JPS59129794A - Production of zn-fe alloy electroplated steel sheet - Google Patents

Abstract

PURPOSE:To prevent the burning by acid on the non-plating surface of a steel strip and to improve chemical convertibility in the stage of subjecting one surface of the steel strip to plating by electroplating a Zn-Fe alloy on the inlet side of a plating line on the other surface then passing the steel strip in a non-conducting state through the plating soln. CONSTITUTION:A Zn-Fe alloy is electroplated on the other surface of a steel strip as well on the inlet side of a plating line to form a protective film in the stage of subjecting one surface of the steel strip to the intended Zn-Fe alloy electroplating. When the other surface of the steel strip is thereafter passed through the plating state in a non-conducting state, the Zn-component in the above-described protective film is preferentially dissolved and the protective film is enriched with Fe. If the time when the strip passes in the plating soln. in the non-conducting state is suitably selected, the Fe-component in the protective film is made adequate on the outlet side of the plating line. The burning by acid on the other side, that is, non-plating surface is thus prevented and chemical convertibility is improved. More particularly, the steel sheet which is plated on both sides in multiple layers at different thickness and have the corrosion preventive layer and the layer improved in the adhesion of the paint coated film is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a Zn-Fe alloy plated steel sheet, and in particular, a method for producing a Zn-Fe alloy plated steel sheet, in particular, a method for manufacturing a Zn-Fe alloy plated steel sheet, and in particular, a method for manufacturing a Zn-Fe alloy plated steel sheet.
The present invention relates to a differential thickness multilayer double-sided electroplated steel sheet having an n-Fe alloy electroplated layer.

Conventionally, Zn-plated steel materials have been widely used in automobiles, home appliances, building materials, etc. due to the excellent anti-corrosion function of Zn, but Zn-plated surfaces generally have poor corrosion resistance on painted surfaces,
There is a problem in that the anti-corrosion function of the coating film cannot be fully utilized.

In particular, recently, a zinc-iron acid chemical conversion treatment has become popular for medium IB automotive applications. Plated swords made of the same material are no longer desirable.

However, among Zn-based plated steel materials, alloy galvanized steel materials have exceptionally good paint corrosion resistance9, and recently Zn-based zinc-plated steel materials, which are obtained by heat-treating steel materials subjected to electrolytic Zn plating or hot-dip Zn plating, have been developed. Fe-based/alloy plating has become popular. This Zn-Fe alloy plating can be obtained by heat treating Zn plating as described above, as well as by methods disclosed in JP-A-56-142885, JP-A-56-133488, and JP-A-57'-51283. It can also be obtained by electroplating.

When obtaining Zn-Fe alloy plating by electroplating, the plating bath generally has a low pH (pH = 1 to 3).
A sulfuric acid bath is used. When single-sided electroplating is performed in such a plating bath, the surface of the steel plate on the non-plated side will be dissolved by the free H2S04 and Fe3+ ions present in the bath, resulting in blackening of the surface and, in some cases, pinoting. A phenomenon (hereinafter referred to as acid burn) occurs. When such acid burn occurs, the appearance is significantly impaired and the commercial value is reduced, and at the same time, the chemical conversion treatment properties are also significantly deteriorated.

For this reason, a countermeasure for single-sided electroplating in Zn-Fe alloy plating has been desired. Therefore, the inventors of the present invention have considered removing the discolored surface of the non-plated surface with acid burns using H2SO4 electrolysis or grinding it with a nylon brush or the like.

As a result, although it was possible to restore the discolored surface in terms of appearance, it was confirmed that chemical conversion treatments such as zinc phosphate treatment could not be restored. The inventors go further,
After researching a Zn-Fe alloy electroplating method that can prevent the appearance of acid burns and form a non-plated surface with excellent chemical conversion treatment properties, it was found that protective plating is also applied to the non-plated surface when plating copper strips. In addition, we discovered that by making the final composition of the plating film on the non-plated side Fe IJ Sochi, it is possible to prevent acid burns on the non-plated side during plating and improve chemical conversion treatment properties. He came up with an invention.

The object of the present invention is to provide a Zn-Fe alloy electroplated steel sheet that can prevent acid burns on the non-plated surface and improve its chemical conversion properties, particularly a differential thickness steel sheet that has an anti-corrosion layer and a layer that improves paint film adhesion. An object of the present invention is to provide a method for manufacturing a multilayer double-sided plated steel sheet.

That is, according to the first invention, when applying the desired Zn-Fe alloy electroplating to one surface of the copper strip, Zn-Fe alloy is also applied to the other surface of the copper strip at the entry side of the menki line.
Fe alloy electroplating is applied to form a protective film, and then the other surface is passed through a plating solution in a non-energized state to preferentially dissolve the Zn content in the protective film,
Thereby, there is provided a method for manufacturing a Zn--Fe alloy electroplated steel sheet, characterized in that the coating on the other surface is made of Fe IJ.

According to the second invention, in the plating line in which the Metxel for the anti-corrosion layer and the layer for improving paint film adhesion are sequentially arranged, the anti-corrosion layer and the coating are made by passing the Metxel sequentially on one side of the copper strip. Zn- for film adhesion improving layer
1; Form an 'e alloy electroplating film, and protect the other side of the copper strip by applying Z n -F e alloy electroplating in a corrosion protection layer metxel when plating the above one side for the corrosion protection layer. A film is formed, and then the Zn component in the protective film on the other surface is preferentially dissolved by passing through each downstream Metsuki cell in a non-energized state,
Thereby, there is provided a method for manufacturing a Zn--Fe alloy electroplated steel sheet, characterized in that a Fe'J Sochi coating film adhesion improving layer is formed on the other surface.

According to the sixth invention, in the plating line in which the MENKI CEL for the anti-corrosion layer and the coating film adhesion improving layer are successively arranged, the MEN KICEL for the anti-corrosion layer and the coating film adhesion improving layer are sequentially passed through one side of the copper strip, thereby forming the anti-corrosion layer and coating. Zn- for film adhesion improving layer
A Fe alloy electroplating film is formed, and on the other side of the copper strip, Zn-Fe alloy electroplating is applied to a part of the corrosion protection layer metal cell when plating the corrosion protection layer on the above one surface. A protective film is formed, and then the protective film on the other surface is dissolved by passing it through the downstream MENKI CEL for the corrosion protection layer in a non-energized state, and then Zn of Fe IJ Nochi −
Zn-Fe characterized by applying Fe alloy electroplating
A method of manufacturing an alloy electroplated steel sheet is provided.

Zn-1'i'e alloy electroplating on steel plates can be composed of two layers or a multilayer of two or more layers: an anticorrosion layer for corrosion resistance and a coating adhesion improving layer for paintability. many. The anticorrosion layer is Zn rich, preferably Fe≦40
Zn-Fe, particularly preferably l'i' e = 30
It has an alloy composition and constitutes the inner layer of a multilayer plating structure. On the other hand, the coating film adhesion improving layer is made of Fe'), preferably Fe'
It has a Zn--Fe alloy composition of 260%, particularly preferably Fe=90, and constitutes the outer layer.

In order to apply multilayer Zn-Fe alloy electroplating to a steel strip as described above, in a plating line consisting of a plurality of plating cells, the inner layer is plated in several cells on the inlet side, and the outer layer is plated in the outlet cell. It is common to perform plating. For this reason, the inner layer and outer layer mesh cells are each filled with a plating bath corresponding to the composition of each plating film forming the inner layer and the outer layer.

If an anti-corrosion layer is to be formed on only one side of the steel strip in such a plating line, acid burns may occur on the non-plated surface due to the plating bath during each menki cell of the plating line, and the chemical conversion treatment properties may deteriorate. arise. Therefore, in the present invention, the following measures are taken in order to improve the acid burn prevention and chemical conversion treatment property of the non-plated surface.

(1) In the first few cells of Methoxel for the inner layer,
An anti-corrosion film, for example, a Zn-Fe alloy plating film having an alloy composition of Fe≦40, is deposited on the non-plated surface using the plating bath for the inner layer, and then passed through the non-plated surface in a non-electrified state in the subsequent Metsuki cell. . In general, Z n
- When Fe alloy plating is immersed in a plating bath without electricity, the Zn in the alloy plating will preferentially dissolve into the plating bath, reducing the amount of alloy plating and reducing the amount of Zn in the alloy plating. The Fe content increases relatively.Therefore, by appropriately selecting the amount of Zn-Fe alloy plating on the non-plated surface with the inner layer methoxel and the subsequent immersion time in the plating bath in a non-energized state,
On the exit side of the plating line, the composition of the Zn-Fe alloy plating film on the non-plated surface is changed to Fe lynch, preferably Fe26.
It can be set to 0%.

(2) In the first few cells of the inner layer Menkicell, an anticorrosive coating such as Fe is applied on the non-plated surface as in (1) above.
A Zn-Fe alloy plating film having an alloy composition of 540% is deposited at a deposition amount of 5 y/77L" or less, and then the plating film is dissolved by passing through the plating bath in the inner layer Menkicell without electricity. to reduce the adhesion amount to 1.5 y/m2 or less.After that, in the outer layer Metsuki cell, Fe is applied to the non-plated surface in the same way as the plated surface.
For example, 17 notches of Zn--Fe alloy plating containing 60% Fe are electrodeposited with a deposition amount of 5 shrinkage 2 or less. The amount of plating deposited on the non-plated surface of Metsukicell for inner layer is 3y/T.
The reason for setting it below L2 is that if the amount of Zn eluted during the subsequent dissolution process of the plating film does not change depending on the amount of plating deposited, if the plating peak is over 3y/m2, the Zn content in the film will be relatively low. This is not preferable because it will increase the number of females and decrease the P value. In this case, the purpose of dissolving the plating film until the adhesion amount becomes 1.5'/m2 or less is to relatively increase the Fe content of the remaining film. The reason why the amount of plating deposited in the outer layer Metxel was set to 5 geta or less was for economical reasons.

In both methods (1) and (2) above, the plated surface of the steel strip, that is, the surface to be coated with anti-corrosion coating, is coated with an inner layer of anti-corrosion coating and An outer layer for improving paint film adhesion is sequentially formed. In the case of (1), one side is coated with Zn') for corrosion protection, preferably Fe≦60%.
Zn-Fe alloy coating 75 has an inner layer consisting of an inner layer and an Fe-rich Zll-Fe alloy coating 75 with Fe≧60 for improving paint film adhesion. On the other hand, Fe1J Sochi preferably has Z of Fe≧60.
A steel plate having a coating adhesion +S upper layer made of an n-Fe alloy layer is produced. On the other hand, in case (2), 75 balls remain on the plated surface, which is substantially the same as in (1), and on the non-plated surface, Zn-rich inner layer ii remains, and on top of that, F
Preferably, the e-rich material has an outer layer made of a Zn--Fe alloy film with Fe≧60%.

In addition, in methods (1) and (2) above, if possible, the plating film deposited on the non-plated surface of the inner layer methoxel can be printed on the exit side of the subsequent non-energized methoxel. Melting may be carried out so that the amount of coating becomes 0.

As described above, according to the method of the present invention, when plating only one side of the copper strip, protective plating can be provided on the other side to prevent acid burn due to the plating solution. And the outermost layer on the non-plated surface is Fe') notched Zn-1'
Since the i'e alloy film is formed, it is possible to provide a non-plated surface with excellent paint corrosion resistance, especially paint film adhesion.

In the above description, the case where the Zn=Fe alloy plating consists of only an inner layer and an outer layer is shown, but the present invention can also be applied to a multilayer plated steel sheet having two or more layers.

Next, the effects of the present invention will be explained using examples.

Embodiment 1 Figure 1 shows the installation layout of a normal electroplating device, in which the copper strip uncoiled from the uncoiler 1 is degreased in an alkaline electrolytic degreasing tank 2, washed with water in a washing tank 6, and then transferred to a pickling tank. After being pickled in step 4, washed with water in a washing tank 5, and plated on one side in an electroplating tank 6. The plating tank 6 is divided into 11 tanks A-,
Eight tanks -H are for inner layer plating, and six tanks 1 to 2 are for outer layer plating. There is still a washing tank 7 between the H tank and the 1st tank, which washes away the inner layer plating solution adhering to the copper strip. Furthermore, after passing through the electroplating tank 6, it is washed with water in a washing tank 8, dried in a drier 9, and rolled up in a recoiler 10.

Using the continuous electroplating apparatus shown in Fig. 1, using a copper strip of rl]900+n+n and a plate thickness of 0.8 am, Zn
-Fe-based two-layer ``glaze plating'' was performed. Table 1 shows the composition of the plating bath for the Zn-FeZ layer. In addition, F in the bath
The e3+ concentration was controlled within the range of 3.0 to 3.5 t/l in both columns.

The running speed of the copper strip in Table 1 was 50 m/xπ, and the amount of adhesion on the plated surface was 25'? /m2, outer layer is 57
/TL2 The current density was controlled as much as possible.

As a result, the inner layer of the plated surface was 50% Fe and 7 Zn.
0%, outer layer, and 90% Fe and 1[]% Zn plating were obtained, each 2'597 m2.55F/@'.

However, since the non-plated surface was immersed in the inner layer and outer layer plating baths for about 35 seconds, the non-plated surface turned black and was partially pinoted (0.1 m deep).
m, diameter 0.1 mm).

Therefore, while plating the plated surface in the plating bath 6A or 6A, 6B, electroplating is applied to the non-plated surface at various current densities in the same bath, and then
The non-plated surface was left unplated and left in an immersed state between 60 and 60.

As a result, acid burns on the non-plated surface could be prevented.

After that, this copper strip is collected and plated silk is formed on the non-plated side.
In addition to investigating the amount of adhesion, chemical conversion treatment and cationic electrodeposition were performed on the non-plated surface under the conditions shown in Table 2.

Table 2 shows the chemical conversion treatment properties, including the appearance of the chemical conversion film, the amount of adhesion, and the P value (Pho).
Phosphyl ite /Phosphoph
yl lite + Hope ite) was investigated. On the other hand, the corrosion resistance after coating was evaluated as "1" when the tape was peeled off after salt water spray irradiated on the cross-cut portion of the coating film.The results are shown in Table 6.

Example 2 In the same manner, plating was applied to the non-plated surface at various current densities in a 6A plating tank, and the non-plated surface was immersed between 6B and 6H to prevent acid burn, and At 6K, outer layer plating was deposited on the non-plated surface as well as the plated surface. Thereafter, chemical conversion treatment properties and coating corrosion resistance were evaluated in the same manner as in Example 1.

The results are shown in Table 6.

[Brief explanation of the drawing]

The drawing is an explanatory view showing a steel strip electroplating device. 1... Uncoiler - 2 Alkaline electrolytic degreasing tank 6... Washing tank 4... Pickling tank 5... Washing tank
6... Denki Menki Line 6A-6K... Denki Metsuki Cell 7, 8... Washing tank 9... Dryer 10
・・・Rikoi Gite-7-1 Agent Patent Attorney Yoshi Nagai
)

Claims (1)

[Claims] (1) When electroplating a desired Zn-Fe alloy on one surface of a copper strip, a Zn-Fe alloy is also applied to the other surface of the copper strip on the entry side of the plating line. 'A protective film is formed by plating in the air, and then the other surface is passed through a plating solution in a non-energized state to preferentially dissolve the Zn in the protective film. A method for producing a Zn-Fe alloy electroplated steel sheet, characterized in that the coating on the other surface is of p61J. (2) In the plating line in which the METSUKI CEL for the anti-corrosion layer and the layer for improving paint film adhesion are sequentially arranged, one side of the copper strip is coated with the METSUKI CEL for the anti-corrosion layer and the adhesion improving layer for the paint film. A Zn-Fe alloy electroplating film is formed on the other side of the copper strip, and the other side of the copper strip is protected by ZnFe alloy electroplating in a corrosion-protection layer Metsukicell when the above-mentioned one side is plated for the anti-corrosion layer. A film is formed 7, and then the Zn component in the protective film on the other surface is preferentially dissolved by passing through each of the downstream metxcells in a non-energized state, thereby dissolving Fe on the other surface. A method for producing a Zn--Fe alloy' air-plated steel sheet, characterized by forming a rich coating film adhesion-improving layer. (6) In the plating line in which the METSUKI CEL for the anti-corrosion layer and the layer for improving paint film adhesion are sequentially arranged, one side of the copper strip is made to pass through the METSU KEL in sequence to form the anti-corrosion layer and the layer for improving paint film adhesion. 7. n-Fe alloy electroplating film is formed, and on the other side of the copper strip, Zn-Fe alloy electroplating is performed on a part of the corrosion protection layer metsuki cell when plating the corrosion protection layer on the above one side. After that, the protective film on the other surface is dissolved by passing it through the Metsuki Cell for the corrosion protection layer on the downstream side in a non-energized state, and then Fc-rich Zn is passed through the Metsuki Cell for the coating film adhesion improving layer. A method for manufacturing a Zn, -Fe alloy electroplated steel sheet, characterized by applying -Fe alloy electroplating.