JP2000273696A - Insulating substrate with anodic oxidation coating, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an insulating substrate in which a uniform anodic oxidation coating is formed at the surface of the plating layer of an Al-alloy-plated steel sheet, and to provide its manufacturing method. SOLUTION: In the insulating substrate, an Al-Zn alloy, having a composition consisting of, by mass, 40-60% Al, <=2% Si with inevitable impurities, and the balance Zn, is used as an Al alloy for the plated steel sheet. This insulating substrate can be manufactured by immersing the Al-Zn alloy plated steel sheet as above in an aqueous solution of pH 5.0-10.0 containing alkali salt of weak acid to undergo continuous anodic oxidation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an insulating substrate having an anodized film formed on the surface of a plating layer of an Al-based alloy-coated steel sheet and having a uniform anodized film and capable of forming a dense film. About the method.

[0002]

2. Description of the Related Art The substrate of a solar cell needs to have insulating properties.
It is necessary to withstand heating up to about 350 ° C. For this reason, a glass substrate or a metal substrate has been conventionally used as the substrate. However, although glass substrates are inexpensive, they are vulnerable to impact, so metal substrates are used for applications requiring flexibility. A typical example of this metal substrate is
An insulated substrate having an anodic oxide film formed on the surface of a plating layer of an Al-based alloy-coated steel sheet is known (JP-A-54-11).
6347, 62-89369).

[0003] This insulating substrate is manufactured by using a hot-dip Al-plated steel sheet as a material, immersing it in an acid solution such as sulfuric acid, oxalic acid, or chromic acid, and performing anodic electrolysis. Since the plating layer of the hot-dip Al-plated steel sheet suppresses the growth of the Fe-Al alloy layer having poor workability by adding 5 to 11 mass% of Si during hot-dip plating, the conductivity of the Si portion is higher than that of other portions. And the current distribution becomes non-uniform during electrolysis. For this reason, there has been a problem that the thickness of the anodic oxide film becomes uneven.

[0004]

SUMMARY OF THE INVENTION The present invention provides an insulated substrate having an anodized film formed on the surface of a plating layer of an Al-based alloy plated steel sheet, wherein the anodized film is uniform and a method for producing the same. is there.

[0005]

The insulating substrate according to the present invention is characterized in that an Al-based alloy of a plated steel sheet has an Al content of 40 to 60 mass%,
Si and inevitable impurities: 2 mass% or less, balance:
An Al-Zn-based alloy made of Zn was used. This insulating substrate is manufactured by preparing an aqueous solution containing an alkaline salt of a weak acid having a pH of 5.0 to 10.0 and containing Al: 40 to 60 mass%, Si and unavoidable impurities: 2 mass% or less, and the balance of Zn:
This is performed by a method of immersing a plated steel sheet of an l-Zn-based alloy and continuously performing anodization.

[0006]

[Function] Al-based alloy plating layer converts Al to 40 to 60 mas
s%, 2 mass% or less of Si and unavoidable impurities,
When the anodizing treatment is performed using a plated steel sheet of an Al-Zn-based alloy consisting of Zn, even if Si is contained,
Since the Si content is small, the current that tends to concentrate on the Si site is uniformly dispersed by dissolution of Zn, so that an anodic oxide film having a uniform thickness can be formed. Al is 40mas
When the Zn content is less than s% and the Zn content is more than 58 mass%, the dissolution rate of Zn is higher than the generation rate of the oxide film, so that a continuous oxide film is not formed.
If Zn is less than 38 mass%, the dissolution reaction of Zn decreases, so that the efficiency of forming an oxide film decreases, and
The sacrificial anticorrosion action on the steel sheet is also reduced.

The Al—Zn alloy-plated steel sheet may be manufactured by any of a hot-dip plating method, a vapor deposition method, and an electroplating method, but is preferably manufactured by an inexpensive hot-dip plating method. In this case, if the amount of Si added during hot-dip plating for suppressing the growth of the Fe-Al alloy layer is 2 mass% or less, the anodic oxide film does not become non-uniform. For this reason, Si is preferably set to 1 to 2 mass%. Inevitable impurities include B originating from the refining process of Al and Zn.
i, Sb, Sn, Fe and the like.

The thickness of the anodic oxide film is preferably at least 0.1 μm in order to ensure sufficient insulation. The insulating property of the anodic oxide film is constant at about 1 μm, and when it is thicker, it is difficult to form. For this reason, in consideration of economy, a maximum of about 1 μm is sufficient, but if necessary, it can be further thickened.

In the anodic oxidation treatment, in order to form a barrier layer film having a dense structure without pores, the electrolytic bath uses an aqueous solution that does not dissolve the formed film, that is, an alkaline salt of a weak acid is used for the electrolyte. An aqueous solution, preferably a buffer solution, is used. Here, a weak acid means that the ionization constant K is small (K <10).
^-3 ) Polyvalent inorganic acids and organic acids, for example, boric acid, phosphoric acid, tartaric acid and the like. pH is 5.0 to 10.0
To If the pH is lower than 5.0, the dissolution reaction of the entire plating layer takes precedence, and if the pH is higher than 10.0, hydroxide is generated in the electrolytic bath to lower the electrolytic efficiency, and both forms an anodic oxide film. It is hard to be done. The electrolysis is performed at a current density of 1 to 10 mA / c by direct current or pulse current or a combination thereof.
It is suitable to carry out in the range of m ² . When it is lower than 1 mA / cm ² , an anodic oxide film is not formed so much that 10 mA / cm ²
Even if it is higher than cm ^2, the generation efficiency of the anodic oxide film does not improve. The bath temperature is suitably in the range of 20 to 60C. 20
When the temperature is lower than 0 ° C., the dissolution reaction of Zn becomes difficult to occur, and 6
If the temperature is higher than 0 ° C., the anodic oxide film will be dissolved, and the production efficiency of the anodic oxide film will decrease.

[0010]

EXAMPLE 1 The plating layer composition was as shown in Table 1 in an electrolytic bath of an aqueous solution having a boric acid concentration of 0.5 mol / L, a sodium tetraborate concentration of 0.05 mol / L and a pH of 7.6. A hot-dip Al-Zn alloy-plated steel sheet or an Al-Si-based alloy-plated steel sheet (each having a coating weight of 20 µm) was immersed in the steel sheet to obtain a current density of 1
Anodizing treatment was performed under the conditions of 0 mA / cm ² and a bath temperature of 25 ° C. In addition, the thickness of the anodic oxide film was adjusted by changing the energizing time. After the treatment, the thickness of the anodic oxide film and the insulating property were investigated. The insulating property was indicated by a symbol ○ when the insulation resistance value was 10 ⁶ Ω or more, and a Δ when the insulating resistance value was 10 ² Ω or more and less than 10 ⁶ Ω. Those having a resistivity of less than 10 ² Ω were evaluated with the symbol x. Table 2
The results are shown in FIG.

[0011]

[Table 1]

[0012]

[Table 2]

[0013] From the results in Table 2, for the plated steel sheet B,
In Examples 3 to 7 in which the energization time was 80 seconds or more, the film thickness was 0.1 μm or more, and good insulation was exhibited. Regarding the plated steel sheet A, even when the energizing time was 600 seconds, the film thickness did not become 0.1 μm or more. As for the plated steel sheet C, a coating thickness of 0.1 μm or more is obtained,
The insulation is not good. This is because 9 mass% of S
In order to contain i, Si will be deposited in the electrolytic process,
This is considered to be because the precipitated Si has conductivity and causes a decrease in insulation.

Example 2 A hot-dip Al—Zn alloy-plated steel sheet B shown in Table 1 of Example 1 was immersed in various electrolytic baths having different bath compositions and pHs.
Anodizing treatment while keeping the electrolysis conditions in each bath constant,
The insulation properties were evaluated in the same manner as in Example 1, and the thickness of the anodic oxide film was measured. Those having a thickness of 0.1 μm or more were evaluated with a symbol ○, and those having a thickness of less than 0.1 μm were evaluated with a symbol x. Table 3 shows the results. For the electrolytic bath, the ion concentration of the acid was 0.5 m
ol / L was kept constant, and the pH was adjusted by changing the salt concentration of the acid or by using sulfuric acid or sodium hydroxide.

[0015]

[Table 3]

From the results shown in Table 3, the pH of the electrolytic bath was adjusted to 5.0 to 10.
It can be seen that when a mixed solution of boric acid and its alkali salt in the range of 0 is applied, an anodic oxide film having good thickness and good insulating properties can be formed. Similarly, for phosphoric acid and tartaric acid, an anodic oxide film excellent in insulation can be formed by applying a solution having a pH within a predetermined range with a mixed solution with an alkali salt.

[0017]

As described above, in the insulating substrate having the anodic oxide film formed on the surface of the plating layer of the Al-based alloy plated steel sheet, the Al-based alloy of the plated steel sheet is changed to Al: 40 to 60 ma.
When an Al—Zn-based alloy composed of ss%, Si and inevitable impurities: 2 mass% or less, and the balance: Zn, the thickness of the anodic oxide film becomes uniform, and a plated steel sheet made of the Al-based alloy as described above is used. P containing an alkali salt of a weak acid
When immersed in an aqueous solution of H5.0 to 10.0 and continuously anodized, a barrier-type anodized film can be formed.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keiichi Sawatani 7-1, Takatani Shinmachi, Ichikawa-shi, Chiba Pref. 7 Nisshin Steel Co., Ltd., Ritsumeikan Co., Ltd.

Claims (3)

[Claims] 1. An insulated substrate having an anodized film formed on the surface of a plating layer of an Al-based alloy plated steel sheet, wherein the Al-based alloy of the plated steel sheet is Al: 40-60 mass%, Si
And inevitable impurities: 2 mass% or less, balance: Zn
An insulating substrate having an anodic oxide film, wherein the insulating substrate is made of an Al-Zn alloy. 2. An insulating substrate having an anodized film according to claim 1, wherein the thickness of the anodized film is 0.1 μm or more. 3. A pH of 5.0 containing an alkali salt of a weak acid.
Al in a 10.0 aqueous solution: 40-60 mass%, S
i and inevitable impurities: 2 mass% or less, balance: Z
n-Al-Zn alloy plated steel sheet
A method for producing an insulating substrate having an anodized film, characterized by continuously performing anodization.