JPS6199691A - Steel sheet electroplated with combined layer - Google Patents

Abstract

PURPOSE:To obtain the titled steel sheet superior in various characteristics such as corrosion resistance, by laminating Zn-Ni alloy plated layer, Zn-Fe alloy plated layer having a suitable Fe content, and Zn-Fe alloy plated layer having a suitable adhered quantity and Fe content in order, on steel sheet. CONSTITUTION:Steel sheet electroplated with combined layer composed of Zn-Ni alloy plated layer as the first layer, Zn-Fe alloy plated layer having 60-90wt% Fe content as the second layer, and Zn-Fe alloy plated layer having 0.1-3g/m<2> adhered quantity and <60% Fe content as the uppermost layer therein, and is superior in bare corrosion resistance, chemical conversion treatability, electrodeposition coating property, water resistant adhesive property and corrosion resistance after coating, press workability, spot weldability, etc. In said sheet, it is preferable to adjust the first layer to 5-50g/m<2> adhered quantity, 8-15% Ni content, the second layer to 1-10g/m<2> adhered quantity, 70-80% Fe content, the uppermost layer to 0.5-2.0g/m<2> adhered quantity, 30-55% Fe content.

Description

[Detailed description of the invention]

[Industrial application field] The present invention relates to a multilayer electroplated steel sheet, and further relates to a multilayer electroplated steel sheet.

[Two-layered electroplated steel sheet with excellent bare corrosion resistance, chemical conversion treatment properties, 11-layer paintability, water-resistant adhesion after painting, corrosion resistance after painting, break-in workability, and weldability. 1. Prior Art 1.FII Recently, zinc-based plated steel sheets have been widely used to combat corrosion of automobile bodies, and in particular, Zn-depressed alloy electroplated steel sheets have been industrially produced. I started to
It has been used as a rust-proof steel plate for automobiles. And the second Zn-Ni alloy electroplating F! Steel plates have superior corrosion resistance when not painted (referred to as bare corrosion resistance) compared to conventional hot-dip galvanizing, electrolytic galvanizing, alloyed hot-dip galvanizing, etc. , C7-/Porous corrosion in areas where paint cannot penetrate, such as the inside of bag structures such as cars and panels (
pcrrolaLion). In addition, scab-like corrosion (scab-like corrosion) on the car's exterior paint film is caused by scratches caused by various causes.
ion), plating the outer surfaces of automobiles, which were previously made of cold-rolled steel sheets, has been considered and partially implemented. Regarding the use of this plated steel sheet, it is required that the plated steel sheet has coating properties equivalent to those of cold-rolled steel sheet, but Zn-Ni alloy electroplated steel sheet, like the zinc-based plated steel sheet, cannot be coated. Properties such as phosphate treatment properties, water-resistant adhesion of coatings, corrosion resistance after coating, and crater properties during cationic electrodeposition coating are inferior to those of cold-rolled steel sheets. In order to improve the properties of this Zn-Ni alloy plated steel sheet after painting, the present inventor applied Fe plating or Fe-Znlk alloy plating with a Zn content of 40 wt% or less on top of the Zn-Ni alloy electroplating. This Zn-Fe/Zn Ni double-layer plated steel sheet was evaluated by water-resistant adhesion after 3-coat coating for automobiles and salt water spray test after electrodeposition coating. The corrosion resistance after coating is superior to that of Zn-Ni alloy plating. However, the inventor of the present invention has conducted various investigations in an attempt to apply the above-described two-layer plated steel sheet having a Zn-Fe alloy plating layer as an upper layer and a Zn-Ni alloy plating layer as a lower layer to automotive applications. However, it was found that there were some shortcomings as explained below. (1) Zn-Fe alloy plating tends to cause unevenness on the plating and surface along the flow of the plating solution during plating. Even after zinc treatment, it remains as a shade of color, and in severe cases, even after electrodeposition painting, it remains as an uneven surface, deteriorating the painted appearance. The unevenness and surface non-uniformity of this Zo-Fe alloy plating is caused by F.
There is a marked tendency to become worse when the e content is about 80 wt% or less. (2) When this double-layer coated steel sheet is subjected to a cycle test of salt spray → wet → drying that simulates an automobile exterior panel, the paint film peels off around the flaw even though the paint film does not blister. This phenomenon is caused by scratches on the paint film, where the underlying plating layer is exposed and there are 7 nodes.
The plating layer under the paint film around this flaw acts as a cathode and the corrosion reaction progresses, producing alkali in the paint film around the flaw, and this alkali strengthens the adhesion between the paint film and the underlying outer plating layer. It's happening in order to degrade it. This phenomenon tends to become significant when the Fe content of the upper layer of the Zn-Fe alloy plating layer is about 80 wt% or more, and therefore, the unevenness of the plating explained in (1) and the m film explained above tend to become significant. It is impossible to eliminate both cathode peeling and cathode peeling by adjusting the Fe content in the upper layer of the Zi-Fe alloy plating layer, and some other method must be used. (3) Furthermore, compared to conventional zinc-based plated steel sheets, this double-layer plated steel sheet has improved crater characteristics when painted with Kanao Den't1, but it tends to be slightly inferior when compared to cold-rolled steel sheets. As the number of external uses of plated steel sheets increases, it is feared that craters will occur more easily than before, and further improvements in crater properties are required. Problem 1 to be Solved by the Invention As explained above, the present invention solves the problem that, although various types of 811i plates have been used as steel plates for automobiles in the past, they are still not sufficient. Based on the numerous findings of the inventor regarding plated steel sheets for automobiles, the present inventor has further developed the I! , As a result of 6N research, corrosion resistance, workability, weldability,
It has excellent properties such as a 31-layer surface and paintability! Make the waste into a 3M structure? ! They developed a scrap electroplated steel sheet. [Means for Solving Problem 1] The feature of the multilayer ITλ-plated steel sheet according to the present invention is that the first layer is a Zn-Ni alloy plating layer on the steel sheet, and
Zn-Fe alloy plating layer containing i160-90wt% as second layer and attached 1): Li is 0.1-3g/-2 and F
The reason is that a Zn Fe alloy plating layer having an e content of less than 60 wt% is provided as the uppermost layer. In addition, when the adhesion amount is 5 to 5 OTi/a'' and the Ni content is 8 to 1
The first layer should be a 5wt% Zn-Ni alloy plating layer, and the Fe content should be 71 with an adhesion of 11 to 10 g/m''.
1 to 80 wt% of Zn-Fe alloy plating 8M is used as the second layer, and F
This can be done by using a Zn-Fe alloy plating layer with an e content of 30-55 wt% as the uppermost layer. The multilayer electroplated steel sheet according to the present invention will be explained in detail below. First, the first layer of the Zn-Ni alloy plating layer, Fe-containing ii
The second layer of Zn-Fe alloy plating layer of 60-90 wt% and the adhesion amount is 0.1-3 g/w' and the Fe content is 60
Each of the uppermost layers of the Zn-FePS alloy plating layer of less than wt% will be described. (1) Regarding the first layer. This Zn-Ni alloy plating layer as the first layer is a layer that exhibits the corrosion resistance of the composite electrolyte and steel plate.The reason why this tIS1 layer is made of a Zn-N1 alloy plating layer is that This is because the corrosion resistance against bare corrosion and pitting corrosion is the best among zinc-based platings when compared in terms of coating weight. This Zn-N is preferable from the viewpoint of
(2) Regarding the second layer, the corrosion resistance can be further improved by incorporating trace amounts of Fe, Co%C, Mo, etc. into the i-based alloy plating layer. A second layer with an Fr content of 6 to 90 is provided on top of the first layer. In addition to improving the perforation corrosion resistance when used for toilet use,
Zn-Fe containing less than 60 wt% of Fe at 3 g/m'
Due to the additive effect of the alloy plating layer with the m3 layer, the crater characteristics during cationic electrodeposition coating and unevenness during phosphate treatment are reduced to t+.
It is effective for qn. First, to explain the perforation corrosion resistance, conventional
Zinc alloy plating layer such as n-Ni type or Zn-Fe type,
Zn-F with Fe content of about 61)wt% or more in the upper layer
If E-based alloy plating is used, the upper layer is considered to be a layer that improves paintability, and the pitting corrosion resistance of this layer should be considered! It had not been done. This means that the Zn content of the upper layer is 40 wt% or less, and the amount of plating is about 4 g/-'', which is the typical coating amount of the lower Zn-Ni alloy plating layer. There are 20
~40g/wb'', so it could not be considered that the upper layer would have an effect on the perforation corrosion resistance. However, the inventors of the present invention Me! Steel plate (adhesion amount 3017m) and Z
Top M (adhesion 1) of n-Fe (80wt%) based alloy plating layer
4g/m2) and Zo-Ni (13wt%) based alloy plating layer under N ('1t2611/II'') Jl/) PaJl, salt water spray n (35℃ x 6H r) + drying. (50°C
3wt%) type alloy plating layer has a thickness of 0.
．． Although pitting corrosion occurred through eight holes, corrosion of only a maximum of 0.5 - spade occurred in the double-layered galvanized steel plate. As is clear from this experiment, the 8 layers of Zn-Fe alloy plating on the Zn-N1 alloy plating layer contribute to improving the pitting corrosion resistance due to the additive effect with the χn-Ni alloy plating layer. I found out that it is. The reason for this is that when the Zn-N: alloy plating layer is corroded, Zo is selectively corroded, and the potential in the sprayed saline solution gradually shifts to a negative direction, eventually becoming more noble than the base steel plate. A so-called potential reversal phenomenon occurs, and as a result, Z
In the case of single-layer plated steel sheets coated with n-Ni alloy, corrosion may progress and if the base steel plate is exposed, corrosion of the base steel plate may be accelerated. In a double-layer plated steel sheet with a Zn-Fe alloy plating layer on top of the Zn-Fe alloy plating layer, the upper Zn-Fe alloy plating layer corrodes first, but the lower Zn-Fe alloy plating layer corrodes. Alloy Meri! When a part of the layer is exposed, the Zn-Ni alloy plating layer becomes more Zn-
Since the Zn--Ni-based alloy plating layer is more base than the Fe-based alloy plating layer, the Zn--Ni-based alloy plating layer corrodes preferentially, so that the corrosion of the Zn--Fe-based alloy plating layer is suppressed. However, the Zn-Ni alloy plating layer becomes a liability as the corrosion progresses, and the potential of the Zn-Fe-based alloy plating layer gradually becomes a culprit, and the corrosion of the Zn-Ni alloy plating layer is suppressed. The Fe-based alloy plating layer is corroded. In this way, in the case of a double-layer plated steel sheet, between the upper layer of the Zn-Fe alloy plating layer and the lower layer of the Zn-NlJA alloy plating layer, the Since the corrosion reaction stagnates in Zn-N, the time it takes for the potential of the plating layer to become the same as that of the steel plate is
The i-based alloy plating layer is longer than that of a single-layer plated steel sheet. Therefore, the upper layer of the Zn-Fe alloy plating layer and the Zn-Ni
The plated steel sheet having the lower layer of the Zn-based alloy plating layer is
It is assumed that the steel plate is protected for a longer period of time by sacrificial anode action than a steel plate with a single Ni-based alloy layer, and as a result, the perforation corrosion resistance is better. As is clear from the above explanation, the upper layer of the Zn-Fe alloy plating layer and the lower layer of the Z and n-Ni alloy plating layer alternately move in potential, that is, the pores are formed by interaction. It improves corrosion resistance and is not just for improving paintability. Therefore, improving the pitting corrosion resistance of the Zn-Fe alloy plating layer is closely related to the Fe content.
When the content is 60wt% or more, Z! 1 - The effect of pitting corrosion resistance is remarkable in places where the potential of the Fe-based alloy plating layer is low, and furthermore, this Zn-Fe-based alloy plating layer has excellent resistance to blistering of the coating film in the salt spray test after painting, It has a remarkable effect on water adhesion, but this is the best! Phoshop layer is preferred for corrosion resistance in phosphate treatment
hylliLe(ZnzFe(P(L)z ・4rho
), and cathode peeling of the coating film does not occur until the Fe content is 90 wt%. Therefore, the Fe content is 60~
It is set to 90wt%. In this way, Zn-F with Fe content of 160-90w1%
12 layers of e-based alloy plating layer and Zn Ni-based alloy plating layer 1
In order to improve the perforation corrosion resistance due to the phase opening effect with the first Im of the layer, it is desirable that the adhesion 17i of this ttS2 layer is 1 to lOg/s', and if the adhesion amount is less than 167 m2, the perforation corrosion resistance will be The improvement effect is small, and if the coating weight exceeds 10 g/metal, this effect will be saturated, and the second layer, which has a high electrodeposition stress, will be excessively large, so the workability of the second layer plating scrap will deteriorate. I come to do it. (3) Regarding the top plating layer. As explained in detail above, a steel sheet having a Zn-Ni alloy plating layer as the first layer and a Zn-Fe (60-90wt%) alloy plating layer as the second layer is used as a rust-preventing steel sheet for automobiles. In this case, there are still problems with uneven appearance during phosphate treatment and crater characteristics during cationic electrodeposition coating.
The uppermost layer of the Zn-Fe alloy plating layer with an Fe content of less than 60 wt% in m'' has an Fe content of 60-90 as described above.
It is provided on the second layer of the Zn-Fe alloy plating layer of wt%, and therefore, the interaction between the top layer and the second layer suppresses the appearance unevenness during phosphate treatment, and furthermore, the cationic electrolyte This improves the crater characteristics during coating. The amount of adhesion of this top layer and the crater during cationic electrodeposition coating
To explain the relationship between characteristics, in general, until now,
In order to prevent the occurrence of craters during cationic electrodeposition coating, it has been considered advantageous to provide a Zn-Fe continuous coating layer with an Fe content of 60 wt% or more on the surface layer. On top of the second layer of the Zn-Fe alloy plating layer having a content of 6 (let% or more), a crater layer is further added as the top layer.
A Zn-Fe alloy plating layer with an Fe content of less than 3160 wt%, which is said to have poor properties, is deposited at a coating weight of 0.1 to 3 g/m'.
Deme! When a layer was applied, phosphate treatment and cationic electrodeposition coating were performed, the unevenness after phosphate treatment was reduced, and as shown in Figure 1, the top layer 11 with plating was
It was found that the number of craters generated was extremely small in the range of 0.1 to 3.0 g/m''. This decrease in crater generation occurred when the coating weight of the top layer was 0.5 to 2.0 g7'+ This is particularly noticeable in the range of ``. In addition, the conditions for electrodeposition coating are voltage 250~.
', 7 The area ratio of the node to the cathode was 25:1, and the voltage was applied in steps after entering the tank. The uppermost plating layer needs to be a Zn-Fe alloy plating with an Fe content of less than 60 wt%, and it is desirable that the Fe content is at least 630 wt% or more. To explain the phenomenon of the top layer, the amount of adhesion, the Fe content, etc., and the effect of the top layer during phosphate treatment, phosphate treatment is a type of electrochemical reaction, and When the surface comes into contact with the phosphating solution, local 7 nodes and local cathodes are formed due to various inhomogeneities on the surface, the sample is dissolved at the local 7 nodes, hydrogen is generated at the local cathode, and phosphate nuclei are formed. is formed,
This nucleus grows to become an lf+ acid salt crystal and covers the surface. In phosphate treatment, it is said that the larger the amount of crystal nuclei generated at the initial stage of the reaction, the more uniform the phosphate crystal will be, and the more uniform the phosphate crystal will be. It becomes uniform and even, and the Z of the top layer
It can be said that the eight n-Fe alloy plating layers caused microscopic potential non-uniformity on the surface. For example, Z with an Fe content of 30 to 55 w1% in the top layer of the Zn-Fe (less than 60 wt%) alloy plating layer.
In the case of an n-Fe alloy plating layer, it is a mixture containing two or more types of Zn-Fe alloy phases such as a, F, δ1, and
Since these different alloy phases naturally have different potentials, a 7-node cathode pair is formed between the crystals of the different alloy phases, and the phosphate film becomes uniform. Also, Zn-Fe (less than 60 wt%) alloy Metsu! When the coating weight of the top layer is as small as 0.1 to 3.0 g/m'', the surface of the second layer is generally not completely covered and the second layer is partially exposed. The difference in potential based on the difference in Fe content between the exposed second layer and the top layer forms a 7-node cathode pair, contributing to uniformity and miniaturization of the phosphate film. The amount of attached yeI on the top layer is 3
, 0g7m' is unfavorable and the interaction with the top layer of m2M is important. Note that during the phosphate treatment, seven local nodes are dissolved, but since the amount of dissolution is usually about 1 g/J, it is thought that a considerable portion of the top layer and a portion of the second layer will be dissolved. The second layer of the Zn-Fe (60-90 wt%) alloy plating layer and the top layer of the Zn-Fe (less than 60 wt%) alloy plating layer both contain Fe, so some of the dissolved Fe ions are is added to the phosphate film and converted to P hophophyllite, and Pl+osphophyllit in the conophosphate film
The higher the ratio of e, the better the corrosion resistance and water resistant adhesion after painting. If the content is too small (less than 30 wt%), Fe ion atoms added to the phosphate crystals will decrease, and the Ph of the phosphate film will decrease.
This is undesirable because it results in a decrease in the ratio of ospho+hyllite. In addition, suppression of crater generation during electrodeposition coating of the top layer
These effects can be achieved by making the phosphate crystals finer as described above. Although phosphate crystals are insulators, there are gaps between the phosphate crystals, and during Ti electrodeposition, current flows through these gaps 1111 (vacancies), generating hydrogen gas and causing paint U (
Fat adhesion occurs, and as the phosphate crystals become finer, the number of these gaps (vacancies) increases, but individual pores (
The area of the gap 1111 (void) decreases, and the area of the gap 1111 (void) decreases as a whole.
The area ratio of hydrogen decreases, the sites of hydrogen generation are dispersed, and the current flowing to each site decreases. Also, is it a crater-producing rock? In A, the generated hydrogen is I
One theory is that due to the flow of the coating FA resin during baking, which is incorporated into the I pattern, the area where hydrogen escapes is not repaired and remains as a crater, and the other is that the temperature around the hydrogen generation site increases due to excessive current.8 (There is a theory that when fat changes its quality and seizes, craters of 1 and 4 (overwritten by repelling fat) are generated around it when fat flows, but whichever of these is correct is correct. As phosphate crystals become finer, the current flowing to each hydrogen generation site decreases, suppressing crater formation!i11
be done. Figure 2 shows the porosity and average crystal diameter of the sample in Figure 1 after phosphate treatment, and Figure 1 shows that the top layer deposition rate at which crater generation is reduced is 0.1 to 3.0 H/m. It can be seen that the porosity decreases and the crystal grains become finer within the range of and F
The e content is different, and methods for changing the Fe content of Zn-Fe alloy plating include changing the ratio of Zn ions and Fe ions in the plating bath, that is, changing the plating bath composition, as well as changing the cathode current density. There is a method of changing the current density, but if this current density control method is used, it becomes possible to plate the MS2 layer and the top layer with a plating bath having the same composition, and the apparatus can be simplified. As an example, ferrous sulfate (FeSO4・7HzO) 3θOg/l
Zinc sulfate (ZnSO, 7H, 0) 25g/l
Ammonium sulfate ((MHI)2SO1) J13g
Using a plating bath with a composition of /l, bath temperature 6 (1'c, bath ρ
11p) 12. Cathode under O condition? The flow density 3 (IA/
If d■2, then fII2Ff! [e] suitable for plating layer
If the Zn-Fe alloy plating layer with a content of 75~(%) can be MN, and the cathode current density is 5A/cla', the Fe-containing frLS' Owt% Zn is suitable for the topmost layer.
- A Fe-based alloy plating layer is obtained. Note that other conventionally known Zn--Fe alloy electroplating methods may be used. [Example 1] An example of a multilayer electroplated steel sheet according to the present invention will be described, and a comparative example will also be described. Example A multilayer electroplated steel sheet according to the present invention shown in Table 1 and a plated steel sheet of a comparative example were produced by an electroplating method.
1) Corrosion resistance test using sampled holes, (2) Uniformity of phosphate treatment film, (3) Crater characteristics during cationic electrodeposition coating, (
4) The one-cand releasability of the coating film and the water resistant adhesion of the (S) coating film were tested, and the results are shown in Table 2. Note that all plated original plates used were aluminum killed cold-rolled lLw4 plates with a thickness of 0.13+m. (]) AI material perforation corrosion resistance test After sealing the end and back surfaces of the as-plated specimen, the following corrosion cycle test was conducted for 30 cycles. Salt water fountain? ! ((35°(x6Hr)-+Drying(50'C
X4Hr) → Humidity fA (50℃X14Hr, relative humidity 95
%)→Salt spray... 1 Day off was kept wet all day and not counted as a cycle. 1 After the test, the specimen was rust removed and the maximum corrosion depth was measured. In addition, 0,8 meal! without plating! i's cold ■
Corrosion penetrated to the back surface of the rolled steel plate after 2o cycles. Evaluation Maximum erosion depth: 0 0.4 m + w or less Δ 0.4 to 0.8 mm The appearance after the phosphate treatment was evaluated in the following three grades. ○: Uniform and no color unevenness Δ: Slight color unevenness along the flow of the metal P8 solution is observed ×: Significant unevenness (3) Crater characteristics during cationic electrodeposition coating Specimen after phosphate treatment A cationic electrodeposition coating was applied to the surface, and the number of crater-shaped defects generated on the surface was measured. The smaller the number of craters generated, the better the crater characteristics. In addition, the voltage of electrodeposition coating is 250V, and the area ratio between 7 nodes and can is 7.
Node: cathode = 25:1, voltage was applied in a step manner after the specimen was placed in the bath. Evaluation Number of craters 0 10 pieces/da” or less Δ 11-100 pieces/d-2×
101 solids/dll” or more (4) Cand peeling resistance of the paint film A specimen coated with 3 coats of immersion phosphate treatment → cationic electrodeposition → intermediate top coat was tested for chipping defects on the paint film using a gravel meter. The following corrosion cycle test was carried out for 30 cycles: Salt water spray n (35°C
・Hr) - Humidity fl (50℃ x 14Hr, relative humidity 9
5%)→Salt spray...[On holidays, it was kept wet all day and not counted as a cycle, 1. After taping, the peeled area of the paint film was measured on the specimen after the test, and the ratio of peeled area to the total area was measured. However, the part where the paint film was peeled off during chipping was excluded from the peeled area of the paint film. Evaluation Peeling area ratio 0 2% or less Δ 2-20% After 10 days of immersion at a temperature of 40° C., 100 pieces of base grains were cut at two-dimensional intervals using a cutter knife, and evaluation was made based on the number of base grains that remained after taping. Evaluation Number of remaining substrates 0 100 pieces △ 99~51111i1×
The following can be seen from Table 2: 50 or less. The multi-layer electroplated steel sheets according to the present invention in Examples 1 to 7 have a Mogami 117) attachment 1), l force (1,1~: (g/+*') 1)
The pH is within 14, and the crater characteristics of (3) are good. Comparative Example 1 without the top layer and Comparative Example 2 with an excessive amount of top layer deposited had poor crater properties during cationic electrodeposition coating. Comparative Example 3, which does not have the ptS2 layer, has poor perforation corrosion resistance of the wire and crater properties during cationic electrodeposition coating. In Comparative Example 4, the second layer having a high Fe content of 95 wt% had poor cathode peeling resistance of the coating film. The single layer Zn N+ alloy plated steel sheet of Comparative Example 5 was poor in wire hole corrosion resistance, crater properties during cationic electrodeposition coating, and water resistant adhesion of the coating film. The porosity of the phosphate in Figure I'12 is calculated by polarizing the steel plate before and after phosphate treatment in the cathode direction at a scanning rate of 2 mV/sec in 5% saline, and by calculating the current at a potential of -201) mV from the natural potential. The value was measured and calculated using the following formula. Porosity (%) = (Current value after phosphate treatment (A/csQl
/(Current value before phosphate treatment (A/c+s)×100 [Effect of the invention 1 As explained above, the multi-layer electroplated steel sheet according to the present invention has the above-mentioned structure. It has excellent wire rod perforation corrosion resistance, phosphate treatment properties, electrodeposition coating properties, corrosion resistance after coating, etc., and is an excellent material for automobiles.
It is one board.

[Brief explanation of drawings]

Figure tjS1 and Figure tB2 are diagrams showing the number of craters and the porosity of phosphate in the uppermost layer of the multilayer electroplated steel sheet according to the present invention. 1 mouth reserved

Claims (4)

[Claims] (1) First layer of Zn-Ni alloy plating layer on steel plate, F
A Zn-Fe alloy plating layer with an e content of 60 to 90 wt% is the second layer, and a Zn-Fe alloy plating layer with a deposition amount of 0.1 to 3 g/m^2 and an Fe content of less than 60 wt% is the second layer. A multilayer electroplated steel sheet characterized by having an upper layer. (2) Ni content is 8 to 1 with adhesion amount of 5 to 50 g/m^2
A multilayer electroplated steel sheet according to claim 1, characterized in that the first layer is a 5wt% Zn-Ni alloy plating layer. (3) Fe content is 70 to 70 with a coating amount of 1 to 10 g/m^2
The multilayer electroplated steel sheet according to claims 1 and 2, characterized in that the second layer is an 80 wt % Zn-Fe alloy based plating layer. (4) Claim 1, characterized in that the uppermost layer is a Zn-Fe alloy plating layer with a coating weight of 0.5 to 2.0 g/m^2 and an Fe content of 30 to 55 wt%. , the multilayer electroplated steel sheet according to items 2 and 3.