JP5343155B2 - Cadmium elution prevention method for copper alloy piping equipment and copper alloy piping equipment using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for inhibiting elution of cadmium from piping equipment made of a copper alloy, such as a valve or a pipe joint, by which piping equipment made of a copper alloy is provided by reusing a copper alloy containing cadmium and elution of cadmium from the piping equipment made of a copper alloy is restrained, and to provide the piping equipment made of a copper alloy. <P>SOLUTION: The method for inhibiting elution of cadmium from piping equipment made of a copper alloy such as a valve or a pipe joint includes: immersing at least a liquid contact part of the piping equipment made of a copper alloy, in which cadmium is dissolved as a solid solution, into an aqueous metal salt solution containing a metal nobler than cadmium; and replacing cadmium in a surface layer of the liquid contact part of the piping equipment by the metal nobler than cadmium to restrain the elution of cadmium. <P>COPYRIGHT: (C)2012,JPO&amp;INPIT

Description

  The present invention relates to a cadmium elution prevention method for copper alloy piping equipment such as valves, pipe joints and faucets, and a copper alloy piping equipment using the same.

  Copper alloys such as bronze and brass are excellent in castability, machinability, and economic efficiency, and have a high antibacterial action that is difficult for other materials to exhibit. Generally used as a material for piping equipment such as valves, pipe joints, strainers, and faucets. This copper alloy consists of various metal elements such as copper, zinc, and tin, and among them, cadmium is in a solid solution state because of its similar chemical behavior and properties. ing. Cadmium is a harmful element and its water quality standards are being reviewed because it adversely affects the human body. However, since most of the elution sources are from piping equipment, it is extremely important to suppress elution from the piping equipment. It has become.

  When this type of piping equipment is manufactured from a copper alloy, it is generally expensive to collect each element constituting the copper alloy and manufacture it from scratch. Increasingly, it is dissolved and reused. In this case, in Japan, pure zinc purified from natural zinc ore, special zinc, electric zinc such as ordinary zinc, or distilled zinc is often used. On the other hand, in many cases, recycled zinc ingots that reuse zinc oxide generated during the casting process and recycled products that have been once distributed as zinc products such as die-cast products are often used.

  In this case, for example, the pitting corrosion-resistant copper-based alloy tube material of Patent Document 1 is known as a copper alloy in which the cadmium content is prevented by suppressing the cadmium content. This copper-based alloy tube material contains zinc and phosphorus, and is heat-treated in a non-acidified atmosphere at 600 ° C. to 1050 ° C. for 1 minute to 5 hours.

JP 2001-247923 A

However, when electrozinc is used when reusing copper alloy scrap to provide piping equipment, it is possible to reduce the cadmium content, but the cost increases significantly. On the other hand, since distilled zinc contains a large amount of cadmium, it becomes easy for cadmium to be mixed into piping equipment that reuses this distilled zinc. In particular, brass with a high zinc ratio contains a lot of cadmium, and when zinc is added to a copper alloy scrap with a high copper content, more cadmium is contained and the cadmium is more easily eluted. There is also a risk.
Also, cadmium is likely to be generated in the recycled zinc ingot during its collection and regeneration process, and the cadmium content will be close to that of distilled zinc purified with natural zinc ore. There is a risk of easy brass.

  On the other hand, the pitting corrosion-resistant copper-based alloy tube material of Patent Document 1 is not based on the premise that copper alloy scrap or the like is reused as a material, and newly uses the material to suppress the cadmium content in the copper alloy. Because it was provided, it led to cost increase.

  The present invention has been developed as a result of intensive studies in view of the above-described circumstances, and the object of the present invention is to recycle a copper alloy containing cadmium and to provide a copper alloy piping device. Another object of the present invention is to provide a cadmium elution prevention method for copper alloy piping equipment such as valves and pipe joints that suppress the elution of cadmium from the copper alloy piping equipment and the copper alloy piping equipment.

  In order to achieve the above object, the invention according to claim 1 is directed to a metal salt aqueous solution comprising nickel nitrate containing nickel, which is a noble metal from cadmium, in a wetted part of a copper alloy piping device in which cadmium is dissolved. The surface of the wetted part is reduced by reducing the amount of elution of cadmium from the surface of the wetted part by immersing it in the inside and replacing nickel ions, which are noble metals in the aqueous metal salt solution, with cadmium on the surface of the wetted part It is a cadmium elution prevention method of the copper alloy piping equipment which suppressed elution of cadmium.

  The invention which concerns on Claim 2 is a copper alloy piping equipment which suppressed the elution of the cadmium of the liquid-contacting part surface layer using the cadmium elution prevention method.

  According to the first aspect of the present invention, cadmium on the surface layer of the wetted part can be replaced with a noble metal, and elution of cadmium from this part can be suppressed. Therefore, the amount of cadmium eluted can be suppressed even when copper alloy piping equipment such as valves, pipe joints, strainers, and faucets is provided by reusing a copper alloy containing cadmium. Moreover, although it is low-cost as copper alloy scrap, it is compared with the case where the cadmium content of the entire copper alloy is suppressed by using distilled zinc or recycled zinc ingot containing a large amount of cadmium as a material and performing cadmium elution prevention treatment only on the surface layer. Thus, the number of processing parts can be reduced, so that processing facilities and operations can be simplified. Furthermore, since it is possible to easily process the formed piping equipment instead of the molding stage such as casting, it is possible to prevent cadmium from being eluted from a large amount of piping equipment in a short time. Moreover, the elution of zinc can also be suppressed by preventing the elution of cadmium.

  In addition, the cadmium elution prevention treatment can be carried out without damaging the surface layer of the piping equipment, and characteristics such as aesthetic appearance, corrosion resistance, and abrasion resistance of the external surface of the piping equipment can be secured.

  According to the invention according to claim 2, while preventing the elution of cadmium from the surface layer of the wetted part, it can be formed by reusing copper alloy scrap containing cadmium, etc., and a valve / pipe joint, strainer, Various copper alloy piping equipment such as faucets can be provided.

It is a flowchart which shows the 1st example of the elution prevention process by substitution of cadmium. It is a flowchart which shows the 2nd example of the elution prevention process by substitution of cadmium. It is a flowchart which shows the 3rd example of the elution prevention process by substitution of cadmium. It is a flowchart which shows the elution prevention process by the membrane | film | coat of the organic substance which consists of an unsaturated fatty acid of cadmium. It is the graph which showed the analysis result by FT-IR analysis. It is a flowchart which shows the elution prevention process which introduce | transduced the washing process by a mixed acid in the elution prevention process of FIG. (A) is a flowchart showing step 1; (B) is a flowchart showing step 2; (A) is a flowchart showing step 3; (B) is a flowchart showing step 4. (A) is a flowchart showing step 5; (B) is a flowchart showing step 6; It is explanatory drawing which showed the ionization tendency of the main elements. 4 is a graph showing the relationship between the treatment conditions and the leaching amount of the metal element in the Ni nitrate Ni substitution treatment in Step 1; 12 is a graph showing the relationship between processing temperature and processing time in FIG. 11. 4 is a graph showing the relationship between the treatment time in step 1 and the leaching concentration of a metal element. 6 is a graph showing the relationship between the treatment time in step 2 and the leaching concentration of a metal element. 6 is a graph showing the relationship between the treatment time in step 3 and the leaching concentration of a metal element. It is the graph which showed the relationship between the processing time in the process 4, and the leaching concentration of a metal element. 6 is a graph showing the relationship between the treatment time in step 5 and the leaching concentration of a metal element. 4 is a graph showing the relationship between the Ni nitrate concentration in step 1 and the amount of metal element leaching. 6 is a graph showing the relationship between the Ni nitrate concentration in step 5 and the leaching amount of the metal element. It is the graph which showed the substitution processing capability of Ni nitrate Ni substitution processing and copper nitrate substitution processing. It is the microscope picture which showed the surface of the cadmium plating goods. It is an enlarged photograph of FIG. It is the microscope picture which showed the surface of the cadmium plating goods which surface-polished. It is an enlarged photograph of FIG. It is the graph which showed the analysis result by FT-IR analysis of a cadmium plating product. 10 is a flowchart showing an elution prevention step in step 7. 10 is a flowchart showing an elution prevention step in step 8. 10 is a flowchart showing an elution prevention step in step 9. 10 is a flowchart showing an elution prevention step in step 10. 10 is a flowchart showing an elution prevention step in step 11.

  In the following, an embodiment of a cadmium elution prevention method for copper alloy piping equipment such as valves and fittings in the present invention and a copper alloy piping equipment using the same will be described. The general content of cadmium in the zinc ingot contained in this copper alloy will be described. In the cadmium elution prevention method of the present invention, distilled zinc and regenerated zinc, which are cheaper than electrozinc, are targeted, but the component ratio of electrozinc is also shown for comparison with these components. In addition, you may make it give a cadmium elution prevention process to electro zinc by this invention.

  First, regarding the content ratio of cadmium in the zinc ingot, Table 1 shows the component ratio (%) of zinc ingot components (electro zinc and distilled zinc) defined in JIS H2107. In addition, Table 2 lists the bullion components of recycled zinc as an example. In Table 1, the purest zinc bullion, special zinc bullion, and ordinary zinc bullion are electro-zinc. Distilled zinc bullion special species, distilled zinc bullion 1 type, distilled zinc bullion 2 types are distilled zinc. is there.

  As shown in Table 1, distilled zinc has a higher cadmium content than electrozinc, and thus it can be said that cadmium is more easily eluted than electrozinc. On the other hand, the regenerated zinc shown in Table 2 also has a high cadmium content and it can be said that cadmium is likely to be eluted. Moreover, since regenerated zinc depends on the material supplied in the collection / regeneration process, the content of cadmium is not necessarily constant, and there is a possibility that it will be larger than the values in the table.

  Subsequently, Table 3 shows the content of cadmium in a copper alloy made of a zinc ingot in which cadmium is dissolved, and the results of a cadmium leaching (elution) test in this copper alloy. Here, solid solution refers to a state in which other atoms enter the crystal structure and are mixed in a solid state while maintaining the shape of the original crystal structure. Conditioning in the table is a method defined in the JIS S3200-7 leaching performance test, and is an operation for exchanging the leachate at least 9 times out of 14 days. A leaching test with conditioning, and a leaching test without conditioning is what was not performed.

  Cadmium can be dissolved in a zinc ingot theoretically at a rate of about 900 ppm at room temperature, and in a state of being dissolved in a copper alloy, unlike lead. From this, a ball valve made of copper alloy, a gate valve, a copper alloy scrap and a concentrated cadmium brass test piece made by casting distilled zinc or recycled zinc ingot (zinc ingot containing 738 ppm of cadmium). (Hereinafter referred to as a brass test piece) was used as a test product, and the cadmium content analysis of this test product and the amount of cadmium leached into tap water based on JIS S3200-7 were measured.

  In addition, according to JIS S3200-7, the leaching measurement of each element including cadmium was performed with an ICP emission spectroscopic analyzer or an ICP mass spectrometer. Both ICP emission spectroscopic analysis and ICP mass spectrometry are analytical methods for measuring concentration by comparing the signal intensity obtained according to the sample concentration between a standard sample and an unknown sample. Therefore, the obtained results are indicated by 2 to 3 significant figures regardless of the concentration except near the detection limit.

The ICP emission spectroscopic analysis apparatus is an emission spectroscopic analysis using inductively coupled plasma as an excitation source. When the element introduced into the ICP is excited and returns to the ground state, it emits an electron wave having a wavelength characteristic of the element. Therefore, by measuring these wavelengths and intensities, the type and concentration of the element are measured. is there.
On the other hand, since many elements in ICP are in the state of ions in the ICP mass spectrometer, these generated ions are introduced into a mass spectrometer and measured.

In Table 3, test samples 1 to 3 are size 1/2 brass 600 type ball valves, and the wetted area ratio (the wetted area of the test product / the capacity that can be filled to the maximum of the test product) is 4568 cm ^2. / L. The test products 4 and 5 are 125 type gate valves made of size 1/2 brass, and the test product 6 is a 125 type gate valve made of size 1/2 bronze, and the liquid contact area ratio is 2174 cm ² / L. The test products 7 and 8 are 125 type gate valves made of size 3/4 brass, and the liquid contact area ratio is 2000 cm ² / L.
The test product 9 is a brass test piece, and this brass test piece is a copper alloy formed using distilled zinc or recycled zinc ingot made of scrap or the like, and a cylinder having a diameter of 20 mm and a thickness of 10 mm. The liquid contact area ratio is 1256 cm ² / L.

  From the results in Table 3, there is a correlation between the content of cadmium in the copper alloy and the amount of leaching into tap water, and the amount of leaching into tap water tends to increase as the amount of cadmium increases. . When comparing the test piece 5 made of brass and the test piece 6 made of bronze having almost the same shape, the amount of cadmium leached from the test piece 5 which is a brass valve having a large zinc component in which cadmium can be dissolved is greater. Increased.

  In the leaching test with conditioning shown in Table 3, since the scale of minerals in tap water covers the surface of copper alloy piping due to the conditioning effect, cadmium elution is suppressed in all test products compared to the leaching test without conditioning. However, for the reason that it is difficult to discriminate when comparing the test products, the subsequent measurement is performed by a leaching test without conditioning.

  The specimen 9 of the above leaching test is a brass test piece having a cast surface. In this case, it is useful for identifying faucet fittings in which the water contact portion is a cast surface product. However, as shown in Table 4, in contrast to the fluorescent X-ray analysis in which the overall component distribution of the brass test piece was investigated, in the EPMA (Electron Probe Micro Analyzer) analysis, in which the component analysis of the cast skin surface only can be seen, the elemental component is to differ greatly. The EPMA analysis used this time was performed using a JXA880RL device manufactured by JEOL Ltd., with an acceleration voltage of 15.0 kV, an irradiation current of 1.198E-06A, and a beam diameter of 50 μm.

As a result, it was confirmed that lead, bismuth, aluminum and the like, which are originally contained in trace amounts, are segregated on the surface layer by EPMA analysis. Further, this segregation varies from place to place based on the results shown in Table 4. On the other hand, a brass test piece with a cut surface obtained by cutting and removing the cast surface of the surface layer is useful for identifying a valve or the like in which the water contact portion is often a cut surface. As shown in Table 4, the distribution of metal components is the same at all observation points in the EPMA analysis, and the difference from the fluorescent X-ray analysis is small.
This is meaningful for considering the correlation between the cadmium content in brass and the cadmium leaching amount, and makes it possible to predict the cadmium content in the piping equipment and the cadmium leaching amount when wet.

  For comparison with the test piece 9 brass test piece, a zinc ingot containing 738 ppm of cadmium and having approximately the same wetted area ratio as the test piece 9 is used as a zinc test piece, and the increase or decrease in the cadmium content has an effect on the cadmium leaching. The cadmium leaching test of this zinc test piece was conducted. The test results are shown in Table 5.

  According to the results of Table 5, the cadmium content in the zinc ingot of the same volume is almost equal to the cadmium content of the brass test piece (180 to 200 ppm). I couldn't see it. Thereby, the correlation between the cadmium content and the leaching amount in the copper alloys in Table 3 is caused by the influence of various elements constituting the copper alloy, and this correlation is unique to the copper alloy. It was confirmed. That is, it was found that when cadmium is contained in at least brass, cadmium is leached more easily than zinc in which cadmium is solid-solved.

By the way, in the ionization tendency, cadmium is E ⁰ = −0.40V. For this reason, when this cadmium is defined as a base metal compared with hydrogen of E ⁰ = 0 V, it is expected that the cadmium is dissolved in these solutions when washed with an acid or alkaline solution. However, although a brass test piece containing cadmium in acid or alkali was immersed, leaching of cadmium could not be reduced.

  In order to investigate the cause, EPMA analysis was performed before and after acid treatment or alkali treatment on a brass test piece having a cut surface obtained by cutting and removing a cast surface of the same brass test piece as that of the test product 9. The acid treatment was a mixed acid of nitric acid 0.6 mol / L and hydrochloric acid 0.047 mol / L, and the alkali treatment was a 50 g / L NaOH aqueous solution. The EPMA analysis results are shown in Table 6.

  From the results in Table 6, there is no difference in the cadmium components in the acid treatment, and conversely, the cadmium components are increased in the alkali treatment.

  In the case of acid treatment, the zinc layer in the brass containing cadmium is eluted together with cadmium and as a result, the result is the same as the overall corrosion. As a result, there is no difference in the components of cadmium.

  In the case of alkali treatment, zinc, which is an amphoteric metal, dissolves, but cadmium does not dissolve, so zinc in the brass is selectively dissolved, resulting in cadmium richness. Alternatively, in this alkali treatment, cadmium dissolved in zinc and zinc is dissolved out, but cadmium which is relatively noble compared with zinc may be re-deposited on the surface of the copper alloy. As a result, as shown in Table 6, the cadmium component increases conversely.

  Subsequently, a leaching test was also performed, and the results are shown in Table 7. As shown in the table, cadmium leaching could not be reduced in both acid treatment and alkali treatment. Therefore, the method of removing cadmium in the copper alloy by acid treatment or alkali treatment is ineffective. In Table 7, “Untreated → SUS wire blasting” was performed by polishing the surface by performing SUS wire blasting on the cast brass test piece in order to remove segregation elements (lead, aluminum, Bi) on the surface layer. This was replaced with a fully-cut brass test piece.

Based on the above facts, an embodiment of a cadmium elution prevention method, a copper alloy piping device and a copper alloy piping device using the same according to the present invention will be described in detail.
The method for preventing cadmium elution in the first invention is to immerse at least a wetted part of a copper alloy piping device in which cadmium is solid-dissolved in a metal salt aqueous solution containing a metal nobler than cadmium. The cadmium on the surface layer is replaced with a noble metal to prevent cadmium elution. Thereby, by reducing the amount of cadmium elution from the surface layer of piping equipment without being concerned with the cadmium content in the copper alloy, at least obtaining a copper alloy piping equipment material in which elution of cadmium on the surface of the wetted part is suppressed Is possible.

A metal salt is a compound in which H (hydrogen) of an acid is replaced with a metal ion, and is a nitrate, sulfate, chloride or the like.
Some of these metal salts can be dissolved in water, in which case they are dissolved as cations and anions. When dissolved in water, the balance between cation and anion becomes pH. Table 8 shows actual measurement values of each metal salt aqueous solution and pH test paper.

  By immersing a copper alloy containing cadmium in an aqueous metal salt solution comprising Ni or copper, which is a noble metal than cadmium, due to the difference in ionization tendency, noble metal ions such as Ni and copper in the solution and piping equipment The surface cadmium can be replaced. Table 9 shows the results of EPMA analysis using the cut surface cadmium brass test pieces before and after the replacement treatment. The thing which used Ni ion for the noble metal has Ni increased after processing, and Cd and Zn have decreased. In the case of using a precious metal with Cu ions, Cu increases after processing, Cd and Zn decrease, and Zn decreases greatly. In the case of Cu ions, since copper adheres as an oxide, the increase in oxygen is remarkable in addition to the metal elements shown in Table 9.

  As the metal salt aqueous solution, nitrate, sulfate, acetate, or the like may be used. On the other hand, as the metal salt aqueous solution, copper chloride, which is used in the ISO 6509 anti-dezincification corrosion test and is known to elute zinc in a copper alloy, is also conceivable, but this copper chloride is often used for piping equipment. Since it corrodes NiCr plating, it is not suitable for use as a metal salt aqueous solution. However, when the metal salt aqueous solution is made of copper nitrate, copper sulfate, or copper acetate, cadmium is easily dissolved in the substitution processing stage.

  On the other hand, nitrates, sulfates, and acetates differ greatly in the amount dissolved in water. For example, Table 10 shows the amount dissolved in water at room temperature.

  In order to replace cadmium, the total amount of copper ions and Ni ions dissolved in water greatly affects copper nitrate and Ni nitrate among metal salts.

  From the comparison between test product 5 and test product 6 in Table 3, the copper alloy piping equipment made of brass with a large amount of cadmium leaching, on the contrary, contains less lead than the one made of bronze. In many cases, surface treatment for removal is not performed. Therefore, in the case of brass, the process shown in FIG. 1 can be considered as a cadmium elution prevention process.

The surface of copper alloy piping equipment may be covered with anti-rust oil for rust prevention, cutting oil may remain during cutting, or dust or dust may have adhered to the surface due to long-term storage . If they remain, the cadmium cannot be effectively eluted and removed, so that the cadmium is lifted from the surface in order to facilitate removal of the cadmium.
This degreasing step is performed, for example, by being immersed in an alkaline chelate degreasing agent or the like.

The water washing step is performed to remove the degreasing agent after the anti-rust oil, the cutting oil, and dust and dust are lifted from the surface by the degreasing step. This water washing step is performed, for example, by putting piping equipment into a tank (not shown), manually swinging and then immersing. By this washing process, a light specific gravity such as oil floats on the surface of the water, and a heavy specific gravity sinks to the bottom, so that the floating oil can be removed by overflowing water within a predetermined time. .
In particular, when the unevenness of the cast skin surface of the target piping equipment is severe and removal is not sufficient in the water washing step, dust, dust or the like stuck to the surface causes discoloration in the subsequent immersion treatment. For this reason, you may make it implement a faucet process again as needed.

  In the dipping process, when the piping equipment is immersed in the metal salt aqueous solution, the piping equipment is placed in an appropriate container or the like, and then the piping equipment is any one of the above copper nitrate, copper sulfate, and copper acetate. Is immersed in a metal salt aqueous solution at a predetermined temperature for a predetermined time. Thereby, the cadmium on the surface of the piping equipment can be replaced with Cu ions to prevent elution of cadmium.

  The water washing step after the dipping step is performed to remove the aqueous solution and cadmium ions in the aqueous solution, and the aqueous solution adhering to the piping equipment by this water washing step is washed with an ultrasonic cleaning device. After this water washing step, in the water droplet removal step, water droplets attached to the piping equipment are removed by appropriate means.

  In recent years, since water quality standards have become stricter, for example, it is conceivable to combine this method with the elution prevention treatment of lead and nickel. In that case, it may be carried out after washing with an acid or alkaline solution such as the step shown in FIG. This is because cadmium elution prevention treatment can be performed on zinc in a copper alloy in which cadmium is solid-solved after removing lead and aluminum segregated on the surface layer and plating solution residue caused by plating treatment. . Furthermore, a method of performing simultaneously as shown in FIG. 3 is also conceivable.

  The cadmium elution prevention method according to the second invention is a method of forming a film with an organic substance composed of an unsaturated fatty acid on at least a wetted part of a copper alloy pipe device in which cadmium is solid-dissolved, and zinc on the surface of the wetted part of the pipe device Is applied to suppress elution of cadmium dissolved in zinc. This makes it possible to provide a copper alloy piping device in which elution of cadmium on the surface layer of the wetted part is suppressed. Furthermore, the film formed on the surface of the copper alloy is insoluble in water and has a function of preventing the scale in tap water from adhering due to the water repellency of the alkyl group.

  Similarly, in this method, the comparison between the test product 5 and the test product 6 in Table 3 shows that the copper alloy piping equipment made of brass with a large amount of cadmium leaching contains less lead than the bronze product. For this reason, surface treatment for elution and removal of lead is often not performed. Therefore, the process shown in FIG. 4 is performed as the cadmium elution prevention process.

  The unsaturated fatty acid here is a fatty acid having one or more unsaturated carbon bonds. These unsaturated fatty acids are abundant in nature and are divided by the number of unsaturations. Those having one unsaturated carbon bond in the hydrocarbon chain are referred to as monoenoic acid, monounsaturated fatty acid, or monounsaturated fatty acid. Those having a plurality of unsaturated carbon bonds in the hydrocarbon chain are called non-conjugated polyenoic acid and polyunsaturated fatty acid. Specifically, two are diunsaturated fatty acids, and three are triunsaturated. Saturated fatty acids, 4 are tetraunsaturated fatty acids, 5 are pentaunsaturated fatty acids, and 6 are hexaunsaturated fatty acids.

  The unsaturated fatty acid has a lower melting point as the number of carbon bonds is larger. This works favorably for variable temperature animals such as fish inhabiting cold regions, so there are sardine acid derived from sardines and nisin acid derived from herring. However, on the other hand, the greater the number of unsaturated carbon bonds, the easier the auto-oxidation, the faster the fats and oils deteriorate, and the more difficult the stable management of the coating agent becomes as industrialization. In addition, since the amount of natural abundance is small, it is expensive and unsuitable for mass production because the cost of the coating increases. For this reason, it is suitable for monounsaturated fatty acids and diunsaturated fatty acids.

  Unsaturated fatty acids are IUPAC names according to the IUPAC nomenclature, and those having names before that are commonly used as two, and the unsaturated fatty acids are shown below. Unsaturated fatty acids that are often produced from natural products generally contain saturated fatty acids or different unsaturated fatty acids as inevitable impurities, but do not have a significant adverse effect on the action. Monounsaturated fatty acids in Table 11, diunsaturated fatty acids in Table 12, triunsaturated fatty acids in Table 13, tetraunsaturated fatty acids in Table 14, pentaunsaturated fatty acids in Table 15 and hexaunsaturated fatty acids in Table 16 Examples of unsaturated fatty acids are shown.

  Unsaturated fatty acids are abundant in nature, but the crude oil extracted from oil seeds, etc. that exist mainly contains gums, free fatty acids, and pigments such as carotenoids and chlorophylls. A refined oil obtained by removing these and purified or having a purity higher than that of white squeezed oil is preferred. In addition, in the JAS standard, it is quantified, and oleic acid is preferably 70% or more, and contains other inevitable impurities. Table 17 shows the main inevitable impurities.

In this case, the unsaturated fatty acid used for film formation is preferably water-insoluble and has 10 or more carbon atoms in the hydrocarbon chain. In particular, organic substances such as monounsaturated fatty acid oleic acid or diunsaturated fatty acid linoleic acid are suitable. This is because the cadmium elution prevention protective film forming agent for forming the cadmium elution prevention film (protective film) is naturally abundant and inexpensive, and because it is stable, the coating agent can be managed. Because it is easy.
When a film is formed with such an organic substance, this film is formed on zinc contained in the copper alloy, and as a result, elution of cadmium dissolved in zinc can be prevented.

  Here, the presence of a film of an organic material such as oleic acid or linoleic acid was also confirmed by FT-IR analysis. FT-IR is an apparatus for examining the intensity distribution of each wavelength of infrared light using Fourier transform with a Fourier transform infrared spectrophotometer. Infrared spectroscopy is a method for identifying a target object by obtaining a spectrum by irradiating a measurement substance with infrared rays and dispersing transmitted light. In this infrared spectroscopy, since the spectrum shows a unique shape of the molecule, the film on the polished brass test piece and the electrozinc test piece (Zn 99.97%) is scraped, and infrared light is radiated in the FT-IR analysis. Irradiation was performed, and the presence of the film with organic substances such as oleic acid and linoleic acid was analyzed. The result is shown in FIG.

In the peak of oleic acid and linoleic acid shown in FIG. 5, an independent peak near 1750 cm ⁻¹ showing the characteristics of the carboxyl group clearly appears. However, the film on the brass test piece and the electrozinc test piece does not show any independent peak at 1750 cm ⁻¹ , indicating that all of the other substances have changed. In addition, since the peak of the electrozinc test piece moves to the same position as that of zinc stearate as comparison data, it can be seen that oleic acid and linoleic acid are chemically reacted with each other and bonded to zinc. On the other hand, the brass test piece has a peak in the same position as the peak of the copper reactant of stearic acid, which is the comparative data. Similarly, oleic acid and linoleic acid chemically react with each other and bind to the copper-rich surface. You can see that

  By the way, the film of unsaturated fatty acid does not bond to all metals, and cannot bond to a metal surface that can form a passive film by supplying oxygen such as air or water, such as stainless steel or aluminum. Therefore, it was found that this film can be bonded only on a limited metal surface such as zinc or brass.

  When forming an organic substance film composed of unsaturated fatty acid on copper alloy piping equipment, after the degreasing process and water washing process as in the case of the cadmium elution prevention treatment by the above-mentioned immersion, the piping equipment is used in the immersion process. It is immersed in an organic film aqueous solution that is an unsaturated fatty acid at a predetermined temperature and a predetermined time. Thereby, a film can be formed in the surface layer of copper alloy piping equipment, and cadmium elution prevention can be aimed at.

After the cadmium elution prevention treatment, in the air blowing process, air blow is applied to the surface of the copper alloy piping equipment to remove the organic film aqueous solution adhering to the surface of the piping equipment, and a uniform film is formed on the surface of the piping equipment. . Therefore, when performing the air blow process, the air blow is strengthened to prevent uneven spots in a uniform state.
Thereafter, in the drying process, for example, the piping equipment is put in a furnace such as a constant temperature drying furnace, and dried at a predetermined temperature for a predetermined time to form a uniform film on the surface of the piping equipment.

  When a film is formed with an unsaturated fatty acid consisting of oleic acid and linoleic acid in the wetted part, there is a carboxyl group contained in the unsaturated fatty acid, and it is easy to bind to zinc in which this functional group and cadmium are in solid solution. In particular, elution of cadmium can be more effectively prevented in brass containing a large amount of β phase rich in zinc.

  At this time, saturated fatty acids are also present as organic substances, but unsaturated fatty acids are preferred for forming a film, and the reason for this is the difference in molecular structure between the two. When increasing insolubility and water repellency to water, the length of the alkyl group is important, and the alkyl group in saturated fatty acids expands the range in which the molecules can move freely as the length increases, and into a wide three-dimensional space. Will exist. For this reason, the distance between molecules of saturated fatty acid bonded to zinc is increased, the density of the film becomes coarse, and the frequency with which zinc directly contacts water molecules increases.

  On the other hand, in the case of unsaturated fatty acids, since there are double bonds in the molecular structure, the molecule has a planar structure with this part as the axis, and there is a restriction on the range in which this molecule can move freely. become. As a result, the distance between molecules bonded to zinc can be narrowed to increase the density of the film.

  Examples of unsaturated fatty acids containing a lot of double bonds include docosahexaenoic acid (DHA) and nisinic acid, which have the disadvantage of being easily oxidized by a large number of double bonds. When these are oxidized, a rot odor is likely to be generated. Therefore, it is not preferable to use them for a copper alloy pipe member using tap water or the like as a fluid.

Therefore, it is preferable to use an unsaturated fatty acid composed of oleic acid or linoleic acid for preventing the generation of a rotting odor for preventing cadmium elution from a copper alloy piping device.
Oleic acid and linoleic acid are both unsaturated fatty acids having 18 carbon atoms. The difference is that oleic acid has one double bond in the molecular structure, and linoleic acid has a double structure in the molecular structure. There are two points. This difference in the number of double bonds gives a difference in the stability of the molecule at high temperatures. Specifically, as described above, in order to form a uniform film on the surface of piping equipment, it is exposed to high temperatures in the drying process, which is disadvantageous for linoleic acid which lacks stability at high temperatures. . Generally, linoleic acid is such that refrigerated storage is required for stable storage, and oleic acid is more suitable when stability is required.

  In recent years, since water quality standards have become stricter, for example, it is conceivable to combine this method with the elution prevention treatment of lead and nickel. In that case, it may be carried out after washing with an acid or alkaline solution. As an example, FIG. 6 shows an acid solution into which a cleaning step using a mixed acid composed of 0.6 mol / L nitric acid and 0.047 mol / L hydrochloric acid is introduced. This is because cadmium elution prevention treatment can be performed on zinc in a copper alloy in which cadmium is dissolved, after removing the segregated lead and aluminum on the surface layer and the plating solution residue caused by the plating treatment.

  In addition to the organic thin film described above, a method of forming a film on a metal for preventing cadmium elution can also be used to form a thin film by plating. Usually, copper alloy piping equipment is subjected to NiCr plating for improving the decorativeness like a faucet fitting, or NiCr plating for the purpose of improving the functionality like a ball valve. In order to prevent elution of cadmium by using such a plating process, it is necessary to cover the wetted part of the piping equipment. For this reason, the body of the valve or the body of the faucet fitting may be subjected to electroless plating instead of electroplating, which is difficult to cover the inner surface wetted part.

  When performing plating treatment on piping equipment, the above-mentioned NiCr plating, Ni plating, copper plating, tin plating, zinc plating, silver plating, etc. can be considered, but tin plating, zinc plating, etc. are used after the valve is formed once However, it is not possible to apply uniformly. NiCr plating is difficult to apply to those that cannot exhibit the required plating accuracy. Although copper plating and Ni plating have the merit that NiCr plating can be performed by post-processing, there is a possibility that the leaching standard value of copper and Ni determined in the water quality standard and the water quality standard management setting item may be exceeded. Therefore, measures to reduce leaching of copper or Ni may be required.

  Originally, the inner surface of valves and faucet fittings is the target, so electroplating and electroless plating with excellent wraparound are good, but this time we investigated the reduction of cadmium leaching using various types of electroplating using brass test pieces. . In addition, this time, the leaching trend of other elements affected by the plating film was checked and summarized in Table 18. The NiCr plating in Table 18 has a plating thickness of 8 μm Ni plating and 0.2 μm Cr plating, which is one of the general specification conditions. Each of Ni plating, copper plating, tin plating, zinc plating, and silver plating is 1 μm. The plating thickness was used.

  As shown in Table 18, when the plating process is performed, it is possible to suppress the elution of cadmium to some extent, but since there is a new risk that the plating material itself will be eluted, it is not a preferable processing method.

Although the plating film is significant as a reduction of cadmium leaching, in this case, the leaching of elements forming the plating becomes large. This is not preferable in consideration of water quality standards in which the leaching amounts of various elements are determined.
For example, silver plating, gold plating, platinum plating, rhodium plating, palladium plating, and iridium plating have high costs, tin plating has the disadvantages of soft hardness and poor appearance beautification, and alloy plating that includes these platings. Even when applied to a copper alloy, it is not preferable to apply such plating because the hardness of the plating film may adversely affect the specifications of water supply equipment such as galling and leakage.

  The first method and the second method for preventing cadmium elution described above may be combined. By the first method, the cadmium on the surface of the wetted part of the piping equipment immersed in the metal salt aqueous solution is precious metal. Then, by the second method, a film is formed on the surface layer of the wetted part with an organic substance composed of an unsaturated fatty acid, and the zinc of the surface part of the wetted part of the piping equipment is coated and dissolved in zinc. The elution of cadmium may be prevented. In this case, it is possible to further enhance the cadmium elution prevention effect by treating the wetted part by these two treatment methods.

The cadmium elution prevention method in the third invention is to wash the unevenly distributed metal component containing Pb of at least the wetted part surface layer of the copper alloy piping equipment in which cadmium is dissolved, with a mixed acid containing nitric acid and hydrochloric acid, From the surface of the wetted part, metals that are in a mixed acid and are nobler than cadmium, for example, copper and nickel, are eluted as copper ions and nickel ions, respectively. Alternatively, in a mixed acid, copper and nickel constituting a metal salt such as copper chloride, nickel chloride, nickel sulfate, and nickel hydroxide are similarly eluted as copper ions and nickel ions. The copper ions and nickel ions are substituted for cadmium on the surface layer of the wetted part to prevent elution of cadmium.
In this case, the mixed acid may contain a metal that is nobler than cadmium and baser than hydrogen before washing.
In these cases, elution of the cadmium can be suppressed by washing the unevenly distributed metal component (particularly Pb) on the surface of the wetted part with a mixed acid and substituting the cadmium with the metal eluted from the surface of the wetted part.

Next, the Example which applied the cadmium elution prevention method of copper alloy piping equipment materials, such as a valve and a pipe joint in this invention, is explained in full detail.
First, what is suitable as a metal salt aqueous solution for substituting with a noble metal is confirmed by experiment. Here, as described above, since many copper alloy piping equipment has been subjected to NiCr plating, the influence of each anion on the NiCr plated product when the anion paired with a noble metal ion is changed. Was confirmed visually. The results are shown in Table 19.

  From the results of Table 19, it was confirmed that copper chloride attacked NiCr plating by chloride ions which are anions. For this reason, it can be said that copper chloride is not suitable as a metal salt aqueous solution.

  Subsequently, using the above copper nitrate, copper sulfate, and copper acetate as an aqueous metal salt solution, a brass test piece is immersed in the aqueous metal salt solution, and whether cadmium can be replaced with noble metal ions by this immersion is determined as cadmium. Measured by leaching test.

  As a cadmium elution prevention process, the degreasing process, the water washing process, the immersion process, the water washing process, and the water droplet removal process shown in the above-described embodiment were performed on the brass test piece. As a degreasing step, a brass test piece was immersed in an alkaline chelate degreasing agent 50 g / L at 50 ° C. for 10 minutes to remove surface contamination. As the water washing step, the brass test piece was washed with water for 10 minutes to remove the surface degreasing agent.

  In the dipping process, a brass test piece is used for an aqueous metal salt solution of 0.6 mol / L of silver nitrate, copper nitrate, copper sulfate, or nickel nitrate (copper acetate is 0.15 mol / L because of its solubility limit in water). Was soaked at 50 ° C. for 30 minutes, and cadmium was replaced with metal ions to perform elution prevention treatment. After this dipping step, the brass test piece was washed with water for 10 minutes in the water washing step to remove the surface metal salt aqueous solution, and then the water droplets were removed in the water drop removing step. Table 20 shows the results of the cadmium leaching test of the brass test piece after these steps.

  On the other hand, a C3771 brass plated with 1 μm of cadmium plating was used as a plating test piece. This plating test piece was immersed in an aqueous metal salt solution in the same manner as described above, and the amount of cadmium leaching was measured by a cadmium leaching test. The results of this cadmium leaching test are shown in Table 21.

As a result of the cadmium leaching test of the plating test piece in Table 21, it was confirmed that cadmium can be replaced by a noble metal ion of Cu or higher even when the cadmium plating test piece is dipped.
Therefore, when the results of the brass test piece in Table 20 and the plating test piece in Table 21 are compared, in the case of the brass test piece, the leaching of cadmium ions when replacing with Ni ions is reduced. At this time, Ni ions, which are base metals rather than Cu ions, have a slower reaction speed for substitution with cadmium ions, and as a result, in a cadmium-rich plating test piece, substitution with Ni is not possible with a 30 minute immersion time. It's over enough. In the plating test piece, the residual cadmium is subjected to galvanic corrosion due to the replacement Ni, and the amount of cadmium leaching is larger than that in the case of being untreated.
Compared to this, the brass test piece has a smaller amount of cadmium in the surface layer than the plating test piece, so even if the metal salt aqueous solution is Ni ion, cadmium can be sufficiently replaced, and cadmium leaching. Has led to a reduction in

  In addition, in order to capture changes in the wetted surface that are directly related to leaching in comparison with the fluorescent X-ray analysis that is effective in analyzing the entire sample, the analysis range is large, and WDX (Wave-length Dispersive X-ray) is highly sensitive to high resolution spectra By measuring the test piece before and after the test by the EPMA of the spectrometry method, it is also possible to detect the constituent elements of the test piece surface layer and analyze the ratio of the constituent elements. In this case, the state of the surface layer can be confirmed in more detail.

  From the above, it is possible to select a noble metal higher than Ni ion as the metal ion in the metal salt aqueous solution, and the anion paired with this metal ion is nitrate ion, excluding chloride ion, Sulfate ions are preferred. In addition, acetate ions can be selected as other anions.

  In particular, an aqueous solution of Ni nitrate having a pH of 6 to 7 can also prevent cadmium from leaching out of piping equipment parts other than copper alloy made of zinc, which is easily mixed with cadmium, for example, zinc white (zinc oxide). The leaching of cadmium from a rubber sheet material such as an O-ring as a raw material can be reduced without damaging the rubber sheet. Unlike other metal salts, Ni nitrate including copper nitrate, which is a weak acid, can be dissolved in alcohol, which is an organic solvent. Originally, a rubber sheet material is a substance exhibiting hydrophobicity, but a substitution reaction can also be smoothly performed due to the property of being dissolved in alcohol. For example, the entire butterfly valve having a large wetted area of the rubber sheet material can be immersed in the aqueous metal salt solution, and the cadmium elution prevention treatment can be performed while preventing the rubber sheet material from deteriorating.

  Next, a noble metal such as Cu or higher than Ni ions is selected as a material for piping equipment, and the effect on the actual manufacturing process is confirmed. The lead and nickel elution prevention treatment method described above is combined with the mixed acid solution containing nitric acid and hydrochloric acid used in the lead elution prevention method of Japanese Patent No. 3345569 and the nickel elution prevention method of Japanese Patent No. 4197269. The cadmium elution preventing process shown in FIGS. 8 and 9 can be considered. Here, the cadmium elution prevention process in FIG. 7A is the process 1, FIG. 7B is the process 2, FIG. 8A is the process 3, FIG. 8B is the process 4, and FIG. Step 5 and FIG.

  First, it was verified under the processing conditions shown in Table 22 below whether the above combined process is effective. As a degreasing process common to all processes, it shall be immersed in a 50 g / L alkali chelate degreasing agent at 50 ° C. for 30 minutes, and as a water washing process, it shall be immersed in running water for 10 minutes. It shall be processed by air blow.

  A brass test piece was used as a test piece used in each step. Each test piece was subjected to an elution prevention treatment step in each step, and then the Cd leaching amount was measured. Table 23 shows the measurement results of the Cd leaching amount after each processing step.

  As shown in Table 23, in the mixed solution with the mixed acid, the behavior of the Ni ion and the Cu ion was greatly different, and the substitution of Cd was not confirmed for the Cu ion in the presence of the acid. In the mixed solution with this mixed acid, the difference in the behavior of Ni ions and Cu ions seems to be due to the ionization tendency of each element. Here, the ionization tendency of the main elements is shown in FIG.

  In FIG. 10, Ni is a noble metal rather than Cd, but it is in a lower position than H (hydrogen) of the mixed acid. Therefore, even if the mixed acid and Ni nitrate are mixed, there is no influence, and Ni and Cd are not affected. The substitution reaction proceeds. On the other hand, since Cu is in a noble position with respect to H of the mixed acid, substitution of H and Cu present in large numbers in the mixed solution occurs first. Therefore, Cu does not replace Cd but adheres to the brass test piece, and the leaching test promotes the galvanic corrosion of the remaining Cd and deposited Cu. It is thought that it will increase.

  From the above, it can be said that steps 1 to 5 are applicable in the actual manufacturing process. Subsequently, the optimum conditions in each step from step 1 to step 5 were narrowed down by a leaching test of a brass test piece. Table 24 shows the leaching amount of each element when the brass test piece was not yet processed.

  Table 25 shows the results of leaching tests of brass test pieces under various conditions in the Ni nitrate Ni substitution treatment step of Step 1 in which the concentration of Ni nitrate and the level of treatment time were assigned to appropriate values. At this time, the Ni nitrate concentration was assigned as a level up to a solubility limit of Ni nitrate of 3.0 mol / L.

  Table 26 shows the results of leaching tests of brass test pieces under various conditions in the copper nitrate replacement treatment step of Step 2 in which the concentration of copper nitrate and the level of treatment time were allocated to appropriate values. At this time, the concentration of copper nitrate was assigned as a level up to 6.0 mol / L which is the solubility limit of copper nitrate.

  Table 27 shows the results of leaching tests of brass test pieces under various conditions in the Ni nitrate Ni substitution treatment step of Step 3 in which the concentration of Ni nitrate and the level of treatment time were assigned to appropriate values.

  Table 28 shows the results of leaching tests of brass test pieces under various conditions in the copper nitrate substitution treatment step of Step 4 in which the concentration of copper nitrate and the level of treatment time were assigned to appropriate values.

  Table 29 shows the results of the leaching test of the brass test piece under the respective conditions in which the Ni nitrate concentration and the treatment time level were allocated to appropriate values in the Ni nitrate Ni substitution treatment step of Step 5. At this time, the concentration of Ni nitrate was assigned as a level up to a solubility limit of Ni nitrate of 3.0 mol / L.

  The above Cd leaching test results are not different from Step 1 to Step 5, and the concentrations of Ni nitrate and copper nitrate are the lowest 0.06 mol / L, the treatment time is the shortest 5 minutes, and the treatment temperature is Although it is possible at room temperature, unlike the film processing method of Example 5 described later, the Cd leaching amount did not become zero even when the concentration, time, and temperature conditions were increased. Therefore, the optimization conditions were examined together with Cu, Zn, Ni, and Pb measured simultaneously with Cd. It should be noted that the relationship of 1 mg / L = 1000 μg / L with respect to μg / L, which is the unit of leaching amount shown below.

  Regarding the relationship between the processing temperature and the processing time, when the relationship between the processing temperature is derived from FIG. 11 from the degree of Ni leaching that is not included in the base metal in the Ni nitrate Ni replacement processing in Step 1, 0.6 mol / L · 50 ° C. · Since the Ni leaching data for 5 minutes and 0.6 mol / L · room temperature 25 ° C. · 30 minutes are equivalent, it can be confirmed that there is a 6-fold difference in reaction rate with an increase of 25 ° C. The lower limit of the temperature is 10 ° C. to prevent freezing of the treatment solution, and the upper limit of the temperature is 50 to prevent air pockets in the faucet fitting due to bubbling of air dissolved in the solution or bubbling due to boiling. C. FIG. 12 shows the relationship between the minimum required processing time and the upper limit / lower limit of the temperature.

  Regarding the relationship between the treatment time and the treatment concentration, the leaching behavior of Cu, Zn, and Ni from Step 1 to Step 5 is shown in FIGS. 13 to 17 corresponding to the leaching test results from Table 25 to Table 29, respectively. . In the figure, the majority of the behavior was completed in 5 minutes in all treatment methods and concentrations, and no major change was confirmed after 10 minutes or more. When the treatment temperature is fixed at 50 ° C., in any treatment step, the reaction is almost completed after 5 minutes regardless of the concentration.

  Among these steps, step 1, step 3, and step 5 have a Ni nitrate replacement step, and therefore, the reaction is considered to proceed more as the concentration reaches 3.0 mol / L. Accordingly, the behaviors are shown in FIGS. 18 and 19 in correspondence with the results of the leaching tests in Table 25 and Table 29, respectively. 18 and 19, the relationship between the concentration and the amount of leaching was shown for the Ni nitrate replacement step in Step 1 and Step 5 on the minimum and maximum sides of the Cd leaching amount. In each case, the concentration was 0.6 mol. It was confirmed that the effect reached a peak at around / L, and the effect could not be expected even when the concentration was set higher.

  When Table 27 and Table 28 are compared with respect to the difference in copper and Ni substitution processing ability, the Cd leaching amount reduction effect is almost the same, but the leaching of elements other than Cd is also shown in FIG. As described above, since copper and Ni are equivalent, it can be said that there is almost no difference in the substitution processing ability between copper and Ni.

  In step 2 and step 4 having a copper nitrate substitution step, the reaction seemed to progress as the MAX concentration reached 6.0 mol / L, but in the copper nitrate substitution step in step 2 and step 4 also 0.6 mol / It was found that the effect can be sufficiently exhibited in the vicinity of L.

  Comparing the difference in the leaching tendency between the plating treatment and the substitution treatment with Ni nitrate and copper nitrate, the newly supplied elements will adhere to the surface in both the plating treatment and the substitution treatment. When comparing the results of leaching amounts of “various Ni nitrate substitution” and “Ni plating” and “various copper nitrate substitution” and “copper plating” in Table 31 due to the differences in the processes in Table 30, their behaviors are greatly different. ing. This is because the replacement process is performed in a state where the supplied element is oxidized unlike the plating process, so that an oxide film is formed on the surface of the test piece, and the supplied element does not dissolve in water. This is considered to be significantly reduced compared to the plating process. Thereby, when reducing the leaching of cadmium, it can be said that the substitution process is more effective than the plating process.

An oleic acid was used as an unsaturated fatty acid, brass was immersed in the unsaturated fatty acid, an organic film was applied to the brass, and a cadmium leaching test of the copper alloy formed with the film was performed.
As a test product used for the test, a ball valve made of a copper alloy, a gate valve, and the aforementioned brass test piece containing 180 to 200 ppm of cadmium were used.

In Table 32, the test products 1 to 3 are size 1/2 brass 600 type ball valves, and the wetted area ratio is 4568 cm ² / L. The test products 4 and 5 are 125 type gate valves made of size 1/2 brass, and the test product 6 is a 125 type gate valve made of size 1/2 bronze, and the liquid contact area ratio is 2174 cm ² / L. The test products 7 and 8 are 125 type gate valves made of size 3/4 brass, and the liquid contact area ratio is 2000 cm ² / L. The test product 9 is the brass test piece described above.

  As a treatment before the cadmium leaching test, a brass test piece was subjected to a degreasing process and a water washing process, and then as a film forming process, an unsaturated fatty acid of 0.8 wt% oleic acid (organic film aqueous solution) was used. ) Was immersed in a brass test piece at 50 ° C. for 5 minutes to prevent cadmium elution. After this film formation treatment, an air blowing step and a drying step were performed. In the air blowing step, the brass test piece was subjected to air blowing for an appropriate time to remove the organic film aqueous solution. As a drying process, a brass test piece was placed in a constant temperature drying oven at 70 ° C. for 30 minutes, and the brass test piece was dried. Table 32 shows the results of the cadmium leaching test of the brass test piece after these steps. In the table, untreated cadmium is an actual measurement value of a leaching test without conditioning shown in Table 2, and mixed acid treatment consists of 0.6 mol / L nitric acid and 0.047 mol / L hydrochloric acid before the film formation step. A copper alloy is washed with a mixed acid.

  From the results in Table 32, the leaching amount of cadmium with a film formed from an organic substance (only the organic film in Table 21 is cadmium) is compared with untreated (untreated cadmium in Table 32) in any test product. Is also kept to a small amount. This is because leaching of cadmium which is bonded to zinc and dissolved by an unsaturated fatty acid such as oleic acid or linoleic acid is suppressed.

  Furthermore, by performing the mixed acid treatment before the film formation treatment, the amount of cadmium leaching was suppressed as compared with the case of only the film treatment step as shown in Table 32. As described above, when the object to be subjected to the film treatment is a copper alloy, the effect can be enhanced by performing the acid treatment before the treatment. This is because, especially after casting, there are many segregated substances such as lead, iron, and aluminum on the surface layer, and zinc that easily binds to unsaturated fatty acids such as oleic acid and linoleic acid does not appear on the surface layer. By removing the inclusions on the surface layer by acid treatment, the coating treatment on the copper alloy surface was promoted, and the leaching of cadmium was reduced.

  Using the above-mentioned brass test piece, the change in the amount of cadmium leaching was measured when the concentration difference of the unsaturated fatty acid used in the film formation step in the step of FIG. 6 was changed, and the leaching reduction effect caused by the concentration difference was verified. . The unsaturated fatty acid used included oleic acid as a representative. It should be noted that oleic acid is insoluble in water and oil-water separated and cannot be directly diluted with water. Therefore, the concentration level of oleic acid was assigned to an appropriate value by diluting an organic film aqueous solution in which oleic acid was dissolved in water with a solvent component. In the film formation process at this time, the brass test piece was immersed at 50 ° C. for 5 minutes, and then an air blowing process and a drying process were performed. As the air blowing process, the brass test piece was subjected to air blowing for an appropriate time to remove the organic film aqueous solution, and as the drying process, the brass test piece was placed in a constant temperature drying oven at 70 ° C. for 30 minutes and dried. .

  The leaching amount of each element when the brass test piece is not yet processed is shown in Table 24 described above. The level of the oleic acid concentration is assigned as shown in Table 33, and the amount of leaching of each element in the brass test piece at this time is shown in the same table.

  From the results in Table 33, it can be said that the leaching amount of each element is small when the oleic acid concentration is 0.004 wt% or more. Therefore, when the oleic acid concentration ≧ 0.004 wt%, the film treatment can be effectively performed. In this case, a higher oleic acid concentration is more effective in terms of film treatment, but oleic acid that is insoluble in water is dissolved in water using a solvent component to form a non-flammable organic film solution. It is desirable that the oleic acid concentration shown in Table 33 is oleic acid concentration ≦ 16.00 wt%, and 16.00 wt% is the upper limit of the concentration.

The wetted area ratio of the brass test piece used in Table 33 is 1256 cm ² / L, but the wetted area ratio of the 600-type ball valve made of brass 1 to 3 used in Table 3 is 4568 cm ² / L. The difference is about 3.64 times. Therefore, when the data in Table 33 is multiplied by 3.64, it can be regarded as a numerical value equivalent to a brass 600 type ball valve, and when the oleic acid concentration is 0.004 wt%, it is 0.008 mg / L, and the oleic acid concentration is 0.00. When it is 0016 wt%, it is 0.067 mg / L. In addition, with respect to these corresponding actual measurement values, the valve is a water supply device installed in the middle of the pipe defined in JIS S3200-7, and the correction value for comparison with the new standard value 0.003 mg / L is the actual measurement value. × 0.04, and when the oleic acid concentration is 0.0016 wt%, the lower limit is 0.004 wt% or more because the oleic acid concentration is 0.003 mg / L.

  From the result of FIG. 5 described above, since oleic acid binds to zinc and zinc in brass, the leaching of zinc is reduced in Table 33. Further, leaching is similarly reduced for copper.

  On the other hand, the temperature in the constant temperature drying furnace in the drying process was also tested. As conditions at this time, it was assumed that they were left in a constant temperature drying oven at 70 ° C. for 30 minutes, in a constant temperature drying oven at 50 ° C. for 30 minutes, and left at a normal temperature of 25 ° C. for a long time (144 hours). As the test piece, a test piece made of surface-polished electro-zinc material, a test piece obtained by subjecting the surface-polished material to cadmium plating with a thickness of 30 μm, a cadmium plating material with an unsaturated fatty acid, or oleic acid of 30 μm thickness, The test piece was formed with a linoleic acid film.

At this time, toxic cadmium plating was also similarly tested with plated products. Cadmium is easily deteriorated in the air, and as shown in the photographs of FIGS. 21 and 22, an oxide film is formed on the surface only by plating treatment, and discoloration occurs. Therefore, the test piece on which cadmium plating having a thickness of 30 μm was subjected to surface polishing as shown in the photographs of FIGS. 23 and 24, and the oxide film formed on the plating surface was removed.
FIG. 25 shows the state of existence of a film of an organic material such as oleic acid or linoleic acid by FT-IR analysis of each test piece.

From the results of FIG. 25, it was confirmed that the film of unsaturated fatty acid oleic acid and linoleic acid can form a film on zinc or cadmium at a temperature of 50 ° C. for 30 minutes in a constant temperature drying furnace in the drying process. It was. Further, it has been confirmed that a film is formed on zinc even if it is left at room temperature for 144 hours, but it can be said that it is not economically meaningful to perform a long-time treatment on an actual product.
It has been confirmed that the lower limit temperature in the constant temperature drying furnace in the drying process is 50 ° C. On the other hand, the upper limit temperature can be expected to be higher as the temperature is higher. Since it evaporates while generating bubbles accompanying boiling, it is not preferable for forming a film. Therefore, it can be said that the preferable temperature in the constant temperature drying furnace in the drying step is preferably about 70 ° C.

  Subsequently, the cadmium elution prevention treatment process in the case where the treatment process including the Ni nitrate Ni substitution process or the copper nitrate substitution process in Example 3 described above and the treatment process including the film formation process of Example 5 were combined was verified. . The cadmium elution prevention process in this case is shown in FIGS. 26 to 30, respectively. The cadmium elution prevention process in FIG. 26 is the process 7, FIG. 27 is the same process 8, FIG. 26 is the same process 9, and FIG. Process 10 and FIG.

The unsaturated fatty acid used was represented by 0.8 wt% oleic acid. In the film forming process, the brass test piece was immersed at 50 ° C. for 5 minutes, and then subjected to an air blowing process and a drying process. In the air blowing step, the brass test piece was subjected to air blowing for an appropriate time to remove the organic film aqueous solution. As a drying process, a brass test piece was placed in a constant temperature drying oven at 70 ° C. for 30 minutes, and the brass test piece was dried.
The leaching amount of each element amount when the brass test piece is not yet processed is shown in Table 24 described above.

  The concentration of Ni nitrate used in the Ni nitrate Ni substitution treatment step in Step 7 and the trial production level of the treatment time were allocated, and the results of the leaching test conducted after the trial production are summarized in Table 34.

  Table 35 summarizes the results of the leaching test conducted after the trial production by assigning the prototype concentration of the copper nitrate concentration and treatment time used in the copper nitrate substitution treatment step of Step 8.

  Trial production levels of Ni nitrate concentration and treatment time used in the Ni nitrate substitution process in Step 9 were assigned, and the results of the leaching test conducted after the trial production are summarized in Table 36.

  Table 37 summarizes the results of the leaching test conducted after the trial production by assigning the prototype concentration of the copper nitrate concentration and treatment time used in the copper nitrate substitution treatment step of Step 10.

  Trial production levels of Ni nitrate concentration and treatment time used in the Ni nitrate Ni substitution treatment step of Step 11 were assigned, and the results of the leaching test conducted after the trial production are summarized in Table 38.

By comparing the results of Table 25 and Table 34, Table 26 and Table 35, Table 27 and Table 36, Table 28 and Table 37, and Table 29 and Table 38, the process of combining Example 3 and Example 5 Further reduction of Cd leaching was achieved. Furthermore, leaching reduction was also confirmed in Cu, Zn, and Ni.
In the present invention, the copper alloy piping equipment such as a valve, a pipe joint, and a faucet has been described. However, the present invention is not limited to this, and for example, food processing made of copper alloy that requires high thermal conductivity. It can also be applied to utensils, copper alloy cooking utensils, copper alloy food storage containers that require antibacterial properties, and copper alloy beverage storage containers.

Claims (2)

  The wetted part of the copper alloy piping equipment in which cadmium is dissolved is immersed in a metal salt aqueous solution made of nickel nitrate containing nickel, which is a noble metal than cadmium, and the noble metal in the metal salt aqueous solution is immersed in the metal salt aqueous solution. A copper alloy pipe characterized in that elution of cadmium on the surface of the wetted part is suppressed by substituting certain nickel ions and cadmium on the surface of the wetted part to reduce the amount of cadmium eluted from the surface of the wetted part Method for preventing cadmium elution of equipment.   The copper alloy piping equipment which suppressed the elution of the cadmium of the said liquid-contact part surface layer using the cadmium elution prevention method of Claim 1.

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