KR20020085331A - Process for plating brass-metalloid composite - Google Patents

Abstract

PURPOSE: A brass-nonmetal composite coating process is provided which not only maintains a unique beautiful color tone, superior electric conductivity and corrosion resistance of brass coating, but also improves mechanical strength and abrasion resistance of a plating layer. CONSTITUTION: The brass-nonmetal composite coating process comprises the process of reacting the plating solution with the aqueous ammonia by adding aqueous ammonia to a plating solution comprising a nonmetallic powder selected from the group consisting of SiC, Al2O3, and a mixture thereof using brass as the anode, wherein concentration of SiC and Al2O3 is 25 to 35 g/L per plating solution, the addition amount of aqueous ammonia is 0.5 to 2 ml/L per plating solution based on 28 % aqueous ammonia, and the brass-nonmetal composite coating process comprises first step in which inactive powder onto which metallic ions are selectively adsorbed is moved to the surface of the cathode by convection current, and the amount of the adsorbed metallic ions determines amount and magnitude of an electric charge to be carried; second step in which the inactive powder is adsorbed onto the surface of the cathode by electrophoresis with the surface of the cathode in a diffusion boundary layer, too fast stirring speed obstructs eutectoid; and third step in which the metallic ions are reduced and occluded into a metal layer that is rapidly grown to the circumference.

Description

Process for plating brass-metalloid composite

The present invention relates to a brass-non-metal composite plating method, and more particularly, using a brass as an anode, and adding ammonia water to a plating solution containing a non-metal powder selected from the group consisting of SiC, Al ₂ O ₃ and mixtures thereof. It relates to a brass-non-metal composite plating method characterized by reacting by.

Composite plating of metal ions and non-metal powders is a method of imparting physically and chemically new functions to the surface of a metal base material. In recent years, attention has been focused on industrial applications.

Meanwhile, copper plating has been widely used for its unique beautiful color, excellent electrical conductivity and corrosion resistance, but its mechanical strength and abrasion resistance have limited industrial applications. In addition, brass plating has been widely used as a substitute for gold plating due to the beautiful color similar to gold, but has been required to improve due to problems such as adhesion and easy wear.

Recently, in order to improve the strength and abrasion resistance of the metal plating layer, research has been mainly conducted through a kind of dispersion strengthening effect method by plating non-metal powders such as SiC, WC, Al ₂ O ₃ and SiO ₂ together. It is simpler and more economical than the process.

The main factors of composite plating are the characteristics of the nonmetallic powder used and the plating conditions. The characteristics of the nonmetallic powders are size, zeta potential and surface voltage, and the plating conditions are the concentration of the powder and the properties of additives which are particularly important in brass plating. However, due to the large number of factors affecting the complex plating, the electrodeposition mechanism is not yet clear. In 1972, Guglielmi reported a mechanism in which inert powder was adsorbed in two stages due to strong adsorption by electric field due to weak adsorption. Presented the theory.

Although the research on the electrodeposition mechanism has been carried out, the research on the wear resistance and the effect of the additives are hardly performed, so there are many problems in the practical application.

Accordingly, it is an object of the present invention to provide a brass-nonmetal composite plating method which improves the mechanical strength and wear resistance of the plating layer while maintaining the beautiful color, excellent electrical conductivity and corrosion resistance peculiar to brass plating for industrial application.

1 is a device configuration of the brass-non-metal composite plating according to an embodiment of the present invention,

2 is a graph showing the surface area fraction according to the concentration of nonmetallic powder,

3 is a photograph taken with an electron microscope (SEM) of the brass-alumina composite plating layer according to the concentration of Al ₂ O ₃ ,

4 is a graph showing the surface area fraction of Al ₂ O ₃ according to the additive;

5 is a photograph taken with an electron microscope (SEM) of a brass-alumina composite plating layer according to the addition of ammonia water (a: Al ₂ O ₃ 40 g / L, b: Al ₂ O ₃ 40 g / L + NH ₄ OH 1 mL)

6 is a graph showing the degree of wear according to the concentration of nonmetallic powder.

<Description of the symbols for the main parts of the drawings>

1: circulator 2: stirrer

3: magnetic bar 4: brass anode

5: cathode 6: power supply

In order to achieve the above object, the present invention is characterized in that by using a brass as an anode, by adding ammonia water to the plating solution containing a non-metal powder selected from the group consisting of SiC, Al ₂ O ₃ and mixtures thereof. Provides a brass-nonmetal composite plating method.

The concentration of SiC and Al ₂ O ₃ is 25 to 35 g / L with respect to 1 L of the plating liquid, and the amount of the ammonia water added is 0.5 to 2 mL / L based on 28% ammonia with respect to 1 L of the plating liquid. When ammonia water is added, the color of the plating layer is beautiful, but when it is added in excess (more than 2 mL / L), problems such as the formation of two-toned plates are generated. desirable.

First, the principle of composite coating applied to the present invention will be briefly described as follows.

When an electric field is applied to the powder suspended in the electrolyte, the powder is accelerated, and the moving speed at this time is expressed by Equation 1 below.

U = v / E

Where U: eletrophoretic mobility (μm · cm / V · s)

v: terminal velocity (μm / s)

E: electric field (V / cm)

The driving force at this time is the voltage difference between the solvent and the shear plane around the particles, and this voltage difference is called zeta potential. The zeta potential is a driving force of electrophoresis and is represented by the following Equation 2.

ζ = εE / (vη)

Where ζ: zeta potential (mV)

ε: dielectric constant

E: electric field (V / cm)

η: viscosity

In addition, the process of complex plating is known to be the vacancy of the non-metal powder by the three steps proposed by Guglielmi and Celis. In the first step, the inert powder in which metal ions are selectively adsorbed is moved to the surface of the cathode by convection, and the amount of adsorbed metal ions determines the amount and size of charge to be carried. In the second step, the inert powder is adsorbed on the cathode surface by electrophoresis and the cathode surface in the diffusion boundary layer. Too fast agitation at this stage is reported to impede vacancies. In the third step, metal ions are reduced and occluded in a metal layer growing rapidly around.

EMBODIMENT OF THE INVENTION Hereinafter, the specific structure of this invention is described in detail using an Example.

Example 1: Apparatus and Method

Brass-SiC or brass-Al ₂ O ₃ composite plating experiments were performed in a typical vertical cell, the configuration of which is shown in FIG. 1. The powder characteristics of SiC and Al ₂ O ₃ used in the examples of the present invention are shown in Tables 1 and 2, respectively.

Powder Characteristics of Alumina Crystalline form Average size water α-Al ₂ O ₃ 2-3 μm 99.9%

Powder Characteristics of Silica Crystalline form Average size water Specific Area (BET) α-SiC 2-3 μm 〉 99.99%

The negative electrode used a copper plate of 6 cm × 5 cm size, the current was controlled by a power supply (HP6642A, Hewlett Packard). The temperature was kept constant with a circulation device (DTRC-620, JEIO TECH).

The negative electrode plate was subjected to negative electrode degreasing for 30 seconds at 1.5 A constant current at room temperature, washed with distilled water, and then polished nickel plated at 55 ° C. and 1.5 A constant current for 5 minutes. SUS 304 was used as the cathode degreasing and nickel was used as the anode during the nickel plating. The brass plating bath used in the experiment was used to make a commercially available brass salt (brass salt) in distilled water to a concentration of 150 g / L. Brass-silica, brass-alumina composite plating was performed for 3 minutes at 1 A constant current at 45 ℃, brass was used as the anode. In order to uniformly suspend the powder and prevent sedimentation, the electrolyte was stirred at a speed of 360 rpm using a magnetic bar. Figure 1 shows the device configuration of the brass-non-metal composite plating according to an embodiment of the present invention.

The distribution of SiC and Al ₂ O ₃ powders in the plating layer was observed by an electron microscope (SEM, JEOL-5310), and the amount of vacancy on the surface was analyzed by an image analyzer. In order to investigate the mechanical properties of the composite plating layer, abrasion resistance test was performed using a reciprocating wear tester. Test conditions of the wear tester used in the Examples of the present invention are shown in Table 3. The wear resistance of the composite plating layer was confirmed by measuring the weight change before and after the test.

Wear test condition Cycle speed 60 DS / min Load 3 kg Wear paper 15 μm Al ₂ O ₃ Wear area 30 × 21 mm Frequency 100

Example 2: SiC and Al in Plating Solution ₂ O ₃ Influence of concentration

The amount of SiC and Al ₂ O ₃ concentration of 10~40 g / L while changing the vacancy in the plated layer after performing a plating SiC and Al ₂ O ₃ up to investigate the effects of SiC and Al ₂ O ₃ powder concentration in the plating solution Was measured. Figure 2 is a graph showing the surface area fraction according to the concentration of non-metallic powder, in the case of SiC the amount of vaccinated SiC increased as the concentration was increased, the surface area fraction is increased to about 9.8% when the concentration in the plating solution is 30 g / L The maximum vacancy was recorded. This is because as the SiC concentration increases, the amount of powder reaching the diffusion boundary layer increases and more SiC is vacant. The amount of vacancies did not increase any more at the concentration of 30 g / L or more. This was because the viscosity of the suspension increased with increasing concentration, and the powders in the electrolyte were not sufficiently stirred.

In the case of Al ₂ O ₃ , as the concentration increased, the amount of vaccinated Al ₂ O ₃ increased to about 2% by surface area fraction, but did not increase above 30 g / L. The maximum amount of vacancy was recorded when the concentration in the plating liquid was 30 g / L. The reason why Al ₂ O ₃ is less vacant than SiC is because the point of zero charge (PZC) of SiC is lower by about 2 to pH than Al ₂ O _{3, which} is more negative. This may be due to the increase in the amount of metal ions to be moved to the cathode, which can be confirmed by the work of Song and Celis.

Brass according to the concentration of 3 is Al ₂ O ₃ - alumina composite plated layer as a picture taken by an electron microscope (SEM), the vacancy of Al ₂ O ₃ amount of change with the concentration of Al ₂ O ₃ by SEM photograph It is shown. As can be seen from Figure 3, that the concentration of Al ₂ O ₃ 10 g / in L by 30 g / L, the amount of vacancies Al ₂ O ₃ can confirm that the increased. However, 40 g / L in a slight decrease You can check it.

Example 3: Influence of Additives

To investigate the effect of additives on the composite plating, compared to the case of adding 40 g / L Al ₂ O ₃ to the ammonia solution (28%) in a concentration of 1 mL / L, the vaccinated Al ₂ O ₃ in the plating layer The amount of was confirmed.

4 is a graph showing the surface area fraction of Al ₂ O ₃ according to the additive, when 1 mL / L of ammonia water is added, the amount of Al ₂ O _{3 in} the plating layer is vacancy up to 5% and when Al ₂ O ₃ alone In comparison, the amount of vacancy in Al ₂ O ₃ was increased 2-3 times. When the ammonia water was added to the brass plating bath, the cathode current efficiency was increased, so that the metal ion plated on the cathode was increased, so that a larger amount of powder was plated.

5 is a photograph taken with an electron microscope (SEM) of the brass-alumina composite plated layer according to the addition of ammonia water, and the case where the ammonia water (1 mL / L) was not added in addition to Al ₂ O _{3 in the} electrolyte and the case where it was added The results are shown in SEM photographs. It was confirmed that Al ₂ O ₃ was more vaccinated when ammonia was added than Al ₂ O ₃ alone.

On the other hand, even in the case of brass-silica composite plating, it was confirmed that the amount of vacancy in SiC increased when ammonia was added to the plating solution.

Example 4: Wear Resistance Test of Plating Layer

6 is a graph showing the degree of wear according to the concentration of the non-metal powder, the weight of the specimen before and after the plated while changing the concentration of SiC and Al ₂ O _{3 in} the plating solution from 0 to 40 g / L using a reciprocating wear tester The result of the measurement is shown. Here, the greater the weight change, the greater the wearability.

In the case of SiC composite plating on the brass plated layer, the wear resistance of the plated layer was increased due to the high hardness of SiC, and the wear resistance was further increased as the concentration of SiC in the plated layer was increased. Under the conditions of the present example, the weight change of about 17% was reduced after the abrasion resistance test in the case of 40 g / L SiC to improve wear resistance.

In addition, even when Al ₂ O ₃ composite plating on the brass plating layer, it was also confirmed that the wear resistance increased as the concentration of Al ₂ O _{3 in} the plating solution increased, similarly to SiC. Under the conditions of the present example, in the case of 40 g / L Al ₂ O _3, the weight change before and after the abrasion test was reduced by about 29%, thereby obtaining the effect of maximally improving wear resistance.

As described in detail above, the present invention has the effect of improving the mechanical strength and wear resistance of the plating layer while maintaining the beautiful color, excellent electrical conductivity and corrosion resistance unique to brass plating by providing a composite plating method of brass-nonmetal, Therefore, there is a very useful feature in the actual plating industry.

Claims (3)

A brass-nonmetal composite plating method comprising using brass as an anode and adding ammonia water to a plating solution containing a nonmetal powder selected from the group consisting of SiC, Al ₂ O _3, and mixtures thereof. The method of claim 1, wherein the concentration of SiC and Al ₂ O ₃ is 25 to 35 g / L. The method of claim 1, wherein the amount of the ammonia water added is 0.5 to 2 mL / L based on 28% ammonia water.