frequently discard the degraded plating solution and prepare a new plating solution, which also leaves problems from the viewpoint of operating cost and environmental load.

The present invention provides a chromium plating solution and an electroplating method, as well as a method for manufacturing the aforementioned chromium plating solution, in view of the above-mentioned results. The plating process can suppress the increase of the concentration of hexavalent chromium in the anode and can be carried out for a long time. Good plating treatment is the goal.

The inventors of the present invention have focused their research to achieve the above-mentioned object and found that the above-mentioned object can be achieved by a plating solution containing at least one selected from the group consisting of palladium ions and gold ions, and the present invention has been completed.

That is, the present invention includes, for example, the subjects described in the following items.

Project 1. A chromium plating solution is characterized in that it contains trivalent chromium ions and at least one selected from the group consisting of palladium ions and gold ions.

Project 2. A chromium plating solution is characterized in that it contains: trivalent chromium ions, hexavalent chromium ions, and at least one selected from the group consisting of palladium ions and gold ions.

Project 3. The chromium plating solution described in item 2 above, wherein the concentration of hexavalent chromium ions (g/L) relative to the concentration of all chromium ions (g/L) is a ratio of 5-50%.

Item 4. The chromium plating solution described in any one of items 1 to 3 above, wherein the concentration of palladium ion or gold ion is 0.1 mg/L or more and 1000 mg/L or less.

Item 5. An electroplating method characterized in that a metal containing 10% by mass or more of chromium is plated on an object to be plated with the chromium plating solution described in any one of items 1 to 4 above.

Item 6. The electroplating method described in item 5, wherein an anode containing palladium and/or gold is used.

Item 7. A method for manufacturing chromium plating bath, which is as described in any one of items 1 to 4 above The manufacturing method of the chromium plating solution described is characterized by a step of dissolving at least one selected from the group consisting of metallic palladium, palladium alloy, palladium compound, metallic gold, gold alloy and gold compound, and impregnating selected from metallic tin, At least one step of the group consisting of palladium alloy, palladium compound, metallic gold, gold alloy and gold compound, and introducing palladium ion or gold ion through at least one of the foregoing steps.

The chromium plating solution of the present invention contains at least one selected from the group consisting of palladium ions and gold ions as essential ions. During chromium plating, the increase in the concentration of hexavalent chromium in the anode can be suppressed, and it can last a long time. Perform good chrome plating.

In addition, the electroplating method of the present invention uses the above-mentioned chromium plating solution for plating treatment, and therefore can suppress the increase in the concentration of hexavalent chromium, and can perform good chromium plating over a long period of time.

The method for producing the chromium plating solution of the present invention can efficiently produce the above-mentioned plating solution, so it is an appropriate method for producing the aforementioned chromium plating solution.

[Figure 1] A graph showing the results of the plating treatments of Example 1 and Comparative Example 1, and plotting the relationship between the energization time and the concentration of hexavalent chromium.

[Figure 2] A graph showing the results of the plating treatments of Examples 2 to 6 and Comparative Examples 2 to 4, and plotting the relationship between the energization time and the concentration of hexavalent chromium.

Hereinafter, the implementation mode of the present invention will be described in detail.

<Chrome plating solution>

The chromium plating solution of this embodiment contains trivalent chromium ions and at least one selected from the group consisting of palladium ions and gold ions. In addition, another type of this embodiment, the chromium plating solution, contains trivalent chromium ions, hexavalent chromium ions, and at least one selected from the group of palladium ions and gold ions. Hereinafter, a chromium plating solution containing trivalent chromium ions and at least one selected from the group of palladium ions and gold ions is referred to as the "first chromium plating solution"; and containing trivalent chromium ions, hexavalent chromium ions, and selected from At least one chromium plating solution in the group of palladium ions and gold ions is referred to as the "second chromium plating solution" for short. In addition, the "first chromium plating solution" and the "second chromium plating solution" are collectively described as "chromium plating solution".

The trivalent chromium ion (Cr ³⁺ ) constituting the chromium plating solution is obtained by dissolving the substance that becomes the source of the trivalent chromium ion, or by introducing the hexavalent chromium ion and the reducing agent into the chromium plating solution. The source of trivalent chromium ions for introducing trivalent chromium ions (Cr ³⁺ ) into the chromium plating bath, for example, a trivalent chromium compound can be cited.

The type of the trivalent chromium compound is not particularly limited, and for example, conventional trivalent chromium compounds can be exemplified. More specifically, chromium sulfate, chromium chloride, chromium hydroxide, chromium carbonate, chromium alum, ammonium chromium alum, chromium sodium alum, chromium acetate, chromium oxalate, chromium citrate, chromium formate, chromium acetate, fluoride Chromium, chromium malonate, chromium succinate, chromium lactate, chromium phosphate, chromium hydrogen phosphate, etc. The particularly preferred trivalent chromium compound is chromium oxalate. In this case, it has the following advantages: it is difficult to accumulate counter ions and chromium ions during repeated supply. Its decomposition products.

In the case where trivalent chromium ions are introduced by the reaction of hexavalent chromium ions and a reducing agent, the source of hexavalent chromium ions can be exemplified by conventional hexavalent chromium compounds. More specific hexavalent chromium compounds, Examples of chromic acid, anhydrous chromic acid, dichromic acid, or these salts, etc., in the case of salts, ammonium salt, potassium salt, calcium salt, zinc salt, etc. can be exemplified. The particularly preferred hexavalent chromium compound is anhydrous chromic acid, which has the following advantages: it does not introduce unnecessary cations.

The type of the aforementioned reducing agent is not particularly limited, and examples thereof include alcohols such as methanol and aldehydes such as formaldehyde, and other examples include formic acid, citric acid, and oxalic acid. Formic acid and oxalic acid have the advantage of not leaving behind because their decomposition products are gases. The particularly preferred reducing agent is oxalic acid. This situation has the following advantages: the reacted oxalic acid becomes carbon dioxide gas and is removed from the plating solution, and the unreacted oxalic acid can be used as a complexing agent.

The trivalent chromium compound derived from the trivalent chromium ion may be one type alone, or two or more types may be combined.

The hexavalent chromium ion (Cr ⁶⁺ ) constituting the chromium plating solution is obtained by introducing the hexavalent chromium ion source material into the chromium plating solution. The source of hexavalent chromium ions can be, for example, the aforementioned hexavalent chromium compound. A particularly preferred hexavalent chromium compound is chromic anhydride, and this case has the following advantages: it does not introduce unnecessary cations.

The hexavalent chromium compound derived from the hexavalent chromium ion may be one type alone, or two or more types may be combined.

The first chromium plating bath is usually one that does not contain hexavalent chromium ions, but it may also contain hexavalent chromium ions like the second chromium plating bath. For example, hexavalent chromium ions contained unavoidably can be contained in the first chromium plating bath. When the first chromium plating bath contains hexavalent chromium ions, the concentration of hexavalent chromium ions (g/L) is less than 5% relative to the concentration of all chromium ions in the first chromium plating bath (g/L) The ratio is preferably less than 1%, more preferably less than 0.01%.

The concentration of all chromium ions in the first chromium plating bath is not particularly limited, and contains sufficient The amount of chromium ion for chromium plating is sufficient.

The second chromium plating solution contains hexavalent chromium ions as essential ions. Therefore, the second chromium plating solution can be called a compromise solution of hexavalent chromium and trivalent chromium.

The total chromium ion concentration of the second chromium plating bath is not particularly limited, and it may contain chromium ions in an amount sufficient for chromium plating.

The hexavalent chromium ion concentration (g/L) of the second chromium plating bath should be 5-50% relative to the concentration (g/L) of all chromium ions in the second chromium plating bath. More preferably, the ratio of the concentration of hexavalent chromium ions in the second chromium plating solution is an upper limit of 20% relative to the concentration of all chromium ions in the second chromium plating solution.

The concentration of hexavalent chromium ion (g/L), if it is the first chromium plating solution, can refer to JIS K0102 65.1.1, which can be determined by the diphenylcarbazide absorption spectrophotometric method. On the other hand, in the second chromium plating bath (compromise bath), the concentration of hexavalent chromium ions (g/L) can be measured by direct absorption spectrophotometry (measurement of absorption by chromic acid ion at alkaline 370 nm). In addition, the total chromium concentration can be measured by the above-mentioned direct absorption spectrophotometry by oxidizing trivalent chromium to hexavalent chromium by sodium hydroxide and hydrogen peroxide. In addition, the trivalent chromium concentration can be calculated by taking the difference between the above-mentioned total chromium concentration and the measurement result of the hexavalent chromium concentration.

In addition, the palladium ion concentration (g/L) can be determined by atomic absorption spectroscopy.

The source of palladium ions for introducing palladium ions into the chromium plating solution, for example, may include at least one selected from the group of metallic palladium, palladium alloys, and palladium compounds. In addition, the te ion in this specification is not limited to Pd ²⁺ , and may contain a complex of Pd(II) or a palladium ion other than divalent.

Metallic palladium refers to palladium alone.

Palladium alloy is an alloy composed of palladium and other metal elements. Other metal elements The element is not particularly limited, and it may be selected from the group consisting of iridium, ruthenium, rhodium, iron, cobalt, nickel, tin, copper, silver, gold, platinum, titanium, zirconium, hafnium, niobium, tantalum, chromium, molybdenum and tungsten. The alloy of metal material and palladium. The other metal elements constituting the palladium alloy are only one or more than two.

Palladium compounds, including palladium sulfate, sulfite, organic acid salt, citrate, nitrate, nitrite, carbonate, acetate, sulfide, chloride, oxide, hydroxide, halide Wait. A particularly preferred palladium compound is palladium sulfate powder, which has the following advantages: it can prevent deterioration during storage and does not introduce unnecessary anions.

The palladium compound can be obtained by using only one compound or a combination of two or more compounds.

The source of gold ions for introducing gold ions into the chromium plating solution can be, for example, at least one selected from the group of metallic gold, gold alloys, and gold compounds. In addition, the gold ions in this specification are not limited to Au ³⁺ , and may contain Au(I) or Au(III) complexes or other valence gold ions.

Metallic gold refers to individual gold itself.

Gold alloy is an alloy composed of gold and other metal elements. Other metal elements are not particularly limited, and can be exemplified selected from iridium, ruthenium, rhodium, iron, cobalt, nickel, tin, copper, silver, platinum, palladium, titanium, zirconium, hafnium, niobium, tantalum, chromium, molybdenum and tungsten The group of metal materials and gold alloy. The other metal elements constituting the gold alloy are only one or more than two.

Gold compounds, including gold chlorides, bromides, iodides, fluorides, sulfites, thiosulfates, organic acid salts, thiourea complexes, other organic complexes, gold cyanide salts, and fluorine Gold chloride, gold chloride, gold bromide, gold iodide, etc. The particularly preferred gold compound is gold sulfite. In this case, it has the following advantages: it is not compatible with gold and the substances brought into the plating solution. Prone to problems.

The gold compound can be obtained by using only one compound or a combination of two or more compounds.

In the chromium plating solution of this embodiment, the palladium ion concentration (mg/L) and gold ion concentration (mg/L) of the chromium plating solution can be appropriately set according to the anode material, anode area and composition adjustment method. For example, for the palladium ion concentration (mg/L) or gold ion concentration (mg/L) of the chromium plating bath, the lower limit is 0.1 mg/L and the upper limit is 1000 mg/L. In this case, it becomes easier to suppress the increase in the concentration of hexavalent chromium in plating, and good chromium plating can be easily performed over a long period of time, and poor plating is also difficult to occur. In particular, the first chromium plating solution whose palladium ion concentration is in the above range is very effective in suppressing the occurrence of poor plating. In the chromium plating solution of this embodiment, the lower limit of the palladium ion concentration of the chromium plating solution is preferably 1 mg/L, and the upper limit of the palladium ion concentration of the chromium plating solution is 100 mg/L. In addition, in the chromium plating solution of this embodiment, the lower limit of the gold ion concentration (g/L) of the chromium plating solution is preferably 200 mg/L.

The chromium plating solution of this embodiment may contain other additives other than the above-mentioned ions as long as it does not hinder the effects of the present invention. Such additives are not particularly limited. For example, organic acids, inorganic acids, and salts of these generally added to plating solutions can be mentioned. In addition, it can also contain pH buffer, conductive salt, reduction accelerator, surface regulator, gloss agent, pit inhibitor, stress regulator, film hardness regulator, complexing agent, and source of alloy metal ions for alloy plating , For composite coating of solid particles, etc. For example, oxalic acid may be added to the second chromium plating solution. In this case, oxalic acid is reduced on the cathode side during the plating process, and carbon eutectoids can be made.

The solvent of the chromium plating bath is usually water. The type of water is also not particularly limited. Examples include pure water, ion-exchanged water, distilled water, purified water, tap water, etc., usually in order to avoid chloride ionization. The mixing of the sons is ion-exchanged water or distilled water.

In the chromium plating solution of this embodiment, any one of the first chromium plating solution and the second chromium plating solution contains at least one selected from the group of palladium ions and gold ions as essential ions. As a result, the chromium plating using the chromium plating solution can suppress the increase in the concentration of hexavalent chromium in the anode, and can perform good chromium plating over a long period of time. Various reasons can be considered for suppressing the increase in the concentration of hexavalent chromium in the anode. One of the reasons is to predict that palladium compounds or gold compounds are formed on the anode surface by electrolysis, which promotes the generation of oxygen, or suppresses the oxidation of trivalent chromium to 6 Valence chromium.

Compared with the traditional chrome solution, the anode, because "Cr ³⁺ + 3e ^- → Cr ^6+" of the reaction likely to occur by the concentration of hexavalent chrome, the present embodiment patterns the chrome solution, the system can suppress the concentration of hexavalent chromium Producer.

As mentioned above, because the chromium plating solution of this embodiment can suppress the undesired increase in the concentration of hexavalent chromium, it is difficult to cause plating defects, and it also reduces frequent waste of degraded plating solution and preparation of new plating solution It is necessary and excellent from the viewpoint of operating cost and environmental load.

The method of preparing the chromium plating solution of this embodiment is not limited. For example, the first chromium plating solution can be prepared by mixing the aforementioned trivalent chromium ion source, palladium ion source and/or gold ion source, and water in a predetermined amount. In addition, the second chromium plating solution can be prepared by mixing the above-mentioned trivalent chromium ion source, hexavalent chromium ion source, palladium ion source and/or gold ion source, and water into a predetermined amount. The order of these mixing is not limited and can be arbitrary. In addition, the added additives can also be added at the same time as needed.

Palladium ions, for example, by dissolving at least one selected from the group of metallic palladium, palladium alloys and palladium compounds (hereinafter referred to as the "dissolving step"), and impregnating metals selected from metallic palladium, palladium alloys and palladium compounds At least one step in the group (hereinafter referred to as the "impregnation step") to One less step is introduced into the chrome plating bath. Gold ions, for example, at least one selected from the group consisting of metallic gold, gold alloys and gold compounds are also introduced into the chromium plating solution through the same dissolving step and/or dipping step as described above.

In the dissolution step, the palladium ion source and/or the gold ion source are dissolved in water to generate palladium ions and/or gold ions; the immersion step, the palladium ion source and/or the gold ion source is gradually dissolved in the water to generate palladium ions And/or gold ions. When the source of palladium ions and/or the source of gold ions are dissolved in water, chromium ions or other additives can also be introduced into the water in advance. In addition, the palladium ion source and/or the gold ion source are also immersed in water, and chromium ions or other additives can also be introduced into the water in advance.

The method of dissolving or impregnating the source of palladium ions and/or the source of gold ions is not particularly limited. For example, it can be carried out by a conventional process. The temperature at which the source of palladium ions and/or the source of gold ions is dissolved or immersed in water is also not particularly limited, and it can be carried out at room temperature of about 25°C, or can be carried out under heating. In this process, substances that promote the dissolution of palladium and/or gold, such as acids and/or complexing agents, can also be used together, and the impregnated palladium ion source and/or gold ion source can also be used as the electrode to adjust the dissolution by electrolysis speed.

For example, when the palladium ion source is dissolved in water, ammonia water may be used in combination. In this case, the palladium ion source is easier to dissolve in water.

In addition, when the palladium ion source and/or the gold ion source are dissolved or immersed, the trivalent and/or hexavalent chromium ion source can be introduced into the water in advance to make the trivalent and/or hexavalent chromium ion exist, and use this existence 3 The water of valence and/or hexavalent chromium ions is subjected to the above dissolving step and immersion step. Alternatively, before introducing trivalent and/or hexavalent chromium ions into the water, perform the above-mentioned dissolution step and immersion step, and introduce the source of palladium ions and/or gold ions into the water, and then introduce trivalent and/or hexavalent chromium ions into the water. / Or hexavalent chromium ion. Of course, the introduction of trivalent and/or hexavalent chromium ions into water and the introduction of palladium ions and/or gold ion sources into water can also be carried out simultaneously, and the sequence is not limited.

Any one of the dissolution step and the immersion step is to form the desired te ion concentration and gold ion concentration, and appropriately adjust the amount of palladium ion source and gold ion source used, dissolution time, immersion time, temperature, etc. can.

When preparing the chromium plating solution, either one of the above-mentioned dissolution step and the immersion step may be selected, or both may be selected. However, from the viewpoint of preparing the chromium plating solution by a simpler step, the selection of the dissolution step and the immersion step One of them is better.

The chromium plating solution prepared as above contains palladium ions or gold ions as essential ions, so that the increase in the concentration of hexavalent chromium can be suppressed during chromium plating, and good chromium plating can be performed over a long period of time.

<Plating method>

The method of plating the object to be plated using the above-mentioned chromium plating solution is not particularly limited. For example, a conventional plating method can be used.

The anode is not particularly limited. For example, an insoluble anode or other electrode can be used. Specific examples of the anode include iridium oxide-coated titanium, ruthenium oxide-coated titanium, other oxide-coated titanium, platinum and platinum-coated titanium, carbon, lead, and lead alloys.

As the anode, an anode containing palladium and/or gold ions can also be used. In this case, both anode and palladium ion and/or gold ion source can be combined. That is, with the palladium anode and/or gold ion anode, palladium ions and/or gold ions can be introduced into the plating bath. In this case, as the palladium and/or gold gradually dissolve with the plating, it is easier to suppress the increase of hexavalent chromium generated during the plating process, and it can be Better plating is performed over a long period of time.

The anode containing palladium and/or gold ions may be an electrode composed of palladium and/or gold alone, or may be an electrode composed of a material containing at least palladium and/or gold. An electrode composed of a material containing palladium can exemplify an electrode composed of palladium alloy, palladium-coated titanium, palladium alloy-coated titanium, and palladium oxide-containing oxide-coated titanium; an electrode composed of a material containing gold can exemplify an electrode composed of gold alloy, gold Electrode coated with titanium, gold alloy coated titanium, and gold oxide containing oxide coated titanium. In addition, the above-mentioned anode containing palladium and/or gold ions may be used in combination with other electrodes for electroplating.

By using the plating method of the chromium plating solution of this embodiment as described above, the plating object, for example, can be plated with a metal containing 10% by mass or more of chromium. That is, by the above-mentioned plating method, a plating alloy containing 10% by mass or more of chromium or a composite plating film containing 10% by mass or more of metallic chromium can be formed on the object to be plated by chromium plating.

In the case of alloy plating, alloy components other than chromium include boron, carbon, nitrogen, oxygen, sulfur, phosphorus, iron, cobalt, nickel, copper, molybdenum, tungsten, etc. If oxalic acid or formic acid is added, carbon can be contained in the plating film together with chromium. In addition, if nickel sulfate is added, nickel can be contained together with chromium.

Composite plating is formed by suspending solid particles in the plating solution and penetrating into the film while the plating is deposited. The particles used for this can be exemplified by alumina, tungsten carbide, silicon carbide, diamond, cubic boron nitride, fluororesin and the like.

[Example]

Hereinafter, the present invention will be explained in more detail through examples, but the present invention is not limited to the aspects of these examples.

(Example 1)

Dissolve 26g/L of chromium sulfate (containing 7g/L of trivalent chromium), 160g/L of sodium sulfate as a conductive salt, 75g/L of boric acid as a pH buffer, and 10g/L of malic acid as a complexing agent in distilled water, Here, ammonia water and palladium sulfate were added to make the palladium concentration 50 mg/L.

Electroplating is performed using the above trivalent chromium plating solution. As the anode, an iridium oxide coated titanium anode of 1 cm ^{2 was used} . The electroplating tank uses porous glass that separates 50 mL of the cathode chamber and 50 mL of the anode chamber. This assumes that the hexavalent chromium produced at the anode has not been reduced at the cathode but has accumulated. The plating conditions are: anode and cathode current density 5A/dm ² , pH 3.4, temperature 60°C.

(Comparative example 1)

In the preparation of the trivalent chromium plating solution, except that palladium sulfate was not used, a trivalent chromium plating solution was prepared under the same conditions as in Example 1, and chromium plating was performed. The concentration of palladium ions in the trivalent chromium plating bath is 0 mg/L.

Figure 1 shows the results of the plating treatments of Example 1 and Comparative Example 1, showing the relationship between the energization time and the concentration of hexavalent chromium in the trivalent chromium plating bath.

Compared with Example 1, the concentration of hexavalent chromium hardly increased even after the energization time passed, and could be maintained below the detection limit of about 2 mg/L. In Comparative Example 1, it was observed that the hexavalent chromium concentration increased significantly with the passage of the energization time. increase. It can be seen that the presence of te ions significantly inhibits the increase in the concentration of hexavalent chromium.

(Example 2)

In order to form a trivalent chromium concentration of 88g/L, a hexavalent chromium concentration of 16g/L, and a oxalic acid concentration of 230g/L, 200g/L of anhydrous chromic acid as a source of hexavalent chromium ions and oxalic acid as a reducing agent and a complexing agent Hydrate 640g/L is reacted in distilled water, and 75g/L ammonium sulfate as conductive salt and pH buffer and about 200mg/L palladium sulfate are added here to perform a compromise solution of trivalent chromium and hexavalent chromium (second chromium plating Liquid) of the preparation. The concentration of palladium ions in the obtained plating solution was 100 mg/L. In addition, trivalent chromium is introduced by the reaction of hexavalent chromium and oxalic acid, and the initial concentration of all plating ions in the plating solution is 104 g/L.

Using the above compromise solution, chrome plating is performed. The anode uses an iridium oxide-coated titanium anode of 0.1 dm ² ; the cathode uses an iron electrode of 0.1 dm ² . The tank uses a single tank with a capacity of 1000 mL. This is because it is inconvenient to reduce or increase the concentration of hexavalent chromium in the compromise bath. Therefore, the effects of the generation of hexavalent chromium at the anode and the reduction of hexavalent chromium at the cathode are evaluated in total. The plating conditions are anode and cathode current density 20A/dm ² , pH 2.0, temperature 60°C.

(Example 3)

Except that the amount of palladium sulfate in the preparation of the compromise solution was changed to about 20 mg/L, chromium plating was performed under the same conditions as in Example 2. The palladium ion concentration in the obtained plating solution was 10 mg/L.

(Example 4)

Except that the amount of palladium sulfate in the preparation of the compromise solution was changed to about 2 mg/L, chromium plating was performed under the same conditions as in Example 2. The palladium ion concentration in the obtained plating solution is 1mg/ L.

(Example 5)

Palladium sulfate is not used in the preparation of the compromise solution, and the palladium-coated platinum anode is energized for 5 hours before plating to introduce the palladium ions into the plating solution, and the palladium-coated platinum anode is directly plated. Otherwise, chromium plating was performed under the same conditions as in Example 2. The palladium ion concentration in the plating solution during plating is 8 mg/L.

(Example 6)

Palladium sulfate is not used in the preparation of the compromise solution, and gold ions are introduced into the plating solution by energizing the gold anode for 5 hours before plating, and the iridium oxide-coated titanium anode is used for plating during plating. Chrome plating was performed under the same conditions as in Example 2. The concentration of gold ions in the plating solution during plating is 200 mg/L.

(Comparative example 2)

In the preparation of the compromise solution, a compromise solution of trivalent chromium and hexavalent chromium was prepared under the same conditions as in Example 1, except that palladium sulfate was not used, and chromium plating was performed. The concentration of palladium ions in the plating solution is 0 mg/L.

(Comparative example 3)

Except that palladium sulfate was not used in the preparation of the compromise solution and the anode was changed to a lead anode, chromium plating was performed under the same conditions as in Example 2. The concentration of palladium ions in the plating solution is 0mg/L.

(Comparative Example 4)

Except that palladium sulfate was not used in the preparation of the compromise solution and the anode was changed to a platinum anode, chromium plating was performed under the same conditions as in Example 2. The concentration of palladium ions in the plating solution is 0 mg/L.

Figure 2 shows the results of the plating treatments of Examples 2-7 and Comparative Examples 2-4, showing the relationship between the energization time and the concentration of hexavalent chromium in the compromise solution.

With the passage of the energization time, in Examples 4 and 6, although the concentration of hexavalent chromium increased, the degree was small. In Examples 2, 3, and 5, the concentration of hexavalent chromium hardly increased. In contrast, Comparative Examples 2 to 4 , It can be observed that the concentration of hexavalent chromium increases significantly with the passage of the electrification time. It can be seen that the presence of palladium ions and the presence of gold ions significantly inhibit the increase in the concentration of hexavalent chromium. In addition, from the comparison between Example 3 and Example 5, it can be seen that when a palladium anode is used as the anode, the effect of suppressing the concentration of hexavalent chromium is high.

Further evaluation of the plating quality of each plating solution after 50 hours of electrification showed that normal plating was obtained compared to Examples 2, 3, 4, 5, and 6, and Comparative Examples 2 to 4 were poor in plating. In addition, Examples 2, 3, and 5 also obtained normal plating after 100 hours of electrification. It can be seen that by the presence of palladium ions or gold ions, good chromium plating can be performed over a long period of time.

From the above results, for example, the first chromium plating solution can suppress the increase in the hexavalent chromium concentration of the plating solution caused by the generation of hexavalent chromium in the anode to less than 2mg/L. In addition, the second chromium plating solution (Compromise solution), it can be suppressed to less than 40g/L.

【Industrial Utilization】

According to the present invention, in the plating process, the increase of the harmful hexavalent chromium concentration can be suppressed, and good plating can be performed for a long period of time. Therefore, decorative applications and industrial applications can be applied to various fields while suppressing the load on the environment.

Claims (7)

A chromium plating solution, characterized in that it contains trivalent chromium ions, and at least one selected from the group consisting of palladium ions and gold ions, and does not contain halogen ions. A chromium plating solution, characterized in that it contains trivalent chromium ions, hexavalent chromium ions, and at least one selected from the group consisting of palladium ions and gold ions, and does not contain halogen ions. For the chromium plating solution described in item 2 of the scope of patent application, the concentration of the aforementioned hexavalent chromium ions (g/L) relative to the concentration of all chromium ions (g/L) is a ratio of 5-50%. For example, the chromium plating bath described in any one of items 1 to 3 in the scope of the patent application, wherein the concentration of palladium ion or gold ion is above 0.1 mg/L and below 1000 mg/L. An electroplating method characterized by the chromium plating solution described in any one of items 1 to 4 in the scope of the patent application for plating a metal containing 10% by mass or more of chromium on an object to be plated. The electroplating method described in item 5 of the scope of patent application, wherein an anode containing at least one selected from the group consisting of palladium and gold ions is used. A method for manufacturing a chromium plating solution, which is the method for manufacturing a chromium plating solution as described in any one of items 1 to 4 in the scope of the patent application, and is characterized by dissolving metal palladium, palladium alloys, palladium compounds, metal gold, The step of at least one of the group of gold alloys and gold compounds, and the step of impregnating at least one selected from the group of metallic palladium, palladium alloys, palladium compounds, metallic gold, gold alloys and gold compounds, and by At least one of the foregoing steps is to introduce palladium ions or gold ions.

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