KR101469967B1 - Anti-corrosion plated steel tube - Google Patents

Abstract

An embodiment of the present invention is a steel pipe comprising: a steel pipe; A zinc plated layer formed on an outer surface of the steel pipe; A chromium layer formed on the zinc plated layer; A first fluororesin layer formed on the chromium layer and made of a mixture of aluminum and fluorine resin; And a second fluororesin layer formed on the first fluororesin layer.

Description

{ANTI-CORROSION PLATED STEEL TUBE}

The present invention relates to a corrosion-resistant steel pipe, and more particularly, to a corrosion-resistant steel pipe having excellent corrosion resistance.

In general, the corrosion-resistant steel pipe forms a coating layer on the outer surface of the steel pipe, thereby preventing the surface of the steel pipe from being rusted or corroded. Such a corrosion-resistant steel pipe can be used as a condenser of a cooling device such as a refrigerator, or as a fuel pipe for a vehicle or as a supply pipe for lubrication, and is used where high durability and reliability are required.

For example, when the corrosion-resistant steel pipe is used as a supply pipe for transferring brake oil or fuel of a vehicle, the use conditions of the supply pipe are very difficult. This is because the supply pipe is provided on the bottom surface of the vehicle and should not cause corrosion from the snow removing agent sprayed on the road surface in the winter and should not be crushed or scratched when the vehicle strikes against the bouncing stones during driving do. That is, the supply pipe provided on the bottom surface of the vehicle must satisfy conditions of corrosion resistance, impact resistance, scratch resistance, and the like.

As described above, the corrosion-resistant steel pipe forms various coating layers on the surface of the steel pipe to enhance the corrosion resistance, impact resistance, scratch resistance and the like.

FIG. 1 is an example of a conventional corrosion-resistant steel pipe, and a corrosion-resistant steel pipe forms various coating layers on the surface of the steel pipe 1 to protect the steel pipe 1 from the outside. That is, a zinc plating layer 2 is formed on the upper part of the steel pipe 1, a chromium layer 3 is formed on the zinc plating layer 2, and an epoxy layer 4 is formed on the chromium layer 3 And the fluororesin layer 5 is formed on the upper portion of the epoxy layer 4 to enhance the corrosion resistance of the steel pipe 1. [ That is, the coating layer covered on the outside of the steel pipe 1 protects the steel pipe 1 from the outside, thereby preventing the steel pipe 1 from being corroded.

However, the chromium layer 3 is made of hexavalent chrome (Cr ^{6 +} ). Microcracks are generated in the bent portion of the corrosion-resistant steel pipe during the bending process. Water or snow remover is easily penetrated into the microcracks, ), Which causes corrosion of the steel sheet. This can shorten the product life of the corrosion-resistant steel pipe.

In addition, since hexavalent chromium (Cr ^{6 +} ) is scattered, it is dangerous to workers, and it is difficult to treat wastewater, which causes water quality and soil pollution when the corrosion-resistant steel pipe is disposed.

And the epoxy layer 4 for bonding the chromium layer 3 and the fluororesin layer 5 has a weak adhesive strength, which lowers the strength and corrosion resistance of the corrosion-resistant steel pipe.

Therefore, various researches and developments have been made on corrosion-resistant steel pipes which are superior in corrosion resistance to conventional corrosion-resistant steel pipes and can prolong the service life of the products.

In order to solve the above problems, it is an object of the present invention to provide a corrosion-resistant steel pipe which prevents the occurrence of microcracks and enhances the bonding strength of the coating layer.

According to an aspect of the present invention, A zinc plated layer formed on an outer surface of the steel pipe; A chromium layer formed on the zinc plated layer; A first fluororesin layer formed on the chromium layer and made of a mixture of aluminum and fluorine resin; And a second fluororesin layer formed on the first fluororesin layer.

In one embodiment of the present invention, the first fluororesin layer contains 10 to 20% of aluminum (Al) and 15 to 25% of fluororesin (F) in weight% ≪ / RTI >

In an embodiment of the present invention, the first fluororesin layer and the second fluororesin layer may be formed of polyvinyl fluoride (PVF).

In one embodiment of the present invention, the chromium layer can be formed of a trivalent chromium (Cr ^{+ 3).}

The effect of the corrosion-resistant steel pipe according to the present invention described above will be described below.

According to the present invention, the corrosion-resistant steel pipe is provided with a first fluororesin layer in which aluminum and fluorine resin are mixed, and is superior in corrosion resistance to a corrosion-resistant steel pipe provided with a conventional epoxy layer. That is, the first fluororesin layer forms an aluminum oxide film that forms a dense layer, thereby enhancing the corrosion resistance of the corrosion-resistant steel pipe.

According to the present invention, since the chromium layer is made of trivalent chromium (Cr ^{3 +} ), a thin coating layer can be formed as compared with a chromium layer made of hexavalent chromium (Cr ^{6 +} ), and microcracks Can be prevented. The chrome layer made of trivalent chromium (Cr ^{3 +} ) is harmless to the human body, thereby improving the working environment and reducing environmental pollution. In addition, trivalent chromium (Cr ^{3 +} ) contains less metal components than hexavalent chromium (Cr ^{6 +} ), which makes wastewater treatment easier.

It should be understood that the effects of the present invention are not limited to the above effects and include all effects that can be deduced from the detailed description of the present invention or the configuration of the invention described in the claims.

1 is an exemplary view of a conventional corrosion-resistant steel pipe.
2 is an exemplary view of a corrosion-resistant steel pipe according to an embodiment of the present invention.
3 is a sectional view taken along the line I-I of FIG. 2, according to an embodiment of the present invention.
FIG. 4A is an exemplary view showing a first pre-processing unit according to an embodiment of the present invention, and FIG. 4B is an exemplary view showing a second pre-processing unit according to an embodiment of the present invention.
5 is an analysis graph showing the composition analysis of the first fluororesin layer according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "indirectly connected" . Also, when an element is referred to as "comprising ", it means that it can include other elements, not excluding other elements unless specifically stated otherwise.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a cross-sectional view taken along the line I-I of FIG. 2 according to an embodiment of the present invention. FIG. 4A is a cross-sectional view of the corrosion-resistant steel pipe according to an embodiment of the present invention. 1 preprocessing unit, and FIG. 4B is an exemplary view showing a second preprocessing unit according to an embodiment of the present invention.

2 to 4, the corrosion-resistant steel pipe includes a zinc plating layer 200, a chrome layer 300, a first fluororesin layer 400, and a second fluororesin layer 500 on the outer surface of the steel pipe 100. [ Are sequentially covered to increase the corrosion resistance of the corrosion-resistant steel pipe.

The steel pipe 100 enhances the adhesion efficiency of the zinc plating layer 200 through a pretreatment process before coating the zinc plating layer 200 so that the zinc plating layer 200 is stably coated on the steel pipe 100.

4A and 4B, the pretreatment of the steel pipe 100 may be performed through the first pretreatment unit 10 and the second pretreatment unit 20, and the first pretreatment unit 10 may include a heater unit 11 And a first gas supply unit 12.

The heater unit 11 heats the steel pipe 100 to a predetermined temperature so as to increase the elongation of the steel pipe 100. The temperature range at this time may be 700 to 800 ° C.

The first gas supply unit 12 supplies the mixed gas to the interior of the first pretreatment unit 10 to create a reducing atmosphere. This is to prevent the surface of the steel pipe 100 in a heated state from being oxidized black, and to ensure stable plating treatment.

The steel pipe 100 passing through the first pretreatment unit 10 is moved to the second pretreatment unit 20 and the second pretreatment unit 20 is moved to the body part 21, the second gas supply unit 22, (23) may be included.

The body portion 21 forms an outer shape of the second pretreatment portion 20 and the steel pipe 100 moves along the center portion of the body portion 21. [ At this time, the second gas supply unit 22 supplies the mixed gas to the interior of the second pretreatment unit 20 to create a reducing atmosphere.

The mixed gas supplied from the second gas supply unit 22 may be composed of hydrogen and nitrogen, which are reducing gases, and the mixed gas may be composed of 5 to 30% of hydrogen and 70 to 95% of nitrogen. It is needless to say that the kind and the mixing ratio of the mixed gas can be variously formed.

The mixed gas supplied from the first gas supply unit 12 to the interior of the first pretreatment unit 10 may be the same as the mixed gas supplied from the second gas supply unit 22. [ Thus, since the inside of the second pretreatment unit 20 is formed in a reducing atmosphere, the surface of the steel pipe 100 in a heated state is prevented from being oxidized black, and the plating process can be performed stably on the upper surface.

The cooling water supply unit 23 supplies cooling water to the interior of the body 21 to cool the steel pipe 100. At this time, the cooling water supply unit 23 anneals the steel pipe 100 while cooling the steel pipe 100 to 500 ° C or less. Here, the cooling water is heat-exchanged in a state in which it is not in direct contact with the steel pipe 10.

Thus, the zinc plating layer 200 is covered on the upper portion of the pre-treated steel pipe 100. At this time, the zinc plated layer 200 is formed on the upper portion of the steel pipe 100 by a general electro-galvanizing method. The electro-galvanizing method is a method in which a zinc thin layer is electrodeposited on a steel pipe 100 of a negative electrode through a current flow to zinc sulfate or a blue zinc chloride solution. The operator inserts a chloride-based solution into the zinc sulfate or zinc blue solution, Conductivity can also be increased. At this time, when the chloride-based solution is added to the electrodialyzed plating solution, the chloride-based solution may be further added to the extent that the surface is not roughened by the increase of the current density.

On the other hand, a chromium layer 300 is provided on the zinc plating layer 200 and the chrome layer 300 is made of chromium (Cr ^{3 +} ). Since the chrome layer 300 made of trivalent chrome (Cr ^{3 +} ) is difficult to be directly applied to the steel pipe 100, the zinc plated layer 200 is formed on the steel pipe 100 and then the chrome layer 300 is sequentially laminated . A chromium layer 300 made of trivalent chromium (Cr ^{3 +} ) can form a thin coating layer as compared with a chromium layer made of hexavalent chromium (Cr ^{6 +} ) and microcracks are generated in the chromium layer during bending of the steel pipe . In addition, the chrome layer 300 made of trivalent chrome (Cr ^{3 +} ) is harmless to the human body and can improve the work environment for manufacturing the corrosion-resistant steel pipe. In contrast to the chromium layer made of hexavalent chromium (Cr ^{6 +} ), The occurrence of contamination can be reduced. The chromium layer 300 made of trivalent chromium (Cr ^{3 +} ) has a plating rate higher than that of the chromium layer made of hexavalent chromium (Cr ^{6 +} ), so that the manufacturing time of the corrosion-resistant steel pipe can be shortened.

The chromium layer 300 made of trivalent chrome (Cr ^{3 +} ) has a covering power superior to that of the chromium layer made of hexavalent chromium (Cr ^{6 +} ), and the surface of the zinc plating layer 200 is uneven It is excellent in adhesion even in a state. The chrome layer 300 made of trivalent chromium (Cr ^{3 +} ) has an excellent hardness, which improves the oxidation resistance and wear resistance of the corrosion-resistant steel pipe. That is, the chrome layer 300 prevents the surface of the steel pipe 100 from being rusted and discolored by coating the surface of the steel pipe 100 with chrome (Cr ^{3 +} ).

The first fluororesin layer 400 is a mixture of fluororesin and aluminum having excellent bonding properties and the first fluororesin layer 400 is formed by increasing the bonding force between the chromium layer 300 and the second fluororesin layer 500 do. That is, the bonding strength between the first fluororesin layer 400 and the chromium layer 300 is strengthened at the bottom and the bonding strength with the second fluororesin layer 500 is strengthened at the top. In other words, the first fluororesin layer 400 enhances the durability and corrosion resistance of the corrosion-resistant steel pipe by enhancing the bonding strength of the coating layer.

The first fluororesin layer (400) contains an aluminum metal component to improve the corrosion resistance of the corrosion-resistant steel pipe. That is, the first fluororesin layer 400 provided with the aluminum component forms an aluminum oxide film that forms a dense layer, thereby preventing the first fluororesin layer 400 from being corroded. The first fluororesin layer 400 containing an aluminum component has a higher strength than the conventional epoxy layer or the fluororesin layer, thereby enhancing impact resistance, scratch resistance, and the like.

The fluororesin included in the first fluororesin layer 400 may be made of polyvinyl fluoride (PVF). At this time, the first fluororesin layer 400 contains 10 to 20% by weight of aluminum (Al) and 15 to 25% by weight of the fluororesin (F), and the balance of carbon (C) and other components.

The second fluororesin layer 500 may be formed on the first fluororesin layer 400 and the second fluororesin layer 500 may be formed of polyvinyl fluoride (PVF).

The second fluororesin layer 500 has excellent adhesion and is excellent in corrosion resistance, heat resistance, chemical resistance, and the like, so that the corrosion resistance of the steel pipe 100 is enhanced. That is, the second fluororesin layer 500 is a primary blocking member for protecting the steel pipe 100 from the outside, and the first fluororesin layer 400, the chrome layer 300, the zinc plating layer 200, 100 from being corroded. The second fluororesin layer 500 has excellent corrosion resistance and is provided outside the corrosion-resistant steel pipe.

The corrosion-resistant steel pipe provided with the first fluororesin layer 400 is subjected to a salt spray test (SST), a cutting salt spray test (Cutting SST) and a chipping SST (Chipping SST) Evaluation was made.

First, Example 1 is a corrosion-resistant steel pipe in which an electro-galvanized layer 200, a chrome layer 300, a first fluorine resin layer 400 and a second fluorine resin layer 500 are sequentially covered, A first fluororesin layer 400 having a composition of 14.78% of aluminum (Al), 20.53% of a fluororesin (F), 64.19% of carbon (C) and 0.5% .

FIG. 5 is an analysis graph showing the composition analysis of the first fluororesin layer according to an embodiment of the present invention. The composition analysis of the first fluororesin layer 400 provided on the corrosion-resistant steel pipe is performed by Energy Dispersive X-ray Spectroscopy (EDS) ) Analyzer. The EDS analyzer accelerates the electrons generated by the application of the current to cause a collision with the sample, thereby spectrometry the energy of the X-ray region resulting from the stabilization of the electron repelled from the sample, And performs quantitative analysis.

On the other hand, Comparative Example 1 is a corrosion-resistant steel pipe in which an electro-galvanized layer 200, a chromium layer 300, a third fluorine resin layer (not shown) and a second fluorine resin layer 500 are sequentially covered, (Not shown) is provided instead of the first fluororesin layer 400. The third fluororesin layer The third fluororesin layer (not shown) of Comparative Example 1 is made of polyfluorinated vinyl (PVF), the second fluororesin layer 500 is made of polyfluorinated vinyl (PVF), and the same fluororesin layer This is a steel pipe having a two-layer structure of an upper layer and a lower layer.

Comparative Example 2 is a corrosion-resistant steel pipe in which an electro-galvanized layer 200, a chromium layer 300, a fourth fluorine resin layer (not shown) and a second fluorine resin layer 500 are sequentially covered, (Not shown) is provided instead of the first fluororesin layer (400). The fourth fluororesin layer (not shown) of Comparative Example 2 is made of polyfluorinated vinylidene (PVDF), the second fluororesin layer 500 is made of polyfluorinated vinyl (PVF), and the upper and lower layers Is a steel pipe composed of different fluororesin layers.

Comparative Example 3 is a corrosion-resistant steel pipe in which an electro-galvanized layer 200, a chrome layer 300 and a second fluorine resin layer 500 are sequentially covered. In Example 1, the corrosion- resistant steel pipe 400 in which the first fluorine- to be.

Comparative Example 4 is a corrosion-resistant steel pipe in which an electro-galvanized layer 200, a chrome layer 300, an epoxy layer (not shown) and a second fluorine resin layer 500 are sequentially covered. In Example 1, There is only a difference in that an epoxy layer (not shown) is provided instead of the ground layer 400.

That is, in the comparative example, a third fluororesin layer (not shown) or a fourth fluororesin layer (not shown) or an epoxy layer (not shown) was applied instead of the first fluororesin layer 400 of the embodiment, All the configurations other than those provided in the steel pipe are the same.

Table 1 below shows corrosion resistance test results of corrosion-resistant steel pipes of Examples and Comparative Examples.

First, the Salt Spray Test (SST) is a test for evaluating the corrosion resistance of an object to be tested by spraying salt water on the test object. That is, the corrosion resistance of the corrosion-resistant steel pipe is measured by spraying salt water on the surface of the corrosion-resistant steel pipe and the time until the rust is generated in the steel pipe 100. In other words, the corrosion resistance of the corrosion-resistant steel pipe was analyzed through the time from when the brine was corroded by the coating layers of the corrosion-resistant steel pipe to the time when the steel pipe was corroded by contacting the steel pipe 100 positioned inside.

Cutting Salt spray test (Cutting SST) is a test for evaluating the corrosion resistance of a test object by spraying a brine with a part of the coating layer of the test object being cut. That is, the corrosion resistance of the corrosion-resistant steel pipe is measured through the time from the time when a portion of the coating layer of the corrosion-resistant steel pipe is cut to spray the brine and the rust is generated in the steel pipe 100. At this time, in the cutting salt spray test, the second fluorine resin layer 500 was cut along the longitudinal direction of the corrosion-resistant steel pipe by a predetermined length, and then the corrosion resistance of the corrosion-resistant steel pipe was analyzed by spraying with salt water.

Chipping SST (Chipping SST) is a test for evaluating the corrosion resistance of a test object by spraying brine with a small stone or sand against the surface of the corrosion-resistant steel pipe to damage the coating layer. That is, when a small object hit by a vehicle during traveling, for example, sand or gravel on the road bottom, is impinged on the surface of the corrosion-resistant steel pipe in a state of being accelerated while traveling, the coating layer is damaged, and salt water is sprayed on the corrosion- Were analyzed.

Here, all the experimental conditions such as the type of brine used in the examples and the comparative example, the spray pressure of the brine, the spray amount of the brine, the length of the cutting, the chipping environment,

As a result of analyzing the corrosion resistance of the examples and comparative examples through three salt spray tests, it was found that the corrosion-resistant steel pipe of Example 1 was much superior in corrosion resistance than Comparative Examples 1 to 4. That is, the corrosion-resistant steel pipe of Example 1 exhibited a corrosion resistance of 12,000 hours in the salt spray test, 1000 hours of corrosion resistance in the cutting salt spray test (SST), and 1000 hours in the chipping SST spray test . This indicates that the corrosion resistance of the steel pipe is much higher than that of Comparative Example 1 which shows corrosion resistance of 6,000 hours in the salt spray test and Comparative Example 1 which showed the corrosion resistance of 480 hours in the cutting salt spray test (Cutting SST) and the chipping SST spray test .

In other words, it is understood that the corrosion-resistant steel pipe having the first fluorine resin layer 400 containing aluminum of Example 1 is superior in corrosion resistance to the corrosion-resistant steel pipe provided with the third fluorine resin layer (not shown) of Comparative Example 1 have.

Further, in place of the first fluororesin layer 400, Comparative Example 2 in which a fourth fluororesin layer (not shown) is provided, and Comparative Example 2 in which an epoxy layer (not shown) is provided instead of the first fluororesin layer 400 Corrosion resistance of the corrosion resistant steel tubes of Examples 4 and 3 was 2800 to 3000 hours in the salt spray test, 220 to 245 hours in the cutting salt spray test (Chipping SST) Shows that the corrosion resistance is inferior to that in Example 1, showing 215 to 250 hours. That is, it can be seen that the corrosion-resistant steel pipe provided with the first fluororesin layer 400 of Example 1 maintains higher corrosion resistance than Comparative Examples 1 to 4.

The corrosion-resistant steel pipe having the first fluororesin layer 400 in which the aluminum and the fluororesin of the example were mixed was composed of the corrosion-resistant steel pipe having the third fluororesin layer (not shown) of Comparative Example 1 and the fourth fluororesin layer Corrosion resistance was maintained as compared with that of the corrosion-resistant steel pipe having the steel pipe (not shown). In other words, in Examples and Comparative Examples 1 and 2, the fluororesin layer is provided on the upper layer of the chrome layer 300, but as shown in Table 1, the corrosion-resistant steel pipe of the embodiment has twice or more corrosion resistance . ≪ / RTI > That is, the first fluororesin layer 400 of the embodiment contains 10 to 20% of aluminum (Al) and 15 to 25% of a fluororesin (F) in weight percent, and the remaining amount of carbon (C) It is seen that the corrosion resistance is significantly improved as compared with the fluororesin layers of Comparative Examples 1 and 2.

As the first fluororesin layer 400 and the second fluororesin layer 500 are laminated in this order, the first fluororesin layer 400 is protected by the second fluororesin layer 500 from the outside And provides chemical resistance to the corrosion-resistant steel pipe.

The corrosion resistant steel pipe provided with the first fluororesin layer 400 can maintain high corrosion resistance even when a thin coating layer is formed due to a strong adhesion force between the layers, It is possible to manufacture a corrosion-resistant steel pipe of various shapes.

It will be understood by those skilled in the art that the foregoing description of the present invention is for illustrative purposes only and that those of ordinary skill in the art can readily understand that various changes and modifications may be made without departing from the spirit or essential characteristics of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

100: Steel pipe 200: Zinc plated layer
300: chrome layer 400: first fluorine resin layer
500: second fluorine resin layer

Claims (4)

Steel pipe;
A zinc plated layer formed on an outer surface of the steel pipe;
A chromium layer formed on the zinc plated layer;
A first fluororesin layer formed on the chromium layer and made of a mixture of aluminum and fluorine resin; And
And a second fluororesin layer formed on the first fluororesin layer,
Wherein the first fluororesin layer contains 10 to 20% of aluminum (Al) and 15 to 25% of fluororesin (F) in weight%, and the balance of carbon (C) and other components. delete The method according to claim 1,
Wherein the first fluororesin layer and the second fluororesin layer are made of polyvinyl fluoride (PVF). The method according to claim 1,
Wherein the chromium layer is made of trivalent chromium (Cr ^< ^{3 + &} gt ^; ).

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