JPH02170987A - Zn alloy plating method by vapor deposition - Google Patents

Abstract

PURPOSE:To tightly adhere a Zn alloy plating layer by preplating a metallic material as a base with Zn or Zn alloy by electroplating or hot dip plating and by forming the Zn alloy plating layer by vapor deposition. CONSTITUTION:A metallic material as a base is subjected to alkali degreasing and pickling or reduction with hydrogen and preplated with Zn or Zn alloy by electroplating or hot dip plating. When Zn alloy plating is carried out on the preplated material by vapor deposition, a Zn alloy plating layer can be formed with satisfactory adhesion without requiring special pretreatment. The ideal compsn. of a plating layer is not obtd. by electroplating or hot dip plating because of various restrictions but the compsn. can freely be regulated by plating by vapor deposition. The Zn alloy plating layer can tightly be adhered without requiring troublesome pretreatment and a plated material having high corrosion resistance and not causing pickup phenomenon or powdering phenomenon in a press forming stage is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for producing a Zn alloy vapor-deposited plating material that has good plating adhesion and excellent workability.

The metal materials to which the present invention is applied include various metal materials such as iron, various alloy steels, and aluminum, and their shapes can be plate-like, rod-like, tubular, corrugated, or irregular in L-shaped or H-shaped cross sections. Although various shapes such as rod-like shapes are applicable, this specification mainly describes the most typical steel plate.

[Prior art] Plated materials made by applying Zn-based alloy plating to steel sheets have good corrosion resistance, so they have traditionally been used as outer panels of automobiles, vehicles, household electrical appliances, etc., and as construction materials. It is widely used, and there are three commonly used plating methods: electroplating, hot-dip plating, and vapor deposition plating.

By the way, since these plating materials are processed into a shape according to the intended use by means such as press molding, workability is also considered to be an important required characteristic. The influencing factors that control the workability of Zn-based alloy coated steel sheets include: ■ Adhesion between the plating layer and the base steel sheet, ■ Hardness, brittleness, and lubricity of the coating layer, and ■ Coating weight (film thickness). There are three examples:

Of these, ■ is naturally determined by the type of plating material, and as the plating area weight increases, the build-up phenomenon (the phenomenon in which the plating material adheres to the mold during press molding) and the powdering phenomenon (the plating layer adheres to the mold) It is desirable that the basis weight be within a range that does not become excessive, since this tends to cause the phenomenon of peeling off into powder. However, if the basis weight is insufficient, the sacrificial corrosion protection ability will be insufficient and satisfactory corrosion resistance will not be exhibited, so a certain level of basis weight must be ensured.Also, the plating adhesion described in This is the most important factor in obtaining a good adhesion, and if the adhesion is poor, a build-up phenomenon will occur during press molding, causing surface scratches and significantly deteriorating the quality of the final product. Therefore, among the above-mentioned influencing factors, the greatest attention must be paid to adhesion.

Pretreatment to obtain excellent adhesion varies depending on the plating method; electroplating uses a combination of alkaline degreasing and pickling, and hot-dip plating uses hydrogen reduction. For the first time, satisfactory plating adhesion was achieved.

On the other hand, pre-treatments when producing Zn alloy plated materials using vapor deposition plating methods include (1) removing the oxide film on the surface of the base steel plate by ion sputtering or ion bombardment, (2) removing the oxide film from the surface of the base steel plate using hydrogen gas. The following methods are known: (3) removing the oxide film by mechanical grinding in a non-oxidizing atmosphere; and (3) removing the oxide film by mechanical grinding in a non-oxidizing atmosphere. However, these methods each have the following problems and lack versatility.

First, in the case of (1) ion sputtering method or ion bombardment method, it is possible to activate the base steel plate as long as sufficient time is spent, but when the steel strip is continuously processed while running, pretreatment is required. Since it is not possible to spend sufficient time for this, the vapor deposition process tends to be carried out in an insufficiently activated state, resulting in poor adhesion. On the other hand, in order to ensure sufficient pretreatment time, the traveling speed of the steel plate must be extremely slow or a very long pretreatment device must be used, which reduces productivity and increases equipment costs. do not have.

In addition, in the hydrogen gas reduction method (2) above, a base steel plate is heated to about 500 to 800°C under normal pressure in a hydrogen gas or hydrogen-nitrogen (or argon) mixed gas atmosphere to reduce the oxide film on the surface of the steel plate. This method exposes the active surface by
If the moisture content of the atmospheric gas, that is, the dew point, is insufficiently controlled, reduction will not proceed well, making it difficult to produce extremely low dew point gas and control the dew point. Furthermore, in order to continuously vapor-deposit the activated copper strips, the activated steel sheet must be cooled to the vapor-deposition plating temperature in a non-oxidizing atmosphere under normal pressure, and then placed in a high-vacuum vapor deposition chamber. Therefore, pretreatment equipment such as non-oxidizing cooling parts and a differential pressure chamber (vacuum seal chamber) is extremely large-scale. Furthermore, heating the base steel plate to high temperatures not only deteriorates the mechanical properties of the steel itself, but also has many disadvantages, such as promoting the concentration phenomenon ((R4 analysis) of impurities contained in the steel in the surface layer). bring about.

In addition, the mechanical grinding method (3) above is the simplest method in terms of equipment and is suitable for continuous processing;
This is exposed as an uneven pattern on the surface after vapor deposition plating, and thus deteriorates the appearance of the product. Moreover, if vapor deposition is performed with abrasive grains such as alumina or SiC contained in the grinding brush or ground copper powder still attached to the surface of the steel plate, the adhesion of the plating on that part will be extremely poor. The problem is also pointed out.

[Problems to be Solved by the Invention] The present invention has been made in view of the problems of the prior art as described above, and its purpose is to provide a vacuum plating method that is particularly easy to obtain homogeneous and excellent corrosion resistance among plating methods. In view of the vapor deposition plating method, an attempt is made to provide a method that can solve the problem of pretreatment, which is said to be a difficult point, and can produce a Zn-based alloy vapor-deposited plating material that exhibits excellent adhesion with high productivity. It is something.

[LIi! [Means for Solving Problem]] The structure of the present invention that can solve the above problem is to apply Z to a base metal material by electroplating or hot-dip plating.
The gist is that after applying n-based underplating, a Zn alloy plating layer is formed by a vapor deposition method.

[Operations and Examples] In the present invention, Zn or Z is added to the surface of the base steel plate as described above.
A base plating layer made of an n-alloy is formed by electroplating or hot-dip plating, and a vapor-deposited plating layer made of a Zn alloy is formed thereon. In other words, when electroplating or hot-dip plating is used, the plating pre-treatment can be carried out efficiently by a combination of alkaline degreasing and pickling, or by hydrogen reduction treatment, as described above. Excellent plating adhesion to steel plates can be obtained. Again like this Z
If a base plating layer made of n or Zn alloy is formed, the base plating layer can be processed without any special preliminary treatment.
A vapor-deposited plating layer made of a Zn alloy can be formed with good adhesion.

By the way, when performing Zn alloy plating using the electroplating method, the plating composition is determined by the solubility of the Zn compound and other metal compounds that make up the plating solution, the amount of electrolytic deposition, etc., so it is not always possible to find the best plating composition. Furthermore, in the case of hot-dip plating, the melting points of Zn and other metals are quite different, so it is not always possible to obtain the desired plating bath composition.

On the other hand, with the vapor deposition plating method, the plating composition can be freely adjusted by simply controlling the amount of evaporation of Zn and the metals combined, and the best plating composition can be obtained depending on the objective such as corrosion resistance. It has the advantage of being able to

Therefore, in the present invention, electroplating or hot-dip plating, which can obtain excellent adhesion through simple pretreatment, is utilized exclusively as a means for forming the base plating layer, and this base plating layer is made of Zn or Zn. By forming an alloy, it is possible to improve the adhesion with the highly corrosion-resistant Zn-based alloy vapor-deposited plating layer formed thereon, and to form a Zn alloy plating layer that exhibits excellent adhesion and corrosion resistance as a whole. The base plating layer and the Zn alloy vapor-deposited plating layer are both Zn-based,
Since the compatibility between the two is good, they adhere firmly without any special mutual diffusion treatment, but in the vapor deposition plating process, the base plating is removed! If the steel material is heated appropriately, a certain degree of mutual diffusion will occur between the base plating layer and the vapor-deposited plating layer, and the adhesion can be further improved.

As described above, in the present invention, the base plating layer acts as a binder to enhance the adhesion of the vapor-deposited plating layer, and the base plating layer may be quite thin as long as it can exhibit this function. However, if this plating weight is insufficient, it will not be possible to reliably and uniformly cover the entire surface of the base steel sheet, and the vapor-deposited plating will fail! ! Since the adhesion of the layer may deteriorate partially, the basis weight should be 0.1 g/m2 or more.
More preferably, it is desired to be 1 g/m' or more. On the other hand, the upper limit of the area weight is not limited at all in terms of improving adhesion, but even if the area weight is increased, the adhesion will not improve proportionally, so considering productivity and cost. It is preferable to suppress it to about Log/m' or less.

As mentioned above, the electroplating method or the hot-dip plating method is adopted as a means for forming the base plating layer. Among them, the electroplating method is easy to obtain a plating layer with a uniform and thin coating weight, and it also reduces the thickness of the base metal material. It is prized because it has the advantage of wide selectivity and does not cause deterioration of the base metal material. In addition, the base plating material may be selected from a plating material that has a strong affinity with the vapor-deposited plating material depending on the type of the plating material, but common plating is pure n% Zn-Ni alloy or Zn-Fe alloy plating. Among these, pure Zn plating can be said to be the best base plating material in terms of productivity, cost, and compatibility with the vapor-deposited plating layer.

By the way, in the previous explanation, if the base plated steel sheet is preheated during the Zn alloy vapor deposition plating process, the base plated layer and the Zn
As mentioned above, mutual diffusion occurs to some extent between the alloy vapor-deposited rice plating layers and the adhesion increases, but on the other hand, if the preheating temperature at this time is too high, the weak Fe-
A Zn intermetallic compound layer may be formed, which may impair workability. Particularly in the vacuum evaporation process, the temperature of the steel plate after forming the vapor-deposited Zn alloy plating increases due to sensible heat and latent heat when the metal vapor is evaporated, so when preheating the steel plate, take these points into consideration. It is desirable to set the temperature.

For vapor deposition plating of Zn alloy, a method is adopted in which Zn and alloy components are individually heated and evaporated in a vacuum according to a conventional method, or a method is adopted in which a Zn alloy bath is heated and evaporated and then evaporated onto a base plated steel sheet. In addition to high-energy beam heating such as electron beams and high-frequency waves, resistance heating using Kanthal heaters, molybdenum heaters, etc. can also be used.

In this case, the adhesion between the base plating layer and the vapor-deposited plating layer can be improved by using the ion blating method to ionize the metal vapor using high-frequency waves, etc., and depositing it on the base-plated steel plate to which a bias voltage is applied. It is possible to form a strong, dense plating layer with no pinhole defects or the like.

Vapor-deposited plating materials come in various Z sizes depending on the application and required performance.
The n-alloy plating may be selected appropriately, but common examples include Zn-Mg alloy, Zn-Al alloy, Zn-T
Zn alloy plating such as i alloy, Zn-Cr alloy, Zn-Mn alloy, etc. In addition, Zn alloy plating is a combination of Zn and alloying elements of 2 fff1 or more, such as Zn-Mg-Fe, Zn-Mg
- Multi-element Zn of three or more elements such as Al, Zn-Mg-Ti, etc.
Of course, alloys can also be used.

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention, in which a strip-shaped steel plate 1 coated with pure Zn or Zn alloy undercoat after pretreatment is introduced into a preheating chamber 3 through a differential pressure chamber 2, Here, it is preheated to an appropriate temperature and then sent to the vacuum deposition chamber 4.

In this vapor deposition chamber 4, Zn and alloying elements evaporated from the heating evaporation tanks 5a and 5b are vapor deposited, and the steel plate after vapor deposition passes through a differential pressure chamber 6 and is continuously wound up. In this case, the steel plate may be subjected to base plating on a separate line, then rolled up and then sent to the vapor deposition plating process, or the base plating process and the vapor deposition plating process may be performed continuously on one line. Of course it is possible.

[Effects of the Invention] The present invention is configured as described above, and by applying base plating in advance by electroplating or hot-dip plating prior to vapor deposition plating, Zn can be coated without any complicated pretreatment.
It has now become possible to provide a Zn alloy vapor-deposited plating material with high corrosion resistance, which allows the alloy vapor-deposited plating layer to be firmly adhered and which does not cause pick-up phenomena, bacterial phenomena, etc. during the press molding process.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention. 1: Base plated steel strip 2: Differential pressure chamber 3: Preheating chamber 4: Deposition chamber 5a, 5b: heating evaporation tank 6: Differential pressure chamber Figure 1 the law of nature

Claims (1)

[Claims] A vapor-deposited Zn alloy plating method, which comprises applying a Zn-based base plating to a base metal material by electroplating or hot-dip plating, and then forming a Zn alloy plating layer by vapor deposition.