JP2000096270A - Method for reducing elution of lead from lead-containing copper alloy and water service instrument made of lead- containing copper alloy - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for preventing the elution of lead from the water service instruments made of lead-contg. copper alloy and the water instruments made of lead-contg. copper alloy with the elution of lead reduced. SOLUTION: When a lead-contg. copper alloy 1 is plated with nickel or chromium, the alloy is ordinarily dipped in a plating soln. Accordingly, the outer surface of the lead-contg. copper alloy is plated, and the lead 2 on the inner surface is dissolved and removed at the same time. Meanwhile, even though an alkaline degreasing soln. is used as the cleaning stage before plating, an oxidizing agent is incorporated therein to promote the dissolving and removing of the lead on the inner surface of the alloy. Besides, when fluorides are added to the chromium plating soln., precipitate of lead chromate is more efficiently dissolved. Further, the outer surface of the alloy is plated, then the alloy is dipped in a chromating soln. to form a chromate coating film on the inner surface, and hence the elution of a minute amt. of lead left on the surface is reduced. Phosphoric acid is preferably incorporated into the chromating soln.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead elution reducing plating method for reducing elution of lead from a lead-containing copper alloy, and to a lead-containing copper alloy water supply device with reduced lead elution.

Water supply equipment includes water heaters, water heaters, water coolers, ice makers, water purifiers, hot water boilers, vending machines, ball taps, low tanks, valves (water faucet fittings), fittings,
This includes pipes, sinks, wash basins, toilets, bathtubs, housing equipment units, and other equipment that is directly connected to the water supply pipe.

[0003]

2. Description of the Related Art Conventionally, faucet fittings are generally made of bronze,
It is manufactured by casting or forging a copper alloy such as brass, adjusting the shape by cutting, polishing, or the like, and applying nickel chrome plating or the like. Lead is added to a copper alloy in order to improve the machinability of the copper alloy during the cutting process during the manufacturing process.

[0004]

FIG. 4 is a schematic diagram of the structure of a copper alloy to which lead has been added.
Near the surface, lead, lead oxide, lead hydroxide, and the like are collected, and exist inside as a single element of lead 2. The concentration of lead 2 near the surface is several times higher than the concentration of lead inside. . For example, in a bronze casting faucet fitting to which lead is added, about 50% of lead is added.
0 ppb is eluted, and lead is eluted into water from the surface of a water passage of a water supply device made of a lead-containing copper alloy, and drinking the water for a long time may have a bad effect on the human body.

However, copper alloy materials to which lead is not added have poor machinability, and the development of alternative copper alloy materials has not progressed much.

Accordingly, the present invention provides a plating method for reducing lead elution of a lead-containing copper alloy for reducing the elution of lead from a faucet fitting or the like made of lead-containing copper alloy, and a lead-containing copper alloy in which lead is prevented from being eluted. It is intended to provide an appliance for water supply.

[0007]

SUMMARY OF THE INVENTION The present invention focuses on the fact that a plating process such as nickel-chromium plating applied to a lead-containing copper alloy is usually immersed in a plating solution. Is dissolved and removed.

An alkaline degreaser is used as a pre-cleaning step before the plating step, and an oxidizing agent is contained therein to promote the dissolution and removal of lead from the inner surface of the lead-containing copper alloy material. Further, when a fluoride is added to the chromium plating solution, the precipitation of lead chromate is dissolved, which is more effective.

Furthermore, after plating the outer surface of the lead-containing copper alloy material, it may be immersed in a chromate solution to form a chromate film on the inner surface. By this film formation, the elution of lead slightly remaining on the surface can be reduced. Preferably, the chromate solution contains phosphoric acid.

[0010] A lead-containing copper alloy material is degreased with an alkaline degreasing solution in a pre-plating cleaning step containing an oxidizing agent, and after acid activity and nickel plating, is plated with a chromium plating solution containing fluoride. The lead on the inner surface can be dissolved and removed while nickel chrome plating is applied to the outer surface of the.

Further, after degreased with an alkaline degreasing solution in a pre-plating washing step containing an oxidizing agent, and after acid activity and nickel plating, plating is performed with a chromium plating solution containing a fluoride, and further, a chromate solution is formed. To form a chromate film on the inner surface, so that lead on the inner surface can be dissolved and removed while nickel-chrome plating is performed on the outer surface of the lead-containing copper alloy material. Preferably, the chromate solution contains phosphoric acid.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A faucet fitting is mainly made of a lead-containing copper alloy material such as bronze and brass, and is subjected to various platings for the purpose of improving the appearance of the external surface, improving corrosion resistance and abrasion resistance, and the like.
In the present invention, since the lead elution reduction treatment of the inner surface is performed while plating the outer surface of the lead-containing copper alloy, the lead elution reduction treatment can be performed in various plating steps including nickel chromium plating.

The plating step usually comprises a degreasing step and a plating step. In the degreasing step, in order to ensure the adhesion of the plating, etc., in the step of removing dirt such as oils and fats adhering to the material, sodium hydroxide, potassium hydroxide, sodium carbonate, sodium phosphate, sodium tripolyphosphate, sodium metasilicate are used. , Sodium orthosilicate or the like, or an alkaline solution in which several kinds are dissolved.
The concentration is generally several g / l to several tens g / l, and is appropriately determined depending on the combination of components used. The temperature is 6
About 0-90 degreeC is desirable. Immersion time is several minutes to several tens
Minutes is desirable.

In order to improve the penetration and wettability of the alkaline degreasing, a surfactant is added for the purpose of lowering the surface tension of the solution. As the surfactant, an anionic surfactant or a nonionic surfactant is often used, and these may be used alone or in combination. Examples of the anionic surfactant include higher fatty acid sodium, sulfated oil, higher alcohol sodium sulfate, sodium alkylbenzene sulfate, higher alkyl ether sulfate, and α-olefin sodium sulfate. Examples of the nonionic surfactant include alkyl polyoxyethylene ether, alkylphenyl polyoxyethylene ether, fatty acid ethylene oxide adduct, and polypropylene glycol ethylene oxide adduct (Pluronic). The amount of addition is generally several g / l to several tens g / l.

A chelating agent may be added to the alkaline degreasing bath. Examples of the chelating agent include E
DTA, ethylenediamine, triethanolamine, thiourea, Rochelle salt, tartaric acid and the like. The concentration of each component is preferably several g / l to several tens g / l.

When an oxidizing agent is added to the alkaline degreasing solution,
Lead is oxidized and dissolved in alkali via lead oxide (such as PbO) (reaction formula (2) in FIG. 1). This reaction (2) is faster than the reaction (1) and thus promotes the dissolution of lead. This effect improves the adhesion of the plating on the outer surface and promotes the dissolution of lead on the inner surface. Examples of the oxidizing agent include organic oxidizing compounds such as sodium metanitrobenzenesulfonate and sodium paranitrobenzoate, hypochlorite, bleaching powder, hydrogen peroxide, potassium permanganate, persulfate, perchlorate, and the like. Is used. The concentration of each component is preferably several g / l to several tens g / l.

As a plating bath used for chromium plating, a generally known sargent chromium plating bath comprising chromic anhydride and sulfuric acid can be used. The chromium fluoride bath is obtained by replacing a part or all of sulfuric acid in the Sargent bath with fluoride.

When chromium plating is performed in these chromium plating solutions, lead is dissolved while dissolving the entire copper alloy material due to the strong oxidizing property of the chromium plating solution while the outer surface is chromium plated. . However, if there is no fluoride, a precipitate may remain as lead chromate (reaction formula (3) in FIG. 2), but the fluoride serves to dissolve the precipitate. (Reaction formula (4) in FIG. 2), the plating temperature is preferably 40 to 60 ° C., and the plating time is preferably several tens seconds to several minutes.

As the fluoride, sodium fluoride, potassium fluoride, ammonium fluoride, hydrofluoric acid, borofluoric acid,
Most of the fluorine compounds such as hydrofluoric acid, sodium fluorosilicate, potassium fluorosilicate, and chromium borofluoride can be used.

The additives used for the chromate treatment are based on chromic anhydride, phosphoric acid, sulfuric acid, and in some cases, add or replace nitric acid, hydrofluoric acid, acetic acid, oxalic acid, chromate and the like. A commercially available chromating agent such as zinc plating may be used. The concentration of each component is several g / l to
Several tens g / l is desirable. Processing temperature and processing time are from room temperature
60 ° C. and several seconds to several minutes are desirable. By immersing the plated product on the outer surface in this chromate solution, a chromate film is formed on the inner surface by the reaction formula shown in FIG.
Suppresses lead elution. By adding phosphoric acid to chromic anhydride, which is the main component of the chromate solution, the synergistic effect further increases the effect of suppressing lead elution.

[0021]

EXAMPLES (1) Alkali degreasing solution Table 1 shows the lead elution effect when an oxidizing agent and a chelating agent are added to the alkali degreasing solution.

[0022]

[Table 1] The treatment method is as follows. A faucet of a bronze casting is immersed in various alkali degreasing solutions shown in Table 1 at 80 ° C. for 3 minutes, and then washed with water for 30 seconds to obtain a commercially available chrome fluoride plating solution having a fluorine content of about 1 g / L. Plating at 45 ° C for 3 minutes, washing with water for 30 seconds, 60
Washed with hot water at 30 ° C for 30 seconds.

Next, JIS S3200-7 (199)
7 years) According to the "water supply equipment-leaching performance test method", the eluted lead concentration was analyzed for the treated faucet fittings. FIG. 1 is a schematic view showing a state in which lead is eluted by alkali etching. According to the reaction formula shown in FIG.
Lead 2 on the surface is selectively removed.

As is clear from the results in Table 2, the untreated sample without etching has a lead leaching amount of 500 ppb, whereas the sample treated with the present invention has a significantly reduced lead leaching amount, and the oxidizing agent and The addition of the chelating agent further reduced the amount of lead eluted.

(2) Chromium plating solution The faucet of the bronze casting was alkali-degreased (sodium hydroxide 50 g / l, sodium metanitrobenzenesulfonate 2 g / l, EDTA 2 g / l, ethylenediamine 2 g / l).
1) After washing at 80 ° C. for 3 minutes, the plate was washed with water for 30 seconds, and chromium plating was performed at 45 ° C. for 3 minutes as shown in Table 2.
Thereafter, the elution concentration of lead was analyzed according to JIS S3200-7 (1997). The results are as shown in Table 2.

[0026]

[Table 2] As is clear from Table 2, chromium plating greatly reduces the amount of lead eluted, but the chromium fluoride bath is more effective than the conventional Sargent chromium bath. It is considered that the Sargent bath containing no fluoride had a slightly higher lead concentration because the precipitate remained as lead chromate. (Reaction formula (3) in FIG. 2) Since the fluoride dissolves, it is considered that the chromium fluoride bath was more effective than the Sargent chromium bath. (Reaction formula (4) in FIG. 2) It is clear that chromium plating alone has a lead elution effect.

(3) Chromate treatment The faucet of the bronze casting was alkali-degreased (sodium hydroxide 50 g / l, sodium metanitrobenzenesulfonate 2 g / l, EDTA 2 g / l, ethylenediamine 2 g / l).
l) After washing at 80 ° C. for 3 minutes, washing with water for 30 seconds, chromium plating at 45 ° C. for 3 minutes in a chromium fluoride plating bath (the above-mentioned commercially available bath having a fluorine content of about 1 g / l), and washing with water for 30 seconds. Then, a chromate solution having a composition shown in Table 3 was added at 30 ° C.
Chromate treatment for 20 seconds, wash with water for 30 seconds, 60 ° C,
Washed with hot water for 30 seconds.

Next, JIS S3200-7 (199)
7 years), and the elution concentration of lead was analyzed. The results are as shown in Table 3.

[0029]

[Table 3] As shown in Table 3, as compared with the case without the chromate treatment, the amount of lead eluted is reduced in the chromate-treated one. By the chromate treatment, a chromate film is formed and the elution of lead is suppressed by the reaction formula in the schematic diagram showing the state of the chromate treatment in FIG. It is also clear that chromate treatment alone is effective for lead elution.

[0030]

According to the present invention, in the plating step such as nickel-chromium plating applied to the outer surface of a lead-containing copper alloy, the outer surface is plated while the lead on the inner surface is dissolved and removed.

Further, after plating the outer surface of the lead-containing copper alloy material, it may be immersed in a chromate solution to form a chromate film on the inner surface. By this film formation, the elution of lead slightly remaining on the surface can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state in which lead is eluted by immersion in an alkaline degreasing solution containing an oxidizing agent.

FIG. 2 is a schematic diagram showing a state after chromium fluoride bath plating.

FIG. 3 is a schematic diagram showing a state of a chromate treatment.

FIG. 4 is a schematic view of a structure of a copper alloy to which lead is added.

[Explanation of symbols]

 1: Copper alloy 2: Lead

Claims (16)

[Claims] 1. A lead elution reducing plating method in which an outer surface of a lead-containing copper alloy is plated while removing lead on the inner surface. 2. The plating method for reducing lead elution of a lead-containing copper alloy according to claim 1, wherein the plating step is a step of performing chromium plating after nickel plating. 3. An alkaline degreaser in the pre-plating cleaning step contains an oxidizing agent.
The lead elution reduction plating method of the lead-containing copper alloy described in the above. 4. The plating method for reducing lead elution of a lead-containing copper alloy according to claim 2, wherein the plating solution for chromium plating contains a fluoride. 5. The plating method for reducing lead elution according to claim 1, wherein after plating the outer surface of the lead-containing copper alloy, it is immersed in a chromate solution to form a chromate film on the inner surface. 6. The method according to claim 1, wherein the immersion is carried out in an alkaline degreasing solution in a pre-plating cleaning step containing an oxidizing agent, and after nickel plating, plating is carried out with a chromium plating solution containing fluoride. 3. The plating method for reducing lead elution of a lead-containing copper alloy according to items 2 and 3. 7. Dipping in an alkaline degreasing solution in a pre-plating cleaning step containing an oxidizing agent, nickel plating, plating with a chromium plating solution containing fluoride, and further immersing in a chromate solution, 3. The plating method for reducing lead elution of a lead-containing copper alloy according to claim 1, wherein a chromate film is formed on the inner surface. 8. The plating method for reducing lead elution of a lead-containing copper alloy according to claim 5, wherein the chromate solution contains phosphoric acid. 9. A water supply device made of a lead-containing copper alloy in which the outer surface of a lead-containing copper alloy is plated while removing the lead on the inner surface. 10. The lead-containing copper alloy water supply device according to claim 9, wherein in the plating step, chromium plating is performed after nickel plating. 11. The lead-containing copper alloy water supply device according to claim 9, wherein the alkaline degreasing solution in the pre-plating cleaning step contains an oxidizing agent. 12. The lead-containing copper alloy water tool according to claim 10, wherein the plating solution for chromium plating contains a fluoride. 13. After plating the outer surface of the lead-containing copper alloy,
The lead-containing copper alloy water supply device according to claim 9, wherein the device is immersed in a chromate solution to form a chromate film on the inner surface. 14. The plating method according to claim 9, wherein the substrate is immersed in an alkaline degreasing solution in a pre-plating cleaning step containing an oxidizing agent, plated with nickel, and then plated with a chromium plating solution containing fluoride. And a lead-containing copper alloy water supply device according to claim 10. 15. Dipping in an alkaline degreasing solution in a pre-plating cleaning step containing an oxidizing agent, plating with nickel, plating with a chromium plating solution containing fluoride, and further immersing in a chromate solution, The water-supply device made of a lead-containing copper alloy according to claim 9 or 10, wherein a chromate film is formed on the inner surface. 16. A water supply device made of a lead-containing copper alloy, wherein the chromate solution contains phosphoric acid.