JPS59118896A - Plated steel sheet having excellent corrosion resistace after painting and bare corrosion resistance and its production - Google Patents

Abstract

PURPOSE:To provide corrosion resistance after painting and bare corrosion resistance by forming a Zn-Fe plating layer on one surface of a steel sheet and a Zn-Ni plating layer on the other surface. CONSTITUTION:A steel sheet S is introduced into galvanizing device 1 and molten Zn is injected onto one surface by a one-side plating method using a nozzle 13. Said plate is introduced into a heating furnace 2 for alloying thereby forming a Zn-Fe alloy plating layer on the one surface. The steel sheet is then introduced through an air cleaning device 3 and a water quenching device 4 into an electrolytic pickling tank 5 where the steel sheet is pickled. The pickled sheet is introduced through a scrubber 6 into a Zn-Ni alloy electroplating device 7. The non-plated surface is electroplated thereon with the Zn-Ni alloy in said device.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plated steel sheet with excellent post-coating corrosion resistance and bare corrosion resistance, and a method for manufacturing the same.

Conventionally, zinc-
Iron alloy plated steel sheets are widely manufactured.This plated steel sheet is hot-dip galvanized and then subjected to 1-alloy treatment, or galvanized on an electrogalvanizing line and then heat treated to form a zinc-iron alloy plating), or is manufactured by zinc-iron alloy electroplating and has excellent corrosion resistance after painting. Conventionally manufactured galvanized steel sheets of this type are hot-dip galvanized on both sides and then alloyed on one side, or galvanized on both sides by electroplating a zinc-iron alloy on an electrogalvanizing line. - with iron alloy plated surface, after hot-dip galvanizing as described above, alloying treatment on only one side so that one side is zinc-iron alloy side and the other side is galvanized side, and after galvanizing only one side There are three types of plated steel sheets that have been subjected to alloying treatment so that one side is a zinc-iron alloy side and the other side is a non-plated side, but each of these plated steel sheets has the following problems. That is, the non-plated surface of the steel plate has good paint finish and good primary adhesion after painting, but has poor corrosion resistance.

The corrosion resistance after painting is poor, and as mentioned above, the zinc-iron alloy plated surface has excellent corrosion resistance after painting, but it has the disadvantage that it has poor bare corrosion resistance, and furthermore, it has poor corrosion resistance after ViYn coating on a simple galvanized surface. Therefore, among the plated plates with upper u[1], the corrosion resistance of the unpainted side of the steel plate with zinc-iron alloy on both sides is #+j, <, and the corrosion resistance of one side with zinc-iron alloy.
Iron alloy [steel plate with aluminum and the other side is lead plated,
Good pf when partially painting on galvanized surface.
Corrosion-resistant gold cannot be ensured after painting, and steel sheets that have one side of a zinc-iron alloy surface and the other side that is not plated have problems in terms of corrosion resistance. On the outer panels of home appliances, etc., paint is applied uniformly to the outside, but there are many cases where the paint does not go around in some areas, or does not go around at all. Therefore, it cannot be said that any of the above-mentioned conventional plated steel sheets are fully satisfactory as materials for such outer panels.

The present invention was devised in view of the above circumstances, and is a material for exterior panels that has good post-painting corrosion resistance on painted surfaces, as well as good corrosion resistance and appropriate paint adhesion on non-painted surfaces. Another object of the present invention is to provide a plated steel sheet with excellent properties, and another object of the present invention is to provide a method that can stably produce such a plated copper sheet.

The plated steel sheet provided by the present invention is characterized by having a zinc-iron alloy plating layer on one side and a zinc-nickel alloy plating layer on the other side, and forming such a plating coating M on both sides. In addition, it is possible to obtain a plated steel sheet that is particularly satisfactory as a material for outer panels.Among the different types of plating on both sides, the amount of zinc-iron alloy plating on one side is 30 to 12017 m'', of which iron The content rate is between 8 and 20.

This point is no different from the conventional zinc-iron alloy plated surface.On the other hand, the zinc-nickel alloy plated surface on the other side
A suitable range of ViIO to 30 r/m' is p, and
The Ni content in this plating layer is 10 to 15 in terms of corrosion resistance.
It is preferable that the range be regulated within the following range. According to the inventors' confirmation, the zinc-nickel alloy plated surface has extremely superior bare corrosion resistance compared to the zinc-plated surface and the zinc-iron alloy plated surface. Figure 1 tj shows the results of its naked corrosion resistance in comparison with other plated surfaces.
(1) is zinc-nickel alloy plating, (2Hi, zinc plating).

(3) is a zinc-iron alloy plating. The conditions for each plating are as follows.

(1) jTtj lead-niracle alloy plating medium plating solution sulfuric acid! lIj, lead: 200f/nickel sulfate: 300W/sodium sulfate: 6 (lf/lpH: 2.
0 Temperature = 60°0 Medium current density', 10~40 A/dm, ``Plated under these conditions and adjusted the nickel content to 10~15.

(2) Galvanizing [Hot-dip plating] Galvanized iron plate by hot-dip galvanizing method by Sendzimer (NOF method) CGL.

[Electroplating]

■Plating solution Zinc sulfate: 5 (10 fμ Sodium sulfate: 200 t/L Sodium acetate: 50 f/j pH: 4.0 Temperature: 50'0 ■Current density: 20-50 A/drfL' (3) Zinc-
Iron alloy plating [Hot-dip plating] After plating by hot-dip galvanizing method using Sendzimer (NOF method) CGL, the entire plating layer is F by reheating treatment.
E-ZN alloyed, [Electroplating] ■Plating solution Zinc sulfate: 300f/l Furnace 221-11 people: 2onf/L Sodium sulfate: 501μ pTI: 1~2 Temperature: 50°O th current Density: 30-51:) A/dyn" Each plating sample material obtained in this way was
As is clear from the figure, the time required for red rust to appear was investigated using the 4th salt water spray test.

It can be seen that the zinc-nickel alloy plating has superior bare corrosion resistance not only to the zinc-iron alloy plating but also to the zinc plating.

The table below shows the corrosion resistance after painting of the plated surfaces constituting the plated steel sheet of the present invention. The plating conditions for each plated surface are the conditions (1) to (3) above (however, galvanized - For iron alloy plating, method C), which is the same as hot-dip plating), was adopted. Plating f is 3017m for the zinc-iron alloy plated surface and 30y for the zinc-nickel alloy plated surface.
m,! As a comparative example, the galvanized surface f was 3017 m''.The test method was to apply a normal zinc phosphate treatment to each of the above plated surfaces, and then apply an ED of 15 to 20 μm to the surface.
After painting, each of these test materials was examined for corrosion resistance by the same salt spray test as described above, and for blister formation 4000 hours after the test.

As is clear from the above table, the corrosion resistance of the Zn-Fe plated surface is greatly improved after painting, and the occurrence of 'L fc blisters is also suppressed to a small level. On the other hand, the Z-Ni plated surface, which is the other plated surface, is also Zn-Fee.
Not enough corrosion resistance? It turns out that there is a benefit.

As described above, the plated steel sheet of the present invention has one side coated with Zn-Fe which has excellent corrosion resistance after painting.

In addition, since the other surface is composed of a Zn--Ni plated surface which has extremely excellent bare corrosion resistance, it can be said that the inner surface 41+1 is most suitable as a coating material for outer panels where VC coating is difficult to apply.

Next, the manufacturing method of the present invention will be explained. In the present invention,
The above-described plated steel sheet is first galvanized on one side by spraying molten zinc onto one side of the steel sheet, then alloyed on the plated side, and then instant lead-nickel alloy electroplated on the other side. By applying such a method, the above-mentioned plated frog I plate can be stably manufactured. Figure 2 shows the 85 series plating equipment to be used for carrying out the present invention, in which (1) is a hot-dip galvanizing equipment, (2) is an alloying processing furnace, (3) is an air cleaning equipment, and (4) is an air cleaning equipment. Water quench equipment, (5) Ir:j:, electrolytic pickling 4'#L (fi) is a scrubber, (7) t; tZn-N1 alloy electroplating equipment, (8) ij rinse, (9) is a dryer , 01 is a skin pass mill and a tension leveler, (11) a chemical conversion treatment tank, and C1 is a winding machine. In this way, in the continuous processing equipment, the sushi plate (S) is first introduced into the hot-dip galvanizing equipment (1), and molten zinc is injected into the single-sided plating method using the nozzle 01f. , plated. Next, this plated surface is heated in an alloying treatment furnace (2) to form a zinc-iron alloy plating layer on one side. In this alloying treatment, an alloy layer having an Fe content of about 8 to 20 iron is usually obtained. After the j:i,j board (S) was further air cleaned and cooled 7'11, it was pickled in an electrolytic pickling tank (5) to remove the oxide film formed on the non-plated surface number, and then, The armor plate (S), which has been plated on both sides in this way, is coated with zinc and nickel on the plated surface using a plating device. It is wound into a coil after undergoing a chemical conversion treatment.In the present invention, the process of single-sided molten zinc, surface alloying treatment, zinc-nickel alloy on the non-plated surface, and air plating is performed continuously. This makes it possible to stably manufacture the desired plated steel sheet.

In addition, the armor plate of the present invention can be manufactured only by electroplating, that is, by applying zinc-iron alloy plating by electroplating on one side and then applying zinc-nickel alloy plating on the other side. B. It is possible to stably produce a plated steel sheet that is the same as the first method described above.

In addition, in the above manufacturing process, when zinc-nickel alloy to air plating is applied to one side, some Ni is replaced by substitution plating on the already plated zinc-iron plating side.
It is thought that about 3 to 8'97m" will adhere,
This adhered 7'' CNL has the effect of making the phosphate treatment film adhere extremely densely and uniformly before painting, and has the effect of completely improving paint adhesion.

According to the present invention described above, it has excellent corrosion resistance after painting as a material for exterior panels, and has excellent properties such as high bare corrosion resistance and moderate paint adhesion on the back side that is not painted or is difficult to coat. In addition, since such plated steel sheets can be manufactured stably, it can be said that the invention has high utility value in terms of production revenue.

[Brief explanation of the drawing]

Figure 1 shows the test results for the corrosion resistance of the zinc-nickel alloy plated surface, comparing it with the zinc-plated surface and the zinc-nickel alloy plated surface. Serial chain 1. It is an explanatory view showing plating equipment. Special edition ηQ person Invented by Hiki Copper Tube Co., Ltd.
131j Filled soil Iwahara Ma 31 Ma 11 High analysis
Seikai dialect 'j+'! 114: Kichi
Hiromu Hara Child box 1 size - N/1 size, it (g/m size)

Claims (3)

[Claims] (1) One side has zinc-iron alloy plating. It has a zinc-nickel alloy plating layer on the other side and has excellent corrosion resistance and durability after coating! Plated steel plate with excellent corrosion resistance. (2) One side of the silver plate is galvanized by spraying molten zinc onto one side, then the plating is subjected to alloying treatment, and the other side is electroplated with zinc-nickel alloy. A method for manufacturing a plated steel sheet with poor corrosion resistance after painting and bare corrosion resistance. (3) Manufacture of a plated steel sheet with excellent single corrosion resistance and bare corrosion resistance after painting, which is characterized by applying MIL lead-iron alloy electroplating on one side of the steel sheet and then applying zinc-nickel alloy electroplating on the other side. Method.