WO2007136024A1

WO2007136024A1 - Method of pretreatment for plating and water service instrument made of lead-containing copper alloy

Info

Publication number: WO2007136024A1
Application number: PCT/JP2007/060330
Authority: WO
Inventors: Yuichi Takamatsu; Masashi Kawamoto; Mitsuo Imamoto
Original assignee: Toto Ltd.
Priority date: 2006-05-22
Filing date: 2007-05-21
Publication date: 2007-11-29
Also published as: JP2007308779A; US20090250354A1

Abstract

[PROBLEMS] To provide a method of pretreatment for plating in which lead, etc. dissolved in an etchant are prevented from being electrodeposited (readhering) to a lead-containing copper alloy as a work to be plated without the necessity of adding a chelating agent which forms an insoluble inert compound. [MEANS FOR SOLVING PROBLEMS] A lead-containing copper alloy as a work to be plated is immersed in an alkaline etchant containing no chelating agent which forms an insoluble inert compound. The lead-containing copper alloy in this state is subjected alternately to electrolysis in which the lead-containing copper alloy is used as one of the positive and negative poles and electrolysis in which the lead-containing copper alloy is used as the other pole (PR electrolysis).

Description

Specification

Plating pretreatment method and lead-containing copper alloy water supply equipment

Technical field

The present invention is obtained by applying a plating pretreatment method in which lead existing in the surface layer of a lead-containing copper alloy is removed in advance before plating the surface of the lead-containing copper alloy and this plating pretreatment method. The present invention relates to a lead-containing copper alloy water supply device.

Background art

[0002] Lead-containing copper alloys having excellent processability and corrosion resistance are generally used as materials for water supply equipment. Since this lead-containing copper alloy contains lead harmful to the human body, the surface is plated in the process shown in Fig. 3 so that lead does not elute!

[0003] Specifically, as a pretreatment, a lead-containing copper alloy is immersed in an alkaline etching solution to remove lead on the surface layer of the lead-containing copper alloy, and thereafter, nickel plating, chromium plating, and chrome plating are performed. After being treated with water, it is washed with water.

[0004] The pretreatment described above is a treatment for facilitating the formation of a plating layer by removing dirt on the surface and preventing lead from elution. As the pretreatment, the present applicant has proposed a method of removing lead with both alkali and acid by adding an oxidizing agent to an alkaline etching solution by paying attention to the characteristic that lead is an amphoteric metal. (Patent Document 1)

[0005] Also known is an alkaline electrolytic cleaning method in which a lead-containing copper alloy is immersed in an alkaline etchant and surface contamination is removed by electrolysis! Electrolysis methods include cathodic electrolysis using lead-containing copper alloy as the negative electrode and anodic electrolysis using lead-containing copper alloy as the positive electrode. Cathodic electrolysis generates oxygen gas on the surface of the lead-containing copper alloy, and this oxygen gas decomposes and removes organic soil on the surface, so it has a great cleaning effect. However, lead-containing copper alloys are melted (etched) by electrical action, so lead-containing copper alloys are ground (over-etched). Therefore, the cathode electrolysis method is also used in which the lead-containing copper alloy does not dissolve and hydrogen gas is generated on the surface of the lead-containing copper alloy. Also known is the PR electrolysis method, in which cathodic electrolysis and positive electrolysis are repeated alternately.

[0006] When cathodic electrolysis is selected as the pretreatment for plating of lead-containing copper alloys, (Copper alloy) is a negative electrode, so lead (Pb +) dissolved in alkali etching and impurities contained in the etching solution are charged positively, such as heavy metals, and the ions are covered by electrical action. Electrodeposits on the surface of the attachment (the same effect as plating) and reattaches. This re-adhesion causes poor adhesion of the plating that will be performed later, and clouding after plating.

[0007] Therefore, a chelating agent that forms an insoluble inactive bond is added to the alkali etching solution, and lead dissolved in the alkali etching is reacted with the above chelating agent to form an insoluble chelating compound. A method has been proposed in which precipitation is carried out before electrodeposition on the surface of the object to be covered (Patent Document 2).

[0008] Patent Document 1: Japanese Patent No. 3182765

Patent Document 2: JP-A-2-274900

Disclosure of the invention

Problems to be solved by the invention

[0009] In the method of removing lead by adding an oxidizing agent to the alkaline etching solution disclosed in Patent Document 1, degreasing power may not be sufficient because it does not depend on electrolysis. Also, as disclosed in Patent Document 2, electrodeposition (re-adhesion) can be prevented by adding a chelating agent that forms an insoluble inactive bond when performing cathodic electrolytic cleaning immersed in an alkaline etchant. In some cases, cathodic electrolysis alone does not provide sufficient degreasing power. Furthermore, since the above chelating agent is added, the cost increases accordingly.

Means for solving the problem

[0010] In order to solve the above-mentioned problems, the present invention is a plating pretreatment method that removes lead existing in the surface layer of a lead-containing copper alloy before nickel plating or chromium plating is applied to the surface of the lead-containing copper alloy. In the state where the lead-containing copper alloy is immersed in an alkaline etching solution, the lead-containing copper alloy is used as either a positive electrode or a negative electrode, and the lead-containing copper alloy is used as either a positive electrode or a negative electrode. The other electrolysis was performed alternately (PR electrolysis).

[0011] In the PR electrolysis, it is preferable that the lead-containing copper alloy is finally used as a positive electrode. Further, as conditions for PR electrolysis, it is preferable that the current density is lAZdm ² or more and 25AZdm ² or less, and the current switching time is 2 seconds or more and 30 seconds or less. Furthermore, the alkaline etch It is also preferable to add an oxidizing agent to the working solution.

[0012] In addition, the lead-containing copper alloy water supply device according to the present invention has a surface that has been fitted, and the lead-containing copper alloy is immersed in an alkaline etching solution as a pretreatment of the plating. A process in which the electrolysis using the lead-containing copper alloy as either the positive electrode or the negative electrode and the electrolysis using the lead-containing copper alloy as either the positive electrode or the negative electrode alternately was performed. is there.

[0013] In the PR electrolysis performed when the lead-containing copper alloy water supply device is obtained, it is preferable that the lead-containing copper alloy is finally used as a positive electrode as described above. Further, as conditions for PR electrolysis, it is preferable that the current density is lAZdm ² or more and 25AZdm ² or less, and the current switching time is 2 seconds or more and 30 seconds or less. It is also preferable to add an oxidizing agent to the alkaline etching solution.

The invention's effect

[0014] According to the plating pretreatment method of the present invention, lead or the like dissolved in the etching solution is electrodeposited (re-deposited) on the lead-containing copper alloy, and sufficient degreasing cleaning is performed. Therefore, a defect such as cloudiness does not occur on the surface after plating, and a chelating agent that forms a more inactive inactive binder is not used, which is effective for cost reduction.

[0015] In addition, by using the lead-containing copper alloy as the positive electrode for the last electrolysis in PR electrolysis, it is effective to deposit (reattach) lead etc. on the surface of the metal object Can be prevented.

[0016] In addition, by adding an oxidizing agent to an alkaline etching solution when performing PR electrolysis, it is possible to effectively remove lead using the characteristics of lead as an amphoteric metal.

Brief Description of Drawings

[0017] [FIG. 1] Process diagram of plating applying the plating pretreatment method according to the present invention.

[Figure 2] Conceptual diagram of PR electrolysis

[Fig.3] Diagram explaining the conventional plating process

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a process diagram of plating applying the pretreatment method according to the present invention, and FIG. 2 is a conceptual diagram of PR electrolysis. In the present invention, as a pretreatment for plating, when performing ultrasonic cleaning and alkali cleaning, PR is performed in parallel. By performing electrolysis, the surface of the object to be covered (lead-containing alloy) is surely cleaned.

Note that ultrasonic cleaning is not always necessary, and only PR electrolysis using an alkaline cleaning solution may be used. Further, following the PR electrolysis using an alkaline cleaning solution, negative electrolysis and anodic electrolysis may be performed alone or in combination as necessary. By doing so, the surface of the object to be covered (lead-containing alloy) is further cleaned and the adhesion of the plating is improved.

[0020] With PR electrolysis without the addition of a chelating agent that forms an insoluble inactive binder, specific experiments were conducted regarding the adhesion and appearance of the plating. The experimental conditions and results are described below. In addition, the covering object was a single faucet of bronze bowl.

[0021] (Electrolytic degreasing conditions Electrolytic solution conditions)

Alkaline etchant (alkali cleaning)

(1) Main component:

The plating process usually includes a degreasing process and a plating process power. In the degreasing process, in order to ensure the adhesion of the plating, the main component of the alkaline etching solution used in the present invention is a process of removing dirt such as oil components adhering to the material. Sodium hydroxide, potassium hydroxide, Use an alkaline solution in which sodium carbonate, sodium phosphate, sodium tripolyphosphate, sodium metasilicate, sodium orthosilicate, etc. are used alone or in solution. The concentration is generally from several g / L to several tens of g / L, and is determined appropriately depending on the combination of components used. (2) Surfactant:

In order to improve the penetration and wettability of the alkaline etching solution, a surfactant is added to reduce the surface tension of the solution. As the surfactant, an anionic surfactant or a non-ionic surfactant is often used, and these are used alone or in combination. The surfactants include higher fatty acid sodium, sulfated oil, sodium higher alcohol sulfate, sodium alkylbenzene sulfate, sodium higher alkyl ether sulfate, and sodium a-olefin sulfate. Nonionic surfactants include alkyl polyoxyethylene ether, alkylphenyl polyoxyethylene ether, fatty acid ethylene oxide adduct, polypropylene glycol ethylene oxide. There is an adjunct (pull mouth nick). The addition amount is generally several g / L to several tens g / L.

(3) Chelating agent:

Chelating agents can be added to prevent lead from re-depositing as hydroxide and to promote lead dissolution. As the chelating agent, for example, it is easy to form a complex with lead such as EDTA, ethylene diamine, triethanolamine, thiourea, Rossiel salt, tartaric acid, etc., and a compound is desirable. The concentration should be several g / L to several tens g / L for each component.

Chelating agents that form insoluble inactive products with heavy metals such as lead can also be added. As a chelating agent that forms an insoluble inactive product, sodium dimethyldithiocarbamate or sodium jetyldithiocarbamate is desirable. The concentration of each component is preferably several gZL to several lOgZL.

(4) Oxidizing agent:

When an oxidant is added to the alkaline etchant, lead is oxidized and dissolved in alkali via acid lead (such as PbO), resulting in the promotion of lead dissolution. Examples of the oxidizing agent include organic acid-soluble compounds such as sodium meta-trobenzenesulfonate and sodium nitrate nitrobenzoate, hypochlorite, bleaching powder, hydrogen peroxide, potassium permanganate, persulfate, An inorganic compound such as perchlorate is used. The concentration of each component is preferably several g / L to several tens g / L.

(Plating conditions)

The following plating was performed.

(1) Chrome plating

As the chromium bath, generally known sergeant baths having chromic anhydride and sulfuric acid power can be used. Alternatively, a chromium fluoride bath may be used in which part or all of the sulfuric acid in the Sargent bath is replaced with fluoride. When chrome plating is performed in a chrome plating solution, the outer surface is chrome plated, and the inner surface is a strong acidity of the chrome plating solution. Dissolve. However, in the absence of fluoride, precipitates may remain as lead and chromate, but fluoride plays a role in dissolving it, so that it can be applied in a chromium fluoride bath. The preferred temperature is 40 to 60 ° C, and the immersion time is several tens of seconds to several minutes. As the fluoride, most of the fluorine compounds can be used such as sodium fluoride, potassium fluoride, ammonium fluoride, hydrofluoric acid, borofluoric acid, kafluoric acid 'sodium fluoride', potassium potassium fluoride, and chromium borofluoride.

(2) Chromate treatment

Additives used for chromate treatment may be added or replaced with nitric acid, hydrofluoric acid, acetic acid, oxalic acid, chromate, etc. depending on the power based on chromic anhydride, phosphoric acid and sulfuric acid. A commercially available chromate agent such as zinc plating may be used.

The concentration of each component is preferably several g / L to several tens g / L. The treatment temperature and treatment time are preferably from room temperature to 60 ° C and from several seconds to several minutes. By immersing the finished plating on the outer surface in this chromate solution, a chromate film is formed on the inner surface to suppress elution of lead. By adding phosphoric acid to chromic anhydride, which is the main component of the cuprate solution, the synergistic effect increases the effect of suppressing lead elution.

[0023] (Evaluation test)

After performing the above electrolytic degreasing and plating (chromium treatment after nickel plating after chromium plating), the following evaluation test was performed.

[0024] (1) Adhesion test

The 21.2 thermal shock test specified in JIS H8504 “Plating adhesion test method” was conducted (test method for examining plating adhesion by thermal shock by heating and quenching the sample). As shown in the following (Table 1), there was no problem in adhesion except for negative electrolysis without a chelating agent that forms an insoluble inactive binder.

[0025] [Table 1]

(2) Appearance test

9.2 Appearance test stipulated in JIS H8617 “Nickel plating and nickel-chrome plating” (Appearance test was conducted by visual inspection. Check for signs of defects, smudges, and nicks). As shown in the following (Table 2), only PR electrolysis gave good results without adding a chelating agent that forms an insoluble inactive binder.

[0027] [Table 2]

Next, anodic electrolysis and PR electrolysis were conducted under the following experimental conditions for adhesion and appearance.

First, the following (Table 3) shows the experimental results of anodic electrolysis with a chelating agent that forms an insoluble inactive binder. The adhesion was all good, but the appearance was poor. Met. The electrolysis conditions were ultrasonic cleaning (1 minute) with ultrasonic waves followed by alkali cleaning (2 minutes).

[0029] [Table 3]

[0030] The following (Table 4) shows the experimental results of anodic electrolysis without a chelating agent that forms an insoluble inactive binder. The adhesion was all good, but the appearance was all It was bad. The electrolysis conditions were ultrasonic cleaning (1 minute) with ultrasonic waves followed by alkali cleaning (2 minutes).

[0031] [Table 4] Pretreatment conditions Appearance quality Ultrasonic cleaning Ultrasonic pulse Al force cleaning Washing power rehabilitation

OA / dm ² ― 1 A / dm ² XX

OA / dm ² ― 10 AZdm ² ― XX

OA / dm ² ― 10 A / dm ² 2 "on 2, off XXX

^2.5 A / dm ² 1 ,, on 3, off 10 A / dm ² XX

^2.5 A / dm ² 1, on 3, off 1 A / dm ² (8 OX) ― XX

^2.5 A / dm ² 1 '' on 3 '' off 10 AZdm ² (8 OV) ― XX

^2.5 A / dm ² ― 10 A / dm ² ― XXX

^2.5 A / dm ² ― ^2.5 A / dm ² ― XXX [0032] The following (Table 5) shows the results of an experiment in which PR electrolysis was performed without a chelating agent forming an insoluble inactive binder, and both adhesion and appearance were all good. The electrolysis conditions were ultrasonic cleaning (1 minute) with ultrasonic waves followed by alkali cleaning (2 minutes).

[0033] [Table 5]

[0034] From the above experiments, it was found that when PR electrolysis was applied, the adhesion and appearance after plating were good without adding a chelating agent that forms an insoluble inactive binder. Therefore, experiments were conducted on the preferred conditions for PR electrolysis (switching period and current density). In the experiment, ultrasonic cleaning with ultrasonic waves was performed for 1 minute, and then alkaline cleaning was performed for 2 minutes.

[0035] The results are shown below (Table 6). From this (Table 6), it is clear that the switching period is 30 seconds or less and the current density is 25AZdm ² or less.

[0036] [Table 6]

Based on the above, we were able to secure plating adhesion and appearance without using a chelating agent that would form an insoluble inactive binder in the case of PR electrolysis. Next, check whether lead elution satisfies NSF and JIS standards. did. Use a single lever faucet made of bronze as a sample. [0038] NSF standard

According to NSF / ANSI61-2003e “9 Mechanical plumbing devices J”, the dissolved lead concentration was analyzed for the above treated samples.

Standard: After conversion l lppb or less

[0039] Standard

According to JIS 33200-7 (2004) “Water supply equipment – Leaching performance test method”, the treated lead samples were analyzed and analyzed for their lead concentration.

Standard: After conversion 7ppb or less

[0040] The experimental results are shown in the following (Table 7-1) and (Table 2-2). As is clear from these (Table 7-1) and (Table 7-2), the product obtained by the plating method to which the plating pretreatment method according to the present invention is applied has a result satisfying the NSF standard and the JIS standard. Obtained.

[0041] [Table 7-1]

N SF Standard test result

* Unit: p p b Correction value = Leaching value X (Internal volume / 1000)

[0042] [Table 7-2]

J I s standard test results

* Unit: p p b Correction value = Leaching value X (Internal volume / 1000)

Claims

The scope of the claims

[1] A plating pretreatment method that removes lead existing in the surface layer of the lead-containing copper alloy before plating on the surface of the lead-containing copper alloy, in which the lead-containing copper alloy is immersed in an alkaline etching solution In addition, the electrolysis using the lead-containing copper alloy as either a positive electrode or a negative electrode and the electrolysis using the lead-containing copper alloy as either the positive electrode or the negative electrode are alternately performed. Pretreatment method.

[2] The plating pretreatment method according to [1], wherein the electrolysis that alternately repeats as a positive electrode or a negative electrode makes the lead-containing copper alloy a positive electrode at the end.

[3] In the plating pretreatment method according to claim 1 or claim 2, the condition force of the electrolysis that repeats alternately as a positive electrode or a negative electrode. The current density is 1 AZdm ² or more and 25 AZdm 2 or less, and the current switching A process for pre-meshing characterized in that the time is 2 seconds or more and 30 seconds or less.

[4] The plating pretreatment method according to any one of claims 1 to 3, wherein an oxidizing agent is added to the alkaline etching solution.

[5] The plating pretreatment method according to any one of claims 1 to 3, wherein the plating applied to the surface of the lead-containing copper alloy is performed by chromium plating after nickel plating. .

[6] A water supply device made of lead-containing copper alloy, and the surface of the water supply device is nailed, and the lead-containing copper alloy is immersed in an alkaline etching solution as a pretreatment for the staking. The electrolysis using the lead-containing copper alloy as either the positive electrode or the negative electrode and the electrolysis using the lead-containing copper alloy as either the positive electrode or the negative electrode alternately were performed. Lead-containing copper alloy water supply equipment.

[7] The lead-containing copper alloy water supply device according to claim 6, wherein the electrolysis is repeated alternately as a positive electrode or a negative electrode, and the lead-containing copper alloy material is finally used as a positive electrode. Lead-containing copper alloy water supply equipment.

[8] In the lead-containing copper alloy water supply device according to claim 6 or claim 7, the current density is less than lAZdm ^{2 when} the alternating electrolysis condition is repeated as a positive electrode or a negative electrode. Top 25AZdm ² or less, lead-containing copper alloy water supply equipment characterized by current switching time of 2 seconds or more and 30 seconds or less.

9. The lead-containing copper alloy water supply device according to any one of claims 6 to 8, wherein an oxidizing agent is added to the alkaline etching solution.