JPH0841686A - Formation of verdigris coating film - Google Patents

Abstract

PURPOSE:To provide a method for efficiently forming an artificial verdigris coating film on a copper material used for a roofing material. CONSTITUTION:In this verdigris coating film forming method by anodically oxidizing a base material, at least the surface layer of which is composed of copper or a copper alloy, in an electrolyte containing hydrogen-carbonate ion, carbonate ion or the like, the verdigris coating film is formed into 5-50mum thickness by passing and dissolving gaseous carbon dioxide in the electrolyte to control pH of the electrolyte to a specific value and replenishing hydrogencarbonate ion or carbonate ion. Since the degradation of the electrolyte is prevented by passing and dissolving gaseous carbon dioxide, the verdigris coating film is continuously formed without changing the electrolyte and excellent productivity is attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for efficiently forming a patina film on a copper material used for a roof or the like by anodic oxidation.

[0002]

[Prior Art] Patina (basic copper salt) on copper roofs of temples, etc.
I often see the formation of. This patina is naturally formed, but it takes nearly 20 years to be completely covered with patina. Therefore, a method of artificially forming patina at an early stage was developed. This patina artificial formation method includes a method in which a copper plate or the like is anodically oxidized in an electrolytic solution to form it electrochemically (Japanese Patent Publication No. 55-12117, etc.), and a method in which it is formed by a chemical reaction in contact with a chemical conversion treatment solution. (Japanese Patent Publication No. 56-9270, etc.), a method of applying chemical conversion treatment after coating and polishing a resin coating containing copper powder (
Japanese Patent Publication No. 56-30396, etc.), and a method of applying a paint mixed with a powder of basic copper carbonate, which is a kind of patina (JP-A-55-139467).
No. etc.), and a method of forming by applying a chemical conversion treatment liquid containing a resin (Japanese Patent Publication No. Sho 62-19910 etc.). Of these,
The method of electrochemically forming patina is a patina film forming method excellent in productivity because a uniform film can be formed in a short time.

[0003]

[0006] However, in the method of forming the electrochemically patina, primarily bicarbonate ions in patina film forming electrolyte (HCO ₃ ^-) and carbonate ions (CO ₃ ^2-) An alkali metal salt containing, for example, Na salt or K
Salt or the like is used. In these patina-forming electrolytes, for example, if a patina film is continuously formed by anodizing a copper plate, black copper oxide is formed in the lower layer of the patina film, and the patina film gradually becomes thinner. Eventually, the entire surface will be covered with black, or the anodic dissolution reaction will occur and no patina film will be formed at all. If this happens, the operation will be stopped and the electrolytic solution will be replaced, resulting in a marked drop in productivity.

The present inventors have conducted extensive studies and found that the above phenomenon is caused by a decrease in anions (HCO ₃ ⁻ , CO ₃ ^2−, etc.) in the electrolytic solution due to the formation of patina (basic copper carbonate), and cations (Na ⁺ , K ⁺ etc.)
It has been clarified that this is caused by the accumulation of the electrolyte and the increase in the pH value of the electrolyte caused by them. An object of the present invention is to provide a method for efficiently regenerating an electrolytic solution to efficiently form a high-quality patina film.

[0005]

According to a first aspect of the present invention, a substrate having at least a surface layer made of copper or a copper alloy is used as an electrolytic solution containing hydrogen carbonate ions or an electrolytic solution containing hydrogen carbonate ions and carbonate ions. In the method for forming a patina film in which anodic oxidation is performed in the electrolyte solution, the pH of the electrolyte solution is controlled to 7.5 to 9.5 by aerating and dissolving carbon dioxide gas in the electrolyte solution, and hydrogen carbonate ion or carbonate ion is replenished. Then, the patina film is formed to a thickness of 5 to 50 μm.

According to the present invention, a decrease in hydrogencarbonate ions and the like in the electrolytic solution at the time of anodic oxidation to form patina and an accompanying increase in the pH value are achieved by dissolving carbon dioxide (CO ₂ ) gas in the electrolytic solution by aeration. This is a method of recovering and is a method of continuously and efficiently forming a patina film without exchanging the electrolytic solution.

A copper or copper alloy plate is usually used as the base material for forming the patina coating, but plating on a material other than copper,
It is also possible to use a material having a copper or copper alloy layer formed by vapor deposition, cladding or the like. Further, the same base material as the anode may be used for the cathode of the counter electrode, or insoluble stainless steel plate or platinum may be used.

In the present invention, if the patina coating formed on the base material has a thickness of less than 5 μm, the adhesion to the base material deteriorates, and it peels off during roof construction or is washed away by rainfall. On the other hand, when the thickness exceeds 50 μm, the outer layer of the patina film becomes porous, the patina once formed is released into the electrolytic solution in a large amount, and the patina formation rate decreases. Also, the patina film is likely to peel off if it is too thick. Therefore, the patina film thickness is 5
Limited to ~ 50 μm.

In the present invention, the pH value of the electrolytic solution is 7.5.
When it is lower than the above range, the solid solution amount of carbon dioxide gas in the electrolytic solution decreases, and the replenishment efficiency deteriorates. On the other hand, if the pH value exceeds 9.5, a black coating of CuO 3 is formed on the base material under the patina coating, resulting in a poor appearance. Therefore, the pH value is limited to 7.5 to 9.5.

In the present invention, when the temperature of the electrolytic solution is lower than 15 ° C. or higher than 35 ° C., the appearance is deteriorated and the adhesion is lowered. It is desirable to maintain the temperature of the electrolytic solution at 15 to 35 ° C, especially at 20 to 30 ° C. If the concentration of alkali metal ions in the electrolytic solution is less than 0.4 mol / dm ³ , the appearance is deteriorated and the adhesion is deteriorated. Therefore, the alkali metal ion concentration in the electrolytic solution is preferably 0.4 mol / dm ³ or more. On the other hand, when the anode current density is less than 7 A / dm ² , the formation rate of the patina film is lowered, the appearance is deteriorated, and the adhesion is lowered. Therefore, the anode current density is preferably 7 A / dm ² or more. Even if the anode current density is too high, the patina coating formation efficiency saturates and becomes uneconomical. Therefore, it is preferable to set the upper limit to about 20 A / dm ² .

According to a second aspect of the present invention, a substrate having at least a surface layer made of copper or a copper alloy is used in an electrolytic solution containing hydrogen carbonate ions and ammonium ions, or in an electrolytic solution containing hydrogen carbonate ions, carbonate ions and ammonium ions. In the method of forming a patina film by anodic oxidation, the pH of the electrolytic solution is adjusted to 7.2 to 9.0 by dissolving carbon dioxide gas in the electrolytic solution by aeration.
Is controlled and the hydrogen carbonate ion or carbonate ion is replenished to form a patina film having a thickness of 5 to 50 μm.

In the present invention, as the alkali metal salt containing hydrogen carbonate ion or carbonate ion, ammonium salt is used in addition to Na salt and K salt. The aqueous solution containing the ammonium salt causes the formed patina film to have relatively high adhesion to the substrate. Instead, NH _{4 in the} electrolyte
⁺ Accumulates, and since this NH ₄ ⁺ is a complexing agent for Cu, a black film of CuO will start to be formed while the pH value is low.

In the present invention, the formation thickness of the patina film is limited to 5 to 50 μm and the pH is limited to 7.2 to 9.0. The temperature of the electrolyte is 15 to 40 ℃, the concentration of alkali metal ions in the electrolyte is 0.4 to 1.1 mol / dm ³ (Note 1), and the anode current density is 7
It is preferable to control each to A / dm ² or more. The reason is the same as in the case of the invention of claim 1. (Note.1) 1.1mo
The reason why l / dm ³ or less is preferable is the same as the reason that 0.4 mol / dm ³ or more is preferable.

[0014]

In the present invention, a green-blue film is formed by anodizing a base material having at least the surface layer made of copper or a copper alloy in hydrogen carbonate ion, or an electrolyte solution containing hydrogen carbonate ion and carbonate ion, or ammonium ion. In the method, pH control of the electrolytic solution and supplementation of hydrogen carbonate ions or carbonate ions are carried out by aerating and dissolving carbon dioxide gas in the electrolytic solution. Therefore, without changing the electrolyte solution,
It can be formed continuously for a long time and has excellent productivity.
Furthermore, a long base material wound on a coil can be continuously processed,
It is possible to significantly reduce productivity and cost.

As the formation of the patina film by anodic oxidation progresses, HCO ₃ ⁻ etc. in the electrolytic solution decreases, and the pH value increases accordingly. When carbon dioxide gas is dissolved in this electrolyte by aeration, as shown in the following reaction formula, H ⁺ and HCO ₃ are contained in the electrolyte.
^- , H ₂ CO ₃ , CO ₂ (aq.), Etc. are regenerated, or OH ^- is decreased, and the pH value decreases. ^{_{2OH - + CO 2 → CO 3}} 2- + H 2 O (pH> 10) OH - + CO 2 → HCO 3 - (pH> 10) H 2 O + CO 2 → H + + HCO 3 - (pH <10) CO 3 2- ^{_{+ H + → HCO 3 - (}} . aq) (. aq) (pH <10) H 2 O + CO 2 (gas) → H 2 O + CO 2 (pH <8) H 2 O + CO 2 = H 2 CO 3 (pH <8 )

Basically, the electrolytic solution should be regenerated by replenishing HCO ₃ ⁻ and CO ₃ ²⁻ which are the main components for forming the patina film. However, there is no liquid called "carbonic acid", and therefore the simple method of liquid replenishment cannot be adopted. Therefore, in the present invention, instead of a liquid called "carbonic acid", carbon dioxide gas is dissolved by aeration in an electrolytic solution to regenerate HCO ₃ ^- and CO ₃ ^2- , but without stopping the operation, pH value control and component In terms of replenishment, it has the same effect as a liquid called "carbonic acid".

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples. (Example 1) Tough pitch copper plate (tempered 1 / 2H, thickness 0.4mm
The step of continuously anodizing 10 sheets of JIS-C1100) and the step of bubbling carbon dioxide into the electrolyte for 2 minutes were repeated 4 times to form a patina film on 40 sheets of copper plate. SUS for cathode
-304 was used. Ammonium hydrogen carbonate 0.3 mol as electrolyte
An aqueous solution of 0.3 mol of ammonium carbamate and 1 dm ³ (ammonium ion concentration of about 0.6 mol / dm ³ ) was used. The electrolytic area of the copper plate was set to 1 dm ² . Anode current density is 10A / dm ² ,
The liquid temperature at the start of electrolysis was adjusted to 25 ° C. The anodic oxidation time was 3 minutes per copper plate, and the anodic oxidation treatment amount per 10 copper plates was 5 A · hrs / dm ³ . Carbon dioxide gas was passed through a glass ball filter at a flow rate of 0.5 × 10 ⁻³ Nm ³ / min. The pH value was measured using a commercially available pH meter before and after aerated with carbon dioxide gas.

Example 2 A patina film was formed in the same manner as in Example 1 except that 0.9 mol / dm ³ sodium hydrogencarbonate aqueous solution 1 dm ³ was used as the electrolytic solution.

(Comparative Example 1) A patina film was formed in the same manner as in Example 1 except that carbon dioxide gas was not passed.

Comparative Example 2 A patina film was formed by the same method as in Example 2 except that carbon dioxide gas was not passed.

Each of the obtained green-blue film-formed substrates was visually observed every 10 sheets, and the quality of the substrate was evaluated on a three-point scale of ◯, Δ, and ×. The thickness of the patina coating was measured by burying the test material in resin and observing it with a scanning electron microscope. The results are shown in Table 1.

[0022]

[Table 1]

As is clear from Table 1, the method product (N
In o.1, 2), the pH value increased with the formation of the patina film, but by dissolving carbon dioxide by aeration, hydrogen carbonate ions and the like were replenished and the pH value decreased. In No.2, the appearance of the patina coating deteriorated somewhat from the 20th sheet, but the aqueous solution was regenerated by aeration and dissolving carbon dioxide, and the patina coating recovered to a good appearance. On the other hand, the comparative example product (No.
(3, 4) did not vent carbon dioxide, so from the 20th sheet,
The patina film begins to blacken partially, and blackening progresses after processing 30 and 40 sheets, and the patina film becomes very thin.
The appearance was bad.

Example 3 Carbon dioxide gas was passed through a glass ball filter to the used electrolytic solution in which the patina film formation was impossible in the comparative example products (Nos. 3 and 4) and 0.5 × 10 ⁻³ Nm ³ / The pH value was measured by aeration for 2 minutes, 10 minutes, 20 minutes, or 30 minutes at a flow rate of min. Table 2 shows the results.

[0025]

[Table 2]

[0026] As apparent from Table 2, by bubbling the electrolyte also carbon dioxide after use of patina film formation becomes impossible, bicarbonate ions (HCO ₃ ^-) and carbonate ions (C
It can be seen that O ₃ ²⁻ ) is replenished, the pH value is recovered, and the electrolytic solution is regenerated.

(Example 4) A tough pitch copper plate (tempered
A 1/2 H, 0.4 mm thick JIS-C1100) was used, on which a patina film was formed by anodic oxidation. S for the cathode electrode
US-304 was used. As the electrolytic solution, 0.9 mol / dm ³ sodium hydrogen carbonate aqueous solution 1 dm ³ was used. The electrolysis area of the base material is 1 dm
² The anode current density was 10 A / dm ² , the liquid temperature at the start of electrolysis was adjusted to 25 ° C., and the anodic oxidation time was 3 minutes. Two copper plates were continuously anodized to form a patina film. The anodic oxidation was performed while passing carbon dioxide through the electrolyte. Carbon dioxide gas was passed through a glass ball filter at a flow rate of 0.5 × 10 ⁻³ Nm ³ / min. The composition, pH, temperature, anode current density, and electrolysis time of the electrolytic solution were variously changed. The pH value of the electrolytic solution was adjusted in advance by anodizing a plurality of copper plates to raise it or by dissolving carbon dioxide to lower it. Other conditions are Example 1
Same as

(Comparative Example 3) The patina film has a thickness of less than 5 μm or more than 50 μm, or the pH value of the electrolytic solution is 7.
A patina film was formed on the substrate by the same method as in Example 4 except that the value was less than 5 or more than 9.5.

The appearance, thickness, and adhesion of the patina were examined for each of the base materials having the patina film formed thereon. The appearance of the patina film was visually evaluated to be very good, and was evaluated in four grades of ⊚, ∘, Δ and ×. The coating thickness was determined in the same manner as in Example 1. Adhesion is JIS-
A 180-degree bending test was performed according to G3312-1994, and the peeling condition of the coating film after the test was observed, and those that did not peel at all were rated as ⊚, below as ○, Δ, and ×. The results are shown in Table 3.
The Δ evaluation is such that there is no practical problem in appearance and adhesion.

[0030]

[Table 3]

As is apparent from Table 3, the method product of the present invention
(Nos. 7 to 24) all have a good appearance and are light blue or blue.
It developed color. Adhesion was also good. The temperature of the electrolyte is
Low as 10 ℃ (No.12), High as 40 ℃ (No.15),
Solution concentration is 0.3 mol / dm³And low (No. 16) are patina film
Formation rate was a little slow. Anode current density is 7 A / dm
²(Nos. 19 and 20) require less time for film formation.
did. Thin patina film (No.8, 19) and thick patina (N
In o.9), the adhesion was somewhat reduced.

On the other hand, in Comparative Example No. 25, since the patina film thickness was less than 5 μm, the underlying copper base material was partially exposed, resulting in poor appearance. The exposed portion was further expanded by the bending test. No. 26 had an excellent appearance because the patina film thickness exceeded 50 μm, but it had poor adhesion and peeled off in the bending test. In No. 27, since the pH of the electrolyte was as low as 7.0, the patina film became particulate and was liberated into the electrolysis solution.
It was only formed to a thickness of ˜2 μm. No. 28 is pH
Since the value was as high as 10.0, the surface of the copper plate had a strong black color, and the patina film was hardly formed.

Example 5 A copper plate was prepared in the same manner as in Example 4 except that an aqueous solution containing 1 to 3 of ammonium carbonate, ammonium hydrogencarbonate, ammonium carbamate and ammonium molybdate was used as the electrolytic solution. A patina film was formed in succession on two sheets.

(Comparative Example 4) An aqueous solution containing ammonium carbonate and ammonium carbamate was used as the electrolytic solution, and the patina film was made to have a thickness of less than 5 μm or more than 50 μm, or the pH value of the electrolytic solution was adjusted. A patina film was formed on the substrate by the same method as in Example 5 except that the value was less than 7.2 or more than 9.0.

With respect to each copper plate having the above-mentioned patina film formed thereon, the appearance, thickness and adhesion of the patina film were examined by the same method as in Example 4. The results are shown in Table 4.

[0036]

[Table 4]

As is apparent from Table 4, the method product of the present invention
(Nos. 29 to 48) all had good appearance and good adhesion. Electrolyte with low temperature of 10 ℃ (No.36), or 45
High (° C) (No.39), NH ₄ ⁺ concentration in the electrolyte is 0.3 mol / d
Those with a low m ³ (No. 40) have a thin patina film compared to the other examples, and those with an anode current density of less than 7 A / dm ² (No. 44, 45) take a long time to form a film. However, the appearance showed good color development of light blue and blue. Adhesion is also 5 for patina film
~ 6 μm thin (No.32,44) and 49-50 μm thick
(No. 33) was slightly inferior, but others were good. Although the adhesion of the patina film to the substrate was better than that of Example 4, the appearance was slightly blackish.
This is due to the effect of NH ₄ ⁺ in the electrolytic solution.

On the other hand, in Comparative Example No. 49, since the patina film thickness was less than 5 μm, the underlying copper base material was partially exposed, resulting in poor appearance. The exposed portion was further expanded by the bending test. No. 50 had an excellent appearance because the patina film thickness exceeded 50 μm, but it had poor adhesion and peeled off in the bending test. In No. 51, the pH of the electrolytic solution was as low as 7.0, so the patina film became particulate and was released into the electrolysis solution.
It was formed only to a thickness of μm. No.52 has a pH value
Since it was as high as 9.5, the surface of the copper plate had a strong black color and almost no patina film was formed.

[0039]

As described above, in the present invention, in the electrochemical method for forming a patina, the deterioration of the electrolytic solution is prevented by aeration and dissolving carbon dioxide gas in the electrolytic solution, so that the electrolytic solution is replaced. It is possible to continuously form a patina film without having to do so and has excellent productivity. Further, it is possible to continuously process a long base material wound around a coil, and it is possible to greatly reduce productivity and cost. Therefore, it has a remarkable industrial effect.

Claims (2)

[Claims] 1. A patina film which anodizes a base material having at least a surface layer made of copper or a copper alloy in an electrolytic solution containing hydrogen carbonate ions or an electrolytic solution containing hydrogen carbonate ions and carbonate ions. In the forming method, the pH of the electrolytic solution is changed by dissolving carbon dioxide gas in the electrolytic solution by aeration.
Is controlled to 7.5 to 9.5, and hydrogen carbonate ions or carbonate ions are replenished to form a patina film having a thickness of 5 to 50 μm. 2. A patina film for anodic oxidation of a substrate having at least a surface layer made of copper or a copper alloy in an electrolytic solution containing hydrogen carbonate ions and ammonium ions or an electrolytic solution containing hydrogen carbonate ions, carbonate ions and ammonium ions. In the formation method, the pH of the electrolytic solution is controlled to 7.2 to 9.0 by aerating and dissolving carbon dioxide gas in the electrolytic solution, and hydrogen carbonate ions or carbonate ions are replenished to form a patina film of 5 to 5%.
A method for forming a patina film, which comprises forming the film to a thickness of 50 μm.