JPH0288800A - Zinc electroplated steel sheet having excellent corrosion resistance - Google Patents

Abstract

PURPOSE:To produce the title zinc electroplated steel sheet having excellent corrosion resistance by electroplating a steel sheet with the zinc having a specified content of silicone oil in specified thickness, uniformly dispersing, and depositing the silicone oil. CONSTITUTION:A plating layer contg. 0.1-20wt.% of the emulsion-type silicone oil expressed by the formula, the balance zinc, and inevitable impurities is formed on the surfaces of a steel sheet at 5-100g/m<2> per surface, and the silicone oil is dispersed and deposited in the plating layer. Meanwhile, one kind among 2-80wt.% iron, 2-25wt.% Ni, 0.1-5wt.% Co, and 15-65wt.% Mn or >=2 kinds of components among iron, Ni, Co, and Mn are incorporated by 2-80wt.% into the plating layer, as required. By this method, a zinc electroplated steel sheet having excellent corrosion resistance is obtained, and a beautifully finished coated surface is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a zinc-based electroplated steel sheet having excellent corrosion resistance and having a dispersed galvanized layer or a dispersed zinc alloy plated layer on its surface.

[Conventional technology]

In order to further improve the corrosion resistance of zinc-based electroplated steel sheets, S is added to the zinc-based plating layer made of zinc or zinc alloy.
02. In recent years, many attempts have been made to improve the corrosion resistance of plating layers by dispersing oxide particles such as TiO□ and Alx(1+).

For example, in Japanese Patent Application Laid-open No. 146-146-228, there are
15wt. zinc-based plating layer having on at least one surface thereof a zinc-based plating layer in which silica particles are dispersed in an amount of
A silica composite electroplated steel sheet is disclosed (hereinafter referred to as “
Prior Art 1). Prior Art 1 states that the zinc-silica composite electroplated steel sheet exhibits about 1.5 to 3 times the corrosion resistance of a conventional pure galvanized steel sheet.

JP-A No. 61-143,597 discloses that 0.13 to 1
．． 8wt. A zinc-silica composite electroplated steel sheet is disclosed (hereinafter referred to as "Prior Art 2") having a zinc-based plating layer on at least one surface thereof having a zinc-based plating layer in which silica particles are dispersed in an amount of %. Prior Art 2 discloses that the above-mentioned zinc-silica composite electroplated mesh sheet exhibits corrosion resistance about 4 to 8 times that of conventional zinc electroplated steel sheet, and furthermore, if the surface of the plating layer is treated with a silane coupling agent, It is stated that the corrosion resistance is about 20 times higher than that of conventional zinc electroplated steel sheets.

Japanese Patent Application Laid-open No. 141,898/1989 includes Sing,
A zinc alloy plating layer made of zinc-nickel, zinc iron or zinc-cobalt, in which one or more types of oxide particles such as Ti (hZnJ, NbJa+ TaJa, AZJ:+, etc.) are dispersed, on at least one surface thereof. with zinc-
An oxide composite electroplated steel sheet is disclosed (hereinafter referred to as “
Prior Art 3). In Prior Art 3, among the above-mentioned zinc alloy plating layers, Zn10g, χNi-10w
A zinc-oxide composite electroplated steel sheet having a zinc alloy plating layer consisting of Zn-13wt, χSiO□ has the highest corrosion resistance, and its corrosion resistance is higher than that of a conventional zinc alloy electroplated steel sheet having a zinc alloy plating layer consisting of Zn-13wt, χNi. about 2
It is stated that it exhibits twice the corrosion resistance.

[Problem to be solved by the invention]

As disclosed in Prior Art 1 to 3 above, the corrosion resistance of zinc-based electroplated steel sheets is further improved by dispersing various metal oxide particles in the zinc-based plating layer made of zinc or zinc alloy. can be done.

However, as described in Prior Art 1 to 3, it is not easy to uniformly disperse and eutectoid metal oxide particles in a zinc-based plating layer. The reason is,
This is because metal oxide particles are negatively charged in a zinc electroplating bath, so they tend to be difficult to deposit on the surface of a steel sheet that serves as a cathode during electroplating. For this purpose, prior art 1
As described in , only a few -t. % of metal oxide particles dispersed in the plating layer.
A zinc electroplating bath containing metal oxide particles at a high concentration of g/l must be used. However, the high concentration of metal oxide particles in the zinc electroplating bath will cause the stability of the zinc electroplating bath to deteriorate, resulting in agglomeration and precipitation of metal oxide particles, which will reduce the stability of the zinc electroplating bath. deteriorate. Also, during zinc electroplating, the electrical resistance of the zinc electroplating bath becomes unnecessarily high, which deteriorates the current efficiency of zinc electroplating and increases the power consumption for zinc electroplating.

Furthermore, in the dispersed galvanized layers formed by Prior Art 1 to 3, the eutectoid state of the metal oxide and its dispersion are non-uniform, and the metal oxide has the effect of keeping corrosive ions away. Because it is not coated, its corrosion resistance is unstable. Therefore, in Prior Art 1 to 3, in order to ensure the performance of the formed dispersed galvanized layer, it is necessary to estimate safety and eutectoid a larger amount of metal oxide. As a result, weldability and chemical conversion treatment properties, which are evaluated by continuous spot welding (the number of spots that can be continuously spot welded with one set of electrodes without damaging the electrodes) during spot welding, deteriorate. A dispersed galvanized layer with the expected quality cannot be obtained.

Therefore, the object of the present invention is to provide a zinc-based plating layer in which particles are uniformly dispersed, its corrosion resistance is stably high, and its weldability and chemical conversion treatability as evaluated by continuous dot performance do not deteriorate. An object of the present invention is to provide a zinc-based electroplated steel sheet having excellent corrosion resistance on at least one surface thereof.

[Means to solve the problem]

From the above-mentioned viewpoint, the present inventors have conducted extensive research in order to efficiently and stably improve the corrosion resistance of the zinc-based plating layer in which particles are dispersed, and to develop a zinc-based electroplated steel sheet with excellent corrosion resistance. As a result, when a small amount of silicone oil is dispersed and precipitated in a zinc-based plating layer, the corrosion resistance of the plating layer can be stably and significantly improved without impairing the weldability and chemical conversion treatability evaluated by continuous dot performance. We found that it can be improved.

The present invention has been made based on the above-mentioned findings, and provides a zinc-based electroplated steel sheet having a predetermined coating amount of a galvanized layer in which particles are dispersed on at least one surface thereof. The plating layer consists of silicone oil: 0.1 to 20 wt, χ, and the remainder: zinc and inevitable impurities, and the amount of adhesion is:
The plating layer should have a weight of 5 to 100 g/rrr per side of the steel plate, and if necessary, the plating layer should have a weight of 2 to 80 wt. %
of iron, 2-25 iit. % nickel, 0.1-5-1
．． χ cobalt, 15-65wt. % manganese or at least two components of iron, nickel, cobalt and manganese in total of 2 to 3 Qi
+t. It is characterized by further containing it in an amount of %.

This is a compound represented by the molecular formula of silicone oil used in this invention. Note that cH3 can also be partially substituted with other functional groups.

The reason why the corrosion resistance of a zinc-based plating layer is stably and significantly improved by dispersing and precipitating silicone oil in the zinc-based plating layer is not clear, but it is presumed as follows.

(a) Corrosion of steel plates is often caused by ions in various aqueous solutions. When silicone oil is dispersed and precipitated in the zinc-based plating layer, the strong water repellency of the silicone oil repels the aqueous solution and prevents contact between zinc and ions. Therefore, the corrosion rate is significantly slowed down.

(b) Silicone oil particles do not simply exist in the plating layer, but exist as zinc, methyl groups, and silicon bonded together with strong affinity. Therefore, even in a corrosive environment, the plating layer forms a chemically stable film of corrosion products on its surface, which acts as an excellent barrier against subsequent corrosion, further improving the corrosion resistance of the plating layer. do.

The content of silicone oil in the plating layer is 0.1 to 2.
0wt. It should be within the range of %. If the content of silicone oil is less than 0.1 wt, χ, high corrosion resistance cannot be stably obtained in the plating layer. On the other hand, when the content of silicone oil exceeds 20 wt, χ, the workability of the plating layer deteriorates significantly.

The particle size of the silicone oil to be dispersed and eutectoided in the plating layer is preferably 500 nm or less. When the particle size exceeds 500 nm, it becomes difficult to uniformly disperse the silicone oil in the plating layer, making it impossible to impart stable high corrosion resistance to the plating layer.

Silicone oil is an emulsion type or self-emulsifying type of silicone oil that is commercially available as an antifoaming agent, fiber treatment agent, mold release agent, or water repellent because it is easy to handle when added to the plating bath. It is preferable to use

In this invention, silicone oil is uniformly dispersed,
The amount of the eutectoid zinc-based plating layer deposited on the surface of the steel sheet should be 5 to 100 g/nf per side of the steel sheet. If the coating amount of the plating layer is less than 5 g/rrf,
The improvement in corrosion resistance of the plating layer was insufficient;
If it exceeds g/rrr, the workability of the plating layer will deteriorate and it will become uneconomical.

In this invention, the metal component of the plating layer in which the above-mentioned silicone oil is uniformly dispersed and eutectoid contains only zinc, and if necessary, iron, nickel,
At least one component of cobalt and manganese may be included.

The structure of the dispersed plating layer of various metal components will be described below.

(a) Dispersion plating layer containing zinc as a metal component: Silicone oil 20.1 to 20 wt, χ, and the remainder: zinc and inevitable impurities.

(b) Dispersion plating layer containing zinc-iron alloy as the metal component: Silicone oil; 0.1-20wt, χ iron
: 2 to 80 t, χ, and the remainder: zinc and inevitable impurities.

Including iron in the plating layer in addition to zinc has the effect of improving the paintability of the plating layer and the corrosion resistance after painting. If the iron content in the plating layer is less than 2-L, χ, the above-mentioned effects are insufficient, while if it exceeds 80 wt, χ, both the workability and corrosion resistance of the plating layer deteriorate. Therefore, when iron is included in the plating layer in addition to zinc, the iron content is 2 to 80 wt. It should be within the range of %.

(C) Dispersion plating layer containing zinc-nickel alloy as the metal component: Silicone oil = 0.1 to 20 tons, χ nickel
: 2 to 25 wt, χ, and the remainder: zinc and inevitable impurities.

Including nickel in the plating layer in addition to zinc has the effect of further improving the corrosion resistance of the plating layer. If the nickel content in the plating layer is less than 2-t, χ, the above-mentioned effects are insufficient; on the other hand, if it exceeds 25iit, χ,
The workability of the plating layer deteriorates, and it becomes uneconomical because it contains a large amount of expensive nickel. Therefore, when nickel is included in the plating layer in addition to zinc, the nickel content should be 2 to 25 wt. It should be within the range of %.

(d) Dispersion plating layer containing zinc-cobalt alloy as a metal component: silicone oil 20.1 to 20 wt, χ.

Cobalt: 0.1-5 wt, χ Remaining: zinc and inevitable impurities.

Incorporating cobalt in addition to zinc in the plating layer has the effect of further improving the corrosion resistance of the plating layer. If the cobalt content in the plating layer is less than Q, 1 wt, χ, the above-mentioned effects will be insufficient, while if it exceeds 5 wt, X, the corrosion resistance of the plating layer will deteriorate. Therefore, when cobalt is contained in the plating layer in addition to zinc, the cobalt content is 0.1 to 5 wt. It should be within the range of %.

(e) Dispersion plating layer containing zinc-manganese alloy as a metal component: Silicone oil = 0.1 to 2 Qivt, χ.

Manganese: 15-65i+t, χ, and the remainder, zinc and inevitable impurities.

Including manganese in the plating layer in addition to zinc has the effect of further improving the corrosion resistance of the plating layer. If the manganese content in the plating layer is less than 15wt, χ, the above-mentioned effects are insufficient, while if it exceeds 65wt, χ,
Electrolytic efficiency during plating decreases and becomes uneconomical. Therefore, when the plating layer contains manganese in addition to zinc, the manganese content should be 15 to 65 wt. It should be within the range of %.

(f) Dispersion plating layer containing zinc-iron, nickel, cobalt, and manganese composite alloy as metal components: silicone oil 20, 1 to 20 gt, at least two components of chi iron, nickel, cobalt, and manganese: 2 to 3Qwt, χ.

Containing at least two components of iron, nickel, cobalt, and manganese in the plating layer in addition to zinc has the effect of further improving the corrosion resistance of the plating layer. If the content of at least two components of iron, nickel, cobalt, and manganese is less than 2 wt. Therefore, when at least two of iron, nickel, cobalt, and manganese are contained in addition to zinc, the content should be 2 to 8 Qvrt. It should be within the range of %.

In this invention, the means for dispersing the silicone oil to be deposited in the dispersion plating layer in the plating bath is as follows:
For example, silicone oil may be made hydrophilic with an emulsifier to form an emulsion, or some of its methyl groups may be substituted with hydrophilic functional groups to form a self-emulsifying emulsion, which may be added to the plating bath.

The concentration of silicone oil in the plating bath is 0.05 to 2.
0 g/N is sufficient, and the concentration is much lower than when adding conventional oxide particles.

Therefore, the stability of the plating bath and the plating current efficiency are not deteriorated.

In this invention, the steel sheet on which a zinc-based plating layer in which silicone oil is uniformly dispersed and eutectoid is to be formed is subjected to a surface treatment such as a cold-rolled steel sheet or a pickled hot-rolled steel sheet. It may be a conventional galvanized steel sheet, or a conventional zinc alloy-plated steel sheet having a plating layer containing at least one component of iron, nickel, cobalt, and manganese in addition to zinc. When using a galvanized steel sheet or a zinc alloy coated steel sheet, the amount of plating layer deposited is not particularly specified, but from the viewpoint of manufacturing cost and workability of the plating layer, the amount of plating layer deposited is 10% per side. It is preferably within the range of ~60 g/nf.

Further, when using a conventional zinc alloy plated steel sheet, the amounts of iron, nickel, cobalt and manganese to be contained in the plating layer in addition to zinc are not particularly specified. However, considering the corrosion resistance and workability of the plating layer, if iron is included in addition to zinc, the iron content should be 2 to 35%.
wt. %, when nickel is contained in addition to zinc, the content of nickel is 2 to 2 Qwt. %, when cobalt is included in addition to zinc, the cobalt content is 0.1 to 5 wt. %, and if manganese is included in addition to zinc, the manganese content is between 15 and 65 iit. It is preferably within the range of %. Further, when at least two components of iron, nickel, cobalt and manganese are contained in addition to zinc, the content thereof is 2 to 35 wt. It is preferably within the range of %.

FIG. 1 shows the amount of each element of zinc, silicon, oxygen, carbon, and iron in the plating layer in which silicone oil is uniformly dispersed in the zinc-based electroplated steel sheet of the present invention using a known ion microanalyzer. This is a graph showing representative results analyzed by. In FIG. 1, the vertical axis indicates the secondary ion intensity (count number) of each element generated by sputtering of the plating layer. The horizontal axis shows the sputtering time (minutes) of the plating layer, and the secondary ion strength of each element corresponding to the depth is determined by the amount of each element at the depth of the plating layer where sputtering is performed. Compatible. The sputtering time corresponds to the depth of the plating layer to which sputtering is being performed.

Silicone oil consists of Si, C, O (and H), so as shown in Figure 1, the silicone oil, that is, St, C, and O, exists uniformly dispersed in the plating layer. I understand that. In addition, in FIG. 1, Fe indicates the iron content of the base steel sheet, and Zn indicates the zinc content in the plating layer.

Next, the present invention will be explained with reference to examples.

[Example 1] A conventional sulfuric acid electroplating bath for electroplating zinc or zinc alloys was used as a basic bath, and a silicone oil emulsion was added to the basic bath at a silicone oil concentration of 0.05 to 20 g/l. Add it so that it becomes, and
A zinc electroplating bath was prepared by adjusting the pH within the range of 1-6. Using the zinc electroplating bath prepared in this way, the silicone oil is uniformly spread on the surface of the steel plate by zinc electroplating, using the zinc plate as the anode and the untreated steel plate as the cathode. In this way, electroplated steel sheets Nα2, 3, 6, 8.11 and 13 of the present invention were obtained.

For comparison, a zinc-based plating layer without silicone oil dispersed was similarly formed using the basic bath described above.
Thus, the comparison zinc electroplated steel sheet Nα1.4,5,
7, 9.10 and 12 were obtained.

Table 1 shows the composition and coating amount of the zinc-based plating layer of these zinc electroplated steel sheets No. 1 to 13. In addition, in a continuous 500-hour salt spray test conducted on these zinc electroplated steel sheets No. 1 to 13,
Table 1 also shows the salt water spray time until red rust appears as bare corrosion resistance.

19 As shown in Table 1, the bare corrosion resistance of ZnSin without silicone oil dispersed and comparison zinc electroplated steel sheet Nαl with an alloy plating layer is 40 hours, whereas that of ZnSin with silicone oil dispersed is 40 hours. Its content is 0.
4wt. The bare corrosion resistance of the present invention zinc electroplated steel sheet No. 2 having a Zn plating layer of 70 hours is 70 hours, and
The silicone oil content is 2.5wt. The bare corrosion resistance of the zinc electroplated steel sheet No. 3 of the present invention having a Zn plating layer of 400 hours was 400 hours.

The bare corrosion resistance of comparison zinc electroplated steel sheet No. 4, which has a Zn-Fe alloy plating layer in which silicone oil is not dispersed, is the same for 40 hours, Zn-Fe-5402
Comparative zinc electroplated steel sheet No. with alloy plating layer,
5 has a bare corrosion resistance of 60 hours, whereas the content of silicone oil dispersed therein is 2.1 wt. %Z
The bare corrosion resistance of the zinc electroplated steel sheet No. 6 of the present invention having an n-Fe alloy plating layer was 500 hours.

Comparative zinc electroplated steel sheet No. 7, which has a Zn-Ni alloy plating layer in which silicone oil is not dispersed, has a naked corrosion resistance of 400 hours, whereas the content in which silicone oil is dispersed is 2.5 hours. 3wt. %Zn-N
Zinc electroplated steel sheet No. of the present invention having an i-alloy plating layer
, 8 had a bare corrosion resistance of 700 hours or more.

The naked corrosion resistance of the comparative zinc electroplated steel sheet NCL9 with the Zn-Co alloy plating layer in which no silicone oil is dispersed is the same for 80 hours (the comparison zinc electroplated steel sheet Nα10 with the Zn-Co-3iO The bare corrosion resistance of Zn with silicone oil dispersed in it is 160 hours, while that of Zn with a content of 3.4 iit.% in which silicone oil is dispersed
The bare corrosion resistance of the present invention zinc electroplated steel sheet N011 having a -Co alloy plating layer was 600 hours.

Comparative zinc electroplated steel sheet No. 12 having a Zn-Mn alloy plating layer in which silicone oil is not dispersed
The bare corrosion resistance of the silicone oil is 400 hours, while the silicone oil content is 1.9wt. %Zn
The bare corrosion resistance of the present invention zinc electroplated steel sheet N013 having a -Mn alloy plating layer was 700 hours or more.

[Example 2] Using a zinc electroplating bath prepared as in Example I, using a zinc plate as an anode and a conventional galvanized steel plate or a zinc alloy coated steel plate as a cathode, zinc electroplating was performed. , a zinc-based plating layer in which silicone oil is uniformly dispersed is formed as an upper layer on the surface of the steel sheet, and thus zinc electroplated steel sheet No. of the present invention is obtained.
14 to 23 were obtained.

Table 2 shows the composition and plating amount of the zinc-based plating layer of the zinc electroplated steel sheets No. 014 to 23 of the present invention, as well as the types of surface-treated steel sheets used. Also,
In a continuous 500-hour salt spray test conducted on these zinc electroplated steel sheets Nα14 to 23 of the present invention,
The time required for red rust to stop is also shown in Table 2 as bare corrosion resistance.

As shown in Table 2, the present invention zinc electroplated steel sheet No.
In Nos. 14 to 23, on the surface of a surface-treated steel sheet such as a galvanized steel sheet or a zinc alloy-plated steel sheet,
As the upper layer is formed of a zinc-based plating layer in which silicone oil is uniformly dispersed and eutectoid, both have high bare corrosion resistance.

Example 3 Comparative zinc electroplated steel sheet N shown in Example 1.

1. A peel test was conducted using a drawbead tester on each of the zinc-based plating layers of the present invention zinc electroplated steel sheets No. 3, conventional zinc electroplated steel sheets, and conventional hot-dip galvanized steel sheets. In the above-mentioned test, the pressing force of the male die of the drawbead tester applied to the plating layer of the steel plate was 500 kg, and the speed at which the steel plate was pulled out was 200+++ m/min.

Further, after performing a peel test using a drawbead tester, the plating layer was further subjected to a peel test using cellophane tape. The results of these tests are shown in Table 3.

As shown in Table 3, in the zinc electroplated steel sheet of the present invention, the amount of peeling of the plating layer in the peeling test using a drawbead tester was smaller than that of any of the conventional steel sheets and comparative steel sheets, and the peeling amount of the plating layer was smaller than that of the conventional steel sheet and comparative steel sheet. Peeling of the plating layer in the peel test did not occur as in conventional zinc electroplated steel sheets, and workability was as good as in conventional zinc electroplated steel sheets.

C. Effects of the Invention] As described above, according to the present invention, the following industrially valuable effects are brought about.

(a) Silicone oil is uniformly dispersed and eutectoid in the zinc-based plating layer, and silicon, carbon, and oxygen are uniformly present in such a dispersed plating layer, so that the dispersion plating layer is uniform. Due to the water repellency and water repellency of silicone oil, the corrosion resistance is extremely stable and excellent compared to conventional galvanized steel sheets.

(b) The concentration of silicone oil in the plating bath is 0.
．． 05-20g/I! This is sufficient, and the concentration is much lower than in the case of dispersing conventional metal oxide particles. Therefore, the stability of the plating bath and the current efficiency are not deteriorated, and the weldability and chemical conversion treatment properties evaluated by continuous dot performance are good.

(C) The silicone oil in the galvanized layer is uniformly dispersed and there is no segregation. Therefore, the smoothness of the plated surface is excellent, and when the plated surface is painted, a beautiful coated surface with a good finish can be obtained, and workability is also good.

[Brief explanation of drawings]

FIG. 1 is a graph showing the results of analyzing the depthwise distribution of each element of zinc, silicon, oxygen, carbon, and iron in the coating layer of the zinc-based electroplated steel sheet of the present invention using an ion microanalyzer. be.

Claims (1)

[Scope of Claims] 1. A zinc-based electroplated steel sheet having, on at least one surface thereof, a galvanized layer having a predetermined adhesion amount in which particles are dispersed, the plating layer comprising: silicone oil: 0.1 ~20wt. %, and the rest consists of zinc and unavoidable impurities, and the amount of adhesion is 5 to 100 g/m^2 per side of the steel plate, and has excellent corrosion resistance. Plated steel plate. 2. The plating layer is made of the following group: Iron: 2 to 80 wt. %, nickel: 2-25wt. %, cobalt: 0.1-5wt. %, and manganese: 15-65wt. %. The zinc-based electroplated steel sheet with excellent corrosion resistance according to claim 1, further comprising any one component selected from the following. 3. The plating layer contains at least two components selected from the group consisting of iron, nickel, cobalt, and manganese.
2-80wt. in total. % of the zinc-based electroplated steel sheet with excellent corrosion resistance according to claim 1. 4. Any of claims 1 to 3, wherein the steel plate is a steel plate without surface treatment, a galvanized steel plate, or a zinc alloy plated steel plate containing at least one of iron, nickel, cobalt, and manganese. A zinc-based electroplated steel sheet having excellent corrosion resistance as described in item 1 above.