JPH0247270A - Surface treated steel sheet having excellent secondary adhesive property of coated film and production thereof - Google Patents

Abstract

PURPOSE:To produce the surface treated steel sheet having the excellent secondary adhesive property of a coated film by forming a galvanized layer on the surface of the steel sheet and successively forming a ferrous plating layer and molybdenum oxide layer of specific thicknesses further thereon. CONSTITUTION:The galvanizing layer or zinc alloy plating layer or composite zinc alloy plating layer is formed as a 1st layer on the surface of the steel sheet and the ferrous plating layer is formed as the 2nd layer on the 1st layer to 0.01-5.0mu, more preferably 0.1-1.0mu. This steel sheet is treated with a soln. contg. >=1 kinds among molybdenic acid ions, tungstenic acid ions and vanadic acid ions to stick >=1 kinds of molybdenium oxide or hydroxide, tungsten oxide or hydroxide and vanadium oxide or hydroxide thereto at 0.1-20mg/m<2>, more preferably 0.5-10mg/m<2> in total in terms of Mo, W, and V. The surface treated steel sheet having the excellent secondary adhesive property of the coated film is obtd. in this way without impairing the chemical conversion treatability of the steel sheet.

Description

Detailed Description of the Invention <Industrial Application Field> The present invention significantly improves the secondary adhesion of coatings on highly corrosion-resistant surface-treated steel sheets, especially zinc or zinc-based surface-treated steel sheets, and also provides excellent continuous welding. The present invention relates to a surface-treated steel sheet with improved properties and a method for manufacturing the same.

<Prior Art> Galvanized steel sheets and zinc-based composite/alloy coated steel sheets have recently begun to be used as anti-rust surface treated steel sheets for automobiles. Here, galvanized steel sheets include electrogalvanized steel sheets and hot-dip galvanized steel sheets, and zinc-based composite/alloy coated steel sheets (hereinafter referred to as zinc-based composite coated steel sheets) include Ni, All or Fe in the zinc layer. etc. from a few% to 30%
It is believed that the corrosion resistance is several to several times better than that of an unpainted or painted state at the same amount of plating.

On the other hand, improvements have been made to coating systems. Conventionally, anionic electrodeposition coatings were used as the undercoat electrodeposition coating, but in recent years cationic electrodeposition coatings, which have better corrosion resistance, have come into use. The three-coat material, which is made by applying a cationic electrodeposition coating (undercoating) to a zinc or zinc-based composite plated steel sheet, followed by an intermediate coating and a top coating, has excellent corrosion resistance as an outer panel of an automobile body. It was found that the secondary adhesion of the coating film was inferior to that of the three-coat material in which mold electrodeposition coating was applied with an intermediate coat and a top coat. The secondary adhesion of a paint film is the adhesion after the paint film has been degraded by some method.
There is a method of immersing for 0 days, immediately after pulling up (within 5 minutes), making goblets on the surface of each of the three coats, and immediately peeling off cellophane tape to judge the secondary adhesion. If the secondary adhesion of the paint film is poor, corrosion will progress from the parts with poor adhesion, causing blistering and rusting of the paint film, so improvement is necessary.

Note that cationic electrodeposition coatings are dense coatings with lower water permeability than anionic coatings, and therefore exhibit excellent corrosion resistance in corrosion tests such as salt water spray tests. One of the reasons is thought to be that when water passes through the paint film and reaches the plated surface, the water cannot escape, causing corrosion to progress under the paint film. In other words, since the zinc or zinc-based composite plating layer is rich in zinc, the water that has penetrated under the coating reacts with the zinc to produce corrosion products such as zinc hydroxide, as well as hydroxide ions, making it alkaline. , the phosphate film dissolves. This is thought to be a major cause of paint film blistering and deterioration of paint film adhesion.

In the secondary adhesion test of the paint film, phosphate crystals are present in the peeling layer of the paint film on both the plated surface and the peeled paint surface, so the layer that is peeling off is the phosphate film. It was revealed by electron microscopy observation and X-ray microanalyzer analysis that it was a layer. The phosphate film formed on the surface of zinc or zinc-based composite towels is called hopeite.
[Zn, (PO4)2.4H20] is the main component, -
1. What is formed on the surface of the steel plate is phosphophy
llite [Zn2Fe (PO4) , 4H,O
Analysis by X-ray diffraction revealed that l was the main component. Experimental results have shown that the secondary adhesion of the coating film is the best on the steel plate surface.

Based on the above findings, it is possible to create a high-quality phosphate film by applying iron-based plating on zinc or zinc-based composite plating.
It has been found that sphophyllite can be formed. Here, the thickness of iron-based plating is 0.0
The thickness is required to be 1 μm or more, and if it is less than 0.01 μm, most of the iron-based plating layer will be dissolved during the phosphate treatment, so that sufficient phosphophyllite cannot be formed.
Therefore, it is effective if the iron-based plating thickness is 0.901 μm, and the effect reaches saturation when the iron-based plating thickness exceeds 5.0 μm.
．． It is preferable to set it to 0 μm.

Such iron-based plating is electroplated with an iron-based plating solution containing ferrous sulfate as a main component, and a target thickness can be easily obtained by changing the amount of electricity. However, there are many network-like cracks in the iron-based topping layer, and in these cracks, the underlying zinc or zinc-based composite topping is partially exposed. Therefore, in the severe secondary adhesion test of paint film, defective areas (
Moisture that enters through cracks) reacts with zinc to produce corrosion products such as zinc hydroxide, and hydroxide ions are also produced and become alkaline, which dissolves the phosphate film and deteriorates the adhesion of the paint film. .

<Problems to be Solved by the Invention> Japanese Patent Publication No. 60-37880 discloses a method of applying chromate treatment as a method to solve such problems, but this method not only solves cracks in iron-based plating, but also
If a chromate film is formed on the surface of iron-based plating, the passivity of the chromate film is too strong, which may reduce phosphate treatment properties, and may also be regulated from a pollution standpoint. was there.

The present invention utilizes the ability to form a good phosphate treatment film on the iron-based plating surface of zinc or zinc-based plated steel sheets as described above, and provides a surface-treated steel sheet with excellent secondary adhesion of the coating film, and the production thereof. The purpose is to provide a method.

Means for Solving the Problems> In order to achieve the above object, according to the present invention, a steel sheet has a zinc plating layer, a zinc alloy plating layer or a zinc composite plating layer as a first layer on the surface of the steel sheet, A second layer is placed on top of the plating layer.
It has an iron-based plating layer with a thickness of 0.01 to 5.0 μm as a layer, and on the iron-based plating layer, molybdenum oxide or hydroxide, tungsten oxide or hydroxide, vanadium oxide one or more of the compounds or hydroxides,
A total of 0.1 to 20 vag/ in OlW and V conversion values
Provided is a surface-treated steel sheet with excellent secondary adhesion of a coating film, which is characterized by adhering to a coating film of m2.

Further, according to the present invention, the surface of the galvanized steel sheet, zinc-based alloy-plated steel sheet, or zinc-based composite plated steel sheet has a thickness of 0.
．． After applying iron-based plating of 01 to 5.0 μm, 1f of molybdate ions, tungstate ions, and vanadate ions! There is provided a method for manufacturing a surface-treated steel sheet with excellent secondary adhesion of the coating film, which is characterized by treating with a solution containing the above.

The present invention will be explained in more detail below.

The surface-treated steel sheet of the present invention has three layers on its surface.

The first layer on the surface of the steel sheet is galvanized, zinc-based alloy plating, or zinc-based composite plating, and has an iron-based plating layer as a second layer on the first layer.

The zinc-based alloy plating layer includes Zn-N15Zn-Fe%Zn-Co, Zn-Cr, Z
Examples include n-Mn%Zn-5n alloy plating, and examples of the zinc-based composite plating layer include Aj! 203.5i
ft, TiO2, ZrO2, Nb2O5, Ta2O,,
Examples include composite plating in which one or more fine particles such as SiC are contained in a Zn or Zn-based alloy plating layer.

Examples of the iron-based plating layer include Fe, Fe-P%Fe-Zn, and the like, and the Fe content in these plating layers is preferably 60 wt% or more. In addition, as for the elements contained in the iron-based plating layer, in addition to Zn%P, one or more elements such as Ni%C01Cr may be present in a small amount.

The thickness of the iron-based plating layer is preferably 0.01 to 5 μm from the viewpoint of phosphate treatment properties, as described above.

A layer of one or more types of oxides and/or hydroxides of molybdenum, tungsten, and vanadium is formed on the second layer made of the iron-based rice plating layer. Here, the term "above the second layer" includes the network cracks existing in the second layer. The amount of adhesion of this third layer is MO
0.1 to 20 mg/l in total in terms of lW and V
n'' is desirable; if it is less than 0 or 1 mg/m', the above effects cannot be expected, and if it exceeds 20 mg/m2, the phosphate treatment properties will deteriorate, which is not preferable.

Furthermore, the amount of the third layer deposited and the thickness of the second iron-based plating layer have a contradictory relationship. That is, the second
The thicker the layer, the smaller the amount of third layer deposited.
On the other hand, if the thickness of the second layer becomes thinner, it is necessary to increase the amount of the third layer deposited. The thickness of the second layer and the amount of adhesion of the third layer are 0.1 to 1.04 m and 0.0 m, respectively. 5~10B/
m2 is more preferred.

Next, a method for manufacturing a surface-treated steel sheet according to the present invention will be explained.

A coating of 0.01 to 5.0 μm is applied to the surface of a galvanized steel sheet, zinc-based alloy-plated steel sheet, or zinc-based composite plated steel sheet by a conventional method.
After applying iron-based plating to a thickness of A plated steel plate or a zinc-based composite plated steel plate is immersed or the steel plate is sprayed with the solution.

Note that the method for treating the iron-based plating surface with the solution is not limited to the above.

The amount of the third layer formed here is 0.1 to 20 mg/m2 in total in terms of Mo, W, and V values.

Through the above treatment, molybdenum, tungsten, and vanadium oxides or hydroxides are less reactive than chromic acid, so they are selectively applied to the network-like cracks that inevitably occur in the iron-based plating layer. It reacts and makes exposed zinc plating, zinc-based alloy plating, or zinc-based composite overlaying layer inert, and inhibits corrosion of zinc from corrosive media such as moisture that enters. That is, since it is difficult to form a strong passive state on the surface of the iron-based plating layer itself, the excellent phosphate treatment properties of the iron-based plating are not impaired.

<Example> The present invention will be specifically explained below based on Examples.

The following Zn-based plated steel plate was used as a test material.

(1) Electrolytic Zn-plated steel sheet (hereinafter referred to as EG) second coating amount 3037m2 (2) Zn-Ni alloy plated steel sheet (hereinafter referred to as Zn-Ni) second coating amount 3037m2, Ni content 1
2wt% (3) Zn-Fe alloy coated steel sheet (hereinafter referred to as Zn-Fe): Area weight 3037m2, Fe content
15wt% (4) Zn-Co-AJZ 203 composite plated steel sheet (hereinafter referred to as Zn-Co-Aft2o3):
Fabric weight: 30 g/m', CO content: 2 wt%, Aft 203 content: 0.5 wt% (5) Alloyed hot-dip Zn-plated steel sheet (hereinafter referred to as GA):
Fabric weight: 45 g/ra2, Fe content: 12
wt% Each of the above-mentioned plated steel sheets was subjected to iron-based polishing under the following conditions.

(1) Fe plating conditions Ferrous sulfate 2501g/It Sodium sulfate 100g/u Bath temperature 60°C Current density 50 A/dm2 (2) Fe-
P plating conditions: Ferrous sulfate 250 g/fL Sodium sulfate 100 g/II.

Sodium hypophosphite o, 2g7Il bath temperature
60℃ Current density 50 A/dm2(3)F
e-Zn plating conditions ferrous sulfate 100-300 g/fl zinc sulfate 10-200 g/II.

Sodium sulfate 50g/fL bath temperature
After iron plating at 50° C. and current density of 100 A/dm2, it was washed with water and a layer of molybdenum, tungsten and vanadium oxides and/or hydroxides was formed under the following conditions.

An additive bath containing a total of 5 to 150 g/u of one or more of sodium molybdate (as Mob4'-), sodium tungstate (as wo4''), and sodium vanadate (as v03-), with a bath temperature of 45°C. ,1
Soaked for ~10 seconds.

Under the above conditions, in the invention example, the thickness of the second layer was 0.01.0
．． 1.1 and 5 μm, and the amount of third layer deposited was 0.1.1 each.
．． As a comparative example, the thickness of the second layer was 0.001 and 10 μm, respectively.
The following conditions (1
) with phosphate treatment and 3-coat painting, (
A secondary adhesion test of the coating film was conducted as described in 2).

(1) Phosphate treatment and painting conditions Assuming the process of manufacturing an automobile body, chemical conversion and painting treatments were performed in the following order.

■Zinc phosphate chemical conversion treatment (manufactured by Nippon Parkerizing ■P)
B3020 treatment liquid used) ■Cationic electrodeposition coating (Nippon Paint ■ Power Top U-100 paint used, 250V, film thickness 20 μm) ■Intermediate coating (Kansai Paint ■ using Amilac Chipping Sealer N3, film thickness 35 ~ 40μm) ■Top coat (Kansai Paint ■Neoamilac BO)
(O2 used, film thickness 35-40 μm) (2) Secondary adhesion test method The test piece after 3 coats was immersed in pure water at 40°C for 10 days, and immediately after pulling it out, cut 100 2 mm squares with a cutter knife. Brat, use Sellotape immediately! I did IJ'm. The evaluation was based on the residual rate of the coating film as described below.

◎ Residual rate = 81-100% ○ Residual rate: 60-80% △ Residual rate: 40-59% × Residual rate: 39% or less In addition, the state of film formation after phosphate chemical treatment was observed, and the following Phosphate treatability was determined based on standards.

◎ Film is formed uniformly ○ Film is formed almost uniformly △ There are uneven areas of film formation
wt%) and then treated with molybdate ions (Zn-N i / Fe -P
/M o ), but similar results were obtained for the following.

In addition, the double frame in the table indicates an invention example.

EG/Fe-P/W.

Zn-Fe/Fe-P/Mo 50wt zero + W 30
wtk + V 20wtJZn-Co-AJZ 20
．． /Fe-P/Mo 70*t96+ W 30wto
4. GA/Fe-P/V Furthermore, the same results were obtained when Fe-Zn (Fe content 90 wt%) was used instead of Fe-P in the above.

Table 2 shows Fe-Zn plating on Zn-Fe (Fe content 6
0wt%) and then treated with molybdate ions, tungstate ions, and vanadate ions (Zn-Fe/Fe-Zn/Mo 50
wt! To + W 30wtX+ V 20wt! ji)
However, similar results were obtained for the following.

EG/Fe-Zn/W, Zn-Ni/Fe-Zn/Mo, Zn-Go-AIL 203/Fe-2n/Mo 70
wt! tG + W 30* to IG^/Fe-Zn/V In the table, the double frames indicate invention examples.

Moreover, the same results were obtained when Fe plating was used instead of Fe-Zn in the above.

In addition, when chromate treatment was performed, the phosphate treatment properties were worse than in the case of the present invention at the same adhesion amount.

Further, as a result of comparing the phosphate treatment properties of the invention examples of each of the above combinations and the invention examples using the same method except that the third layer was made of chromate, the invention examples were better in all cases.

As is clear from Tables 1 and 2, the iron-based plating thickness is 0.
．． 01 μm or more, and the oxides and/or hydroxides of molybdenum, tungsten and vanadium are Mo,
It can be seen that when a total amount of 0.1 to 20 mg/m2 is deposited in terms of W and tungsten, the secondary adhesion of the coating film is significantly improved and good phosphate treatment properties are also exhibited.

<Effects of the Invention> Since the present invention is configured as explained above, Z
It is possible to obtain a surface-treated steel sheet that does not impair the chemical conversion treatment properties of a steel sheet in which iron-based plating is applied on various n-based platings and that has excellent secondary adhesion of a coating film, and a method for producing the same.

In addition, since the surface-treated steel sheet of the present invention has an iron-based plating layer as the second layer, it becomes difficult for the welding tip and Zn to form an alloy, which prevents the tip tip from changing shape and significantly improves continuous weldability. There is also this effect.

Claims (2)

[Claims] (1) A first layer on the surface of the steel sheet is a galvanized layer, a zinc-based alloy plating layer, or a zinc-based composite plating layer, and a second layer with a thickness of 0.01 to 5.0 μm is formed on the plating layer. has an iron-based plating layer, and one or more of molybdenum oxide or hydroxide, tungsten oxide or hydroxide, vanadium oxide or hydroxide is applied on the iron-based plating layer. , Mo, W and ri conversion value total 0.1 ~
A surface-treated steel sheet with excellent secondary adhesion of a coating film, characterized by an adhesion of 20 mg/m^2. (2) The thickness of the surface of galvanized steel sheet, zinc-based alloy-plated steel sheet, or zinc-based composite plated steel sheet is 0.01 to 5.0 μm.
After applying iron-based plating of m, one of molybdate ions, tungstate ions and vanadate ions
Claim 1 characterized in that the treatment is performed with a solution containing at least one species.
A method for producing a surface-treated steel sheet having excellent secondary adhesion of a coating film as described above.