KR100970951B1 - Trivalent chromium electroplating solution for decoration - Google Patents

Abstract

The present invention relates to a decorative trivalent chromium plating solution.

The trivalent chromium plating solution for decoration according to the present invention is a trivalent chromium compound 0.4 to 0.6M to which chromium sulfate (Cr ₂ (SO ₄ ) ₃ ) or chromium chloride salt (CrCl ₃ ) is applied, and malonic acid (malonic acid). ) And a complexing agent that contains at least one of formic acid and inhibits the polymerization reaction of the trivalent chromium compound contained in the aqueous solution, and the trivalent chromium ion including KCl and NH ₄ Cl. 0.8 ~ 1.2M conduction aid to increase electric conductivity, 0.8 ~ 1.2M buffer to stabilize hydrogen ion index of aqueous solution, 8 ~ 12g / l depolarizing agent to inhibit trivalent chromium oxidization, and effective plating Organic ion additive 1 ~ 6.5g / l, which is a plating active additive composed of sulfonamide and sucralose to expand the current range and the effective hydrogen ion index range, and the hydrogen ion index (pH) (KOH), the stability of the plating solution and the adhesion of the plating layer Comprising: a reducing agent, 10 ~ 100ppm, has an effective current applied to the range of 3-5 effective hydrogen ion exponent, and 1 to 25A / dm ² ranges. According to the present invention, there is an advantage that the reactivity is increased and the plating layer is easily formed.

Trivalent chromium, plating solution, organic additives, decorative plating

Description

Trivalent chromium electroplating solution for decoration}

1 is a table showing the composition and electroplating conditions of the trivalent chromium plating solution according to the present invention.

2 is a process flowchart showing a method for producing a trivalent chromium plating solution according to the present invention.

Figure 3 is a hull cell (hull cell) test results showing the thickness change of the plating layer according to the change of the current density in one embodiment of the trivalent chromium plating solution according to the present invention.

Figure 4 is a hull cell (hull cell) test results showing a change in the thickness of the plating layer according to the change in the current density in another embodiment of the trivalent chromium plating solution according to the present invention.

Figure 5 is a photograph showing the current efficiency and thickness of one embodiment in a trivalent chromium plating solution according to the present invention.

Explanation of symbols on the main parts of the drawings

S100. Distilled water heating step S200. First buffer dissolution step

S300. Conduction auxiliary dissolving step S400. Trivalent chrome stirring step

S500. Distillation level ratio step S600. Second buffer dissolution step

S700. Complexing agent addition step S800. Solution mixing step

S900. Hydrogen ion index adjustment step S1000. Addition step

The present invention relates to a decorative trivalent chromium plating solution, and more particularly, to a decorative trivalent chromium plating solution to facilitate the formation of a plating layer by increasing the reactivity.

Chromium plating is a plating process that is the most common among the various plating processes and corresponds to the final treatment, and may be classified into decorative plating for obtaining a beautiful glossy metal surface and hard plating for the purpose of increasing wear resistance.

In the case of decorative plating, the plating thickness is 2 / 10,000 ~ 1 / 1,000mm, and it is mainly used for surface plating of brass in tableware and other disposable products, and hard plating is 5 / 1,000 to 1mm for several minutes depending on the wear life. To this end, it is used for screw fixing part of camera lens, fitting part of precision machine, inner surface of mold, printing plate surface, etc. to prevent wear.

In general, chromium plating is electroplated by using a solution of sulfuric acid (H ₂ SO ₄ ) mixed with hexavalent chromium (CrO ₃ ). The anode is not used with chromium metal and is not eroded by sulfuric acid such as lead. The chromium reduction in solution is supplemented with chromic acid to continue electrodeposition.

In addition, there are high concentrations and low concentrations of chromic acid in the plating liquid used for chromium plating, and various types of plating can be obtained depending on the temperature of the liquid and the density of the current. As such, hexavalent chromium plating has an advantage of excellent reflectivity, color, corrosion, corrosion resistance, and high current efficiency.

However, in spite of these advantages, hexavalent chromium plating generates chromic vapors that are deadly to humans during the process, and when hexavalent chromium ions enter the groundwater or river, it causes fatal environmental pollution. Is holding.

In other words, hexavalent chromium is classified as a cancer-causing substance by the International Agency of Research on the Cancer (LARC), and its replacement technology is required in addition to prohibiting the use of hexavalent chromium in the future. Research for the development of materials is actively underway.

Various attempts to replace hexavalent chromium plating include ion-nitriding, plasma spraying, and ion plating, but the cost is 5 to 10 times that of hexavalent chromium plating. There are problems to be added and difficult to apply to large products.

Accordingly, chromium plating using trivalent chromium is recognized as the most effective and efficient.

However, trivalent chromium ions included in the trivalent chromium plating solution have a very complex coordination chemical structure in an aqueous solution, and have a problem in that a chromium plating layer is difficult to form due to low reactivity.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems, and more particularly, to provide a decorative trivalent chromium plating solution that facilitates plating layer formation by increasing the plating solution reactivity in a low current region.

The trivalent chromium plating solution for decoration according to the present invention is a trivalent chromium compound 0.4 to 0.6M to which chromium sulfate (Cr ₂ (SO ₄ ) ₃ ) or chromium chloride salt (CrCl ₃ ) is applied, and malonic acid (malonic acid). ) And a complexing agent that contains at least one of formic acid and inhibits the polymerization reaction of the trivalent chromium compound contained in the aqueous solution, and the trivalent chromium ion including KCl and NH ₄ Cl. 0.8 ~ 1.2M conduction aid to increase electric conductivity, 0.8 ~ 1.2M buffer to stabilize hydrogen ion index of aqueous solution, 8 ~ 12g / l depolarizing agent to inhibit trivalent chromium oxidization, and effective plating Organic ion additive 1 ~ 6.5g / l, which is a plating active additive composed of sulfonamide and sucralose to expand the current range and the effective hydrogen ion index range, and the hydrogen ion index (pH) (KOH), the stability of the plating solution and the adhesion of the plating layer Comprising: a reducing agent, 10 ~ 100ppm, has an effective current applied to the range of 3-5 effective hydrogen ion exponent, and 1 to 25A / dm ² ranges.

The buffer is characterized in that to stabilize the acceleration of the polymerization reaction of trivalent chromium ion.

The depolarizing agent is characterized by inhibiting the binding of trivalent chromium ion and OH ^- ion.

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The depolarizing agent is characterized in that any one of NH ₄ Br, NaBr, NaF.

The buffer is characterized in that H ₃ BO ₃ is applied.

As the reducing agent, an inorganic material having Fe ²⁺ or Co ²⁺ is applied, and an organic material which is any one of hydrazine, sodiumborohydride, and dimethylaminoborane is optionally included.

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According to the decorative trivalent chromium plating solution having such a configuration, there is an advantage in that the plating solution is easily formed in the low current region (0.25 to 5 A / dm ² ), so that the plating layer can be easily formed.

Hereinafter, the configuration of the decorative trivalent chromium plating solution according to the present invention will be described.

As shown in the drawings, the decorative trivalent chromium plating solution according to the present invention comprises a trivalent chromium compound for providing trivalent chromium ions, and a complexing agent such that the trivalent chromium compound is inhibited from polymerization in an aqueous solution. A conductive aid for increasing the electrical conductivity of the trivalent chromium ion, a buffer for stabilizing the hydrogen ion index of the aqueous solution, a polarizing agent for inhibiting the trivalent chromium ion from being oxidized divalent, and an increase in the ability to form the plating layer It comprises an organic material additive for, and a reducing agent for increasing the stability and plating adhesion of the plating layer liquid.

The trivalent chromium compound is typically present in _two types of sulfides (Cr ₂ (SO ₄ ) ₃ ) and chlorides (CrCl ₃ ). In an embodiment of the present invention, chromium sulfate (Cr ₂ (SO ₄ ) ₃ ) is applied. The chromium sulfate salt is 0.4 to 0.6M in the trivalent chromium plating solution.

Therefore, the trivalent chromium contained in the chromium sulfide eventually forms a chromium film layer and may be configured by applying chromium chloride salt (CrCl ₃ ).

The complexing agent is a component for preventing polymerization (curing) of the trivalent chromium ion contained in the trivalent chromium compound, and malonic acid or formic acid is selectively used. The trivalent chromium plating solution contains 0.8 to 1.2 M.

More specifically, the complexing agent may be used at least one of malonic acid and formic acid.

The trivalent chromium plating solution contains 0.8 to 1.2 M of a buffer. The buffer stabilizes the plating solution by allowing the hydrogen ion index (pH) of the trivalent chromium plating solution to be approximately 4, and boric acid (H ₃ BO ₃ ) is applied in the embodiment of the present invention.

That is, the trivalent chromium ion accelerates the polymerization reaction when the hydrogen ion index (pH) is 4 or more in a localized region due to coordination chemical properties, and the buffer is configured to stabilize the acceleration of the polymerization.

Therefore, the plating is possible only up to the hydrogen ion index 4 using the general trivalent chromium plating solution configuration, but the effective hydrogen ion index can be expanded to 5 using the plating solution.

The trivalent chromium plating solution contains 0.8 to 1.2 M of a conductive auxiliary agent, and the conductive auxiliary agent includes one or more of KCl, NH ₄ Cl, K ₂ SO ₄ , and (NH ₄ ) ₂ SO ₄ . Therefore, when the plating is performed by desalination of the (plated body) semi-finished product which is required to be plated in the trivalent chromium plating solution containing the conductive assistant, the conductive assistant improves the electrical conductivity to help the formation of the chromium film.

The depolarizing agent is included in the trivalent chromium plating solution 8 to 12 g / l. The depolarizing agent is for preventing the formation of the trivalent chromium plating layer by the polymerization reaction occurring when the olation reactors are bonded to each other, and any one of NH ₄ Br, NaBr, and NaF is applied.

More specifically, the trivalent chromium ion is hydrated in the structure of octahedral by combining with six water molecules in an aqueous solution, and the hydrated chromium ion is converted into OH ⁻ ion when the hydrogen ion index is 4 or more. Substituted and hydrolyzed.

Accordingly, hydrolyzed chromium ions, hydrated chromium ions, and hydrolyzed chromium ions are bonded to each other by OH ^- groups to cause an Olation reaction, which causes the Olation reactors to bind to each other and interfere with chromium electrodeposition. Polymerization reaction is induced.

The depolarizer prevents the oxidation reaction by inhibiting oxidation by allowing other anions to be combined with chromium ions instead of OH ⁻ anions.

The organic additive is a plating active additive is added within the concentration range of 1 to 6.5g / l. The plating active additive is configured to extend the effective plating current range by facilitating the plating of the low current region.

The plating active additive, TritonX-100, Gelatin, Benzotriazole, Urea, Oxtoxynol, p-Toluene sulfonamide, Saccharin, aspartame, sucralose, acesulfame-K, 1 to 4 g / l is added It serves to increase the gloss of the surface of the plating layer.

The reducing agent is included to increase the gloss current region of the plating layer, improve adhesion, and increase the plating bath life. The reducing agent may be included in an aqueous solution of 10 to 100 ppm, an inorganic material may be applied, and an organic material may be optionally included.

More specifically, the inorganic material includes Fe ^{2 +} or Co ^{2 +} , FeSO ₄ , FeS, FeCl ₂ , Fe (C ₂ O ₄ ), Fe (CH ₃ CO ₂ ) ₂ , (NH ₄ ) ₂ Fe (SO ₄ ) ₂ , Co (NO ₃ ) ₂ , CoCl ₂ is applied.

And, the organic material is any one of hydrazine, sodiumborohydride, dimethylaminoborane is applied.

Therefore, when electrodeposition plating is performed while the inorganic material or organic material is contained in the trivalent chromium plating solution, the adhesion of the trivalent chromium plating layer on the surface of the semi-finished product is improved.

Hereinafter, a method of manufacturing a decorative trivalent chromium plating solution as described above will be described with reference to FIGS. 1 and 2.

1 is a table showing the composition and electroplating conditions of the trivalent chromium plating solution according to the present invention, Figure 2 is a process flow chart showing a method for producing a trivalent chromium plating solution according to the present invention.

As shown in these drawings, the trivalent chromium compound in the examples of the present invention is Cr ₂ (SO ₄ ) ₃ , formic acid (HCOOH) and malonic acid (CH ₂ (COOH) ₂ ) as a complexing agent, NH ₄ Cl as a conduction aid, a buffering agent. Furnace H ₃ BO ₃ , NH ₄ Br as a depolarizing agent, a plating active additive is applied as an organic additive.

Finally, 100 to 500 ppm of FeSO ₄ was applied to the reducing agent.

Hereinafter, a method of manufacturing a decorative trivalent chromium plating solution configured as described above will be described with reference to FIG. 2.

First, 400 ml of distilled water is put into a first container, and a distilled water heating step (S100) of heating at 70 ° C. is performed. After 60g of the buffer (H ₃ BO ₃ ) is added to the heated distilled water and completely dissolved. (First buffer dissolution step (S200))

53.5 g of a conductive aid (NH ₄ Cl) and 74,5 g of KCl are added to the first container and then dissolved (conductive auxiliary solution dissolution step: S300).

The trivalent chromium compound is added to the first container in which the conduction aid is dissolved, and the trivalent chromium stirring step (S400) of stirring for 16 to 24 hours is performed.

Then prepare a second vessel and fill the second vessel with 200ml of distilled water (distillation level ratio step: S500)

56 g of a buffer (H ₃ BO ₃ ) is added to and dissolved in the second container filled with distilled water. At this time, since the temperature rises sharply, it is cooled to 40 to 50 ℃. (Second buffer dissolving step: S600).

Thereafter, 46 g of the complexing agent (formic acid) is added to the second container, and then cooled to 40 to 50 ° C. (complexing agent addition step: S700).

The solution mixing step (S800) is performed by mixing the solution inside the second container with the complexing agent added thereto and the solution inside the first container.

Then, a hydrogen ion index adjusting step (S900) of adding a hydrogen ion index adjuster (KOH) to the mixed solution is performed.

At this time, the hydrogen ion index (pH) is adjusted by the hydrogen ion index adjuster.

Finally, the addition of 1 to 6.5 g / l of organic substance additive, 8 to 12 g / l of depolarizing agent and 100 to 500 ppm of reducing agent is performed to the mixed solution to complete the preparation of the trivalent chromium plating solution (addition Step: S1000).

The trivalent chromium plating solution prepared according to the above process has a hydrogen ion index (pH) of about 4.

The hull cell experiment was performed under the experimental conditions as shown in FIG.

First, a trivalent chromium plating solution configured as shown in FIG. 1 is prepared inside a plating bath, and then a plurality of specimens are cut to the same size and prepared.

Then, the negative electrode is connected after supporting the specimen in the decorative trivalent chromium plating solution prepared according to the manufacturing method of the present invention described above. In addition, an anode is applied to the plating bath to flow a current.

In this case, it is preferable that graphite and an insoluble anode are used as a portion connected to the anode in the plating bath. More specifically, the insoluble anode is a composite containing at least one of Ir, Ta, Pt is applied.

In addition, when the current is applied, the effective current application range is performed within the range of 1 to 25 A / dm ² .

Hereinafter, the results of measuring the change in current density and thickness by plating with the trivalent chromium plating solution prepared as described above are shown in FIGS. 3 to 7.

That is, FIGS. 3 to 5 are experimental results of the decorative trivalent chromium plating solution, and malonic acid was applied as a complexing agent in FIGS. 3 and 5, and formic acid was applied to FIG. 4.

As shown in FIG. 3, malonic acid was applied as the additive, and SO ₄ salt + Cl salt and Cl salt were applied as conduction aids, respectively, and the current density was changed from 0.25 A / dm ² to 25 A / dm ² when the thickness of the plating layer. Was measured.

As a result of the measurement, when only Cl salt was used as the conductive support agent, a thicker plating layer was formed, and all the colors were silver white.

When the formic acid is applied as the complexing agent under the same conditions as in FIG. 3, the thickness change and the outer surface of the plating layer are as shown in FIG. 4.

In addition, as shown in FIG. 5, when the malonic acid was applied as the complexing agent and the current density was maintained at 10 A / dm ² for 5 minutes, the current efficiency was lowered from 42% to 9.5%, and the hydrogen ion index (pH) was 3.5. Changed from 4.6 to.

The scope of the present invention is not limited to the above-described embodiments, and many other modifications based on the present invention will be possible to those skilled in the art within the scope of the present invention.

As described in detail above, in the decorative trivalent chromium plating solution according to the present invention, a plating active additive which extends the effective plating current range and the effective hydrogen ion index range of the plating solution is added.

Therefore, the plating layer is easier to form, and there is an advantage that the thickness of the formed plating layer is even.

In addition, since the formation speed of the plating layer is increased, productivity is improved.

Claims (10)

delete delete 0.4-0.6 M _trivalent chromium compound to which chromium sulfate (Cr ₂ (SO ₄ ) ₃ ) or chromium chloride salt (CrCl ₃ ) is applied; A complexing agent containing at least one of malonic acid and formic acid, and inhibiting the polymerization reaction of the trivalent chromium compound contained in the aqueous solution, 0.8 to 1.2 M, 0.8 ~ 1.2M conduction aid to increase the electrical conductivity of trivalent chromium ion, including KCl and NH ₄ Cl, 0.8 ~ 1.2M buffer to stabilize the hydrogen ion index of the aqueous solution, 8-12 g / l of a polarizing agent which suppresses trivalent chromium ion from oxidizing to divalent, Organic additives 1 ~ 6.5g / l, which is a plating active additive composed of sulfonamide and sucralose to increase the plating layer formation capacity by expanding the effective plating current range and effective hydrogen ion index range, A hydrogen ion index adjuster (KOH) to adjust the hydrogen ion index (pH), It comprises a reducing agent 10 ~ 100ppm to increase the stability of the plating solution and the adhesion of the plating layer, A decorative trivalent chromium plating solution having an effective hydrogen ion index of 3 to 5 and an effective current application range of 1 to 25 A / dm ² . The decorative trivalent chromium plating solution according to claim 3, wherein the buffer stabilizes acceleration of the polymerization reaction of trivalent chromium ions. The decorative trivalent chromium plating solution according to claim 4, wherein the depolarizing agent inhibits the coupling of trivalent chromium ions and OH ^- ions. The decorative trivalent chromium plating solution according to claim 5, wherein the depolarizing agent is any one of NH ₄ Br, NaBr, and NaF. The decorative trivalent chromium plating solution according to claim 6, wherein the buffer is applied with H ₃ BO ₃ . The method of claim 7, wherein the reducing agent, Inorganic materials having Fe ²⁺ or Co ²⁺ are applied, Decorative trivalent chromium plating solution, characterized in that it optionally contains an organic material of any one of hydrazine, sodiumborohydride, dimethylaminoborane. delete delete

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