JPH04157166A - Method for chemically plating aluminum stock - Google Patents

Abstract

PURPOSE:To electroless-plate the surface of Al stock with a high m.p. metal such as Mo without damaging the stock by treating the surface of the stock with an aq. soln. of a specified complexing agent and immersing the stock in an electroless plating soln. adjusted to a neutral range. CONSTITUTION:The surface of Al stock is pretreated with an aq. soln. contg. 0.0005-0.01mol/l aluminon or 1-10g/l tannic acid as a complexing agent. An electroless plating soln. contg. Mo ions but not practically contg. a reducing agent or a complexing agent is adjusted to the neutral range of pH 7+ or -0.5 with an acid or alkali, the stock is immersed in the plating soln. and an Mo plating layer having superior surface smoothness is formed by electroless plating without damaging the stock.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a novel chemical plating method for aluminum (Aρ) material, and in particular, to a method for chemically plating aluminum (Aρ) material.

), relates to a method suitable for chemically plating a high melting point metal such as tungsten (W) onto an Aβ material.

<Prior Art> Conventionally, Aρ material has a low melting point of 660° C., so its use as it is in products exposed to high-temperature atmospheres has been restricted. A possible means of improving the heat resistance of Al1 is to coat it with another high melting point metal. In particular, as a coating means, chemical plating has an advantage over electroplating that it can easily and inexpensively form a uniform plating film with fewer pinholes.

Conventionally, in order to improve the heat resistance and corrosion resistance of Al1, Zn
Electroless plating of Ni (melting point: 1455° C.) has been performed through displacement plating, but in addition to the low melting point of Aβ, the melting point of Ni is not very high, so heat resistance has not been significantly improved.

Ideally, Mo, which has a higher melting point and is classified as a refractory metal, would be ideal.
(melting point: 2622°C) or W (melting point: 3400°C) to directly coat the A°C material. At this time, in the case of MO, in order to obtain sufficient heat resistance and corrosion resistance, 0.2 to 1.
A Mo film with a thickness of 1.5 cm is required, while Aβ is chemically active and needs to be plated in a short time.

<Problems to be Solved by the Invention> When Mo plating is applied to the β material and chemical plating is applied to the above-mentioned direct attachment, the amount of precipitation reaches a ceiling midway through (see Comparative Example 1).On the other hand, when general-purpose electroless plating It was found that in both cases, it was difficult to form an MO plating film of the required thickness in a short time because the plating speed was slow (see Comparative Example 2). Furthermore, in both cases, the Aρ base material was eroded during plating, resulting in roughened plating surfaces, and the adhesion of the plating film to the Aβ base material was also found to be insufficient.

In view of the above, it is an object of the present invention to provide a chemical plating method that allows continuous plating of a high melting point metal such as MO at a high speed and that does not erode the Aβ base material as much as possible.

<Means for Solving the Problems> In order to solve the above problems, the inventors of the present invention have made extensive efforts in development, and as a result, have come up with a method for chemical plating of β material having the following configuration.

After surface-treating the Heβ material with an aqueous complexing agent solution containing at least one of aluminone and tannic acid as a complexing agent, the material is controlled to be neutral in a chemical plating bath that does not substantially contain reducing agents and complexing agents. The method is characterized in that after chemical plating is performed, chemical plating is performed by immersing the method in a neutral chemical plating bath that does not substantially require a chemical reducing agent.

<Detailed explanation of means> (1) Aβ materials can be used as ordinary materials for various structural materials such as aircraft, vehicles, and building materials, as well as for various non-structural materials such as automobile parts, optical parts, electrical parts, and fillers. It is also possible to use Aρ-coated steel plates or the like as the material.

(2) The aqueous complexing agent solution is an aqueous solution containing at least one of aluminone (chemical name: ammonium alarintricarboxylate) and tannic acid as a complexing agent.

(2) The above essential components are presumed to have the effect of reducing the chemical activity of Aρ, keeping the elution of the Al base material within the amount required for displacement plating, and allowing continuous plating.

■For aluminon (M: 473), the amount of the complexing agent is effective in the concentration range of 0.0005 to O,Olmol/R, preferably 0.001 to 0.0042 mol.
/β range is optimal. Similarly, when tannic acid is used in the treatment liquid, a concentration range of 1-10 g/β is effective, preferably a range of 2 to 7 g/I2. If it is smaller than the above value, sufficient complex forming ability for Al cannot be obtained, and if it exceeds the above value, the Aβ base material surface becomes Aj2
complete coverage with the complex, which is undesirable.

■Ammonium salts, balates, organic acid salts, etc. can be used as the above pH buffering agent, but ammonium chloride, ammonium sulfate, balates, and gluconates are preferable, and boric acid and borates are particularly optimal. . The effective concentration of the pH buffer is in the range of 0.08 to 1.6 mol/g, preferably 0.16 to 1.21 mol/I2.

■The pH of the treatment liquid is adjusted using ammonia, caustic alkali, sulfuric acid or hydrochloric acid, and the treatment liquid is adjusted to pH 7±0.
．． A range of 5 is desirable because it can suppress chemical attack (corrosion) on the β base material during surface treatment. Further, the treatment temperature and time are set within a range of liquid temperature of 70 to 100°C, preferably within a range of 80 to 90°C. The surface treatment time in this case is 5 to 10 mjn.

(2) The chemical plating bath should be a neutral bath that does not substantially contain chemical reducing agents and complexing agents. Usually, plating metal components,
Contains pH adjusters, pH buffers, and additives.

■As plating metal components, in the case of Mo, molybdic acid (Hz MoO4), molybdenum trioxide (MoO5)
, sodium molybdate dihydrate (Na2 MoO4
・2H20), ammonium molybdate tetrahydrate ((NH4)sMOyO*a・4H20) can be used, and its concentration is 0.003 to 0.3 mol/
A range of β is effective, preferably 0.03 to 0.2 mol
/β range is suitable. In the case of W, various W compounds can also be used.

■ pl (As a preparation agent, the same one as the complexing agent aqueous solution can be used. With these pH adjusting agents, the chemical plating bath is kept neutral, and the pH concentration is usually kept in the range of pl (7 ± 0.2). keep.

■If the plating bath contains an ammonia group, it is desirable to operate it at 80°C, and if it is composed of other Na salts, operating it at 90°C will increase the deposition rate and improve plating. can.

■As the above pH buffer, the same ones as the complexing agent aqueous solution can be used, but ammonium chloride, ammonium sulfate, oxalic acid, and sodium gluconate are preferable, and the concentration is 0.
．． A range of 0.8 to 1.6 mol/ρ is effective, and preferably 0.16 to 1.21 mo+/ρ is used.

■ As the above additive, potassium antimonyl tartrate can be used to improve the precipitation efficiency and adhesion of MO, and the range of 0.1-10 mg/I2 is effective, preferably 0.5-5 mg/I2. is suitable.

Furthermore, as an additive, a surfactant can be mentioned in order to improve the condition of the plating interface.

Addition of this surfactant in a very small amount is sufficient.

Since the plating bath has a neutral pH, any of anionic, nonionic, cationic, and amphoteric surfactants can be used as the surfactant.

<Operation of the invention> As in the present invention, after surface-treating the Al material with a specific complexing agent aqueous solution, chemical plating is performed by controlling the neutrality in a chemical plating bath that does not substantially contain a reducing agent or a complexing agent. When done, Aβ
Chemical attack on the base material during chemical plating processing is suppressed to the necessary minimum, and high-speed chemical plating (displacement plating) is now possible. Although the reason cannot be determined, it is presumed to be as follows.

Since the above MO chemical plating bath does not use a reducing agent, MO is deposited on AlI2 only by direct electron transfer through the reaction. At this time, the complexing agent in the surface treatment agent is
It is estimated that it suppresses the chemical activity of r1 and ionizes Aρ into Al230 in the required amount. Just as the A.degree. C. base material is passivated by nitric acid, which is a commonly used oxidizing agent, the ionization of A.beta., which is necessary for displacement plating, is not completely prevented. This plating reaction is essentially displacement plating, and unlike chemical plating (electroless plating) using a reducing agent, hydrogen generation is not observed and plating proceeds quietly.

It is thought that this method, which does not involve hydrogen generation, made it possible to form strong metallic bonds between dissimilar metals.

That is, (1) First, it is considered that at the beginning of plating, Mo metal grows for a while to match the lattice constant of the AJ2 base material, and gradually becomes a lattice constant unique to Mo metal.

■Secondly, minimizing the ionization of 8β and eliminating excessive and unexpected electron supply provides space for the growth of Mo metal crystal nuclei, allowing Mo metal to become the Aβ host. This is thought to be because it helps in epitaxial growth by following the direction of the crystal of the material.

■Thirdly, the softness of Aβ's hardness also seems to play a role in absorbing the stress caused by the difference in crystal structure and lattice constant of both metals.

<Effects of the Invention> The chemical plating method for Aβ material of the present invention allows continuous plating of high melting point metals such as MO at high speed, and the Al base material is not chemically attacked during the plating process.

In other words, the plating bath is made neutral, the complexing agent is removed, and a chemical plating bath of a high melting point metal is created by removing the reducing agent, and the surface of the Aβ base material is treated with a specific complexing agent to increase the chemical activity. By weakening Aβ and then plating, it is possible to continue plating with minimal dissolution of the Aβ substrate, making it possible to form a high melting point metal film with strong metal bonding directly to Aβ.

According to the present invention, it is possible to coat the surface layer of an Al base material with an MO film using a simple method and at low cost.Moreover, it is possible to coat the surface layer of an Al base material with an MO film, and it is also possible to coat the surface layer of an Aβ base material on a thin β part of a thin wire, fine powder, vapor deposited film, hot-dip Aβ plated steel plate, etc. There are great features that can be applied. Furthermore, since thermal damage to the Aβ skin can be prevented by welding or heat processing of the 8β-plated steel sheet, the steel sheet can be kept rust-proof. In addition, materials used in high-temperature parts such as automobiles and aircraft, Aρ foil for heat shielding, and Al
The effect is great because it can be applied to a variety of fields such as heat-resistant fibers.

<Example> An example of a chemical plating bath conducted to confirm the effects of the present invention will be described.

In each example, the plating material was degreased and then treated with a complexing agent aqueous solution (aluminone 0.001 mat/β, oxalic acid 0.48
5 mol/12, pH 7) at 80°C
After surface treatment (immersion) under the conditions of 0 mln, chemical plating was performed using a plating bath having the composition and conditions shown in Table 1. In each comparative example, chemical plating was performed under the plating bath conditions of each composition shown in Table 1 after degreasing treatment without performing the above-mentioned surface treatment.

As the plating material, 100 μm hard aluminum foil manufactured by Toyo Aluminum Co., Ltd. was used.

At this time, in each Example, there was no corrosion of the Al base material, and a glossy and smooth Mo-plated surface was obtained.

(1) Table 1 shows the amount of precipitation for each plating time in each Example and Comparative Example, and the results are shown in FIG.

From FIG. 1, it can be seen that Mo is continuously plated.

Comparing the deposition rates of Examples and Comparative Examples, Table 1 shows that Example 2 (complexed)/Comparative Example 1 (bare), which were plated with the same bath composition, was 2.0, 2.
1, 3.1, 3.6, 4.5.5.5, 5.4
The results showed that the precipitation rate increased dramatically by twice as much.

Comparative Example 3, in which the immersion plating bath of Comparative Example 1 was changed to neutral p)I,
In addition, in the case of Comparative Example 4, in which the electroless plating bath of Comparative Example 2 was further adjusted to a neutral pH to reduce the effects of acids and alkalis, it was not possible to significantly improve the amount and rate of precipitation. Furthermore, in the case of Comparative Examples 5 to 7, in which the complexing agent as a solubility factor and the unnecessary reducing agent were removed, only Comparative Example 6 showed a slight improvement in the precipitation amount and precipitation rate, and each plating In the middle of the bath, precipitation reached a peak and plating stopped.

At this time, the Al base material was corroded and roughened, and the MO
The plated surface became rough, and strong bonding of the Mo film could not be obtained.

(2) A heat resistance test was conducted on Example 2 and the bare aluminum material.

For the heat resistance test, a sample with a width of 3cm x 6c+n was supported on a cantilever at one end in the longitudinal direction, and heated with a gas burner from below at a position 2cm+ from the tip. We investigated whether it would melt and deform over time.

At this time, the standard bare sample was deformed in 6 seconds and the melt was removed. In contrast, the sample of Example 2 was 0.139 mg
/ cm'' was partially wrinkled after 3 minutes, but the original shape remained as it was, and samples with more Mo than that became red-hot after being heated for 15 minutes or more. It did not melt or deform even when

From these results, M was applied to 100 μm thick A2 foil.

If the membrane is raised by 0.2mg/cm” or more,
It can exhibit sufficient heat resistance even when heated for a long time with a gas flame at 50°C, and the one with Mo raised even further is 75.
It can be inferred that heat resistance even higher than 0° C. can be obtained. Furthermore, instead of the AJ2 foil mentioned above, MO can be made of a material with sufficient rigidity, such as casting, Guicast, or 8β-plated steel plate.
When plated, it can be expected that even if it is momentarily exposed to high temperatures during, for example, welding, the heat resistance and corrosion resistance of the outermost MO layer will protect the Al base material or AA layer portion under the MO layer from high temperatures.

[Brief explanation of drawings]

FIG. 1 is a graph comparing changes in the amount of precipitation created based on Table 1. Patent application Hitotsu 1) Jodai 1 Figure +0 15 ff10
25 30 Plating time (min)

Claims (2)

[Claims] 1. After surface-treating the Al material with an aqueous complexing agent solution containing at least one of aluminone and tannic acid as a complexing agent, it is controlled to be neutral in a chemical plating bath that does not substantially contain reducing agents and complexing agents, and then chemically treated. A chemical plating method for aluminum materials, which is characterized by plating. 2. 2. A method for chemically plating an aluminum material according to claim 1, wherein the plating component of the chemical plating bath is molybdenum.