JPH06101065A - Zinc-based electroplated steel sheet with excellent adhesive bondability - Google Patents

Abstract

(57) [Summary] [Constitution] The surface of the plating film is composed of an oxide consisting mainly of zinc oxide (ZnO), and the total thickness of the oxide layer is 10 to 200 Å
2. A zinc-based electroplated steel sheet having an oxide layer in which the molar ratio of oxides other than zinc oxide (oxides such as Fe, Ni, Mn, and Cr) to zinc oxide is less than 0.5. The oxide layer may be zinc oxide only. [Effect] It is a steel sheet that exhibits high adhesive strength and excellent adhesive bondability, and is particularly suitable as a rust-preventing steel sheet used for automobiles, home appliances and the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-based electroplated steel sheet having excellent adhesive bondability, which is used as a material for automobiles, home electric appliances, building materials and the like.

[0002]

2. Description of the Related Art Zinc-plated steel sheets or zinc-based alloy-plated steel sheets have been evaluated for their excellent corrosion resistance and have been widely used in automobiles, home appliances, outdoor equipment, building materials and the like. Further, when it is used as a material for automobiles, higher corrosion resistance is required. Therefore, various alloy-plated steel sheets, resin-coated steel sheets and the like have been developed.

These plated steel sheets and resin-coated steel sheets are incorporated into products through various steps such as working, forming and joining when used, but their spot weldability is not always sufficient, so that they are bonded in the joining step. The application of adhesive bonding, in which a bonding agent is used, is being studied. Compared with welding, this adhesive bonding has the advantages that the product can be made lighter in weight, has excellent rigidity, and that dissimilar materials can be easily bonded together. It is considered that one of the characteristics to be excellent is that the adhesive bondability is excellent.

The zinc-based plated steel sheet is generally manufactured industrially by a hot dip plating method or an electroplating method, but its adhesive bondability is inferior to that of a cold rolled steel sheet which is not plated. In particular, in the plated steel sheet produced by the hot dip plating method, the outermost layer of the plating has impurities such as phosphate, borate, silicate, and heavy metal oxyacid salt, in addition to the oxide, Adhesive bondability is not good.

Regarding the hot-dip galvanized steel sheet, the present inventors firstly found that the thickness of the hot-dip galvanized steel sheet was 10 Å, which consisted of zinc oxide and aluminum oxide whose molar ratio to zinc oxide was 0.5 or less.
The above oxide layer is formed on the surface of the plating film,
We proposed a plated steel sheet with excellent adhesive bondability (Japanese Patent Application No. 4-
No. 167732).

On the other hand, as a zinc-based plated steel sheet produced by the electroplating method, in addition to the electrogalvanized steel sheet whose composition of the plating layer is pure Zn, Zn and Fe, Zn and Ni, Zn and M are used.
There are zinc-based alloy electroplated steel sheets containing n, Zn and Cr, Zn and Co and Mo as the main component, and containing one or more alloy elements to improve various functions such as corrosion resistance. In addition, in order to further improve the corrosion resistance, silica (SiO ₂ ) and alumina (Al ₂ O ₃ ) are added to the plating layer of the above-mentioned plated steel sheet.
It is also possible to include a dispersion-plated steel sheet in which ceramic fine particles such as, an oxide such as titanium oxide (TiO ₂ ) or an organic polymer powder is dispersed.

The surface of such a zinc-based electroplated steel sheet usually has a thickness of about 250 to 400 Å zinc oxide (ZnO).
There is an oxide layer mainly composed of, and as described above, the adhesive bondability is inferior to that of the cold-rolled steel plate, but a study for improving the adhesive bondability of this zinc-based electroplated steel plate has been made. The current situation is that little has been done.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a zinc-based electroplated steel sheet having good corrosion resistance, which is focused on improving adhesive bondability, which is a highly required property of an anticorrosive steel sheet for automobiles. The purpose is to do.

[0009]

[Means for Solving the Problems] There is an oxide layer mainly composed of zinc oxide (ZnO) on the plating surface of a zinc-based electroplated steel sheet, but there is a wide range of adhesion, and various adhesives can be used. However, the adhesiveness is not good. The present inventors, as a result of repeated studies to achieve the above object, the oxide layer present on the plating surface, the molar ratio of the oxide other than zinc oxide to zinc oxide is less than 0.5, and, Overall thickness is 1
It was found that the adhesive bondability can be improved by setting it to 0 to 200Å. The present invention has been made on the basis of the above findings, the gist is, "on the surface of the plating film, consisting of an oxide mainly zinc oxide, the total thickness of the oxide layer is 10 ~ 200 Å, zinc oxide Zinc-based electroplated steel sheet having excellent adhesive bondability, characterized in that an oxide layer having a molar ratio of oxides other than zinc oxide to zinc oxide of less than 0.5 is formed.

The oxide mainly composed of zinc oxide mentioned here includes not only an oxide in which an oxide other than zinc oxide such as Fe and Ni is mixed in zinc oxide, but also an oxide consisting only of zinc oxide.

The zinc-based electroplated steel sheet targeted by the present invention includes electrogalvanized steel sheet plated with pure Zn and Zn.
And Fe, Zn and Ni, Zn and Mn, Zn and Cr, Zn and Co and Mo, and other zinc-based electroalloy-plated steel sheets, and silica (SiO ₂ ) in the plating layers of these steel sheets. , Alumina (Al ₂
It is a dispersion-plated steel sheet in which fine ceramic particles such as O ₃ ), oxides such as titanium oxide (TiO ₂ ) and organic polymer powder are dispersed. The composition of the plating layer may be one that does not change in the thickness direction of the plating layer, that that changes continuously or that that changes stepwise (multi-layer plated steel sheet).

[0012]

The function of the zinc-based electroplated steel sheet of the present invention will be described in detail below.

Generally, the surface of the plating film of a zinc-based electroplated steel sheet is mainly composed of zinc oxide (ZnO) and has a thickness of 2
An oxide layer of about 50 to 400 Å is formed, and the adhesive bondability is not good with any adhesive.

In the zinc-based electroplated steel sheet of the present invention, the oxide layer existing on the surface of the above-mentioned plating film is as thin as 10 to 200 Å. This oxide layer may consist of zinc oxide only.

When the thickness of the oxide layer is more than 200Å, the bonding adhesiveness deteriorates. This is because, when a tensile test is performed on the adhesive joint, cohesive failure of the oxide layer occurs and the joint strength decreases. On the other hand, when the thickness of the oxide layer is less than 10Å, the oxide layer does not cover the entire surface of the plating film, and there is a portion where the metal (surface of the plating film) is exposed. The zinc-based electroplated steel sheet cannot be firmly joined. This is because, as is well known, the adhesive and the metal have poor wettability,
The reason why the metals are bonded together by the adhesive is that they are not bonded directly but via the oxide formed on the surface of the metals.

The oxide layer must be a zinc oxide-based oxide layer in which the molar ratio of oxides other than zinc oxide to zinc oxide is less than 0.5. When the molar ratio is 0.5 or more, for example, when alumina and zinc oxide are present on the surface of the plating film, Al ₂ O ₃ /ZnO≧0.5 and the adhesive bondability deteriorates. Although the reason for this is not clear, it is presumed that the wettability of the surface of alumina is worse than that of zinc oxide, and it is considered that the same applies to oxides other than alumina.

The zinc-based electroplated steel sheet of the present invention can be produced, for example, by the methods (1) and (2) described below, that is, by removing a part of the thick oxide formed on the surface of the plating film. It can be manufactured by a method of reducing the thickness or removing all of it, and then forming an oxide layer containing zinc oxide as a main component on the surface of the plating film.

(1) Cleaning (removal of oxide film) Oxidation that is thick and unevenly formed on the surface of the plating film by treating the plated steel sheet with an alkaline solution (for example, an aqueous solution of NaOH, KOH, etc.) Remove some or all of the objects. They may be removed by mechanical treatment such as grinding, or these methods may be used in combination. After cleaning with these methods, the thickness of oxide remaining is 10-200
If it is Å and the molar ratio of oxides other than zinc oxide to zinc oxide is less than 0.5, then no special treatment is necessary.

(2) Oxide film forming method When most of the old oxide layer originally attached is removed by the treatment of (1) above, the following coating method, reaction method, electrolysis method, heating method, etc. Is used to form an oxide layer mainly containing zinc oxide on the surface of the plating film. These methods may be used in combination.

[Coating Method] Zinc oxide and an oxide other than zinc oxide (alumina, silica, magnesium oxide, titanium oxide, etc.) in the molar ratio specified in the present invention are treated with water, an organic solvent such as alcohol, thinner or the like. A solution such as a colloidal solution or an emulsion solution is used, which is applied to the surface of the plating film and dried as it is. Roll coating method,
Any method such as an immersion method or a spray method may be used.

[Reaction Method] A solution containing phosphate ions, nitrate ions, sulfate ions, halogen ions, chromate ions, etc. is applied to the surface of the plating film, and the metal (Zn, Fe, Ni, Mn, Cr, Co, etc.) to form an “oxide”, and unnecessary ions are washed with water to remove and dried. The application of the solution may be performed by any method such as a roll coater method, a dipping method and a spray method. The solvent of the solution may be water, an organic solvent such as alcohol or thinner, or a mixed solution thereof.

[Electrolysis method] The plated steel sheet is treated with phosphate ions,
Electrolytic treatment is performed in a solution containing nitrate ions, sulfate ions, halogen ions, chromate ions, etc. to form an "oxide" on the plating surface, and the plate is washed with water and dried. The electrolytic treatment may be performed by appropriately using a cathode electrolysis method, an anode electrolysis method, an electrolysis method using an alternating current, or the like.

[Heating Method] In the simplest method, the temperature of the plated steel sheet in the air is lower than the temperature at which the plated coating reacts with the base steel sheet to form an alloy, and "oxide" is formed on the surface of the plated coating. Hold at the temperature indicated. The holding temperature is usually
It is desirable that the temperature be 200 to 350 ° C.

The characteristics required as a steel sheet for automobiles include:
In addition to the above adhesive bondability, there are corrosion resistance, chemical conversion treatment property, press workability, weldability, bake hardenability and the like. Among these required characteristics, regarding the chemical conversion treatability, since the plated steel sheet of the present invention is a steel sheet having an oxide layer formed on the surface, its influence is a concern, but this oxide layer has no chemical conversion treatability. There is no loss. Further, it does not adversely affect other required characteristics.

[0025]

[Example] Zinc-based electroplated steel sheet produced under normal production conditions (electrogalvanized steel sheet, Zn-Ni, Zn-Fe, Zn-Mn,
Zn-Cr and Zn-Co-Mo electroplated steel sheet, electrozinc-alumina, zinc-silica, zinc-titanium oxide and zinc-phenol resin dispersion-plated steel sheet, and Fe-
Zn / Zn multi-layer electroplated steel sheet) surface is treated with NaOH aqueous solution to remove old oxide layer, and then zinc oxide, or zinc oxide and alumina, silica having various molar ratios thereto An oxide layer made of magnesium oxide or iron oxide was formed by applying the above-mentioned coating method. Water was used as the solvent, and coating was carried out by the dipping method. The drying temperature after coating is 120 ° C. The thickness of the oxide layer was adjusted by the concentration of the coating liquid and the squeezing with a roll after the immersion.

The thickness of the oxide layer is measured by photoelectron spectroscopy (XPS) in the case of 100 Å or less, and by secondary ion mass spectrometry (SIMS) in the case of more than 100 Å, and the composition is analyzed by XPS. went. When the layer thickness is measured by SIMS, N ₂ ⁺ is used as the primary ion, the O ⁺ (oxygen ion) intensity is measured, and the depth until the O ⁺ reaches the background level is defined as the thickness of the oxide film. did. Also, X
In the case of PS, the Zn intensity (Z
based on the Auger peak) I _o of NLMM, Zn intensity I _t is I _t = I _o exp metals Zn plating steel sheet oxide layer is present (-t / λsin θ) However, t: thickness of the oxide layer λ: mean free path of Auger electrons θ: take-out angle of photoelectrons.

A plated steel sheet (plate thickness 0.8 mm) having the oxide layer formed on the surface of the plated film by the above treatment is 25 mm wide.
Cut the test piece into a sample and cut it in the longitudinal direction 1 as shown in Fig. 1.
Bend at a right angle at the 50 mm part, apply a commercially available epoxy-based or mastic-based adhesive on one side, then stack plated steel sheets of the same size and heat in an oven heated to 165 ° C.
It was baked and cured for minutes. A spacer was provided and adjusted so that the thickness of the adhesive was 0.15 mm.

Each of these test materials was subjected to a T-type peel test at a repetition number of 5 (n = 5) to determine the adhesive strength. For comparison, a plated steel sheet whose surface has not been cleaned (alkaline treated) as it is manufactured and a steel sheet which has only been subjected to alkali treatment after manufacturing have an oxide layer formed on the surface in the same manner as above. , Was subjected to the test.

The results are shown in Table 1. The table also shows the thickness of the oxide layer formed on the surface of the plating film, the molar ratio of oxides other than zinc oxide to zinc oxide, and the breakdown mode. Interfacial peeling means peeling at the interface between the base steel sheet and the plating film, and cohesive failure means failure at the adhesive portion. The adhesive strength is shown as an average value.

As is clear from these results, the thickness of the oxide layer to be newly formed on the surface of the plating film after cleaning the surface (alkali treatment) and the molar ratio of oxides other than zinc oxide to zinc oxide were determined according to the present invention. Within the range defined by, high adhesive strength is exhibited, interfacial peeling does not occur, and the adhesive bondability of the plating film can be greatly improved.

[0031]

[Table 1 (1)]

[0032]

[Table 1 (2)]

[0033]

[Table 1 (3)]

[0034]

[Table 1 (4)]

[0035]

INDUSTRIAL APPLICABILITY The zinc-based electroplated steel sheet of the present invention has high adhesive strength and is excellent in adhesive bondability, and is particularly suitable as a rust-preventive steel sheet used for automobiles, home electric appliances and the like.

[Brief description of drawings]

FIG. 1 is a diagram (unit: mm) showing the shape of a test piece for a T-type peel test.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Internal reference number FI Technical display location C25D 11/36 C (72) Inventor Tomoaki Usagi 4-533 Kitahama, Chuo-ku, Osaka-shi, Osaka Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] 1. The surface of the plating film is composed of an oxide mainly composed of zinc oxide, and the total thickness of the oxide layer is 10 to 200 Å
And the molar ratio of oxides other than zinc oxide to zinc oxide is
A zinc-based electroplated steel sheet having excellent adhesive bondability, characterized in that an oxide layer having a thickness of less than 0.5 is formed.