JPH0617282A - Production of surface-rear different electroplated steel sheet - Google Patents

Abstract

PURPOSE:To efficiently manufacture a surface-rear different plated steel sheet of high quality on an industrial scale, at the time of applying the electroplating of different kinds of metal to the surface and rear of a steel sheet, by applying the one side with a noble metal and thereafter applying the opposite side with a base metal. CONSTITUTION:At the time of applying the electroplating of different kinds of metal or alloy to the surface and rear of the steel sheet, at first, the one side of the steel sheet is plated by electrochemically noble metal or alloy plating (such as zinc-nickel alloy plating). Then, the plated face is wetted by spraying pure water, and it is charged to the next plating tank where the opposite side of the steel sheet is plated by electrochemically base metal or alloy plating (such as galvanizing) within the deterioration allowable time of the previously plated noble metal or alloy plated layer. In this way, the surface-rear different plated steel sheet of high quality can efficiently be obtd.

Description

Detailed Description of the Invention

[0001]

[Industrial application] For example, in a rust-preventive steel sheet, the front side and the back side have different use environments, and thus it may be better to plate different types of each. The present invention relates to a method for efficiently manufacturing high quality front and back differently plated steel sheets in response to such requirements.

[0002]

2. Description of the Related Art Generally, rust-proof steel sheets used for automobiles have different required quality characteristics because the corrosive environments on the outer and inner surfaces of the vehicle body are different. For such applications, it is most preferable to perform different types of plating on the front surface and the back surface of the steel sheet to take advantage of the characteristics of each type of plating.

However, when actually producing the very best idea, various problems exist in the manufacturing equipment. For this reason, it has not been possible to produce different kinds of front and back electroplating on an industrial production scale.

[0004]

SUMMARY OF THE INVENTION The present invention is an invention relating to a technique for efficiently producing front and back surface different electroplating using existing equipment. Equipment for continuously electroplating steel strips is generally degreasing, pickling, and then electroplating in a water-soluble plating solution. Various methods are used for this electroplating bath. As for the equipment system of the plating tank,
It can be roughly divided into a method of winding on a large roll and plating on each side, and a method of simultaneously plating on both sides by a horizontal or vertical pass. An object of the present invention is to propose a method for efficiently producing front and back surface different plating on both industrial and industrial scales.

[0005]

Means for Solving the Problems The present invention provides a method for electroplating different kinds of metals or alloys on the front and back surfaces of a steel sheet,
First, electrochemically plating a noble metal or alloy on one side,
Then, a method for producing a front and back different electroplated steel sheet characterized by electrochemically plating a base metal or alloy on the opposite surface in the next plating tank, and preferably a different type of metal on the front and back surfaces of the steel sheet. Alternatively, when electroplating an alloy, first, one side is electrochemically plated with a noble metal or alloy, and then the plating surface is wetted with a non-reactive liquid and placed in the next plating tank, and the other side is plated. A method for producing a front and back different electroplated steel sheet, characterized in that electrochemically base metal or alloy plating is performed within a permissible alteration time of the previously plated noble metal or alloy plating layer.

[0006]

[Function] Generally, in the horizontal or vertical type, different types cannot be plated in the same plating cell.
That is, it is necessary to separate the plurality of cells into the first half and the second half and plate the front and back. However, simply plating the first half and the latter half may cause the metal plated in the first half to react with the plating solution in the latter half cell and deteriorate the characteristics, or the steel plate surface may react in the first half with respect to the latter half plating surface. As a result, there arises a problem that the plating adhesion is poor. The sequential plating type in which a steel plate is wound around a large-diameter roll has the same problem, although to a different degree.

The inventor of the present invention has established the conditions for producing the front and back surface dissimilar plating on an actual electroplating line. That is, in any type of plating equipment, the metal or alloy to be plated first is more electrically noble than the metal or alloy to be plated later. When an electrochemically base metal is plated first, the plating solution for plating later is likely to undergo a reaction, resulting in substitutional deposition of the noble metal on the metal surface.

For this reason, in the present invention, the metal to be plated first is an electrochemically noble metal, and it is desirable that the time of contact with the plating solution later is limited to the permissible alteration time of the noble metal plating layer. To be Even if the sequential plating method is used,
When the post-plating, the plating solution soaks in from the edge, or even when it is wrapped around a roll, the plating solution does not intrude. Therefore, good quality cannot be obtained unless the precious metal is electrochemically plated.

Further, in order to obtain good quality, it is preferable to keep wet with a non-reactive liquid, for example, pure water, so that the previously plated surface is not dried in the sequential plating equipment. When the previously plated metal surface dries, it may have a pattern in appearance and the developed oxide film may interfere with the normal development of the conversion coating. Further, as described above, the time required for the post-plating is determined by the resistance of the pre-plating metal (alloy) to the post-plating solution. That is, the change of the pre-plated layer by the post-plating solution is set within the quality standard of the pre-plated layer. Specifically, it may be determined as an operation standard for each plating facility, each plating specification, and each plating solution condition.

[0010]

【Example】

Example 1 Using a sequential plating type electroplating facility, zinc was plated on the front surface and zinc-nickel alloy plating on the back surface in a sulfate solution. As a comparative example, first, zinc plating was performed first, and then zinc-nickel alloy plating was performed on the opposite surface. In this plating order, nickel was displacement-deposited on the galvanized surface, and the surface was discolored to gray black.

Next, as an example, zinc-nickel alloy plating was performed first. Then, when zinc plating was performed next, a beautiful appearance was obtained. However, when the zinc phosphate treatment was performed, a perfect coating was not obtained, and undeveloped portions of the coating, which are generally referred to as suke, occurred. In addition, as an example, first, zinc-
When nickel alloy plating is performed and then zinc plating is performed, pure water is sprayed on the previously plated surface to prevent it from drying, and zinc phosphate processing is excellent and the back surface is zinc-nickel alloy plating. A certain type of front and back surface heterogeneous plating could be manufactured. When the zinc-nickel surface side of this steel plate was chromated, and a compress was applied with an organic resin and dried, a steel plate having excellent perforation resistance was obtained.

[0012] A facility capable of simultaneously plating the front and back surfaces having a horizontal path. Zinc on the surface in a sulfate solution,
The backside was electroplated with zinc-nickel. As a comparative example, first, the upper surface of the cell was plated with zinc, and the lower surface of the cell was plated with zinc-nickel. It turned black.

Next, as an example, first, the lower surface of the cell in the first half was plated with zinc-nickel alloy, and the upper surface of the latter was plated with zinc. Although the appearance was beautiful, it was revealed that when the immersion time in the plating solution in the latter half of the cell was prolonged, fine cracks developed on the plating surface, and the plating adhesion was deteriorated. It was found that the immersion time and the adhesiveness rapidly deteriorate as the time increases, as shown in the graph of FIG.

Next, plating was performed in the same order as in the above-mentioned embodiment, but the current density was increased to make the immersion time in the latter half within 1.8 minutes. By shortening the dipping time, the plating adhesion was also improved, and it was possible to plate the front and back surface dissimilar plated steel sheet in which the surface was zinc and the back surface was zinc-nickel.

[0015]

Industrial Applicability According to the present invention, it is possible for the first time to perform different kinds of electroplating on the front and back of a steel sheet on an industrial production scale. For this reason, since the use environment differs between the front surface and the back surface, as in the case of rust-preventing steel plates for automobiles, it has become possible to produce rust-preventing steel plates with different optimal plating types on an industrial scale.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the plating solution immersion time and the plating adhesion during post-plating on the pre-plated surface.

Claims (2)

[Claims] 1. When electroplating different kinds of metals or alloys on the front and back surfaces of a steel sheet, one side is first electrochemically plated with a noble metal or alloy, and then the other side is electrochemically plated in the next plating tank. A method for producing a front and back different electroplated steel sheet, which comprises plating a base metal or an alloy. 2. When electroplating different kinds of metals or alloys on the front and back surfaces of a steel sheet, first, one side is electrochemically plated with a noble metal or alloy, and then the plating surface is wetted with a non-reactive liquid. The following table is characterized in that it is charged into the next plating tank in such a state that electrochemically base metal or alloy plating is performed on the opposite surface within the permissible alteration time of the previously plated precious metal or alloy plating layer. Manufacturing method of different surface electroplated steel sheet.