KR20120011584A - Trivalent chromium plating solution and plating method using the same - Google Patents

Abstract

PURPOSE: A trivalent chrome plating solution and a plating method using the same are provided to easily electroplate the surface of a mechanical component by improving covering power. CONSTITUTION: A trivalent chrome plating solution comprises a trivalent chrome compound, a complexing agent, a conductive agent, a buffer agent, a plating activation additive, a wetting agent, and a hydrogen-ion exponent adjusting agent. The complexing agent controls the polymerization reaction of the trivalent chrome compound. The conductive agent improves the electric conductivity of the trivalent chrome compound. The buffer agent stabilizes the hydrogen ion exponent of a plating solution. The plating activation additive improves the adhesion strength of the plating solution. The wetting agent removes pitting generated on a plated surface. The hydrogen-ion exponent adjusting agent adjusts the hydrogen ion exponent of the plating solution. The trivalent chrome plating solution is prepared inside a plating bath(S300).

Description

Trivalent chromium plating solution and plating method using the same

The present invention relates to a trivalent chromium plating solution and a plating method using the same, and more particularly, to a hard trivalent chromium plating solution having improved covering power.

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

In the case of decorative plating, the plating thickness is usually 0.2 ~ 0.5㎛, and is mainly used for plating the surface of brass in tableware and other disposable products, and the hard plating varies depending on the wear life requirements, but the screw fixing part of the camera lens is about 5 ~ several tens of ㎛. It is used to prevent wear on fitting parts of precision machines, inner surfaces of molds, printing plates, and the like.

In general, hexavalent chromium plating is electroplated by using a solution of sulfuric acid (H ₂ SO ₄ ) mixed with chromic acid (CrO ₃ ). The anode is not chromium metal and is not eroded by sulfuric acid such as lead. The chromium reduction in the solution is replenished 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 advantages of excellent reflectivity, color, corrosion, corrosion resistance, and high current efficiency.

However, despite these advantages, hexavalent chromium plating generates critical chromic acid vapor during the process and causes toxic environmental pollution when hexavalent chromium ions enter groundwater or rivers. Is holding.

In other words, hexavalent chromium is classified as a cancer-causing substance by the International Agency of Research on the Cancer (IARC), and its replacement technology is required along with the prohibition of the use of hexavalent chromium in the future. Research for development 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 efficient.

However, the conventional trivalent chromium plating solution is not excellent in coating power and there is a difficulty in applying electroplating to the surface of a mechanical part or a product having a complicated shape.

The problem to be solved by the present invention is to provide a trivalent chromium plating solution having excellent coating power.

Technical problems of the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

The composition of the trivalent chromium plating solution of the present invention for achieving the above technical problem is a trivalent chromium compound comprising a compound of formula (1); Complexing agents for inhibiting the polymerization reaction of the trivalent chromium compound in a plating solution; Conduction aids to increase the electrical conductivity of trivalent chromium ions; A buffer agent for stabilizing the hydrogen ion index of the plating solution; Plating active additives for increasing the forming ability and adhesion of the plating layer; A wetting agent to remove the pitting phenomenon occurring at the plating surface; And a hydrogen ion index adjuster for adjusting the hydrogen ion index of the plating liquid.

<Formula 1>

Cr ₂ (SO ₄ ) _n (OH) _6-2 n (n <3)

The manufacturing process of the plating method of the present invention for achieving the technical problem is a step of preparing the trivalent chromium plating solution in the plating bath; Supporting a plated body in the trivalent chromium plating solution; And applying a negative potential to the plated body, installing an insoluble anode in the plating bath, and applying a positive potential to the insoluble anode.

Specific details of other embodiments are included in the detailed description and the drawings.

The trivalent chromium plating solution according to the present invention has excellent coating power. In addition, the compound of Formula 1 is also used as a tanning agent (tanning agent), mass production and low cost. Therefore, a plating solution for supplying a compound of Formula 1 as a trivalent chromium compound was developed for the first time, and when the compound of Formula 1 is used as a source, a highly economical trivalent chromium plating solution can be prepared.

1 is a process flow chart showing a method for producing a trivalent chromium plating solution according to the present invention.
2 is a flowchart of a plating process using a trivalent chromium plating solution according to the present invention.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. The size and relative size of the components shown in the drawings may be exaggerated for clarity of explanation.

Like reference numerals refer to like elements throughout the specification, and "and / or" includes each and every combination of one or more of the mentioned items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. As used herein, the terms "comprises" and / or "made of" means that a component, step, operation, and / or element may be embodied in one or more other components, steps, operations, and / And does not exclude the presence or addition thereof.

Although the first, second, etc. are used to describe various components, these components are of course not limited by these terms. These terms are only used to distinguish one component from another. Therefore, of course, the first component mentioned below may be a second component within the technical spirit of the present invention.

Embodiments described herein will be described with reference to plan and cross-sectional views, which are ideal schematic diagrams of the invention. Accordingly, shapes of the exemplary views may be modified by manufacturing techniques and / or tolerances. Accordingly, the embodiments of the present invention are not limited to the specific forms shown, but also include variations in forms generated by the manufacturing process. Thus, the regions illustrated in the figures have schematic attributes, and the shape of the regions illustrated in the figures is intended to illustrate a particular form of region of the device, and is not intended to limit the scope of the invention.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used in a sense that can be commonly understood by those skilled in the art. In addition, the terms defined in the commonly used dictionaries are not ideally or excessively interpreted unless they are specifically defined clearly.

The trivalent chromium plating solution according to the present invention is a trivalent chromium compound for providing trivalent chromium ions, a complexing agent for inhibiting the polymerization reaction of the trivalent chromium compound in the plating solution, and an electric conductivity for increasing the trivalent chromium ion. Conduction aids, buffer agents to stabilize the hydrogen ion index of the plating solution, plating active additives to increase the formation ability and adhesion of the plating layer, wetting agents to remove the pitting phenomenon occurring on the plating surface, And a hydrogen ion index regulator for adjusting the hydrogen ion index of the plating liquid.

The trivalent chromium compound includes a compound represented by the following Chemical Formula 1.

<Formula 1>

Cr ₂ (SO ₄ ) _n (OH) _6-2 n (n <3)

The trivalent chromium compound may be included in the trivalent chromium plating solution at 0.4 to 1.3 mol / L, and preferably at 0.8 to 1 mol / L. Trivalent chromium contained in the trivalent chromium compound forms a chromium film layer.

The complexing agent may serve to prevent the trivalent chromium ion contained in the trivalent chromium compound from polymerizing in the plating solution. Examples of the complexing agent include formic acid, alkali metal formate, ammonium formate, and the like. The complexing agent may be included in the trivalent chromium plating solution at 0.05 to 2 mol / L, and preferably at 0.4 to 0.6 mol / L.

The conduction aid may serve to help the formation of the chromium film by improving the electrical conductivity when plating the plated body which requires plating in the trivalent chromium plating solution. Examples of conduction aids include sodium sulfate. The conductive auxiliary agent may be included in 0.1 to 0.8 mol / L in the trivalent chromium plating solution, and preferably, 0.2 to 0.4 mol / L.

The buffer allows the hydrogen ion index (pH) of the trivalent chromium plating solution to be stably maintained within a certain range. Buffers include boric acid and aluminum sulfate. High quality plating can be obtained when boric acid and aluminum sulfate as buffers are simultaneously present in the trivalent chromium plating solution. Boric acid may be included in the trivalent chromium plating solution at 0.08 to 1 mol / L, preferably 0.4 to 0.6 mol / L. Aluminum sulfate may be included in the trivalent chromium plating solution at 0.05 to 0.2 mol / L, preferably 0.1 to 0.16 mol / L.

The plating active additive may serve to expand the effective plating current range by facilitating the plating of the low current region. Carbamide may be mentioned as a plating active additive. The plating active additive may be included in 0.1 to 1.2 mol / L in the trivalent chromium plating solution, and preferably in 0.4 to 0.6 mol / L.

Wetting agents may serve to eliminate fitting phenomena that occur on the plating surface. The wetting agent may be a surfactant, and an example of the surfactant may be an organic anion-active surfactant including a sulfonic acid group. Examples of organic anionic surfactants include sodium lauryl sulfate (C ₁₂ H ₂₅ SO ₄ Na). Wetting agent may be included in 0.01 ~ 1g / L in the trivalent chromium plating solution, preferably may be included in 0.05 ~ 0.1g / L.

The hydrogen ion index adjuster may serve to adjust the hydrogen ion index of the trivalent chromium plating solution. Examples of the hydrogen ion index regulator include sulfuric acid (H ₂ SO ₄ ), sodium hydroxide (NaOH), sodium carbonate (Na ₂ CO ₃ ), and the like. The amount of hydrogen ion index modifier added to the trivalent chromium plating solution may be such that the hydrogen ion index of the trivalent chromium plating solution is in the range of, for example, 1.1 to 3.5, preferably 1.4 to 1.8.

Hereinafter, a method for preparing a trivalent chromium plating solution according to the present invention will be described with reference to FIG. 1. 1 is a process flowchart showing a method for producing a trivalent chromium plating solution according to the present invention.

First, the trivalent chromium compound is added to the heated distilled water and stirred (S100). At this time, the temperature of the distilled water may be about 70 ~ 95 ℃, stirred until the trivalent chromium compound is completely dissolved in distilled water.

Subsequently, the solution in which the trivalent chromium compound is dissolved is filtered (S110). The solution can be filtered using paper filters, fiber filters, or other types of filters.

Subsequently, a buffer and a conduction aid are added and dissolved in the filtered solution (S120). At this time, the temperature of the solution may be 70 ~ 80 ℃, the buffer and conduction aid to be added may be a solid (solid), so that the solid phase of the components completely dissolved in the solution.

Subsequently, a complexing agent is added to the solution in which the buffer and the conduction aid are dissolved (S130). The solution in which the buffer and the conduction aid are dissolved is maintained at 70 to 80 ° C., and the complexing agent is slowly added to the solution.

Subsequently, the plating bath is covered with a cover member and the solution to which the complexing agent is added is maintained at a temperature of 70 to 80 ° C. for a predetermined time (S140). You can keep it for about an hour.

Then, to cool the solution maintained for a predetermined time at a temperature of 70 ~ 80 ℃ (S150). The solution can be cooled to about 40-50 ° C.

Subsequently, the plating active additive is added to the cooled solution and then dissolved (S160). The plating active additive may be in a solid phase, and the plating active additive is completely dissolved in the solution at a temperature of 40 to 50 ° C.

Subsequently, the plating bath is covered with a cover member, and the solution in which the plating active additive is dissolved is maintained at a temperature of 40 to 50 ° C. for a predetermined time (S170). You can keep it for about an hour.

Then, to cool the solution maintained for a predetermined time at a temperature of 40 ~ 50 ℃ (S180). The solution can be cooled to room temperature.

Subsequently, distilled water is added to the cooled solution to adjust the volume of the plating solution, the hydrogen ion index of the solution is measured, and then, if necessary, a hydrogen ion index corrector is added to correct the hydrogen ion index of the solution (S190).

Subsequently, the wetting agent is added to the solution whose hydrogen ion index is corrected (S200). Wetting agent may be added in the form of a liquid containing a certain concentration of the wetting agent in distilled water.

Subsequently, distilled water is added to the solution to which the humectant is added to match the final volume of the plating solution, the hydrogen ion index of the solution is measured, and then, if necessary, a hydrogen ion index modifier is added to correct the hydrogen ion index of the solution again (S210). ).

Hereinafter, a plating process using a trivalent chromium plating solution according to the present invention will be described with reference to FIG. 2. 2 is a flowchart of a plating process using a trivalent chromium plating solution according to the present invention.

First, the trivalent chromium plating solution according to the present invention is prepared in a plating bath (S300).

Subsequently, the plated body is supported on the trivalent chromium plating solution (S310).

Subsequently, a negative potential is applied to the plated body, an insoluble anode is installed in the plating bath, and a positive potential is applied to the insoluble anode (S320). In this case, a DSA (Dimensionally Stable Anode) in which a titanium-manganese dioxide anode (TMDA), iridium oxide (IrO ₂ ), ruthenium oxide (RuO ₂ ), or the like is formed on a porous titanium plate as an insoluble anode, or A platinum coated titanium anode or the like can be used. TMDA eliminates the need for spatial separation between the cathode and anode in the plating process and eliminates the release of toxic chlorine gas during the plating process. In addition, the use of TMDA results in significantly less electrochemical oxidation from trivalent chromium to hexavalent chromium.

When the power is applied, the current density may be 15 to 30 A / dm ² , and preferably 10 to 20 A / dm ² .

In the plating process, the hydrogen ion index of the plating liquid may be maintained at 1.1 to 3.5, preferably at 1.4 to 1.8. The temperature of the plating bath may be maintained at 20 ~ 60 ℃, preferably it may be maintained at 30 ~ 40 ℃.

The thickness of the chromium plated film may be several tens of micrometers.

Hereinafter, the present invention will be described in more detail with reference to specific examples and comparative examples.

&Lt; Example 1 >

To prepare 1 L of the plating solution, 1 mol of the compound of formula 1 was added to 0.5-0.7 L of heated distilled water and stirred at 70-95 ° C. until completely dissolved.

<Formula 1>

Cr ₂ (SO ₄ ) _n (OH) _6-2 n (n <3)

Then, the solution to which the compound of formula 1 was added was filtered. 0.15 mol of aluminum sulfate, 0.5 mol of boric acid, and 0.3 mol of sodium sulfate were then added to the filtered solution at 70-80 ° C. The added solid phases were completely dissolved. Subsequently, 0.5 mol of formic acid was slowly added to the solution containing aluminum sulfate, boric acid, and sodium sulfate and maintained at 70-80 ° C. Subsequently, the plating bath containing the solution to which formic acid was added was covered with a cover member and maintained at a temperature of 70 to 80 ° C. for about one hour. Subsequently, the solution kept at a temperature of 70-80 ° C. for about one hour was cooled to 40-50 ° C. 0.5 mol of solid carbamide was then added to the stirred solution at 40-50 ° C. to complete dissolution. Subsequently, the plating bath containing carbamide was covered with a cover member and maintained at a temperature of 40 to 50 ° C. for about one hour. Subsequently, the solution maintained at a temperature of 70-80 ° C. for about one hour was cooled to room temperature. Subsequently, distilled water was added to the cooled solution so that the plating solution had a capacity of 0.9 to 0.95L. Subsequently, the hydrogen ion index of the solution to which distilled water was added was measured, and the hydrogen ion index was adjusted to 1.5 by adding sulfuric acid, sodium hydroxide, or sodium carbonate solution. Subsequently, 0.1 g of sodium lauryl sulfate was added to the solution using a sodium lauryl sulfate solution prepared at a concentration of 10 g / L in advance. Subsequently, the final volume of the plating liquid was adjusted to 1 L using distilled water. Subsequently, the hydrogen ion index of the solution adjusted to the final volume was measured again, and if necessary, the hydrogen ion index was adjusted to 1.5 by adding sulfuric acid, sodium hydroxide, or sodium carbonate solution.

<Example 2>

A plating solution was prepared under the same conditions as in Example 1 except that the hydrogen ion index was adjusted to 1.7.

 <Example 3>

A plating solution was prepared under the same conditions as in Example 1, except that 0.8 mol of the compound of Formula 1 was added.

<Example 4>

A plating solution was prepared under the same conditions as in Example 1 except that 0.2 mol of sodium sulfate was added.

Example 5

A plating solution was prepared under the same conditions as in Example 1 except that 0.8 mol of the compound of Formula 1 and 0.4 mol of formic acid were added.

<Example 6>

A plating solution was prepared under the same conditions as in Example 1 except adding 0.4 mol of carbamide and adjusting the hydrogen ion index to 1.4.

Comparative Example 1

A plating solution was prepared by adding chromium sulfate to 0.5 mol / L, 0.18 mol / L aluminum sulfate, 0.63 mol / L sodium sulfate, 0.45 mol / L carbamide, and 0.66 mol / L sodium formate instead of the compound of Formula 1. , The hydrogen ion index was adjusted to 1.4.

The coating power of the plating solution was evaluated using the plating solutions of Examples 1 to 6 and Comparative Example 1, respectively. Specifically, a disc electrode (S = 1.77 cm 2) of copper foil fixed to a plastic holder was used. Electroplating was carried out using TMDA with a constant current density without spatial separation of the cathode and anode. The plating liquid had a capacity of 0.5L. The current density increased stepwise by every 1 A / dm ² . Electroplating was carried out for 30 seconds for all current density values. The minimum current density corresponding to the point where the chromium is plated on the entire cathode surface was determined visually, and the coating force of the plating solution was measured. The results are shown in Table 1. The temperature of the plating bath was 35 degreeC in the plating process.

Minimum value of current density to deposit 100% of chromium plating on the cathode surface (A / dm ² ) Comparative Example 1 22 Example 1 15 Example 2 14 Example 3 17 Example 4 19 Example 5 17 Example 6 18

Looking at the results of Table 1, it can be seen that the minimum current density of the plating liquid of Examples 1 to 6 is much lower than the minimum current density of the plating liquid of Comparative Example 1. Therefore, the plating solution of Examples 1 to 6 using the trivalent chromium compound of Formula 1 is superior to the plating solution of Comparative Example 1 using a trivalent chromium compound such as chromium sulfate.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the present invention is not limited to the above embodiments but may be manufactured in various forms, and having ordinary skill in the art to which the present invention pertains. It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive.

Claims (13)

A trivalent chromium compound comprising a compound of Formula 1;
Complexing agents for inhibiting the polymerization reaction of the trivalent chromium compound in a plating solution;
Conduction aids to increase the electrical conductivity of trivalent chromium ions;
A buffer agent for stabilizing the hydrogen ion index of the plating solution;
Plating active additives for increasing the forming ability and adhesion of the plating layer;
A wetting agent to remove the pitting phenomenon occurring at the plating surface; And
A trivalent chromium plating solution comprising a hydrogen ion index regulator for adjusting the hydrogen ion index of the plating liquid.
<Formula 1>
Cr ₂ (SO ₄ ) _n (OH) _6-2 n (n <3) The method of claim 1,
A trivalent chromium plating solution containing the trivalent chromium compound at 0.4 to 1.3 mol / L. The method of claim 2,
The complexing agent is formic acid, alkali metal formate or ammonium formate,
A trivalent chromium plating solution containing the complexing agent at 0.05 to 2 mol / L. The method of claim 3, wherein
The conduction aid is sodium sulfate,
Trivalent chromium plating solution containing the conduction aid 0.1 to 0.8 mol / L. The method of claim 4, wherein
The buffer comprises boric acid and aluminum sulfate,
A trivalent chromium plating solution comprising the boric acid at 0.08 to 1 mol / L and the aluminum sulfate at 0.05 to 0.2 mol / L. 6. The method of claim 5,
The plating active additive is carbamide,
A trivalent chromium plating solution containing the plating active additive in an amount of 0.1 to 1.2 mol / L. The method of claim 6,
The wetting agent is sodium lauryl sulfate,
Trivalent chromium plating solution containing the humectant at 0.01 ~ 1g / L. The method of claim 7, wherein
The hydrogen ion index regulator is a trivalent chromium plating solution of sulfuric acid, sodium hydroxide, or sodium carbonate. The method of claim 1,
The trivalent chromium plating solution has a hydrogen ion index of 1.1 to 3.5. A trivalent chromium compound comprising a compound of Formula 1, a complexing agent for inhibiting the polymerization reaction of the trivalent chromium compound in a plating solution, a conduction aid for increasing the electrical conductivity of trivalent chromium ion, and a hydrogen ion index of the plating solution 3, including a buffer for stabilizing the, a plating active additive for increasing the forming ability and adhesion of the plating layer, a wetting agent for removing the fitting phenomenon occurring on the plating surface, and a hydrogen ion index adjusting agent for adjusting the hydrogen ion index of the plating solution. Preparing a chromium plating solution in the plating bath;
Supporting a plated body in the trivalent chromium plating solution; And
Applying a negative potential to the plated body, installing an insoluble anode in the plating bath, and applying a positive potential to the insoluble anode.
<Formula 1>
Cr ₂ (SO ₄ ) _n (OH) _6-2 n (n <3) The method of claim 10,
The anode includes TMDA, iridium oxide (IrO ₂ ) or ruthenium oxide (RuO ₂ ). Plating method using DSA or platinum coated titanium anode formed on porous titanium plate. The method of claim 10,
The current density in the step of applying the power is 15 ~ 30A / dm ² Plating method. The method of claim 10,
Plating method is the temperature of the plating bath is maintained at 20 ~ 60 ℃.

Images