KR101717995B1 - Cable having improved corrosion resistance - Google Patents

Abstract

The present invention relates to a cable having a structure in which a copper tape and a galvanic steel wire are in direct contact with each other, and exhibits excellent corrosion resistance. In particular, the cables according to the invention can be used effectively in ships or offshore structures.

Description

{CABLE HAVING IMPROVED CORROSION RESISTANCE}

The present invention relates to cables exhibiting excellent corrosion resistance. In particular, the cable according to the invention can be used effectively in ships or offshore structures.

Offshore structures such as ships or oil drilling structures are continuously exposed to extreme corrosive environments. In the marine environment, a large amount of salinity (eg, NaCl, MgSO ₄ , MgCl ₂ , CaCl _2, etc.) is present in the marine atmosphere. In particular, Cl ^- ion has a great influence on metal corrosion. Also, in the marine environment, the atmospheric current is generally higher than in the ground environment, so that Cl ^- ions, oxygen, etc. can be continuously supplied on the surface of the metal to be corroded, which can affect the corrosion rate of the metal have.

Due to the various factors described above, the corrosion rate of metals in the marine environment is much greater than in the ground environment. Thus, cables used in marine environments are required to have better corrosion resistance than that required in conventional cables. If the cable does not have sufficient corrosion resistance, the cables must be frequently replaced or repaired due to the inherent malfunction and malfunction of the cable due to corrosion, and the special circumstances of the marine environment make it very difficult to replace or repair the cables.

Various studies have been made in the art to delay the corrosion rate of the cable. For example, an armor is typically used for the purpose of protecting the interior of a cable, such as a conductor and an insulator, from external impacts or from rodents such as mice. In order to retard the corrosion of steel wires which are widely used as the armor, galvanized steel wires have been provided. The galvanic steel wire is obtained by applying a zinc coating on steel, and a hot-dip galvanizing method in which steel is immersed in molten zinc is most widely used. In the galvanic steel wire, due to the potential difference between zinc and iron, more active zinc acts as an anode and less active iron acts as a cathode. As a result, zinc is corroded faster, while iron is a more slowly corroded galvanic corrosion phenomenon, which results in the further protection of galvanic steel wire from corrosion.

In order to further slow the corrosion rate of the galvanic steel wire, S. Nakamura et al. Proposed a new technique in Corrosion resistance of steel bridge wires coated with aluminum-zinc alloy. In the accelerated corrosion test performed in this document, it was observed that the corrosion rate of the steel wire coated with Al-Zn alloy was slower than that of Zn-coated steel wire. However, according to this document, a new type of steel wire coated with an Al-Zn alloy must be separately prepared without using a conventional Zn-coated galvanic steel wire.

Attempts have yet to be made in the art to approach a cable that can use conventional Zn-coated galvanic steel wire as it is, but which can further slow the rate of galvanic corrosion occurring in galvanic steel wires.

S. Nakamura, et al. Corrosion resistance of steel bridge wires coated with Aluminum-Zinc alloy

Accordingly, it is an object of the present invention to provide a cable having excellent corrosion resistance and long life even in a marine environment where corrosion is easy, such as a ship or an offshore structure.

The cable according to the invention comprises a copper tape and a galvanic steel wire. The copper tape and the galvanic steel wire are in direct physical contact.

According to an embodiment of the present invention, the cable includes at least one insulated conductor, an inner sheath, a copper tape, a galvanic steel wire and an outer sheath.

In the present invention, the term "copper tape" is used interchangeably with "CU tape ", which means a tape composed mainly of copper or a tape containing copper as a main component. Preferably, the copper tape is a copper and polystyrene tape having a surface in direct contact with a galvanic steel wire made of copper and an opposite surface made of polystyrene. In the present invention, the term "copper and polystyrene tape" is used interchangeably with "CU / PS tape ".

According to an embodiment of the present invention, the galvanic steel wire is preferably a galvanized steel wire braid (GSWB).

According to an embodiment of the present invention, the projected area ratio of the copper tape and the galvanic steel wire may vary depending on the size of the cable actually manufactured and may be in the range of, for example, 1: 2 to 1: 4 . In the case of the cable shown in FIG. 3, the projected area ratio was 1: 4.

The insulated conductor includes one or a plurality of conductors and an insulating layer.

The cable is suitable for use in ships or offshore structures. In addition, the cable may be an electric cable, an optical cable, or a data transmission cable, and the structure or form of a cable such as a conductor, an insulating layer, a sheath, and the like may be changed depending on the application to which the cable is applied.

The cable according to the present invention can further reduce the galvanic corrosion that occurs in conventional galvanic steel wire due to its structural characteristics.

In particular, the cable according to the present invention exhibits excellent corrosion resistance even in extreme corrosive environments such as marine or offshore structures, so that it has a longer life in the marine environment and can be used for a longer period of time have.

1 shows a cross-sectional view of a cable according to an embodiment of the invention.
Figure 2 shows a cross-sectional view of a cable according to an embodiment of the invention.
3 is a photograph taken after partially removing the layers from a real cable manufactured according to an embodiment of the present invention.
Figure 4 is a photograph of the two samples used in the salt spray test taken with a camera before spraying the salt solution.
5 is a photograph of two samples taken by a stereoscopic microscope after spraying a salt solution in a salt spray test and after 24 hours.
FIG. 6 is a photograph of two samples taken by a stereoscopic microscope after spraying a salt solution in a salt spray test and after 48 hours.
FIG. 7 is a photograph of two samples of a sample taken after 48 hours spraying a salt solution in a salt spray test.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be described in more detail below with reference to embodiments and drawings. It is to be understood, however, that the embodiments and drawings are only illustrative of the present invention in order to provide a more detailed understanding of the structure and effects of the present invention, and the scope of the present invention is not limited by the embodiments and drawings. In addition, those skilled in the art will be able to carry out various modifications and substitutions without departing from the scope of the present invention.

The cable 10 shown in Fig. 1 shows an embodiment in which there are four insulated conductors 3 among the cables according to the present invention, and the cable 10 shown in Fig. 1 < / RTI >

Each insulated conductor 3 comprises a conductor 1 and an insulating layer 2.

The conductor 1 may be made of materials conventionally used in the art and may be made of one or a plurality of metallic materials selected from, for example, copper, a copper alloy, aluminum, and an aluminum alloy.

The insulating layer 2 prevents the current flowing in the conductor 1 from flowing to the outside and maintains the voltage. The insulating layer 2 may be made of materials conventionally used in the art and may be, for example, ethylene propylene, non-halogen ethylene propylene, cross-linked polyethylene, cross-linked non-halogen polyethylene, cross- Or may be made of a bonded polyolefin.

Alternatively, a separating layer (not shown in FIGS. 1 and 2) may be located between the conductor 1 and the insulating layer 2. The separating layer is provided to prevent the rubber material of the insulating layer 2 from adhering to the conductor 1 according to the environmental conditions. The separating layer may be made of materials conventionally used in the art, if necessary, and may be, for example, a polyester tape or a non-woven tape.

Alternatively, an additional layer (not shown in Figures 1 and 2) may be arbitrarily positioned between the conductor 1 and the insulating layer 2 for the purpose of enhancing the properties of the desired cable, such as fire resistance and oil resistance have. If mica tape is used as the additional layer, the overall fire resistance of the cable can be further strengthened.

Alternatively, a separating layer (not shown in Figures 1 and 2) may be located between the insulated conductor 3 and the inner sheath 4. The separating layer may be added for the purpose of fixing various insulated conductors when the insulated conductors are plural or further improving the properties such as fire resistance. The separating layer may be made of materials conventionally used in the art, if necessary, and may be, for example, a polyester tape or a non-woven tape.

The inner sheath 4 and the outer sheath 7 may be made of materials conventionally used in the art for the purpose of enhancing the properties of a desired cable such as fire resistance and oil resistance, For example, Low-Smoke and Halogen-Free (LSHF) compounds, hypalon, crosslinked chlorosulfonated polyethylene, neoprene or PVC. The inner sheath 4 and the outer sheath 7 may be made of the same material or different materials. Inner covering may be used in place of the inner sheath 4.

The copper tape 5 and the galvanic steel wire 6 are physically in direct contact with each other. The projected area ratio of the copper tape 5 and the galvanic steel wire 6 may be appropriately varied depending on the size of the cable.

It is preferable that the copper tape 5 is a copper and polystyrene tape (CU / PS tape) having a surface in direct contact with a galvanic steel wire made of copper and an opposite surface made of polystyrene. Copper-only tapes are less flexible, so that they can be separated from each other by creating a space that is not in contact with the tape and the galvanic steel wire in the process of laying down a thin cable or in a post-installation work environment. The CU / PS tape The use of the polystyrene improves the flexibility of the entire tape, which is advantageous to the present invention in that the tape and the galvanic steel wire can be kept in direct contact with each other.

According to an embodiment of the present invention, the galvanic steel wire 6 is a galvanized steel wire armor (GSWA) or a galvanized steel wire braid (GSWB), and preferably a GSWB. The reason for this is that in the case of GSWB, due to the nature of the structure, the electrolyte is simultaneously contacted to the copper tape between the gaps of the GSWB, and the oxidizing action caused by the copper tape slows the corrosion rate of Zn or Fe of the galvanic steel wire It is considered.

It is believed that, when galvanic steel wire is corroded in the cable according to the present invention, ZnO or Zn (OH) ₂ is produced on the surface of zinc and CuO or Cu (OH) ₂ is formed on the surface of the copper . When metal oxides or hydroxides are formed on the surface of the metal, the galvanic corrosion rate of the galvanic steel wire as well as the cathode reaction rate of the copper tape can be remarkably slowed down.

Figure 3 shows an actually fabricated cable according to an embodiment of the present invention. 3 is composed of an insulated conductor 3, a separation layer (gray), an inner sheath 4, a copper tape 5, a galvanic steel wire 6 and an outer sheath 7. More specifically, the cable has four insulated conductors 3, the separating layer (gray) is made of a mixture of polyester and non-woven fabric, and both the inner sheath 4 and the outer sheath 7 are made of The CU / PS tape was used as the copper tape 5 and the GSWB was used as the galvanic steel wire 6. At this time, the projected area ratio of the CU / PS tape and GSWB was 1: 4.

Salt spray test

The present inventors conducted a salt spray test. This test was conducted to determine the effect of direct contact between GSWB and copper tape on the rate of galvanic corrosion occurring in GSWB. To facilitate corrosion in this test, the saline solution was sprayed directly onto the galvanic steel wire without external sheath.

First, two samples were prepared. The first sample is a cable having a length of 10 cm and has a structure in which the GSWB and the copper tape are in direct contact with each other and is shown at the upper end of Fig. The second sample has GSWB as a 10 cm long cable, but does not have a copper tape, and is shown at the bottom of FIG. For the second sample, three cables were tied with a tie-wrap to prevent the GSWB from loosening, and the tie wrap did not affect the corrosion of the cable.

The salt spray test was carried out on an Erichsen CORROTHERM 610e apparatus according to the NF ISO 9227 standard and the specific parameters are as follows.

Chamber volume 400 liters Chamber temperature 35 ℃ Salt solution 50 g / l ± 5 g / l NaCl PH of salts at 25 ° C ± 2 ° C 6.5 <pH <7.2 Density of salts at 25 ° C ± 2 ° C 1.029 < density < 1.036 Spray pressure of salt 1 bar Total test time 48 hours

The sample was fixed at an angle of 45 [deg.] In the middle of the closed chamber of the apparatus, and then the NaCl salt solution was sprayed onto the sample.

After 24 hours, each sample was removed from the chamber, washed with deionized water, and then dried. Stereoscopic microscopy revealed white rust in both samples with a small amount of yellow staining (Figure 5). At this time, the white rust corresponds to the corrosion of the zinc protective layer on the galvanic steel wire. No significant difference was visually observed between the first sample shown on the left side of FIG. 5 and the second sample shown on the right side of FIG.

After 48 hours, each sample was removed from the chamber, washed with deionized water, and then dried. Observation with a stereoscopic microscope revealed red rust in both samples (Figure 6). At this time, the red rust corresponds to the corrosion of the steel on the galvanic steel wire, indicating that the steel began to corrode after all the zinc layers were corroded. However, a much greater degree of red rust was observed in the second sample (right side of FIG. 6) without copper tape compared to the first sample with copper tape (left side in FIG. 6). FIG. 7 is a photograph taken 48 hours after spraying the salt solution. Here, the first sample at the top of FIG. 7 shows red rust in some areas along with the white rust, but the second sample at the bottom of FIG. And the surface of the green is covered with red rust.

A cable with a structure in which GSWB and copper tape are in direct contact can lead to a significant delay in galvanic corrosion rate in GSWB and consequently to a markedly slower erosion of GSWB.

Comparison of Corrosion Rate Using Corrosion Current

The corrosion rate can be calculated according to Faraday's law as:

Where i _corr is the corrosion current, MW is the molar weight of the metal, n is the oxidation number (i.e., the number of electrons moved), rho is the density of the metal, and F is the Faraday constant. For the cable according to the invention, the molar weight MW of the zinc is 65.38 g / mol, the number of the zinc oxide n = 2, the density of the zinc rho = 7.14 g / cm3 and the Faraday constant F = 96485 C / mol are used. The results shown in Tables 2 and 3 below do not consider the ratio of anode to cathode area ratio of 4: 1.

Corrosion rate of zinc in GSWB Distilled water 0.1 M NaCl i _corr (占 / / cm2) 2.57 10.7 Corrosion rate (mm / year) 0.038 0.1605

Corrosion rate of zinc in GSWB + CU / PS tape Distilled water 0.1 M NaCl i _corr (占 / / cm2) 0.409 7.51 Corrosion rate (mm / year) 0.0061 0.1124

Compared with GSWB without CU / PS tapes, GSWB with direct contact with CU / PS tape showed significant corrosion rate in both distilled water and 0.1M NaCl conditions It was slower. That is, the GSWB with direct contact of the CU / PS tape has a life of about 6.2 times longer under the distilled water condition than the GSWB without the CU / PS tape, and about 1.4 times longer under the salt condition.

In a practical industry field, the GSWB + CU / PS tape of the cable according to the invention is generally surrounded by external sheath, so it will corrode much slower than the corrosion rate calculated by the above equation and will have a longer lifetime. In addition, after the zinc coating is completely corroded, the corrosion of the iron begins to progress. At this time, Fe ₂ O ₃ or Fe (OH) ₃ produced by the oxidation of iron is removed by air or water between the outer sheath and the galvanic steel wire and the copper tape The cable according to the present invention will exhibit better corrosion resistance than predicted theoretically.

1: Conductor
2: Insulating layer
3: Insulated conductor
4: Inner sheath
5: Copper tape
6: Galvanic steel wire
7: External sheath
10: Cable

Claims (7)

(1) comprising at least one insulated conductor (3), an inner sheath (4) on the insulated conductor, a copper tape (5) on the inner sheath, a galvanic steel wire (6) on the copper tape, and an outer sheath ) With a corrosion resistant cable,
The copper of the copper tape 5 and the galvanic steel wire 6 are in direct contact with each other over the entire surface and the surface of the copper tape 5 which is in direct contact with the galvanic steel wire 6 is copper, Characterized in that it is a polystyrene-based copper and polystyrene tape. The method according to claim 1,
Characterized in that the galvanic steel wire (6) is a galvanized steel wire braid (GSWB). The method according to claim 1,
Characterized in that the insulated conductor (3) comprises one or a plurality of conductors (1) and an insulating layer (2). The method according to claim 1,
Wherein said cable is for use in a ship or an offshore structure. The method according to claim 1,
Wherein the cable is an electric cable or an optical cable. delete delete

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