JPH073436A - Zinc alloy plated steel sheet excellent in plating adhesion and corrosion resistance - Google Patents

Abstract

PURPOSE:To improve the adhesion of a vapor plating layer and obtain a plated steel sheet excellent in corrosion resistance by previously applying thin coating at the time of applying plating, by a vapor plating method such as vacuum deposition method, to a steel sheet by using a plating material hitherto considered to be impossible or difficult to use by electroplating or hot-dipping method. CONSTITUTION:This sheet is a precoated vapor-plated steel sheet prepared by applying a thin coating layer consisting of one or >=2 elements among Ni, Fe, Zn, and P and then applying an alloy plating layer consisting of Zn and one or >=2 elements among Mg, Cr, and Al. As compared with the unprecoated vapor-plated steel sheet, plating adhesion is improved (to a degree equal to that of electroplated steel sheet), and as a result, the surface treated steel sheet remarkably excellent in corrosion resistance of plating layer can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to Zn, Mg, Cr and A by vapor phase coating after metal pre-plating.
TECHNICAL FIELD The present invention relates to a zinc alloy-plated steel sheet which is excellent in plating adhesion and excellent in corrosion resistance as compared with a conventional vapor-phase coating material, on a steel sheet plated with an alloy of 1 or 2 or more of 1 above.

[0002]

2. Description of the Related Art In general, vapor phase coating is characterized by the ability to plate metals that are not electrodeposited or difficult to deposit in an aqueous solution. Alloy plating of metals with too different melting points is possible (difficult with conventional melting methods) and high. It is possible to easily plate a melting point metal. Taking advantage of such characteristics, various platings have been carried out and characteristic investigations have been continued. Above all, these vapor-coated steel sheets can be used in various fields such as automobiles, building materials and home appliances. In particular, it is expected that the corrosion resistance of the vapor phase coating will be improved by the new alloy type and alloy composition.

For example, as an anticorrosive steel sheet for automobiles, in a region where rock salt or calcium chloride is sprayed in the winter, a light weighted and highly corrosion-resistant plated steel sheet capable of achieving "5 years without red rust from the outer surface and 10 years without holes" Development is desired. Although this development goal has been issued for a long time, data that it has been clearly achieved has not yet been collected. In overseas countries, that is, in the United States and Europe, there is a strong tendency toward thick galvanized steel sheets represented by thick galvanizing (EG).

On the other hand, in Japan, there is a tendency toward thin plating in view of electric cost, workability, welding capacity of automobile manufacturers, etc., and to date, JP-A-56-9386.
JP-A-56-166389, JP-A-60-967
Zn-F as introduced in many publications such as No. 68 publication
e, Zn-Ni, Zn-Mn, Zn-Cr, and other zinc alloy-plated steel sheets, or a patent publication of an organic composite-plated steel sheet in which chromate and an organic resin coating are further applied on the plating layer, and some of them have been developed, Has already been put to practical use. In the field of building materials, Zn, Zn-Al, Al produced by hot dipping
Galvanized steel sheets are widely used, but from the viewpoint of the problem of acid rain and long-term warranty in recent years, the development of galvanized steel sheets having further excellent corrosion resistance is being promoted.

Therefore, the present inventors have studied to develop a plated steel sheet having excellent corrosion resistance by utilizing the characteristics of the vapor phase coating described above, and as a result, the pretreatment (steel sheet → alkali solution) performed by the electroplating method has been conducted. After degreasing → pickling in a sulfuric acid solution) and then drying and vapor-phase coating of the steel sheet in a vacuum such as Zn-Mg alloy plating, the plating adhesion is not perfect, so the corrosion resistance of the plating layer is sufficient. I realized I wasn't pulling out. For example, as shown in Figure 1,
The plating adhesion when performing Zn-Mg alloy plating by the vapor phase coating method using cold-rolled steel sheets that have been subjected to different plating pretreatments is not sufficient when the pretreatments that are performed in the usual electroplating process are performed. It is sufficient, and the removal of dirt such as surface oxides and oils by argon gas sputtering in vacuum is not perfect. Of course, if sputtering is performed for a longer period of time, the adhesion will be improved, but it is a method that is difficult to use in terms of practicality on an industrial scale.

On the other hand, in the case of vapor phase coating, the surface properties of the steel sheet before plating have an effect on the subsequent plating characteristics.
It is necessary to suppress the growth of oxide films on the surface of the steel sheet as much as possible. Therefore, if the steel plate is plated with 0.1 g / m ² or more in advance (for example, ordinary electroplating),
As a result, a plating layer having good adhesion can be obtained. Moreover, the result of having evaluated the corrosion resistance of the plated steel sheet shown in FIG. 1 is shown in FIG. It can be seen that the better the plating adhesion, the better the corrosion resistance.

Next, FIG. 3 shows the relationship between the kind and amount of thin plating carried out before vapor phase coating and the adhesion of Zn-Mg alloy plating plated thereon by the vapor phase coating method. As a plating species for applying a thin plating layer on one side or both sides of a steel sheet, Ni, Fe, Zn, P, Cr,
The plating metal obtained by electroplating such as Sn has the effect of improving the adhesion of the plating layer by vapor-phase coating, although there are some differences. In addition, as the adhesion amount, 0.05
The effect comes out from g / m ² , but 0.1 g / m ² or more is desirable in order to exert the effect more reliably. The present invention is obtained from the above findings.

[0008]

Means for Solving the Problems That is, the gist of the present invention is to apply a thin metal plating on one or both sides of a steel plate,
On top of that, Zn, Mg, Cr, and Al are formed by a vacuum vapor phase method.
The zinc alloy-plated steel sheet excellent in plating adhesion and corrosion resistance, which is obtained by performing alloy plating of one kind or two kinds or more.

[0009]

EXAMPLES Next, the present invention will be explained based on examples. The cold rolled / annealed steel sheet was alkali degreased, pickled with 10% sulfuric acid and then washed with water, and thin plating before vapor phase coating treatment was carried out under the following conditions. The plating was performed under the following conditions while circulating the liquid with a bench pump.

Ni plating ・ NiSO ₄・ 6 H ₂ O 330 g / l ・ Liquid PH = 4 ・ NiCl ₂・ 6 H ₂ O 45 g / l ・ Liquid temperature = 50 ° C ・ H ₃ BO ₄ 35 g / l ・Current density = 10 A / dm ²

Ni-P plating ・ NiCl ₂・ 6H ₂ O 30 g / l ・ Liquid PH = 4.2 ・ NaH ₂ PO ₂・ H ₂ O 10 g / l ・ Liquid temperature = 60 ° C ・ NaC ₂ H ₃ O ₂・3H ₂ O 5 g / l ・ Electroless treatment ・ Na ₃ C ₆ H ₅ O ₇・ 2H ₂ O 15 g / l

[0012] Fe-Zn plating _{· FeSO 4 · 7H 2 O 350~400} g / l · fluid temperature _{= 55 ℃ · ZnSO 4 · 7H} 2 O 15~200 g / l · Current density = 80~150 A / dm ²・ Free−H ₂ SO ₄ 15 g / l

Fe-Ni plating ・ FeSO ₄・ 7H ₂ O 380 g / l ・ Liquid PH = 1.5 ・ NiSO ₄・ 6H ₂ O 75 g / l ・ Liquid temperature = 50 ° C ・ NiCl ₂・ 6H ₂ O 140 g / l ・ Current density = 30 A / dm ²

Fe plating ・ FeSO ₄・ 7H ₂ O 75 g / l ・ Liquid PH = 1.3 ・ FeCl ₂・ 6H ₂ O 140 g / l ・ Liquid temperature = 50 ° C ・ H ₃ BO ₄ 30 g / l ・ Current density = 10 A / dm ²

[0015] Zn-Cr plating _{· ZnSO 4 · 7H 2 O 150} g / l · Cr 2 (SO 4) 3 100 g / l · organic additive 2 g / l · ferr-H 2 SO 4 10 g / l

Sn plating ・ Sn ²⁺ 20 g / l ・ PSA 20 g / l ・ ENSA 2 g / l ・ EN 2 g / l Zn-Mg, Zn by subsequent vapor phase coating
-Al, Zn-Cr alloy plating conditions are as follows.

(A) Zn-Mg plating-Zn-Mg alloy metals of various compositions are prepared in advance,
Single beam (E
Evaporation was performed in B), and coating was performed under the following conditions.・ Used alloy composition ---- Zn-5, 10, 15, 20, 3
5,50wt% Mg-Substrate temperature ---- 150 ° C-Substrate bias ---- 0, -0.5, -1.0, -1.5
KV ・ Deposition time ---- 20 g / m ² aim

(B) Zn-Cr Plating-Zn and Cr metals are placed in different Mo crucibles, and each metal is irradiated with EB for a predetermined time to evaporate the metal. Then, the evaporated metal was processed into a thin-plated steel plate according to the following conditions. -Metal used ---- 99.99% Zn and 99.9% Cr metal-Substrate temperature--150 ° C.-Substrate bias ---- 0, -0.5, -1.0, -1. 5
KV ・ Deposition time ---- 20 g / m ² aim

(C) Zn-Al plating-Zn-Al alloy metals of various compositions are prepared in advance,
Single beam (E
Evaporation was performed in B), and coating was performed under the following conditions.・ Used alloy composition ---- Zn-5, 10, 15, 20, 3
5,50wt% Al ・ Substrate temperature ---- 150 ° C ・ Substrate bias ---- 0, -0.5, -1.0, -1.5
KV ・ Deposition time ---- 20 g / m ² aim

(D) Zn-Mg-Cr plating-Zn-Mg alloy metals of various compositions are prepared in advance.
The Zn-Mg alloy and the Cr metal are placed in separate Mo crucibles, and each metal is irradiated with EB for a predetermined time to evaporate the metal. Then, the evaporated metal was processed into a thin-plated steel plate according to the following conditions.・ Metal used ---- Zn-5, 10, 15, 20 wt% Mg
Alloy and 99.9% Cr metal ・ Substrate temperature ---- 150 ℃ ・ Substrate bias ---- 0, -0.5, -1.0, -1.5
KV ・ Vapor deposition time ---- aiming at 20 g / m ² Thin plating treatment explained above Zn-Mg, Cr, A
Table 1 summarizes the results of evaluation of the characteristics of the 1-alloy plating (corrosion resistance and plating adhesion).

[0021]

[Table 1]

The evaluation conditions and evaluation criteria are as follows. (1) Corrosion resistance ---- Salt spray test (JIS Z2371)
Observe the occurrence of red rust on the plating layer ◎ ---- No red rust occurred after 500 hours of salt spray ○ ---- 〃Red rust occurred ≦ 10% △ ---- 〃Red rust occurred 10-30% ×- --〃 Red rust occurred> 30%

(2) Plating adhesion ---- Taping after 3t bending (t; plate thickness) ◎ ---- The plating layer does not peel at all and the tape does not blacken. No, but the tape turns black △ ---- Plate layer slightly peels off ---- Plate layer peels off entirely

[0024]

As described above, according to the present invention, as compared with the conventional vapor-phase plated steel sheet without pre-plating, the plating adhesion is remarkably improved (equivalent to electroplating), and as a result, the corrosion resistance of the plating layer is remarkably excellent. A surface-treated steel plate was obtained.

[Procedure amendment]

[Submission date] December 27, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Added

[Correction content]

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between each vapor phase plating pretreatment condition and the adhesion of a Zn—Mg alloy plating layer.

FIG. 2 is a diagram showing the relationship between each vapor phase plating pretreatment condition and the corrosion resistance of the Zn—Mg alloy plated layer.

FIG. 3 is a diagram showing the relationship between the type and amount of thin plating to be subjected to vapor phase pretreatment and the adhesion of Zn—Mg alloy plating thereon.

Claims (1)

[Claims] 1. A thin steel plate is plated on one side or both sides of the steel sheet, and Zn and Mg are further deposited thereon by a vacuum vapor phase method.
A zinc alloy-plated steel sheet excellent in plating adhesion and corrosion resistance, which is obtained by applying an alloy plating made of one or more of Cr and Al.