JP2841995B2 - Molten salt electroplating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a molten salt electrolytic aluminum alloy plating method, and more particularly to a molten salt electrolytic plating method for forming an aluminum alloy film having excellent adhesion.

[0002]

2. Description of the Related Art The molten salt electroplating method is a method in which a molten salt bath is mainly composed of chlorides, and an article to be treated is immersed in the bath to electroplate a desired metal or alloy. Usually, when aluminum alloy plating is performed by this method, a mixed molten salt bath mainly containing anhydrous aluminum chloride and chlorides of other alloy components is used. Conventionally known aluminum alloy plating includes Al-Mn, Al-Ni, Al
-There are alloy plating such as Ti, Al-Ta, Al-Cr, for example,
In the Al-Mn alloy plating, electrolytic plating is performed using a chloride-based molten salt bath containing anhydrous aluminum chloride and manganese chloride.

Conventionally, the surface of a material to be plated by a molten salt electrolysis method (a material to be plated) is activated by a wet process such as pickling and washing with water, and then water harmful to a plating bath is removed. The molten salt electrolytic plating was performed after sufficient drying was performed to perform the drying. However, at that time, even when the drying treatment was performed in an inert gas atmosphere so that an oxide film was not formed on the surface of the material to be plated, there was a case where the adhesion of the molten salt electrolytic plating was insufficient.

On the other hand, the present inventors, when performing aluminum alloy plating on steel materials, as a pretreatment for plating, remove the material to be plated in a molten salt bath, preferably in a molten salt bath separate from the plating bath. The present inventors have invented a method of obtaining a film having good adhesion by performing molten salt electrolytic plating after dissolving the anode (JP-A-63-143282). On the other hand, regardless of whether it is an aqueous plating or a non-aqueous plating, a metal such as Ni is previously thinly plated on the material to be plated as a usual method for improving the plating adhesion, and the desired plating is performed thereon. There is a method (hereinafter referred to as pre-plating, which may be referred to as pre-plating in some cases), and in particular, materials such as stainless steel, aluminum alloy, and titanium alloy that are easily oxidized and whose surface is easily covered with an oxide film. This was done when plating.

[0005] The present inventors have tried the molten salt electrolytic plating by applying the aforementioned method to these easily oxidizable materials, that is, the anodic dissolution method in a molten salt bath as a pretreatment, but the effect is insufficient. Therefore, a film having good adhesiveness was obtained by performing molten salt electrolytic plating after performing Ni plating in advance according to a conventional method.

[0006]

As described above, the present inventors have applied the pre-plating method when performing molten salt electrolytic plating on various materials including easily oxidizable materials such as stainless steel. It is often the case that a plating film with good adhesion cannot be obtained due to differences in the surface state (crystal grain size, crystal orientation, oxidation state, etc.) depending on the material, and the condition of the molten salt plating bath is slightly different depending on the plating chance. There was a problem.

Accordingly, an object of the present invention is to provide an aluminum alloy plating material having excellent adhesion stably even when the conditions of a material to be plated and a molten salt plating bath change, in an aluminum alloy plating method by molten salt electrolysis. It is to propose a plating method for manufacturing.

[0008]

Means for Solving the Problems The present inventors have studied the pretreatment conditions of molten salt electrolytic plating in order to achieve the above object, and as a result, after plating a metal such as Ni on the material to be plated in advance, Furthermore, by performing a two-step pretreatment of adding anodic dissolution treatment in a molten salt bath, molten salt electrolytic plating with excellent adhesion is always stable regardless of the type of the material to be plated and the state of the plating bath. I learned that it can be manufactured.

Furthermore, as a result of various studies on the types of pre-plated metals, it was found that Ni, Co, or Zn plating was effective, and the amount of plating and the amount of anode dissolution were investigated in detail, and their optimum conditions were confirmed. Thus, the present invention has been completed. Here, the gist of the present invention is that when performing aluminum alloy plating by a molten salt electrolysis method, N is used as a pretreatment for aluminum alloy plating.
This is a molten salt electrolytic aluminum alloy plating method characterized in that after i, Co, or Zn is plated, its surface is subjected to anodic dissolution and activated.

[0010] Here, there are no particular restrictions on the type of alloy as the aluminum alloy plating, but for example, Al-Mn, Al-Ni, Al
Any aluminum alloy, such as -Ti, Al-Ta, and Al-Cr alloys, can be used as long as it is an object of molten salt electrolytic plating, and the specific composition is not particularly limited. Further, the material as a substrate for plating, that is, the material to be plated is not limited as long as it can be plated with Al alloy such as ordinary steel, alloy steel, stainless steel, aluminum alloy, and titanium alloy.

[0011]

Next, the operation of the molten salt electrolytic aluminum alloy plating method according to the present invention will be described in more detail with reference to the molten salt electrolytic plating of an Al-Mn alloy using an aluminum chloride-based mixed molten salt as an example. .

The molten salt electrolytic plating according to the present invention comprises:
For example, the following steps are performed. (Alkaline degreasing) → (Washing) → (Pickling) → (Washing) →
(Pre-plating) → (Washing) → (Drying) → (Anode dissolution treatment in molten salt) → (Molten salt electrolytic plating) First, the material to be plated such as ordinary steel, stainless steel, aluminum alloy, titanium alloy, etc. Then, preliminary treatment is performed prior to pre-plating. As the pretreatment, usually, a combination of alkali degreasing, pickling, and washing with water is used to remove and activate the surface oxide film. The kind and order of such pretreatment are not particularly limited as long as surface activation can be achieved.

Next, the material to be plated whose surface has been activated in this way is pre-plated with Ni, Co or Zn. These may be plated by only one kind or may be an alloy plating thereof. As a plating method, a vacuum deposition method, an ion plating method, or the like can be applied in addition to the electrolytic method. Ni, Co, and Zn were selected because they are relatively difficult to be oxidized in the drying process.

The pre-plating method may be a general electroplating method using an aqueous solution, and this is not particularly limited. H, Li, as inevitable impurities contained in the electrolytic solution,
Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, C
l, K, Ca, Sc, Ti, V, Cr, Mn, Fe, etc.
In the present invention, all of the elements other than the target element can be regarded as impurities. Even if one or more such impurities are contained, there is no problem in performing the pre-plating.

The amount of the pre-plated coating is 0.05 to 5 g / m ^2.
The degree is preferred. If the pre-plating amount is less than 0.05 g / m ² , there are too many portions where the pre-plating is not adhered to the surface of the material to be plated, and an oxide film is formed on the portion, causing poor adhesion of the Al-Mn alloy plating film. It is not preferable because there is a possibility. Further, even if the pre-plating amount is more than 5 g / m ^2, there is no particular problem with respect to the function and effect of the present invention, but it is not preferable in terms of cost.

Subsequently, after the material to be plated to which the pre-plating solution has adhered is washed with water, it is sufficiently dried so that moisture does not enter the molten salt bath for the pretreatment (anode dissolution) in the next step. If the atmosphere or temperature is not carefully controlled during the drying, an oxide film is formed on the surface of the pre-plating. Therefore, the drying is preferably performed in an inert gas atmosphere, for example.

The bath temperature of the molten salt for dissolving the anode is preferably in the range of the same temperature as the plating bath to a temperature about 50 ° C. higher. When the temperature is lower than the plating bath temperature, after the anodic dissolution treatment, the low-temperature molten salt attached to the material to be plated is brought into the plating bath, so that the plating bath temperature gradually decreases. As a result,
This is because the appearance of the plating may be adversely affected due to a decrease in conductivity due to an increase in the viscosity of the plating bath.

Further, the aluminum chloride-based molten salt has a high volatility. If the bath temperature is too high, not only the bath composition of the molten salt gradually changes, but also the volatilized aluminum chloride and the vaporization of the upper layer of the plating bath. The reaction of moisture in the phase to form alumina and hydrogen chloride may generate white smoke, which is not preferable in operation. The anodic dissolution condition is not particularly limited as long as the active surface of the pre-plating surface is exposed, and also dissolves the entire pre-plating film and dissolves the surface of the material to be plated thereunder. There is no problem as long as the active surface appears.

The amount of electricity to be dissolved in the anodic dissolution treatment is 0.5 to
About 50 C / dm ² is preferable. In order dissolution quantity of electricity when less than 0.5 C / dm ^2, the Al-Mn alloy plating film partially present appeared not face the active surface portion thereof by dissolution amount insufficient is likely to peel is there. In addition, when dissolved with an amount of electricity of more than 50 C / dm ^2, there is no particular problem from the viewpoint of the function and effect of the present invention, but it is not preferable in terms of cost.

The material to be plated that has been subjected to such two-stage pretreatment is then subjected to electrolytic plating of an aluminum alloy in an aluminum chloride-based molten salt. In this case, the molten salt electroplating method itself is already known, and the plating conditions such as current density, bath composition, temperature, atmosphere, etc. may be according to the conventional method. As long as the processing is performed, there is no limitation on such conditions.

Further, as one embodiment of the method of the present invention, it is possible to perform the anodic dissolution treatment in a plating bath and subsequently perform the plating in the same bath, which activates the surface of the material to be plated. Although there is no problem in the sense, Ni ions dissolved by anodic dissolution with an increase in plating throughput,
As the amount of Co ions or Zn ions mixed into the plating bath increases and adversely affects the quality of the plating film, when the plating treatment amount is large, the anode dissolution treatment and plating treatment must be performed in a separate molten salt bath. It is preferred to do so.

As the molten salt bath for aluminum alloy plating, it is preferable to use a halide molten salt, particularly an anhydrous aluminum chloride-based mixed molten salt. For example, aluminum chloride and a chloride of the other alloy component, for example, MnCl ₂ ,
It contains other chlorides such as inorganic salts together with NiCl ₂ , TiCl ₃ , TaCl ₅ , and CrCl ₃ . Examples of inorganic chlorides include, for example, NaCl, KCl, LiCl and the like. The same applies to the anodic dissolution bath, however, considering the possibility of being brought into the molten salt bath for plating, which is a subsequent step, it is preferable to use the same bath composition as the plating bath, that is, an aluminum chloride-based molten salt.

Although the present invention has been described above with reference to Al-Mn alloy plating, the present invention is similar to Al-Mn.
It is obvious to those skilled in the art from the above description that the present invention can be applied to alloy systems such as Al-Ni, Al-Ti, Al-Ta, Al-Co, and Al-Cr. Here, the mechanism capable of stably forming a plating film having excellent plating adhesion according to the present invention is considered as follows.

First, although the pre-plating itself and the anodic dissolution treatment itself were known as pre-treatment means, however, the combination of pre-plating → anodic dissolution treatment is not known, and there is an idea that pre-treatment is performed in two steps. I couldn't see it. The reverse combination has no effect at all. In other words, Ni, Co, and Zn are relatively stable against oxidation, but are not sufficient by themselves, and the anodic dissolution further promotes the activation of the surface. As a result, excellent results as shown in the examples of the present invention can be obtained. If the reverse is true, no superior effect can be obtained without much difference from the case of only pre-plating. Next, the operation of the present invention will be described in more detail with reference to examples.

[0025]

【Example】

(Example 1) Thickness 0.8 mm x width 100 mm x length 350 shown in Table 1
After various kinds of workpieces of mm were subjected to alkali degreasing, pickling, and water washing in advance, Ni, Co, or Zn was first pre-plated under the conditions shown in Table 2 according to the method of the present invention. After the material to be plated pre-plated as described above is washed with water, and the surface is sufficiently dried in an inert gas atmosphere to remove moisture, an anodic dissolution treatment is performed in a molten salt having the same bath composition as the plating bath. Subsequently, alloy plating of Al-Mn or Al-Ti was performed in a molten salt bath for plating according to the conditions shown in Table 3.

With respect to the obtained plating film, the characteristics of plating adhesion were evaluated. The plating adhesion was evaluated by applying Dupont impact (ball head diameter 1/2 inch, potential energy 0.8 kg-m), then peeling off the cellophane tape, and according to the area ratio of the plating adhered to a 10 mm x 40 mm cellophane tape. The evaluation was made in five steps as shown below. Table 5 shows the results of the adhesion evaluation.
In the five-stage evaluation of Table 4, 4 or more is regarded as a pass.

As is clear from the results in Table 5, the ones listed as comparative examples were not subjected to pre-plating and / or anodic dissolution treatment, or both, because of insufficient pre-treatment. Plating adhesion was poor.
On the other hand, in the example of the present invention, as a pretreatment of the molten salt electrolytic aluminum alloy plating, by performing a two-stage treatment of pre-plating and anodic dissolution treatment, it is possible to avoid formation of an oxide film on the surface of the material to be plated. As a result, aluminum alloy plating having good adhesion was stably obtained irrespective of the type of the material to be plated.

(Example 2) Stainless steel plate (SUS304, thickness
(0.8 mm x width 100 mm x length 350 mm) was used as the material to be plated, and was previously subjected to alkali degreasing, pickling, and water washing.
Molten salt electrolysis Al-Mn under the conditions shown in Table 3 for 5 days a day for 30 days
The production of the alloy plating material was continued.

The adhesion of the sample was evaluated in the same manner as in Example 1 according to Table 4 in five steps. FIG. 1 is a graph showing the change over 30 days in which the average of the adhesion evaluation points of five samples prepared under the same pretreatment conditions was obtained and plotted. As can be seen from FIG. 1, according to the method of the present invention, by using pre-plating and anodic melting together, Al-Mn alloy plating with good adhesion could be stably produced for a long period of time.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

[Table 3]

[0033]

[Table 4]

[0034]

[Table 5]

[0035]

[Table 6]

[0036]

According to the present invention, it is possible to stably produce an aluminum alloy plated material having excellent adhesion even when the conditions of the material to be plated and the molten salt plating bath change.
In particular, with Al-Mn alloy plating, smooth and beautiful plating having excellent corrosion resistance can be obtained, and its practical value is great.

[Brief description of the drawings]

FIG. 1 is a graph showing a comparison of changes in the adhesion of a plating film of an Al-Mn alloy plating material prepared by performing an alloy plating after each of the treatments by three types of pretreatment methods and continuously performing the plating for 30 days. is there.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Yamamoto 4-33, Kitahama, Chuo-ku, Osaka City Inside Sumitomo Metal Industries, Ltd. (72) Inventor Junichi Uchida 4-5-33, Kitahama, Chuo-ku, Osaka Sumitomo Inside Metal Industry Co., Ltd. (72) Inventor Hirohisa Seto 4-5-33 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries Co., Ltd. (72) Inventor Kunihiro Fukui 4-5-33 Kitahama, Chuo-ku, Osaka City Sumitomo Metal Industries Co., Ltd. Hiroshima Research Laboratory Co., Ltd. (72) Inventor Toshio Taguchi 4-6-22 Kannonshinmachi, Nishi-ku, Hiroshima City Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory Co., Ltd. (56) Document JP-A-1-247593 (JP, A) JP-A-5-132794 (JP, A) JP-A-64-87799 (JP, A) JP-A-63-143282 (JP, A) JP-A-63-143 206495 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C25D 3/00-7/12

Claims (2)

(57) [Claims] 1. When performing aluminum alloy plating by molten salt electrolysis, Ni, Co, or Zn is used as a pretreatment.
A molten salt electrolytic aluminum alloy plating method, comprising: performing anodic dissolution treatment on the surface of the aluminum alloy to activate the aluminum alloy; 2. The method according to claim 1, wherein the anodic dissolution treatment is performed using a bath different from the bath for performing the aluminum alloy plating.