JPH02205699A - Zn composite plated material - Google Patents

Abstract

PURPOSE:To obtain a Zn composite plated material having superior press formability and adhesion to coating by successively forming a Zn plating layer contg. water insoluble fine particles and a Zn plating layer contg. a specified amt. of a specified polymer on the surface of a metallic base material. CONSTITUTION:A Zn or Zn alloy plating layer contg. water insoluble fine particles is formed as a first layer on the surface of a metallic base material. About 0.01-30wt.% oxide, metal or resin particles of about 0.1-5mum particle size are suitable for use as the fine particles. The desirable coating weight of the first layer is about >=2g/m<2>. A Zn or Zn alloy plating layer contg. an acrylamide polymer and/or a methacrylamide polymer contg. 10-200mol% M- methylol groups by 0.001-10wt.% (expressed in terms of C) is then formed as a second layer on the first layer by about 0.1-10g/m<2> coating weight. The resulting Zn composite plated material causes no buildup or powdering phenomenon during press forming and exhibits superior adhesion to coating without requiring pretreatment.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a coating layer with good adhesion, excellent press formability and corrosion resistance, and excellent coating film adhesion without any pre-painting treatment. The present invention relates to a Zn-based plated material that is processed to obtain properties, and this treated material is useful for outer panels of automobiles, vehicles, household electrical appliances, and the like.

[Prior Art] Zn-plated materials, which are made by applying Zn plating to steel plates, have good corrosion resistance and have been widely used in automobiles, vehicles, household electrical appliances, and construction materials. However, as the level of technology becomes more sophisticated and the demands of users become more stringent, the corrosion resistance of Zn-based wiped materials is also required to be even higher. .

Conventionally, measures have been taken to meet these demands, such as (a) increasing the amount of plating deposited, and (0) changing to 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 increases, a phenomenon in which the plating layer adheres to the mold during press molding (build-up phenomenon) occurs, In addition, in the method (b) above, since the alloy plating layer is hard, the plating layer peels off during press forming (powdering phenomenon). There was a problem that moldability was impaired.

Furthermore, when plated materials are used for parts such as automobiles and household electrical appliances, they are generally coated, but the Zn-based plating surface has insufficient paint film adhesion, so phosphates and It is necessary to carry out pre-painting treatment using chromate or the like, which tends to make the process complicated.

The present invention was made in view of this situation, and
The purpose of this is to create a Zn material that can provide excellent press formability without causing build-up or powdering phenomena during press molding, and that can also provide excellent paint adhesion without pre-painting treatment. The purpose is to provide plating-treated materials.

[Means for Solving the Problems] The structure of the present invention that can solve the above problems is that a Zn or Zn alloy plating layer containing water-insoluble fine particles is formed on the surface of a metal base material, and on top of that a Zn or Zn alloy plating layer containing water-insoluble fine particles. -1 methylol group
o, oo in terms of C amount of acrylamide and/or methacrylamide polymer containing 0 to 200 mol%
The gist is that a Zn or Zn alloy plating layer containing t~10% by weight is formed.

[Function] The present inventors have investigated the cause of the poor press formability of conventional Zn-plated materials and Zn alloy-plated materials, and have obtained the following knowledge. That is, in conventional Zn plating,
Since the plating layer has a soft texture and the plating surface lacks lubricity, it tends to adhere to the mold, causing a build-up phenomenon.Also, with Zn alloy plating such as Zn-Ni and Zn-Fe, Because the plating layer is too hard compared to the material, the surface layer cracks during machining, leading to powdering. Therefore, if the plating layer is given appropriate hardness and lubricity, the build-up phenomenon during machining can be prevented. It is thought that both powdering phenomena can be suppressed.

On the other hand, regarding paintability, in order to obtain excellent paint film adhesion even without pre-painting treatment such as phosphate treatment, it is necessary to increase the affinity between the plating layer and the paint film, and preferably create a chemical bond between the two, such as a hydrogen bond. It is desirable to form a specific bond.

Therefore, from the above-mentioned viewpoint, we conducted intensive research to provide a coating material with excellent press formability and paintability.As a result, we first developed a coating material with Zn or water-insoluble fine particles dispersed therein as a first layer on the surface of the plating base material. If a Zn alloy plated layer is formed and a Zn or Zn alloy plated layer containing N-methylol-modified acrylamide and/or methacrylamide polymer is formed as a second layer thereon, the superiority of the first layer can be improved. It was found that the press formability and the excellent paintability and press formability of the second layer were effectively exhibited, and the press formability and paintability of the entire plating layer were significantly improved.

That is, in the present invention, the first layer is formed by dispersing water-insoluble fine particles in Zn or Zn alloy plating, and exhibits a high hardness of about Hv100 or more due to the dispersion strengthening effect of the fine particles, which causes the build-up phenomenon. In addition to preventing this, the lubricity of the plating layer increases due to the action of the water-insoluble fine particles, and press formability is significantly improved. Since Zn alloys such as Zn-Ni themselves have high hardness, the dispersion strengthening effect of the fine particles is not so pronounced, but rather the lubricity improvement effect of the fine particles takes priority, and press formability is improved without powdering. Improvements will be made.

The water-insoluble fine particles may be of any kind as long as they have a dispersion-strengthening effect and a lubricating effect on the plating layer, for example, 5 in. Tic2゜＾120s
*Oxide such as ZrO2; Carbide such as SiC, Tic; Nitride such as SiN, BN; Sulfide such as Mo52; Graphite; Diamond; Metal powder such as Ni, Cr, stainless steel; SrCrO4, BaCr0.
, inorganic particles such as water-insoluble compounds such as PbCrO4, and organic particles such as phenol resins, epoxy resins, and polyolefin resins. The particle size of these water-insoluble fine particles is not particularly limited, but in order to uniformly disperse in the plating layer and not adversely affect the appearance after coating, the average particle size is 5 μm or less, more preferably 3 μm.
It is best to use one with a diameter of m or less. However, if the particle size becomes too small, it becomes difficult to fully exhibit the dispersion strengthening effect and lubricating effect, so it is desirable to use particles with a diameter of 0.1 μm or more.

It should be noted that the preferred content of the fine particles cannot be uniformly prescribed because it varies depending on the type and particle size of the fine particles, etc.
In order to effectively exhibit the properties expected of the fine particles and the inherent properties of Zn or Zn alloy plating, the content should be selected from the range of 0.01 to 30% by weight, more preferably from 1 to 10% by weight.

The amount of plating deposited on the first plating layer containing the water-insoluble fine particles is not particularly limited, but if a film that is thinner than the size of the fine particles is formed, the fine particles will fall off before the formation of the second plating layer. In order to prevent corrosion, to exist stably, and to ensure excellent corrosion resistance, it is desirable to set the content to 2 g/la" or more.

By the way, Figure 1 shows water-insoluble fine particles (s) in the Zn plating layer.
Figure 2 shows the relationship between the content of iO2) and the amount of plating peeled off, and Figure 2 shows the relationship between the amount of adhesion of the first plating layer and the amount of plating peeled off, and both tests were conducted after the drawbead test. It is determined by the amount of plating peeling,
It is possible to know the basis for setting the above-mentioned preferred particle diameter and preferred wipe adhesion amount.

The plated layer in which insoluble fine particles are dispersed can be obtained from a plating bath containing Zn alone or a mixed plating bath in which water-insoluble fine particles are added to a Zn-based alloy plating bath. The water-insoluble fine particles may be in the form of a colloid, a sol, or a dispersion, and if there is a problem with dispersion stability, it is effective to add a small amount of a surfactant if necessary.

Next, the second plating layer formed on the surface of the first plating layer is made of an acrylamide-based and/or methacrylamide-based polymer containing 10 to 200 mol% of N-methylol groups in terms of C amount. It is made of Zn or Zn alloy containing 0.001 to ton of Zn, and due to the action of the polymer, the plating layer not only exhibits high hardness of about HvlOO~200 but also has excellent lubricity. , it has very good press formability.

Furthermore, the presence of the polar group contained in the polymer provides good affinity between the surface of the plating layer and the coating film, resulting in excellent coating adhesion even without coating pretreatment. Furthermore, the second
If the amount of N-methylol modified in the polymer contained in the plating layer is less than 10 mol%, the absolute amount of polar groups will be insufficient and a satisfactory effect of improving paintability will not be obtained. This is the theoretical limit for N-methylol modification of the group. FIG. 3 shows the results of an investigation into the relationship between the amount of N-methylol modification of the polymer contained in the second layer and the coating removability, and the experimental conditions were as follows.

Plating amount: 1st layer...bow Og/m' 2nd layer...2
g/ra” Polymer content (in second layer): 0.5 Iij amount% Top coat: Melamine-modified alkyd resin paint, 20 μI Test method: Paint film removal rate when tape was removed after the second Erichsen test. As is clear from Figure 3, it can be seen that coating properties can be significantly improved by adjusting the N-methylol modification amount to 10 to 200 mol%. Therefore, it is preferable to select from the range of 10 to 70 mol% or 120 to 200 mol%. Fig. 4 shows the amount blended in the second plating layer. This is a graph showing the relationship between polymer content, coating peeling rate, and plating peeling amount, and the experimental conditions were as follows.

Plating amount: 1st layer...1087m" 2nd layer...
2 g7m” Polymer N-methylol modification amount = 50% top coat
: Melamine-modified alkyd resin paint, 20 μm Test method: Base material Removal rate of coating when tape is removed after Erichsen test Amount of plating removed: Amount of plating removed after drawbead test As is clear from Figure 4 In addition, when the polymer content in the second plating layer is set in the range of 0.001 to 10% by weight in terms of C content, both the film removability and the amount of plating peeled off are significantly improved. The amount of the second plating layer attached is not particularly limited, but it should sufficiently increase the adhesion of the coating to the top coat and sufficiently reflect the performance of the first plating layer (improved press formability due to excellent lubricity). is 0.
1 to 10 g/+”, more preferably 0.1 to 5 g/m
By the way, Fig. 5 is a graph showing the relationship between the adhesion amount of the second plating layer, the coating peeling rate, and the amount of plating removal (first plating layer adhesion amount: 2037 m2, other conditions are shown in Fig. 4). ), and the above trend can also be confirmed from this figure.

Next, the plating base materials used in the present invention include steel, AI
, Cu, and other metals and alloys that can be plated, and the shape may be plate-like, rod-like, tubular, irregularly shaped, etc. Although the plating method is not particularly limited, the most common method is electroplating.

Next, the present invention will be explained in more detail with reference to Examples.
The present invention is of course not limited by the following examples, and any modification and implementation as appropriate within the scope of the above and below-mentioned spirit is within the technical scope of the present invention.

[Example] A cold-rolled steel sheet that had been pretreated by degreasing and pickling was subjected to the following electroplating treatment. That is, first, electroplating was performed using a Zn plating bath or a Zn alloy plating bath containing a predetermined water-soluble fine powder to form a first plating layer.Next, a predetermined N-methylol modification was applied thereto. Electroplating was performed using a Zn plating bath or a Zn alloy plating bath containing an acrylamide polymer to form a second plating layer. The press formability and paintability of each of the plated steel sheets obtained were examined using the methods described below, and the results shown in Table 1 were obtained.

Press formability: A plated steel sheet was subjected to a drawbead test,
The amount of plating peeled off was evaluated.

◎: Plating peeling amount 0.5 g/m' or less 0: n O, 5-0.8 g/m'Δ:
)) Q, 5-1.5g/m'X:
# 1.5g/m' or more Paintability: Directly apply mefmin-modified alkyd resin paint to a galvanized steel plate without pretreatment to a film thickness of approximately 20μm, and after baking, apply the tape according to the Erichsen test on the base. The coating peeling rate was calculated based on the degree of peeling.

◎: Paint film peeling rate 5% or less O: 5-15% △: 15-30% X:　　　)l 3Q% or more From Table 1, it can be considered as follows.

Experiments Nos. 091 to 7 are all examples that satisfy the specified requirements of the present invention, and the effect of improving press formability due to the insoluble fine powder in the first plating layer and the coating due to polyacrylamide-based polymer eutectoid in the second plating layer. The effects of improving moldability and moldability are exhibited additively or synergistically, and very good results are obtained in both moldability and paintability.

On the other hand, Experiment No. 8.9 was a single-layer plating material made of Zn or Zn alloy (no insoluble fine powder was dispersed).
Therefore, both paintability and press moldability are poor. In addition, in Experiment No. 10, the amount of N-methylol modification of the acrylamide polymer was outside the specified range, and in Experiment No. 11, the amount of acrylamide polymer used was insufficient. Both are comparative examples, and the paintability was particularly poor. .

The reference example of Experiment No. 12.13 is included in the examples of the present invention, and the second plating layer has an appropriate structure and has excellent paintability. Since the amount of insoluble fine powder contained is outside the preferred range, press moldability is somewhat poor.

[Effects of the Invention] The present invention is configured as described above, and includes a first plating layer made of Zn or Zn alloy in which water-insoluble fine powder is dispersed, and a Zn layer containing N-methylolacrylamide-based polymer.
Or, due to the combined effect of the second plating layer made of Zn alloy, it has excellent formability and adhesion without build-up phenomenon or bacterling phenomenon in the press forming process, and also has excellent formability and adhesion without pretreatment. Zn exhibiting coating 11i adhesion
We were able to provide plating treated materials.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between the particle size of the insoluble fine powder mixed in the first plating layer and the amount of plating peeled off.
A graph showing the relationship between the amount of plating layer attached and the amount of plating peeled off,
Figure 3 is a graph showing the relationship between the polymer content in the second plating layer, the amount of plating peeled off, and the rate of peeling of the coating. Graph showing the relationship between film peeling rate. Figure 5 is a graph showing the relationship between the adhesion amount of the second plating layer and the coating film peeling rate.

Claims (1)

[Claims] Zn or Zn containing water-insoluble fine particles on the surface of the metal base material
An alloy plating layer is formed, and acrylamide and/or acrylamide containing 10 to 200 mol% of N-methylol groups are formed thereon.
Or the methacrylamide-based polymer is converted into C amount and is 0.
1. A Zn-based plated material, characterized in that a Zn or Zn alloy plating layer containing 0.001 to 10% by weight is formed.