JPS6370000A - Method for controlling electroplating liquid for zinc or zinc alloy - Google Patents

Abstract

PURPOSE:To efficiently remove lead ion contained in a galvanizing bath in greater quantities, by bringing the galvanizing bath contg. lead ions into contact with hydrated antimony oxide and thereafter bringing this into contact with titania-base composite oxide. CONSTITUTION:Electroplating liquid of zinc and zinc alloy is drawn out from a plating tank 1 and introduced into a storage tank 5 of plating liquid after separating anode sludge with a filter 4. This plating liquid is led to a column 7 packed with an inorganic ion exchanger 8 consisting of hydrated antimony oxide by means of a pump 6 and greater parts of lead ions incorporated in the plating liquid are adsorbed. The plating liquid discharged from the column 7 is introduced into a column 9 packed with an adsorbent 10 consisting of titania-base composite oxide, trace Sb ion and residual lead ion incorporated in the plating liquid are adsorbed, and thereafter it is returned to the storage tank 5. By this method, lead ions can be efficiently removed without forming insoluble ppt. and plating quality can be enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for managing a zinc or zinc alloy electroplating solution.

<Conventional technology> In recent years, Zn, which has excellent corrosion resistance, weldability, paintability, workability, etc.
, Zn-Fe, Zn-Ni, Zn-Co, Zn
-Fe-Ni.

Zinc or zinc alloy electroplated steel sheets such as Zn-Co-Mo have been developed and are used in a wide range of applications such as automobiles, home appliances, and building materials. These zinc-based electroplated steel sheets are manufactured using high-speed continuous electricity using a non-bath anode or a soluble anode as the anode, a sulfuric acid bath or chloride bath as the plating bath, and a horizontal or vertical cell as the electrolytic cell. Manufactured using plating equipment.

By the way, in such an electroplating process, lead alloy electrodes used as non-bath anodes, metals and chemicals such as zinc sulfate, iron sulfate, and sulfuric acid used in bath preparation, and zinc electrodes used as soluble anodes, etc. Therefore, a small amount of lead ions dissolve into the plating bath, but when these mff1 lead ions are contained in the plating film, they do not have various adverse effects on the performance of the plating film. Japanese Patent Application Publication No. 5
Publication No. 2-30728 discloses that trace amounts of lead ions in a zinc or zinc alloy electroplating bath co-deposit on the plating film, deteriorating the plating adhesion and corrosion resistance, and in particular significantly changing the plating adhesion after heating. It has been shown that Furthermore, Japanese Patent Publication No. 58-39236 discloses that trace amounts of lead ions eluted from an insoluble lead anode into the electrolyte eutectoid on the plating film.
It has been shown that uneven gloss and matteness tend to occur.

Various methods are known to remove lead ions that cause such adverse effects from the plating bath, as shown below.

(1) Use chemicals and metals with low lead content.

(2) Add zinc powder to the plating bath.

(3) Perform weak electrolysis.

(4) Use an intolerant electrode other than lead or lead alloy.

(5) Adding strontium or barium carbonate to the plating bath.

However, method (1) uses special reagent grade chemicals and high purity metals, resulting in a significant increase in cost. Methods (2) and (3) have drawbacks in terms of equipment and deposition rate. Method (4) uses a platinum-plated titanium electrode or the like, but there is a problem in economic efficiency because the surface is frequently worn in the plating bath. Method (5) is generally widely used, but
The formed insoluble precipitate adheres to the plated product and causes scratches.

Therefore, the present inventors have developed a method for preventing poor adhesion and poor gloss of plating films due to eutectoiding of trace amounts of lead ions, by bringing a plating solution containing lead ions into contact with an adsorbent made of a titania-based composite oxide. , has developed a technology to perform zinc or zinc alloy electroplating while suppressing the increase in lead ion content in the plating bath, and has already filed a patent application (dated September 1, 1986).

According to this method, the lead ions in the plating solution are adsorbed by the adsorbent made of titania-based composite oxide to a concentration of less than 1 μ/L, resulting in zinc or zinc alloy electroplating with uniform gloss and good adhesion. It will be done.

Moreover, since the adsorbent can be reused and there is no sludge formation, there is an advantage that the cost associated with removing lead ions from the plating solution can be significantly reduced.

<Problems to be Solved by the Invention> However, when the above method was examined in detail, it was found that there were still points to be improved in this method. The reason is that the amount of lead adsorbed by the adsorbent made of titania-based composite oxide is as small as a few orders of magnitude to a few tens of square meters. Therefore, in order to keep the lead content in the plating solution below a predetermined value, it has been necessary to increase the amount of adsorbent packed in the column or to renew the adsorbent-filled column sooner.

The present invention provides a plating solution management method that eliminates the drawbacks of conventional methods.
That is, the object of the present invention is to provide a method for managing a zinc or zinc alloy electroplating solution that can efficiently remove a large amount of lead ions without forming insoluble precipitates in a plating bath.

<Means for solving the problem> The present inventors first synthesized a titania-based composite oxide with a new composition using various soluble metal salts, or performed surface treatment on the titania-based composite oxide. Therefore, we attempted to increase the lead adsorption capacity of titania-based composite oxides. However, although some effects were seen, the performance did not improve significantly. Therefore, various activated carbon, zeolite, 2Mg0
・6SiO□・nll□0゜Mgetlz(S+n0z
) Z・3H2o, 5b203・nH2O, potassium titanate, etc., adsorbents and ion exchangers were used to perform a lead removal test in the plating solution using a batch method. ,0 (antimonic acid or antimony hydroxide) showed the highest lead removal rate.

By the way, it has been known for a long time that sb, o, ・nll□0 is an inorganic ion exchanger that has a unique selective adsorption property, and it also shows a strong selective adsorption property for lead.
It was also reported to have a large ion exchange capacity of q/g. However, despite these features, its use has been delayed due to the drawback that sb<antimony) is released in small amounts during the night. In fact, when exposed to a zinc-based plating solution, sb comes out at a rate of several square meters per liter to several tens of times per liter, although this varies depending on the conditions.

In zinc or zinc alloy electroplating, if sb ions are present in the plating solution in an amount of 2 w/ffi or more, they promote abnormal precipitation of zinc and interfere with the precipitation of zinc alloy plating components such as iron. Because sb ions have such an effect, the sb ion concentration in the plating solution is usually about 1, as in the case of lead.
/l or less. Therefore, 5bzO
Although s·n H,0 has excellent lead selective adsorption and large lead ion exchange capacity, it cannot be applied to lead removal from plating solutions because of the disadvantage of sb ion bathing.

However, as a result of more detailed studies by the present inventors, we found that an adsorbent made of titania-based composite oxide preferentially adsorbs sb contained in a low-pH zinc-based plating solution in the same way as lead. We discovered this and developed the present invention, which can maintain the lead concentration in the plating solution below the control value for a long period of time through a two-stage treatment using an inorganic ion exchanger made of hydrous antimony oxide and an adsorbent made of titania-based composite oxide. It was completed.

That is, in the method for managing a zinc or zinc alloy electroplating solution of the present invention, a zinc or zinc alloy electroplating solution containing lead ions is first transferred to a first stage column filled with an inorganic ion exchanger made of hydrous antimony oxide. Most of the lead ions in the plating solution are adsorbed, and then the plating solution discharged from the first column, that is, the extremely small amount of lead ions and water that could not be adsorbed by the first column, is The plating solution containing IT and sb ions eluted from antimony oxide is guided to the second stage column packed with an adsorbent made of titania-based composite oxide, where it is separated from the extremely small amount of lead ions in the plating solution. By adsorbing sb ions,
It is characterized by keeping the lead ion concentration below a predetermined value.

<Function> According to the method of the present invention, trace amounts of lead ions contained in the zinc or zinc alloy electroplating solution are efficiently adsorbed in large quantities by the inorganic ion exchanger made of hydrous antimony oxide and the titania-based composite oxide. The lead ion concentration in the plating solution is maintained at the control value of 1/l or less over a long period of time. Due to the decrease in the lead ion concentration in the plating solution, the number of buttons eutectoid on the plating film is significantly reduced, so there is no occurrence of uneven gloss on the plating film, and the adhesion of the plating film is reduced even when the plating film is heated. do not. In addition, there is no need to add 7 to the plating tank.
Since there is no contamination of electrolytic precipitates, no scratches will occur on the plating film.

<Example> The zinc or zinc alloy electroplating solution used in the present invention includes all industrially used zinc or zinc alloy electroplating solutions of various compositions, and representative examples include: is a plating solution for sulfuric acid bath that is widely used in Japan, for example 20-500g / I Zn5Oa ・7
20-300g/l Fe1 based on +120
o4・7HzO, NiSO4・68zO, Co50a
- Alloying metal salts such as 7HzO, 20-100g/A of 1hSO4° (Nl+4) 2504. NazSOa
Conductivity improvers such as 5-60g/l HJO3, Cl
1sCOOH, CJIIOt, Cl1tCOONa.

(NL) 3chHs (pH 7 or less with the addition of one or more buffering agents and complexing agents such as h, mostly pl+
Examples include plating solutions with 1-2. These are bath/? L5
It is usually used under plating conditions of 0-60'C, Dk 30-150A/d%, and line speed 50-150m/n+in.

The inorganic ion exchanger made of hydrous antimony oxide used in the present invention has the general formula 5bzOs・ntl, 0 (1≦
Refers to an inorganic ion exchanger mainly composed of a hydrous oxide of pentavalent antimony represented by n≦5). Such hydrous antimony oxides can be prepared, for example, by oxidation of metallic antimony with nitric acid, antimony pentachloride or hexachloroantimonic acid (IIS
It is produced by hydrolysis of bC16), oxidation of antimony trioxide or antimony trichloride with nitric acid or hydrogen peroxide, etc., but products with different water contents and crystal states can be obtained depending on the preparation method and drying conditions. Generally, there are three types: crystalline, glassy, and amorphous, and among these, the crystalline type is said to be particularly stable and has a large ion exchange capacity. Tin, zirconium, and titanium are used when preparing hydrous antimony oxide for the purpose of improving the chemical resistance of hydrous antimony oxide and increasing its lead ion exchange capacity.

A soluble salt such as phosphorus may be reacted to form an antimony compound such as tin antimonate, zirconium antimonate, titanium antimonate, or phosphorous antimonate. These inorganic ion exchangers made of hydrated antimony oxide are in powder form.

It can be molded into any shape such as granules, pellets, or honeycombs.

The adsorbent made of a titania-based composite oxide used in the present invention is a general term for a synthetic inorganic adsorbent with a porous structure composed of a composite of inorganic oxides mainly composed of titania (TiO□). For example, in an aqueous solution of a soluble titanium salt such as titanium tetrachloride, titanium sulfate, titanyl sulfate, or titanium isoboxoxide, sodium metasilicate, sodium orthosilicate, water glass, silicon tetrachloride, ethyl silicate, silica sol, etc. Soluble silicates in water and/or aluminum.

Water of 7-soluble metal salt compounds such as zirconium and magnesium? W? Add aqueous ammonia or a water-cooled solution of sodium hydroxide to the mixed solution of (f) and filter the complex oxides such as titania-silica, titania-silica-alumina, and titania solica magnesoa formed in 1a L. Examples include those that have been washed, dried, or fired.

Similar to the case of hydrous antimony oxide, these can be molded into desired shapes such as powder, pellets, and honeycomb shapes.

It should be noted that it should be understood that the expression "titania-based composite oxide" in the present invention exceptionally includes cases where the oxide is composed only of titania. Naturally, the titania-based composite oxide of the present invention is not limited to those made by the above-mentioned hydrolysis method, but also includes those made by a hydrothermal method or other wet methods. Furthermore, it also includes those synthesized by flux method, slow cooling, calcination method, melt method, etc., such as potassium titanate.

In the present invention, the method of contacting the plating solution containing lead ions with the inorganic ion exchanger made of hydrous antimony oxide and the adsorbent made of titania-based composite oxide is a column method, that is, a column packed with the inorganic ion exchanger ( packed tower)
And 1! ! ! A column packed with the bound adsorbent (
A method in which a plating solution containing lead is passed through a packed tower is preferred. When a large amount of lead ions or sb ions are adsorbed and saturation is reached, it is only necessary to replace the column, so bath management is easy and the inorganic ion exchanger and adsorbent can be easily regenerated. Although other methods are possible, they often complicate bath management and reduce the removal rate of lead and sb. In the case of the column method, the removal rate of 1:) and sb naturally increases as the inorganic ion exchange chemical composition increases as the amount of adsorbent packed increases and as the flow rate of the plating solution in the column decreases. The larger the surface area of the column packing material and the higher the pl+ of the plating solution, the better.

FIG. J is a schematic diagram for explaining the plating solution management method of the present invention.

When managing the plating solution according to the method of the present invention, plating tank 1
The plating solution is continuously or intermittently extracted from the
The plating solution is introduced into the plating solution storage tank 5 after the anode slurry is separated by ti4. On the other hand, another circulation from the plating solution storage tank 5! Through route 7i, the plating solution is guided by a pump 6 to a column 7 filled with an inorganic ion exchanger 8 made of hydrous antimony oxide, and most of the lead ions in the plating solution are adsorbed. Next, the plating solution discharged from column 7 is introduced into column 9 filled with adsorbent 10 made of titania-based composite oxide to adsorb trace amounts of sb ions and residual lead ions in the plating solution, and then returned to the original plating solution storage tank. Return to 5. A method is adopted in which plating liquid with reduced button ions is sent from the plating liquid storage tank 5 to the plating tank l by a pump 11 for plating.

In the figure, 2 is 7 nodes, and 3 is a slip.

Next, practical examples and comparative examples will be shown to further explain the present invention in detail.

The inorganic ion exchanger and adsorbent used in this specific example were subjected to RJ3'' IJ as follows.

(1) <Inorganic ion exchanger made of hydrated antimony oxide> Pour pure water into the reactor and stir (↑ while stirring;
Heat to 40°C. Add this to the 90% turbid solution.
Add 3% l1zOz. After the reaction is completed, the obtained product is dried at 100°C, milled, and classified into 20-42 menonyu.

(2) <Adsorbent made of titania-silica composite oxide> After taking an amount of sodium metasilicate at a predetermined atomic ratio and dissolving it in ion-exchanged water, hydrochloric acid is added to form a plll. A titanium tetrachloride aqueous solution is added to this mixture so that a predetermined atomic ratio is obtained, and 3M ammonia water or sodium hydroxide solution (I volume) is added dropwise to this mixed solution up to p) 18 to precipitate a gel. Wash and dry this kettle for 20
Crush into 0 mesh, mold it with a press and crush it to 20-4
Classify into 2 categories.

(3) <Adsorbents made of other chiknia-based composite oxides> As in the case of (2), at least one soluble metal salt of the target metal is dissolved in ion-exchanged water in an amount to achieve a predetermined atomic ratio. do. A titanium tetrachloride aqueous solution is added to this so that a predetermined atomic ratio is obtained, and the preparation is performed in the same manner as in (2) below.

(4) <Adsorbent made of potassium titanate composite oxide> KzTi40q made with flux properties detailed in Ceramics Association Journal, 88.111-16 (1980) was molded with a press and then crushed to obtain 20-42 Classify into Metsuyu.

In this example, lead removal from the plating solution was carried out using an apparatus as shown in FIG. A plating solution 15 containing lead ions is transferred from a plating tank 12 by a metering pump 13 to an inner diameter 8 filled with a predetermined amount of a hydrous antimony oxide inorganic ion exchanger 16.
The plating solution was introduced into a column 14 having a diameter of 11 φ, and then the plating solution flowing out from the column 14 was sent to a column 18 having an inner diameter of 8 φ and filled with a predetermined amount of a titania-based composite oxide adsorbent 19. Column 1
The plating solution discharged from No. 8 was collected every 20.0 g using a fraction collector 20, and the lead ion concentration and Sb ion concentration were measured by atomic absorption spectrophotometry. In the figure, 17 is glass wool.

Lead removal from the plating solution in this comparative example was carried out using an apparatus as shown in FIG. Plating solution 24 is transferred to plating tank 21
From there, it was sent by a metering pump 22 to a column 23 having an inner diameter of 8 φ and filled with a predetermined amount of an inorganic ion exchanger or adsorbent 25 . The effluent from the column 23 is collected every 20.0 g by the fraction collector 27, and the lead ion concentration and sb ion concentration are measured. The Q degree was measured by atomic absorption spectrophotometry. In the figure, 21 is a plating tank, and 26 is glass wool.

(Example 1) ZnSO4H71120200g/f.

Fe5Oa H711g0 280 g/'
.

(Nl+4)! So4 50g/j! .

c, osot o, s g / 6.

Pb” 5■/A.

Zinc alloy electroplating solution with pl+ 1.8 consisting of 1-
Hydrous antimony oxide (SbzOs ・
2. The solution was passed through a column filled with 1 g of an inorganic ion exchanger made of 1 g of an inorganic ion exchanger made of 1 g of titania-based 1M composite oxide (Ti02:SiO□-80:20) connected thereto. The lead concentration in the discharged plating solution after passing 11 plating solutions was 0.5■/
1. The Sb concentration was 0.3/il, which was within the control value.

(The control value for lead is 1 mg/7!, and the control value for Sb is 1 mg/J (Comparative Example 1-1). 2 g of SrCO in the plating solution lρ with the same composition as Example 1.
3 was added and shaken at room temperature for 2 hours. The lead concentration in the plating solution after filtering the insoluble precipitate was 1.5/1, which exceeded the control value.

(Comparative Example 1-2) A plating solution having the same composition as in Example 1 was used at a flow rate of 11117/ml to form a titania-based composite oxide (Ti02:SiO□=
The solution was passed through a column packed with 1 g of an adsorbent consisting of 80.20). When the plating solution was passed 11 times, the lead content in the discharged plating solution was 1.4 .mu./l, which exceeded the control value.

(Comparative Example 1-3) A plating solution with the same composition as in Example 1 was used at 1ml/lll1l.
Hydrous antimony oxide (Sb2O5.2.51
The solution was passed through a column packed with 1 g of an inorganic ion exchanger consisting of 120). When the plating solution was passed through 1a, the lead concentration in the discharged plating solution was 0.8 N/1, which was within the control value, but the Sb concentration was 1.1 nv/jl, which exceeded the control value.

(Example 2) ZnSOn ・71120 220 g/1
.

Fe5Oa’ 7H20250g/1.

NazSOa 100 g/R.

Citric acid 5g/l.

Pb” 5 nv/1.

1 Inl of pH 2.2 zinc alloy electroplating solution consisting of
Hydrous antimony oxide (SbzOs ・
A column packed with 3 g of an inorganic ion exchanger consisting of 21120) and a titania-based composite oxide (T
The solution was passed through a column filled with 3 g of an adsorbent consisting of iO□:SiO□:MgO=50:45:5). 1 plating solution
The lead concentration in the discharged plating solution at the time when the 011m solution was poured was 0.3 .mu./z, and the Sb concentration was 0.5++wr/ff, both of which were within the control value range.

(Comparative Example 2-1) 3 g of BaC0z in plating solution 1β having the same composition as Example 2
was added and shaken at room temperature for 1 hour. 'd non-coolable sediment
The seismic intensity of 2:2 in the plating solution after 30 minutes was 1.6 ■/l, which exceeded the control limit.

(Comparative Example 2-2) Titania-based composite oxide (Tin□:5iOt:nBo
The solution was passed through a column packed with 3 g of an adsorbent consisting of 50:45:5). When 1.5 g of plating solution was passed through the plating solution, the lead concentration in the discharged plating solution was 1.3 .mu./l, which exceeded the control value.

(Comparative Example 2-2) Same as Example 2) A plating solution of Jl composition was poured into a column filled with 3 g of an inorganic ion exchanger made of hydrous antimony oxide (SbzOs 2110) at a flow rate of 1 m//min.
It liquefied. 81 plating solution! The lead/density in the discharged plating solution at the time of the il solution was 0.6/ρ, which was within the control value, but the Sbi yield was 2.1. mg/f exceeded the control value.

(Example 3) ZnSOn ・7) 1z0 150 g /
1.

Fe5Oa・711zO250g/e.

N15Oa・61120. 250g/f
f.

Na2S0. 30g/1.

83BOi, 30g/IV
,.

Citric acid 10g/l.

Pb” 5 mg/1.

1.5d of zinc alloy electroplating solution with pH 1.5 consisting of
Hydrous antimony oxide (SbzOs・4
A column packed with 3 g of an inorganic ion exchanger consisting of 11□O) and potassium titanate (KzTi
The solution was passed through a column packed with 6 g of adsorbent consisting of aOw).

Discharge plating when 10 fJ of plating solution is applied? (
1, middle) m concentration:: 0.2 w/l + Sba degree was 0.25 mg/l, both within the control value.

Next, add 2ml/2M nitric acid to this used two-stage column.
After passing a 50M solution at a flow rate of min, pure water was washed with a 500mZ solution. Using the thus obtained regenerated column, we conducted the same test as above and found that the plating solution was rated at 10! Lead in the discharged plating solution at Ic when the solution is passed,
・Seismic intensity is 0.22■/F, Si+iW degree is 0.2
■/l, showing the same performance as a new product.

Above, we have explained QQ using examples and comparative examples.
It goes without saying that the present invention is not limited to these embodiments.

<Effects of the Invention> According to the present invention, lead ions during zinc or zinc alloy electroplating are removed using a column packed with an inorganic ion exchanger made of hydrous ayu oxide/timon and an adsorbent made of a titania-based composite oxide. Insoluble substances in the packed column
It can effectively remove a large amount without forming any stains. Part 3: Uniform gloss and plating adhesion of 1'↓ Good plating film strength (stable 1) 17! The life of the Konera column has been significantly extended, and Kara L can be reused. Therefore, the present invention makes a significant contribution to improving the quality of lead alloy electroplating, reducing the process to five elements, and reducing costs.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram for explaining the plating solution management method of the present invention, Figure 2 is a conceptual diagram of a lead removal device used in an example of the method of the present invention, and Figure 3 is a comparison of the methods of the present invention. It is a conceptual diagram of the lead removal device used in the example. L 12.21 is a plating tank, 2 is an anode, 3 is a strip, 4 is a filter, 5 is a plating solution storage tank, 6゜11, 13
．． 22 is the pump? , 9.14.18.23 is column, 8.16 is inorganic ion exchanger, 10.19 is adsorbent, 15, 24 is plating? At night, 17.26 is glass wool, 20°27 is a fraction collector, and 25 is Q [ion exchanger iQ body or adsorbent. Patent applicant Masaharu Kaneko Nippon Kagaku Sangyo Co., Ltd.

Claims (1)

[Claims] A zinc or zinc alloy electroplating solution containing lead ions is first brought into contact with an inorganic ion exchanger made of hydrous antimony oxide, and then brought into contact with an adsorbent made of a titania-based composite oxide, thereby eliminating lead ions in the plating bath. A method for managing a zinc or zinc alloy electroplating solution, characterized by suppressing an increase in content.