JPH07233459A - Flux for hot dip zinc alloy plating - Google Patents

Abstract

PURPOSE:To obtain an aq. flux for Zn-Al alloy plating having satisfactor suitability to plating, excellent in plating work efficiency because of a short drying time and especially suitable for use in hot dip plating of a steel wire. CONSTITUTION:This aq. flux is made of an aq. soln. prepd. by adding 100-600g/l stannous chloride (SnCl.) and 1-20g/l ammonium acetate (CH3COONH4) or an aq. soln. prepd. by adding 100-400g/l SnCl, and with 1-150g/l CH3COONH4 to an aq. soln. acidified with 2-5% hydrochloric acid (HCl).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flux for alloy plating by a zinc-aluminum single bath which is suitable for steel materials, particularly steel wires.

[0002]

2. Description of the Related Art Zinc-aluminum alloy plating with a 1-20% aluminum-zinc alloy bath for steel materials does not form an alloy layer between the steel substrate and the plating layer, and although the plating layer is thin, it has excellent corrosion resistance and a smooth appearance. It is known that it has excellent workability.

However, during alloy plating, the aluminum in the hot dip bath is preferentially oxidized and aluminum oxide (A
l ₂ O ₃ ) to inhibit the adhesion of the plating, and
In the conventional hot dip galvanizing, in the flux composed of zinc ammonium chloride used for suppressing oxides, aluminum in the plating bath forms easily volatile aluminum chloride (AlCl ₃ ) and causes non-plating. Zinc-aluminum alloy plating for the purpose of improving corrosion resistance is carried out by a so-called two-bath plating method in which it is applied on a normal zinc plating applied as a base, and has a problem in economic efficiency such as enormous equipment cost. Was there.

On the other hand, many proposals have also been made for a flux for directly plating a zinc-aluminum alloy on a steel substrate. However, most of them are compositions mainly composed of zinc chloride, and as an aqueous flux of an aqueous solution, the drying time is relatively long, and the plating time is rather long, which causes a problem in workability in actual operation. However, in continuous hot-dip galvanizing of a steel wire having a short length and a high traveling speed of a material to be plated, there is a problem that it is difficult to use from the viewpoint of flux drying time and plating property.

Therefore, in view of the above circumstances, the present invention is an economical hot-dip zinc-aluminum which has good plating properties, has a fast flux drying time, is excellent in workability, and is suitable for one-bath plating of steel wires. It is intended to provide an aqueous flux for alloy plating.

[0006]

To achieve the above object, the present invention provides stannous chloride (SnCl ₂ ) 100-60.
0 g / l and ammonium acetate (CH ₃ COONH ₄ ) 1
A flux for hot dip zinc-aluminum alloy plating, which comprises an aqueous solution prepared by adding about 20 g / l,
SnCl _{2 in} 2-5% by weight hydrochloric acid (HCl) acidic aqueous solution
100 to 400 g / l and CH ₃ COONH ₄ to 15
We propose a flux for hot dip zinc-aluminum alloy plating consisting of an aqueous solution prepared by adding 0 g / l.

[0007]

[Function] SnCl ₂ in the flux component has a large reducing property, has an excellent surface activating function, and improves the wettability of the steel material. On the other hand, even if the amount of addition is increased, the hydrolyzability becomes large and the plating effect does not change so much, rather it deteriorates the drying property of the flux, and since it is expensive, there is a problem in economic efficiency, The amount of SnCl ₂ added is 100 to 600 g /
l is appropriate, 100-400 g / in the presence of HCl
Let l be appropriate.

CH ₃ COONH ₄ complements the action of SnCl ₂ and significantly improves the wettability of the steel material. Therefore, although it helps to save the amount of SnCl ₂ added and enhances the drying property of the flux, if it is too large, the flux drying property and the plating property are rather deteriorated. This C
Suitable amount of H ₃ COONH ₄ is appropriate for from 1 to 20 g / l, in the presence of HCl to appropriate the 1~150g / l.

[0009] HCl suppresses hydrolysis SnCl _2, it helps to reduce the SnCl _2. If the content of HCl is less than 2% by weight, the above effect is brought about but the effect may not be obtained, and if it is 2% by weight or more, a sufficient effect can be obtained. Further, when the content exceeds 5% and increases, the flux drying property and the plating property deteriorate rapidly, so an appropriate amount is made 2 to 5% by weight.

[0010]

Example As a first example, SnCl ₂ was added in a dihydrate salt form (SnCl ₂ · 2H ₂ O) to prepare a flux liquid in which the composition of SnCl ₂ and CH ₃ COONH ₄ was changed, and plating was performed. Hard steel wire rod (JIS G 3506)
SWRH 62A) has a diameter of 2.3 mm and a length of 3
A 50 mm steel wire was used, and after immersion in the flux solution, a plating test was performed in which alloy plating was performed with a molten alloy of 5% Al-Zn.

As a test treatment step, the steel wire is heated to 50 ° C.
After dipping in 15% HCl solution for 15 seconds for pickling, then washing with water at 50 ° C for 5 seconds, then at 70 ° C
After being immersed for 5 seconds in the above-mentioned flux solution held in, the temperature was kept in a temperature range of about 250 ° C. above the electric furnace until it became a dry state, and the time (second) was measured. After that, the steel wire of the flux treatment liquid was dipped in the molten alloy held at about 460 ° C. for 2 to 5 seconds, and the plating state was visually evaluated. The processing time in each of the above steps is based on what is calculated from a standard hot dip galvanizing operation in a continuous hot dip galvanizing plant for steel wires.

The obtained results are shown in Tables 1 and 2 for flux drying property and plating property, respectively. In the case of Table 1 showing the drying properties of the flux, the symbol ⊚ in the table indicates a drying time within 5 seconds, ∘ is 6 to 10 seconds, and Δ is 11 to 11.
15 seconds, all of which are within practical limits, and x indicates 16 seconds or more, which is outside the practical range.

[0013]

[Table 1]

In the case of Table 2 showing the plating property, the symbol ◎ in the table
Shows good appearance, ○ shows a little good, and △ shows a little bad, but all are within the limit that a plating layer is generated and can be practically used, and × is a defect, that is, there is a partial non-plating part Including non-plated products, it is out of the practical range.

Further, in order to investigate the plating adhesion of the steel wire, a bending test was conducted on the obtained plated wire. In this bending test, the plated wire was bent to the self-diameter, and the presence or absence of defects such as peeling and cracks in the plated surface state was observed. The results are shown in Table 3. In the table, the symbol ◯ indicates that there is no defect and the symbol x indicates that there is a defect.

[0016]

[Table 2]

[0017]

[Table 3]

The results are as follows. SnCl ₂ is
CH ₃ COONH ₄ is 16 g / l even if it contains 60 g / l
By adding the above, it is possible to carry out plating with practical use in both flux drying property and plating property. When SnCl ₂ is 100 g / l, CH ₃ COONH ₄ is at least 8 g.
Plating becomes possible by adding / l. SnCl
₂ becomes 200g / l or more, less CH ₃ COON
Even when the amount of H ₄ is short, the drying time is shortened and the plating state is remarkably improved. However, when the amount of CH ₃ COONH ₄ is relatively large, the drying property and plating property of SnCl _{2 are} rather impaired. Even when the amount of SnCl ₂ added is 600 g / l or more, the good plating property is maintained, but on the other hand, the drying property tends to be poor, and it is considered to be disadvantageous from the economical point of view. Regarding the plating adhesion observed in the bending test, it has been shown that if the plating property is good, the adhesion is also good.

Next, as a second embodiment, an HCl solution having a HCl concentration of 1 to 5% by weight is used and the amount of SnC is changed.
l ₂ was added to create a SnCl ₂ solution, to SnCl ₂ solution of each concentration was flux liquid was added to CH ₃ COONH ₄ varying amounts. All other conditions are the same as above
As in the case of the example, the drying time of the flux, the plating property of the wire to be plated, and the plating adhesion in bending thereof were investigated, and the results are shown in Table 4, Table 5 and Table 6, respectively.
It was shown to. The evaluation symbols ⊚, ○, Δ and × in Table 4 showing the flux drying property and Table 5 showing the plating property, and the symbols ○ and × in Table 6 showing the plating adhesion property.
Is the same as that of the first embodiment.

[0020]

[Table 4]

[0021]

[Table 5]

[0022]

[Table 6]

The results of the second embodiment are as follows. S
nCl₂Is a relatively small amount of 100 g / l,
When the HCl concentration is 1%,
(Refer to Table 1 and Table 2), the drying property of the flux is almost unchanged.
However, the plating property is greatly improved. But,
In terms of the adhesion of plating seen in the bending test, the plating film
There was peeling and cracking on the surface, which was not good. Furthermore, HCl
When CH is 2 to 3%, CH₃COONH_FourOf the content of
Regardless of how you improve flux drying and plating
are doing. Especially when the HCl concentration is 2%, SnCl₂Is 15
At 0 g / l, flux drying property and plating property are both
The best effect is obtained. For plating property, H
If Cl2 to 3%, SnCl₂Is 100-600g
CH in the range of / l₃COONH_FourIs 0 to 150g
Good in a wide range of 1 / l, but 3% for dryness
600 g / l high SnCl in HCl₂In the addition area
Poor drying, SnCl₂In the addition range of 400 g / l
Is CH₃COONH_FourPoor drying is noticeable on the high addition side of
ing. HCl 4-5%, further drying and plating
Is gradually decreasing, but CH₃COONH _FourThe addition amount of 10
If it is kept below%, it is possible to perform better plating work.
It That is, high HCl and high CH₃COONH_FourIs SnCl
₂Seems to be one that accelerates the hydrolysis of
That means HCl and CH₃COONH_FourThe balance of
Expensive SnCl₂It is possible to save
Is shown. In addition, plating adhesion seen in bending tests
The plating property is good except for 1% HCl.
If so, it indicates that the adhesion is good.
It

In the case of steel plates and general steel materials,
By considering other plating conditions such as bath temperature and immersion time, the flux of the present invention can sufficiently perform alloy plating.

[0025]

As is apparent from the above description, according to the present invention, a small amount of CH ₃ COONH is added to the SnCl ₂ aqueous solution.
By adding ₄ , zinc can be plated with a relatively small amount of SnCl ₂ added, and the flux drying time is short and the workability is good. Zinc suitable for continuous steel wire plating-
A flux for aluminum alloy plating can be obtained. Further, by using a 2-5% HCl aqueous solution as the base liquid, it is possible to obtain a flux having the same effect with a smaller amount of SnCl ₂ added.

Front page continuation (72) Inventor Morihiko Uchida 1443 Nakajuku, Annaka City, Gunma Prefecture Toho Zinc Co., Ltd.

Claims (2)

[Claims] 1. SnCl ₂ 100-600 g / l and C
H ₃ COONH ₄ 1~20g / l and is characterized in that it consists of an aqueous solution prepared by adding a molten zinc alloy plating flux. 2. Sn is added to a 2-5 wt% HCl acid aqueous solution.
Cl ₂ 100-400 g / l and CH ₃ COONH ₄ 1
A flux for hot-dip zinc alloy plating, characterized by being prepared by adding ˜150 g / l.