JP2003277982A - Surface treatment structure and surface treatment method for metallic pipe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface treatment structure for a metallic pipe which has a corrosion resistance and does not exert an adverse influence on the human body and the environment and a surface treatment method for the metallic pipe. <P>SOLUTION: A galvanizing layer 20 is formed by an electrogalvanizing process on the outer peripheral surface of the metallic pipe 10 to a prescribed layer thickness. The metallic pipe 10 formed with up to the galvanizing layer 20 is immersed into a chemical conversion treating liquid dissolved with an Si complex compound, by which a chemical conversion treatment layer 30 consisting of the Si complex compound is formed. Polyvinyl fluoride is applied to the metallic pipe 10 formed up to the layer 30 and is baked at a prescribed temperature and time to form a fluororesin layer 40. The corrosion resistance equivalent to that of the conventional chemical conversion treatment layer can be obtained by forming the layer 30 consisting of the Si complex compound. Since a harmful chromium compound is not included, the adverse influence is not exerted to the human body and the environment. Further, special apparatus are not introduced for detoxification of waste liquids and therefore the cost for the waste treatment can be reduced. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface treatment structure and a surface treatment method formed on the outer peripheral surface of a metal tube.

[0002]

2. Description of the Related Art Conventionally, for example, JP-A-63-249.
As shown in Japanese Patent No. 644, a surface treatment structure for a metal tube is known. In this surface treatment structure, a zinc plating layer is formed on the outer surface of the metal tube, and a chromate film made of a hexavalent chromium compound is formed on the zinc plating layer. Then, a polyvinyl fluoride film is formed on the chemical conversion treatment layer via a resin intermediate layer made of an epoxy resin.

Further, for example, a surface treatment structure of a metal tube as disclosed in Japanese Patent Laid-Open No. 8-75084 is also known. In this surface treatment structure for a metal tube, a zinc plating layer is formed on the outer surface of the metal tube, and a chromate layer made of a trivalent chromium compound is formed on the zinc plating layer. Then, a polyvinyl fluoride layer or a polyvinylidene fluoride layer or a polyvinyl fluoride layer or a polyvinylidene fluoride layer is formed on the chromate layer via an epoxy resin intermediate layer made of an epoxy resin.

Metal pipes having such a surface-treated structure have not only chemical corrosion resistance but also chipping resistance, impact resistance, etc., and are widely used for piping such as automobile brake oil and fuel.

[0005]

However, in the surface treatment structure disclosed in JP-A-63-249644, a chromate film made of a hexavalent chromium compound is formed. Therefore, the renewal solution of the chromate solution and the washing water need to be rendered harmless by using a special wastewater treatment device, which increases the cost. Further, when the metal tube having this surface-treated structure is discarded, the hexavalent chromium contained in the chromate film may be eluted to the outside, which may adversely affect the human body and the environment.

On the other hand, in the surface treatment structure disclosed in the above-mentioned Japanese Patent Laid-Open No. 8-75084, a chromate layer made of a trivalent chromium compound is formed. Therefore, since it does not contain hexavalent chromium, it is possible to reduce the cost for treating the renewal liquid of the chromate liquid and the washing water. However, trivalent chromium compounds may be oxidized if they are excessively heat-treated in the atmosphere, and this oxidation produces oxides containing hexavalent chromium (eg, chromic acid, dichromic acid). there's a possibility that. For this reason,
When the metal tube having the surface-treated structure is discarded, harmful hexavalent chromium is eluted and may adversely affect the human body and the environment.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to address the above-mentioned problems, and its object is to improve the surface treatment structure of a metal tube, which has corrosion resistance and adversely affects the human body and environment. An object of the present invention is to provide a surface treatment structure and a surface treatment method for a metal tube.

To achieve the above object, the present invention is characterized in that a zinc or zinc-nickel plating layer formed on the outer peripheral surface of a metal tube and Mo, W, V, N formed on the plating layer.
b, Ta, Ti, Zr, Ce, Sr, Si and Be, the surface treatment structure of the metal tube is composed of a chemical conversion treatment layer made of at least one metal complex compound.

In this case, as the metal pipe, for example, SPC
If a single-wound steel pipe made from C steel plate, or a single-wound steel pipe or double-wound steel pipe made from SPCC steel plate that is copper-plated or nickel-plated to a predetermined layer thickness in advance, or electric resistance welded pipe or drawn steel pipe is used, Good. Further, the wall thickness of the metal tube may be thin or thick.

According to this, the chemical conversion treatment layer is Mo, W,
V, Nb, Ta, Ti, Zr, Ce, Sr, Si, Be
Among these, since it is formed from at least one kind of metal complex compound, the chemical conversion treatment layer does not contain any chromium compound. Therefore, even if, for example, the metal pipe having this surface treatment structure is discarded, it does not adversely affect the environment.

Another feature of the present invention is that a resin layer is formed on the chemical conversion treatment layer in order to protect the chemical conversion treatment layer. In this case, the resin layer may be composed of a polyvinyl fluoride layer or a polyvinylidene fluoride layer. Further, the resin layer may be composed of an epoxy resin intermediate layer formed on the chemical conversion treatment layer, and a polyvinyl fluoride layer or a polyvinylidene fluoride layer formed on the epoxy resin intermediate layer. Further, an outer resin layer made of polypropylene and polyethylene may be formed on the resin layer.

The resin layer may be composed of an epoxy resin intermediate layer formed on the chemical conversion treatment layer and a polyamide resin layer formed on the epoxy resin intermediate layer. Further, an outer resin layer made of polypropylene and polyethylene may be formed on the resin layer.

According to this, the resin layer is formed on the chemical conversion treatment layer with sufficient adhesion. Therefore,
The chemical conversion treatment layer is protected from corrosion by the resin layer and can protect the corrosion of the metal pipe for a longer period of time. Also,
Since the chemical conversion treatment layer does not contain a chromium compound, no harmful oxide containing hexavalent chromium is generated by the heat treatment when forming the resin layer. Therefore, even if the metal pipe on which the surface-treated structure of the present invention is formed is discarded, harmful hexavalent chromium is eluted, and against the human body and the environment,
There is no adverse effect.

From another point of view of the present invention, the feature of the present invention is that a zinc or zinc-nickel plating layer is formed on the outer peripheral surface of a metal tube, and Mo, W, V, Nb, Ta, T is formed.
i, Zr, Ce, Sr, Si, Be, the metal pipe having the zinc or zinc-nickel plating layer formed thereon is dipped in a chemical conversion treatment liquid containing at least one metal complex compound,
This is a surface treatment method for a metal tube in which a chemical conversion treatment layer is formed on the zinc or zinc / nickel plating layer.

According to this, since the chemical conversion treatment liquid does not contain a harmful hexavalent chromium compound, it is possible to reduce the waste liquid treatment cost without introducing a special device for detoxifying the waste liquid.

Another feature of the present invention resides in the method for surface-treating a metal tube, which further comprises forming a resin layer on the chemical conversion treatment layer.

Also in this case, the resin layer may be any one of the following first to sixth examples. The resin layer according to the first example is composed of a polyvinyl fluoride layer or a polyvinylidene fluoride layer. The resin layer according to the second example includes an epoxy resin intermediate layer formed on the chemical conversion treatment layer, and a polyvinyl fluoride layer or a polyvinylidene fluoride layer formed on the epoxy resin intermediate layer. The resin layer according to the third example includes an outer resin layer made of polypropylene and polyethylene formed on the polyvinyl fluoride layer or the polyvinylidene fluoride layer of the first example. The resin layer according to the fourth example includes an outer resin layer made of polypropylene and polyethylene formed on the polyvinyl fluoride layer or the polyvinylidene fluoride layer of the second example. The resin layer according to the fifth example is composed of an epoxy resin intermediate layer formed on the chemical conversion treatment layer and a polyamide resin layer formed on the epoxy resin intermediate layer. The resin layer according to the sixth example includes an outer resin layer made of polypropylene and polyethylene formed on the polyamide resin layer of the fifth example.

Further, the metal pipe having the above-mentioned surface treatment structure (or the metal pipe produced by the surface treatment method) is
Since it has excellent chemical corrosion resistance, chipping resistance, impact resistance, etc., it exhibits excellent effects when applied to vehicles and the like.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a surface treatment structure of a metal tube according to this embodiment by a sectional view. The surface treatment structure includes a zinc plating layer 20 plated on the outer surface of the metal tube 10 and a chemical conversion treatment layer 3 formed on the zinc plating layer 20.
0, and a fluororesin layer 40 formed on the chemical conversion treatment layer 30.
It consists of and.

The metal tube 10 is formed as a single wound steel tube from SPCC steel by the roll forming method. The zinc plating layer 20 is formed in a predetermined layer thickness (for example, 13 μm or more, preferably about 16 μm) by an electroplating method using a sulfuric acid acidic electrolytic solution or an alkaline electrolytic solution containing zinc cyanide. The chemical conversion treatment layer 30 is prepared by immersing the metal tube 10 formed up to the zinc plating layer 20 in a chemical conversion treatment solution in which a complex compound of silicon (hereinafter referred to as Si complex compound) is dissolved to obtain a predetermined layer thickness (eg, 0.2 μm The following) is formed. As a supply source of the Si complex compound of the chemical conversion treatment liquid, for example, a silicate such as aluminum silicate is used.

The fluororesin layer 40 is prepared by dispersing polyvinyl fluoride or polyvinylidene fluoride in a solvent such as diethyl phthalate, and immersing the metal tube 10 formed up to the chemical conversion treatment layer 30 in the same solvent to form a predetermined layer. It is formed to have a thickness (for example, about 20 μm). Then, in order to solidify the fluororesin layer 40, the metal tube 10 after being immersed in the solvent is heat-treated at 380 ° C. for 20 to 40 seconds.

Next, the corrosion resistance evaluation results of the chemical conversion treatment layer 30 made of the above Si complex compound will be described in detail below.

In order to evaluate the corrosion resistance of the chemical conversion treatment layer 30, as shown in FIG. 2, a sample in which the chemical conversion treatment layer 30 made of a Si complex compound was formed on the metal tube 10 by the above method (hereinafter referred to as a test piece). And a sample (hereinafter referred to as a comparative product) in which the metal tube 10 was formed up to the chemical conversion treatment layer 30 ′ made of a hexavalent chromium compound. And, about the test piece and the comparative product, JIS Z
Based on the regulations of 2371, conduct a salt spray test,
The time until the deposit containing zinc as a main component (hereinafter referred to as white rust) was deposited was measured. Table 1 shows the measurement results.

[0024]

[Table 1]

The time until the occurrence of white rust was the same for the test piece and the comparative product, as shown in Table 1. This means that the chemical conversion treatment layer 3 made of the Si complex compound of the test piece is used.
0 and the chemical conversion treatment layer 30 ′ made of hexavalent chromium, which is a comparative product, have the same corrosion resistance. That is, white rust is generated by a reaction between a corrosive substance (for example, chlorine) in salt water and zinc of the zinc plating layer 20.
Therefore, it can be considered that white rust is generated after the chemical conversion treatment layer 30 or the chemical conversion treatment layer 30 ′ formed on the zinc plating layer 20 is corroded by the corrosive substance. From this, it can be considered that the chemical conversion treatment layer 30 and the chemical conversion treatment layer 30 ′ have almost the same corrosion resistance because the time until the occurrence of white rust is the same.

As can be understood from the above description, according to the surface treatment structure of the metal tube of the present invention, the chemical conversion treatment layer 30 is S.
It is formed of an i complex compound and has corrosion resistance equivalent to that of a conventional chemical conversion treatment layer containing a chromium compound. Therefore, when the metal pipe 10 to which the present invention is applied to a vehicle,
Provides long-term protection from corrosion. Further, even when the metal tube 10 to which the present invention is applied is discarded, harmful hexavalent chromium is not eluted and does not adversely affect the human body or the environment. Further, since the chemical conversion treatment liquid does not contain a harmful hexavalent chromium compound, no special device is introduced to render the waste liquid harmless, and the waste liquid treatment cost can be reduced.

In the above embodiment, the chemical conversion treatment layer 30 made of a Si complex compound was used, but instead of this, the chemical conversion treatment layer 30 was replaced with Mo, W, V, Nb, Ta,
You may implement as a chemical conversion treatment layer which has at least 1 type of metal complex compound among Ti, Zr, Ce, Sr, and Be. In this case, the Si complex compound is replaced by Mo, W, V, Nb, T
The structure is the same as that of the above embodiment except that at least one metal complex compound is selected from a, Ti, Zr, Ce, Sr, and Be. Therefore, the same effect as that of the above-described embodiment can be obtained.

Further, the metal tube 10 in the above embodiment.
Is not limited to a single-wound steel pipe, for example, SP
It is also possible to use a double-wound steel pipe made from a CC steel plate, an electric resistance welded pipe, or a drawn steel pipe. Further, there is no limitation on the wall thickness of the metal tube 10, and it is possible to use a thin wall tube and a thick wall tube. Further, the metal tube 10 can be employed by plating the outer surface with copper if necessary.

Further, in the above embodiment, the metal tube 1
The zinc plated layer 20 was formed on the outer peripheral surface of
If necessary, a zinc / nickel plating layer may be formed on the outer peripheral surface of the metal tube 10 for implementation. In this case, the chemical conversion treatment layer 30 has the same configuration as that of the above embodiment except that the chemical conversion treatment layer 30 is formed via the zinc / nickel plating layer. Therefore, the same effect as that of the above-described embodiment can be obtained.

Further, in the above embodiment, the fluororesin layer 40 is formed on the chemical conversion treatment layer 30. However, the chemical conversion treatment layer 30 may be formed on the metal tube 10 if necessary. Good. In this case, since the chemical conversion treatment layer 30 has sufficient corrosion resistance, the metal pipe 10 can be protected from corrosion for a long period of time.

Further, in the above embodiment, the fluororesin layer 40 is formed on the chemical conversion treatment layer 30, but if necessary, as shown in FIG. The intermediate resin layer 50 may be formed to a predetermined thickness (for example, about 2 to 3 μm), and the fluororesin layer 40 may be formed on the intermediate resin layer 50. In this case, the configuration is the same as that of the above-described embodiment, except that the resin layer includes the intermediate resin layer 50 and the fluororesin layer 40. Therefore, the same effect as that of the above-described embodiment can be obtained.

If necessary, as shown in FIG.
The resin outer layer 60 made of polypropylene and polyethylene may be formed on the fluororesin layer 40 having the surface treatment structure shown in FIG. 1 to have a predetermined layer thickness (for example, about 1 mm). In this case, the configuration is the same as that of the above-described embodiment, except that the resin layer includes the fluororesin layer 40 and the resin outer layer 60. Therefore, the same effect as that of the above-described embodiment can be obtained.

If necessary, as shown in FIG.
The resin outer layer 60 made of polypropylene and polyethylene may be formed on the fluororesin layer 40 having the surface treatment structure shown in FIG. In this case, the resin layer has the same configuration as that of the above-described embodiment, except that the resin layer includes the intermediate resin layer 50, the fluororesin layer 40, and the resin outer layer 60. Therefore, the same effect as that of the above-described embodiment can be obtained.

In the above embodiment, the fluororesin layer 40 is formed on the chemical conversion treatment layer 30, but the intermediate resin layer 50 is formed on the chemical conversion treatment layer 30 as shown in FIG. A polyamide-based resin layer 40 ′ made of a polyamide-based resin is provided on the intermediate resin layer 50 with a predetermined layer thickness (for example,
The thickness may be 150 μm or more, preferably about 180 μm). In this case, the resin layer is the intermediate resin layer 50.
The structure is the same as that of the above-described embodiment except that the structure is composed of the polyamide resin layer 40 '. Therefore, the same effect as that of the above-described embodiment can be obtained.

If necessary, as shown in FIG.
The outer resin layer 60 made of polypropylene and polyethylene may be formed on the polyamide resin layer 40 'having the surface treatment structure shown in FIG. In this case, the configuration is the same as that of the above-described embodiment, except that the resin layer includes the intermediate resin layer 50, the polyamide resin layer 40 ′, and the resin outer layer 60. Therefore, the same effect as that of the above-described embodiment can be obtained.

Further, the metal tube 10 constructed as described above.
As described above, since it has chemical corrosion resistance, chipping resistance, and impact resistance, it exhibits excellent effects when applied to a vehicle. Further, it is natural that the invention is applied to a device requiring chemical corrosion resistance, chipping resistance, impact resistance, etc. even in applications other than the vehicle.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a metal tube for explaining a surface treatment structure of a metal tube according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view schematically showing a test piece and a comparative product used for evaluating the corrosion resistance of a chemical conversion treatment layer in the surface treatment structure of the metal tube.

FIG. 3 is a cross-sectional view of a metal tube for explaining a surface treatment structure according to a modified example of the metal tube.

FIG. 4 is a cross-sectional view of a metal tube for explaining a surface treatment structure according to another modification of the metal tube.

FIG. 5 is a cross-sectional view of a metal tube for explaining a surface treatment structure according to another modification of the metal tube.

[Explanation of symbols]

10 ... Metal tube, 20 ... Zinc plating layer, 30 ... Chemical conversion treatment layer,
30 '... Chemical conversion treatment layer composed of hexavalent chromium compound, 40 ...
Fluororesin layer, 40 '... Polyamide resin layer, 50 ... Intermediate resin layer, 60 ... Resin outer layer.

Front page continuation (51) Int.Cl. ⁷ identification code FI theme code (reference) C25D 5/26 C25D 5/26 CG 5/48 5/48 F term (reference) 4K024 AA05 AA19 BA02 BB28 BC05 DB04 DB05 DB06 GA10 GA12 4K026 AA02 AA12 AA25 BA01 BB06 BB08 BB10 CA18 CA29 CA30 CA31 DA02 DA03 DA06 DA11 EB08 4K044 AA02 AB03 BA06 BA10 BA12 BB03 BB04 BC02 BC04 CA16 CA17 CA53 CA64

Claims (9)

[Claims] 1. A zinc or zinc-nickel plating layer formed on the outer peripheral surface of a metal tube, and Mo, W, V, Nb, Ta, T formed on the plating layer.
A surface treatment structure for a metal tube comprising a chemical conversion treatment layer made of at least one metal complex compound among i, Zr, Ce, Sr, Si and Be. 2. The surface treatment structure for a metal pipe according to claim 1, wherein a resin layer is formed on the chemical conversion treatment layer. 3. The surface treatment structure for a metal tube according to claim 2, wherein the resin layer is composed of a polyvinyl fluoride layer or a polyvinylidene fluoride layer. 4. The resin layer comprises an epoxy resin intermediate layer formed on the chemical conversion treatment layer, and a polyvinyl fluoride layer or polyvinylidene fluoride layer formed on the epoxy resin intermediate layer. Item 2. The surface-treated structure for a metal tube according to Item 2. 5. The surface treatment structure for a metal pipe according to claim 2, wherein an outer resin layer made of polypropylene and polyethylene is formed on the resin layer. 6. The method according to claim 2, wherein the resin layer comprises an epoxy resin intermediate layer formed on the chemical conversion treatment layer and a polyamide resin layer formed on the epoxy resin intermediate layer. Surface treatment structure for metal tubes. 7. The surface-treated structure for a metal pipe according to claim 6, wherein an outer resin layer made of polypropylene and polyethylene is formed on the resin layer. 8. A zinc or zinc-nickel plating layer is formed on the outer peripheral surface of a metal tube, and Mo, W, V, Nb, Ta, Ti, Zr, Ce, Sr,
The metal pipe having the zinc or zinc / nickel plating layer formed thereon is immersed in a chemical conversion treatment liquid containing at least one metal complex compound of Si and Be to form a chemical conversion treatment layer on the zinc or zinc / nickel plating layer. A method for surface treatment of a metal tube to be formed. 9. The surface treatment method for a metal pipe according to claim 8, further comprising forming a resin layer on the chemical conversion treatment layer.