JPH02104689A - Treating material for zn plating - Google Patents

Abstract

PURPOSE:To produce a composite Zn plated steel sheet having superior press formability and adhesion to coating by forming a composite Zn plating layer contg. a specified acrylamide-based polymer on a steel sheet. CONSTITUTION:When a treated material such as a steel sheet with a Zn plating layer having superior corrosion resistance is produced, a composite Zn plating layer consisting of 0.001-10wt.% (expressed in terms of C) acrylamide-based polymer contg. >=10mol% N-methylol (meth)acrylamide units in polyacrylamide and the balance Zn or Zn alloy is formed as the Zn plating layer. A composite Zn plated steel sheet having superior press formability and also having superior adhesion to coated a film without requiring pretreatment before coating is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a Zn-based plated material in which a Zn-based plating layer made of Zn or a Zn alloy is formed on the surface of a base material.

[Prior Art] Zn-plated materials, which are made by applying Zn-based plating to steel plates, have good corrosion resistance and have been used in a wide range of fields including automobiles, home appliances, and construction materials. However, as technology is rapidly improving these days, even higher corrosion resistance of Zn-plated materials is required. Conventionally, measures have been taken to meet such demands, such as (1) increasing the amount of plating deposited (0) adopting Zn-based alloy plating such as Zn-Ni or Zn-Fe.

[Problems to be Solved by the Invention] However, in the method (a) above, as the amount of plating coating increases, a build-up phenomenon occurs in which the plating layer adheres to the mold during press molding, and ) method, the alloy plating layer is hard, which causes a powdering phenomenon in which the plating layer peels off during press forming, and in the end, both methods (() and (0) impair press formability. There was a problem.

Furthermore, when using plated materials for parts such as automobiles and home appliances, it is common to apply a coating, but Zn
Since the coating film adhesion of the surface coated with the system plating is insufficient, it is necessary to perform a pre-painting treatment using phosphates, chromates, etc., which tends to make the process complicated.

The present invention was developed in view of the above circumstances, and its purpose is to obtain excellent press formability without causing build-up or powdering phenomena during press forming, and to provide a method for pre-painting treatment. An object of the present invention is to provide a Zn-based plated material that can provide excellent paint adhesion without carrying out any steps.

[Means for Solving the Problems] The present invention contains an acrylamide polymer containing 10 mol% or more of N-methylol (meth)acrylamide units in an amount of 0.001 to 101 i% in terms of C content, and the remainder is Zn. Alternatively, the gist is that a Zn-based plating layer made of a Zn alloy is formed on the surface of the base material.

[Function] The present inventors investigated and investigated the cause of the inferior press formability of conventional Zn-plated materials and Zn alloy-plated materials. As a result, the conventional Zn-based plating surface has poor lubricity, which causes build-up, and Zn-N
It has been found that in Zn alloy plating such as i%Zn-Fe, the plating layer is too hard and the hardness is too different from the hardness of the plating material, which causes powdering.

Therefore, we investigated measures to improve the lubricity of Zn plating and the hardness of the Zn-based alloy plating layer, and found that if the plating layer contains an organic polymer, it will have excellent lubricity, and at the same time, the plating layer's hardness will improve. It has been found that the hardness can be set to about HvlOO~200, which is almost the hardness of commonly used plating base materials, and that the press formability of the plated material is improved. On the other hand, as a result of studying paintability, we found that if polar groups are added to the surface of the plating layer, hydrogen bonds will be created between the surface of the plating layer and the paint film due to the action of the polar groups, resulting in excellent paint film adhesion without any pre-painting treatment. The conclusion was that it could be obtained. When a nonionic polyacrylamide polymer or a polyvinyl alcohol polymer was used as the organic polymer, the adhesion of the coating film was not good. Therefore, it has been found that excellent coating film adhesion can be obtained by using an acrylamide-based polymer or a methacrylamide-based polymer in which an acrylamide polymer contains N-methylol (meth)acrylamide. That is, in the present invention, it is believed that the polarity of the methylol groups present in the polymer forms hydrogen bonds between the surface of the plating TK layer and the coating film, thereby improving coating film adhesion.

Figure 1 shows the results of measuring the coating film peeling rate by the Goban Erichsen test (tape peeling test) of the coating material for samples in which the amount of N-methylol acrylamide units in the acrylamide polymer was varied. is Zn
-1% acrylamide polymer plating: 20 get
s2. The coating film was an amino alkyd coating film = 20 μm.

As is clear from Figure 1, if the content of N-methylol (meth)acrylamide units in the acrylamide-based polymer is less than 10%, the content is too small and the adhesion to the coating film is insufficient. The content needs to be 10 mol% or more.

The upper limit of the content is not limited, but even if the content exceeds 70 mol%, no further addition effect can be obtained. Therefore 70
The content is preferably mol % or less.

Next, Figure 2 shows the coating film peeling rate by the Goban Erichsen test of the coating material and the amount of plating peeling after the drawbead test of the coating material for samples prepared with various acrylamide polymer contents in the plating layer. The measurement results are shown (plating film thickness: 40 g/m'').

As is clear from Figure 2, when the content of acrylamide-based polymer in the plating layer is less than 0.001% by weight, there is no improvement effect on either press formability or paintability; %, powdering tends to occur and press formability is impaired.

In addition, from the viewpoint of improving corrosion resistance, Nt is added to the plating layer.

One or two selected from the group of Fe, Co, Cr, and Mn
It is also possible to use Zn-based alloy plating to which 1f1 or more is added. In that case, the amount of the above elements added is preferably 3 to 20% by weight.

If the coating weight is less than 1 g/m'', it is difficult to sufficiently cover the surface of the substrate.
Even if the coating amount exceeds 1, no further effect can be obtained in terms of press formability and paintability, so the coating amount is 1.
˜40 gets” is preferable.

Next, the plating base material used in the present invention is steel plate, A
It can be applied to any material that can be plated, including I plates and Cu plates. In addition, Zn plating, Zn-based alloy electroplating, or, for example, 7-1
Multi-layer plating using alloyed hot-dip Zn plating such as 5 wt% Fe-Zn alloy hot-dip Zn-plated steel sheet as a base material and applying the plating layer according to the present invention on the surface of the plating layer of these plating materials It is also possible to form layers.

Although the plating method in the present invention is not particularly limited, for example, prior to plating, the plating substrate is subjected to surface purification treatments such as degreasing and pickling, and then Zn ions ( In the case of alloy plating, the plating substrate can be electrolyzed by immersing it in an electroplating solution consisting of an aqueous solution containing metal ions (containing metal ions used as an alloy material) and N-methylol (meth)acrylamide polymer. In addition, when using an electroplating bath, the (meth)acrylamide type polymer in the plating bath is 0.1 to 100%
If the content is adjusted so as to contain g/It, it becomes easy to stably form a plated layer having the desired composition.

The plating layer of the present invention may be formed as a single layer on a plating base material, but the case where another plating layer is formed below or above the plating layer as a base is excluded. isn't it.

Examples will be described below, but the present invention is not limited to the following examples, and it is within the technical scope of the present invention to appropriately change the design in accordance with the spirit described above and below.

[Example] A paddy sample was prepared by electroplating a cold-rolled steel sheet that had been pretreated by degreasing and pickling. As a plating bath, Zn
A plating bath and a Zn alloy plating bath to which an acrylamide polymer was added were used, and a plating bath to which no polymer was added was also used for comparative materials. The adhesion weight of the Nata sample was 20 g/m''.

Press moldability and paintability of the prepared samples were measured.

Press formability was evaluated by the amount of plating peeled off after the drawbead test.

Regarding paintability, an amino alkyd paint was applied to a plated steel plate to a thickness of about 20 μm, and evaluated by the rate of paint film peeling according to the Erichsen test. The results are shown in Table 1.

In Table 1, the marks O9Δ and X in the evaluation columns for press formability and paintability have the following meanings, respectively.

Press formability: O: Amount of plating peeled off 1Illt 0.5 g/m" or less Δ:
n O, 5 to 1.0 g/m2X:
n 1.0 g 7 m" or more paintability; ○: Paint film peeling rate 5% or less Δ: 〃 5-30% X: )l 3 o% or more 1st
As is clear from the results shown in Table 1, the Zn-based plated material according to the present invention exhibits excellent performance in both press formability and paintability.

The Zn-based plated material according to the present invention has excellent paintability as described above even without pre-painting treatment such as phosphate treatment, but even if pre-painting treatment is performed, the paintability will not be adversely affected. It is not something that will affect you.

The following experiment was conducted in which the plating layer of the present invention was formed as a second layer on a conventional Zn or Zn alloy plating layer.

After applying various Zn-based (Zn or Zn alloy) plating to cold-rolled steel sheets that had been degreased and pickled, electroplating was performed using a Zn plating bath containing an acrylamide-based polymer to create plating samples. The amount of plating deposited was 20 g/m2 for the lower layer and 5 g/m' for the upper layer (however, the amount of plating deposited on the upper layer in Comparative Example 9 was 0.5 g/s2), and the paintability was examined in the same manner as in Example 1. As a result, the results shown in Table 2 were obtained.

In carrying out Zn-based electroplating according to Example 1 of the previous IL Yu,
Electroplating was carried out while varying the acrylamide polymer content in the plating material and the amount of N-methylolacrylamide units in the polymer. Regarding the obtained samples, the degree of occurrence of plating unevenness was visually observed and the current efficiency was examined, and the results shown in Table 3 were obtained.

[Effects of the Invention] Since the present invention is configured as described above, when performing press molding, excellent press moldability can be obtained without causing build-up phenomenon or bactering phenomenon, and it is also possible to perform pre-painting treatment. It is possible to provide a Zn-based plated material that provides excellent paint adhesion even without it.

[Brief explanation of drawings]

Figure 1 shows the coating film peeling rate measured by the Goban Erichsen test on painted materials coated with a Zn-based plating layer containing an acrylamide polymer, and the N in the acrylamide polymer.
- Experimental diagram showing the relationship with the amount of methylol acrylamide units, Figure 2 shows the Zn containing acrylamide polymer.
The relationship between the paint film peeling rate by the Goban Erichsen test on the coated material with the Zn-based plating layer and the acrylamide-based polymer content in the plating layer, and the relationship after the drawbead test on the plated material with the Zn-based plating layer. It is an experimental diagram showing the relationship between the amount of plating peeled off and the acrylamide polymer content in the plating layer.

Claims (1)

[Claims] A Zn-based plating layer containing 0.001 to 10% by weight of an acrylamide-based polymer containing 10 mol% or more of N-methylol (meth)acrylamide units in terms of C amount, and the remainder being Zn or Zn alloy is on the base material surface. A Zn-based plated material characterized by being formed into.