JPH03236479A - Formation of patina - Google Patents

Abstract

PURPOSE:To stably form a patina film excellent in adhesion and uniform in color tone on the surface of a base material in a short time by forming a thin film of copper or a copper alloy on the base material surface and then treating the thin film with a chemical conversion coating soln. added with an oxidizing agent. CONSTITUTION:The surface of a base material on which patina is to be formed is preferably roughened, and then a thin film of copper or a copper alloy is formed on the surface. The thin film is preferably formed by thermal spraying, and its thickness is appropriately controlled to about 1-100mum or preferably to about 5-40mum. The surface roughness of this thin film is adjusted to about 3-50mum or preferably to about 5-40mum. The thin film is treated with a chemical conversion coating soln. mixed with >= about 3wt.% of an oxidizing agent such as MnO2. Consequently, the patina having a uniform and deep color tone is formed on the surface of the base material regardless of its kind with good adhesion in a short time.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for stably forming a patina with excellent adhesion to a substrate with good productivity.

<Conventional technology and its challenges> Over the years, the surface of copper, which has been used for the roofing of shrines and temples, has been exposed to oxygen and water vapor in the atmosphere.

An elegant and beautiful green patina (Cu CO3・Cu(○H)2゜C
u S Oa・3 Cu(OH)z+ CuC1t・3
It is well known that the material is covered with basic copper salts such as Cu(OH)z, but this patina layer not only creates a profound and unique beauty, but also acts as an anti-corrosion film.
As a result, copper roofs covered in patina can last for hundreds of years.

Therefore, in recent years, "patina film-forming products" that artificially generate a natural-looking patina in a short period of time to prevent corrosion of base materials and have decorative or artistic effects have been developed, which can be used not only for roofing materials but also for interior wall materials in buildings. It has come to be seen in ornaments, etc., and many proposals have been made to date on means of artificially forming a patina that is close to natural.

These conventional artificial patina formation means can be broadly classified as follows.

(A) Chemical conversion treatment method in which contact is made with a chemical solution (for example,
-51468, etc.).

(B) Method of electrolytic treatment in a chemical solution (for example,
12117, etc.).

(C) A method in which a base material is subjected to a chemical conversion treatment and then further coated (for example, a method proposed in JP-A No. 55-8491).

(D) A method of painting with a paint containing a green-blue-forming substance (for example, the method proposed in JP-A-55-139467).

(E) A method in which copper or copper alloy powder is bonded with an adhesive to the surface of a copper plate whose surface has been roughened by sandblasting, and then an artificial patina-generating liquid such as ammonium chloride or ammonium sulfate is applied (for example, Japanese Patent Publication No. 57-52425 methods proposed as such).

However, the above-mentioned artificial patina formation means actually a) produces patina at a slow rate, and b) the patina coating is likely to peel off, requiring a large amount of cost for manufacturing equipment.

C) Unable to stably form green-blue color, resulting in non-uniformity and poor color tone.

d> Poor adhesion of patina.

e) Many man-hours are required to form the green-blue coating, resulting in poor productivity.

Problems such as these have been pointed out, and furthermore, the base material is generally limited to copper or copper alloy, and if the patina surface is not protected by painting etc. There was also the problem that sufficient adhesion could not be maintained. Moreover, the protection of patina by using a paint film cannot provide a fundamental solution to the above problem because the paint film composition deteriorates due to ultraviolet rays.

Therefore, the purpose of the present invention is to establish a means J capable of stably forming a patina coating with excellent adhesion and uniform color tone in a short time regardless of the type of substrate. Was that.

Means for Solving the Problems> As a result of intensive research from various viewpoints in order to achieve the above object, the present inventors have found that "the surface of the base material on which patina is to be formed can be If a thin film made of copper or copper alloy is formed on the surface of the substrate after roughening, and then this thin film is treated with a "chemical conversion treatment liquid containing an oxidizing agent",
A chemical conversion reaction (G-etching product formation reaction) and an oxidation reaction of corrosion products proceed simultaneously between the “thin film made of copper or copper alloy” and the “chemical conversion treatment liquid to which an oxidizing agent has been added”. As a result, a patina film that firmly adheres to the surface of the substrate and has a thick, uniform color that closely resembles natural patina is formed in a short time.
This led us to the following knowledge.

The present invention has been made based on the above-mentioned findings and the like.After forming a thin film of copper or copper alloy on the surface of a base material on which patina is to be formed, the thin film is coated with an oxidizing agent. It is characterized by being able to stably form a patina with excellent adhesion and a good appearance in a short period of time by treating it with a chemical conversion treatment liquid.

Here, the "base material on which patina is to be formed" is not limited to metal materials such as copper and copper alloys, but may also be ceramics, roof tiles, wood, synthetic resin, etc.
The material is not particularly limited.

Hereinafter, the present invention will be explained in more detail and concretely along with its functions and effects.

In the patina formation method according to the present invention, a "thin film made of copper or copper alloy" is first formed on the surface of a base material. The thickness of the thin film is not particularly limited, but is usually 1 to 100 mm.
J! The volume is preferably about 5 to 40 ml. Of course, it is possible to form a patina even if the film thickness is less than 1 mm, but in this case it is not preferable because cracks are likely to occur in the thin film.

On the other hand, if the film thickness exceeds 100 mm, it becomes difficult to obtain a satisfactory color tone and is also unfavorable in terms of production cost.

As a means for forming the above-mentioned "thin film made of copper or copper alloy", known methods such as plating, vacuum evaporation, spa sottering, ion blasting, thermal spraying, etc. can be applied. Therefore, it is necessary to select an appropriate thin film forming method depending on the type of substrate, etc., but since it is a dry process, processing is quick, a wide range of materials can be used, and there is a large The most preferable method is the thermal spraying method, which does not cause any adverse effects.

By the way, there are various thermal spraying methods such as "flame spraying,"'arcspraying,' and "plasma spraying," and it is also known that powders and wires made from copper or copper alloys can be used as raw materials for thermal spraying. However, in the present invention, there are no particular restrictions on the thermal spraying method or the thermal spraying raw materials.However, even if the same material and the same equipment are used, different coatings will be formed if the thermal spraying method (i.e. thermal spraying conditions) is different. However, care must be taken in this regard.For example, atmospheric conditions (mixing ratio of oxygen and acetylene, etc.), spraying distance, wire feeding speed, etc., sensitively affect the hardness of the sprayed coating.

In addition, the relative speed of the thermal spray gun and the workpiece, the coating thickness per bath, the temperature of the workpiece during thermal spraying (in order to increase the adhesion strength of the coating, it is preferable to preheat the base material to an appropriate temperature) There are many factors that affect the properties of thermal spray coatings, such as the pressure and flow rate of gas or air.

Furthermore, it is generally said that even if the thickness of a thermal spray coating is the same, one made of many thin layers is stronger than one made of fewer thick layers. need to be considered. In addition, increasing the spray thickness per bath can cause overheating, so in the case of internal diameter thermal spraying, the relative speed of the spray gun and the workpiece should be increased to avoid overheating. Particular care must also be taken to reduce the thickness.

As mentioned above, when forming a "thin film made of copper or copper alloy" by thermal spraying, the type of base material.

Thermal spraying conditions etc. need to be selected appropriately depending on the thickness of the thermally sprayed coating, the desired surface roughness, etc.

On the other hand, when forming a "copper or copper alloy thin film" by plating, etc., the purpose can be achieved relatively stably by simply applying the known electrolyte composition, electrolytic conditions, etc. .

The surface roughness of the "thin film made of copper or copper alloy" thus formed is not particularly limited, but if the surface roughness of the thin film is less than 3, the degree of green-blue coloring will be low; If it exceeds -, the adhesion strength between the base material and the thin film tends to decrease, so it is usually 3 to 50jI21, preferably 5 to 407E11.

By the way, "thin film made of copper or copper alloy" on the surface of the base material
Roughening the surface of the base material prior to the formation of the coating improves the adhesion between the base material and the "thin film made of copper or copper alloy", and thus the adhesion of the patina coating to be formed. This is extremely desirable. Therefore, before forming a thin film from copper or copper alloy, the surface of the base material is roughened as necessary to roughen the base material surface and temporarily activate the surface. will be promoted.

Generally, two types of methods for roughening the surface of a substrate are known: a chemical method (including an electrochemical method) and a physical method (mechanical method). Examples of the former include "method of immersion in acid or alkali (i.e., etching treatment method)" and "electrolysis method," and examples of the latter include "method of immersion in acid or alkali (i.e., etching method)" and "electrolytic method," and examples of the latter include "method of immersion in acid or alkali (i.e., etching treatment method)" and "electrolysis method."
Examples include the "water jet method", the "moving crab method", the "hand tool method", etc. Therefore, the "
When roughening the surface of a base material prior to forming a "thin film made of copper or copper alloy," it is necessary to select the roughening method appropriately depending on the type of the base material and the roughness of the surface of the target patina-formed product. For example, when the base material is a metal material, it is possible to roughen the base material surface with high efficiency, and at the same time, it is also possible to remove rust and other corrosion products that have occurred on the base material surface. It can be said that "blasting method" is suitable.

Moreover, in the Plast method, abrasive materials with various hardness levels such as silica sand, steel grid, stainless steel, fused alumina (artificial corundum), alundum, carborundum, glass beads, synthetic resin particles, etc. are used as the abrasive material. is used, so it is possible to select a suitable one according to the type of base material etc.
Another advantage is that the surface roughness can be adjusted by changing the blasting conditions.

In addition, blasting methods are classified into types from various viewpoints. For example, from the viewpoint of the method, spraying of abrasive materials can be classified into "method of blasting using compressed air" and "method of blasting using centrifugal force." Further, depending on the dry and wet state of the abrasive to be sprayed, it can be classified into "dry method" and "wet method", but in the present invention, there are no particular restrictions on the types or combinations thereof.

The surface roughness of the base material after the surface roughening treatment is preferably 3 μm or more, preferably 10 to 30 μm. This is because if the surface roughness is less than 3IIn, the effect of improving the adhesion with the "thin film made of copper or copper alloy" is not significant. On the other hand, when the surface roughness exceeds 50 mm, although the adhesion is good, distortion occurring in the base material becomes a problem, which is not realistic.

Now, in the present invention, after a "thin film made of copper or copper alloy" is formed on the surface of a base material, the thin film is treated with a chemical conversion treatment solution containing an oxidizing agent, which is one of the major features of the present invention. ” is applied, and the oxidation treatment of the chemical conversion coating that is generated along with the chemical conversion treatment is performed simultaneously.

In general, "chemical conversion treatment" is a process in which metal is chemically reacted with a corrosive solution (chemical treatment solution) adjusted to specific conditions to form a layer of water-insoluble corrosion products that stick to the surface of the metal. The physical or chemical properties of the corrosion products are used to prevent rust, paint bases, lubrication bases for plastic working, etc.

The "chemical conversion treatment" referred to in the present invention has almost the same concept, but in the present invention, in particular, the "thin film made of copper or copper alloy" formed on the base material is treated with a "chemical conversion treatment solution containing an oxidizing agent." ”
It can also be said to be unique in that it is processed to form a distinctive patina.

The “chemical conversion treatment liquid before oxidizing agent addition” used in the present invention is
The type is not critical as long as it forms a water-insoluble corrosion product layer on the surface of copper or copper alloy. and,
Conventionally, such substances include ammonium salts, hydrochloric acid, and caustic soda. Solutions containing sulfides, sulfates, nitrates, acetates, carbonates, monobicarbonates, alum, etc., and combinations thereof (including, of course, what is called artificial patina-generating solutions, and solvents) However, more specific examples include the following chemical conversion treatment liquids.

A) An aqueous solution prepared by adding an alkali metal chloride and/or an alkaline earth metal chloride to hydrochloric acid, nitric acid, and ammonium sulfate.

B) Aqueous solution to which cupric chloride has been added.

C) An aqueous solution of an alkali metal chloride and/or an alkaline earth metal chloride (for example, Na(j, KCf, NHaCl, etc.) with copper sulfate added thereto.

On the other hand, in the present invention, there are no particular restrictions on the oxidizing agent added to the chemical conversion treatment solution, such as a) manganese dioxide (MnOz).

b) Lead dioxide (PbOli).

C) Permanganates (KMnOa, NaMnO*, etc.) d) Chromates and/or dichromates (including chromic acid and dichromates).

e) Iodine compounds containing free iodine (for example, iodopotassium solution containing free iodine, etc.) can be exemplified, and these can be used alone or in combination.

As mentioned above, in the present invention, there is no particular restriction on the type of chemical conversion treatment liquid or oxidizing agent added thereto, and the concentration of these chemical conversion treatment liquids (the concentration of active ingredients is also not particularly limited, but usually 5 to 50% by weight). , preferably 20 to 30% by weight) and an oxidizing agent (the amount of the oxidizing agent added is also not particularly limited, but is usually 3% by weight or more, preferably 5 to 20% by weight).
A treatment solution prepared by appropriately combining and mixing the above is applied to a "thin film made of copper or copper alloy" formed on a base material by a method such as coating or spraying, or by a method such as immersing the thin film in the chemical conversion treatment solution. , causing an oxidation reaction to occur simultaneously with the chemical conversion reaction.

When this treatment is carried out, the "thin film made of copper or copper alloy" turns white, albeit briefly. Thereafter, as time passes, the formation of a patina can be observed by changes in the color of the thin film.

In this case, if the "thin film made of copper or copper alloy" is formed by thermal spraying, a chemical reaction is likely to occur and better results can be obtained. This is because the thermal spray coating is a laminate of particles that have been rapidly cooled from a high temperature and collided with the surface of the base material, and because there are residual stress due to thermal distortion, oxides, pores, etc., the electrode potential is relatively base. This is thought to be because.

This "mechanism of patina formation when a thin film made of copper or copper alloy is treated with an oxidizing agent-added chemical conversion treatment solution" has not been clearly elucidated at present, but X-ray diffraction has revealed that the patina formed by the treatment is chemically It has been confirmed that it is a basic cupric chloride (Cuclz.3Cu(OH)z) that is stable. Furthermore, although it depends on the type of oxidizing agent such as manganese dioxide added to the chemical conversion treatment solution, it is not only involved in the simple oxidation reaction, but also in Cu.

It is also presumed that it acts as a catalyst for the oxidation of Cu, ○, CuCZ, etc.

The base material on which a patina has been formed by treatment with a chemical conversion treatment solution containing an oxidizing agent is preferably subjected to curing that also serves as drying. There is no particular need for heating in this curing, and it is usually sufficient to carry out the curing at room temperature for 2 to 24 hours.

In this way, it is possible to form a uniformly colored patina with extremely good adhesion in a short time.

Next, the present invention will be explained in more detail with reference to Examples.

<Example> Example 1 First, a pre-degreased copper plate (360m width x 360n length x
0.3 + n thickness) was prepared, and the surface of the copper plate was roughened by blasting using alundum powder with a particle size of 50 to 11250 at an air pressure of 1.5 to 5 kg/aj (gauge pressure). Ta.

Next, a copper wire was applied to the roughened surface of the copper plate to a thickness of 25 mm.
A thermal sprayed film (copper) was formed.

The thermal spraying conditions at this time were: thermal spraying method: arc thermal spraying (using a 4RC type machine manufactured by Metco).

Thermal spraying distance: 150 Tsuru ±80tm.

Thermal spray gun speed: 40 m/win.

Pitch: 20-30u.

Working voltage: 35V.

Usage current: 50A.

Air gap: Ftne+ Air pressure: 80psi (5.6kg/cj).

Copper wire: 1.6m x 2 pieces.

Met.

Next, a reaction layer was formed by uniformly applying a chemical conversion treatment solution, a solution in which 5% by weight of manganese dioxide powder was added to an aqueous solution of 30% by weight of cupric chloride, on the copper sprayed film. Thereafter, curing, which also served as drying, was performed at room temperature for 8 hours.

and “patina formed by the above-described method of the present invention”,
The state of each patina surface was observed using a SEM (scanning electron microscope) for "natural patina that has been used for more than 30 years", "commercially available artificial patina plate", and "commercially available artificial patina slate".

This SEM observation photograph is shown in Figs. 1 to 4.

As is clear from the comparison of FIGS. 1 to 4, it can be seen that the patina formed by the method of the present invention is very similar to natural patina in shape, particle size, etc.

In addition, the patina formed by the method of the present invention has a deep bluish green tone, and even when the patina film is rubbed with a fingertip, no peeling occurs at all, and it is as good as or better than natural patina. It was confirmed that the film had good adhesion.

Furthermore, analysis by X-ray diffraction confirmed that the patina formed by the method of the present invention is basic cupric chloride (Cu(Jz.3Cu(OH)z), which is the main component of natural patina. .

Furthermore, when we conducted SEM observations on the cross sections of the "patina formed by the method of the present invention" and the "natural patina," we found that the patina formed by the method of the present invention was different from the base material (Fig. 5).
Almost the entire cross section of the sprayed film that has bitten into the roughened surface of the copper plate (copper plate) has turned into a patina, creating a structure that is tightly adhered to the base material, and there are also minute pores in the sprayed film (which has turned into a patina). is clearly recognized, and the case and structure of natural patina shown in Figure 6,
It was found that they were extremely similar in terms of appearance, density, etc.

Example 2 Common salt (
A patina was formed in the same manner as in Example 1 except that an aqueous solution containing 10% by weight of Na(J) and 20% by weight of copper sulfate was used.

The patina coating thus obtained was uniform and had extremely excellent adhesion with no peeling material.

In addition to these examples, various methods other than thermal spraying can be used to form copper or copper alloy thin films, and various known oxidation methods can be used in various known chemical conversion treatment solutions (including those called artificial patina generation solutions). It was confirmed through tests using various combinations of treatment with a treatment solution containing a treatment agent that, if the method of the present invention is followed, almost the same good results as in the above example can be obtained in all cases.

Summary of Effects> As explained above, according to the present invention, patina that exhibits a deep color tone similar to natural patina and has extremely excellent adhesion can be stably applied to all kinds of substrates in a short time. In addition, since no special equipment is required, on-site construction is possible, and it is easy to apply, for example, to the repair of patina products. Therefore, it can contribute to expanding the concept of creations in a wide range of fields, such as not only roofing materials but also interior wall materials and decorative items, resulting in extremely useful effects in industry and social life.

[Brief explanation of drawings]

FIG. 1 is a metallographic photograph taken by a scanning electron microscope (magnification: about 500 times) showing the state of the "patina" surface formed by the method of the present invention. FIG. 2 is a metallographic photograph taken with a scanning electron microscope (magnification: approximately 8,000 times) showing the state of the natural patina surface after more than 30 years. Figure 3 is a metallographic photograph taken with a scanning electron microscope showing the surface condition of a commercially available artificial patina plate (magnification: approx. 80
00 times). Figure 4 is a metallographic photograph taken with a scanning electron microscope (magnification:
approximately 8,000 times). FIG. 5 is a metallographic photograph taken with a scanning electron microscope (magnification: about 300 times) showing the cross-sectional state of "patina formed by the method of the present invention". FIG. 6 is a metallographic photograph taken with a scanning electron microscope (magnification: about 360 times) showing the cross-sectional state of natural patina after more than 30 years. :jko l! Figure 1

Claims (3)

[Claims] (1) A method for forming a patina, which comprises forming a thin film made of copper or a copper alloy on the surface of a base material on which a patina is to be formed, and then treating the thin film with a "chemical conversion treatment solution containing an oxidizing agent." . (2) The method for forming a patina according to claim 1, wherein the surface of the substrate on which the patina is to be formed is roughened, and then a thin film made of copper or a copper alloy is formed. (3) The method for forming a patina according to claim 1 or 2, wherein a thin film made of copper or a copper alloy is formed by thermal spraying.