JP2009221569A - Corrosion prevention structure for steel structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a sacrificial anode to steel structures with various shapes by a simple method. <P>SOLUTION: In a corrosion prevention structure for a steel structure (1) where a part is buried into a base (2), a hollow material (10) for corrosion prevention composed of an aluminum alloy comprising 2 to 20 mass% Zn, and in which the concentration of Cu is regulated to ≤0.1 mass%, and the balance Al with impurities is wound around the outer circumferential face of the verge part directly on the buried part in the steel structure (1), and further, the hollow material (10) for corrosion prevention and the steel structure (1) make conductive. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an anticorrosion structure for a steel structure installed on a ground such as soil or concrete.

  In steel structures such as guardrails, signposts and fences installed on the ground, and manholes such as manholes buried underground, the buried part of the steel structure serves as the cathode, and the ground directly above the buried part of the exposed part Macrocell corrosion occurs at the edge as an anode. For macro cell corrosion of such steel structures, a method is known in which a corrosion protection tool made of a base material having a corrosion potential lower than that of the steel structure is attached to the ground, and the corrosion protection tool is used as a sacrificial anode for sacrificial corrosion. . (See Patent Documents 1 to 6)

  In patent document 1, the technique which attaches a zinc anode sheet to a concrete wall surface with respect to underground underground piping (made of iron) which penetrates a reinforced concrete structure, and conducts this zinc anode sheet to piping and prevents macrocell corrosion is disclosed. Yes.

Moreover, in patent documents 2-6, as a ring-shaped anticorrosion tool attached to the outer periphery of a steel-made facility body, it is made of metal such as zinc-based, aluminum-based, magnesium-based, and a pair of two semicircular ring halves. Are listed. The two ring halves are arranged facing each other around the facility body, combined in a ring shape, the butt portion is fastened with screws or pins, and connected to the facility body using bolts or wedges from the outer periphery of the ring. The Then, a conductive or water-absorbing filler is inserted between the facility body and the split ring to ensure contact between the ring and the installation surface, thereby ensuring an energized state.
Japanese Patent Application Laid-Open No. 11-209885 JP 2002-227149 A Japanese Patent Laid-Open No. 2002-226983 JP 2002-226984 A JP 2002-226985 A JP 2002-226986 A

  All of the above-described sacrificial anodes require a lot of time for installation, and in particular, the split rings of Patent Documents 2 to 6 have a drawback that it takes a lot of time for fastening. Moreover, the split ring of patent documents 2-6 had to produce a ring according to the outer periphery shape of a facility body, and there existed a problem that it lacked versatility.

  In view of the above-described technical background, an object of the present invention is to provide an anticorrosion structure, an anticorrosion method, and an anticorrosion tool for a steel structure using a sacrificial anode that can be easily attached to steel structures of various shapes.

  That is, this invention has the structure as described in following [1]-[11].

[1] A corrosion prevention structure of a steel structure partly embedded in the base,
Aluminum alloy containing Zn: 2 to 20% by mass, Cu concentration is regulated to 0.1% by mass or less, and the balance is made of Al and impurities on the outer peripheral surface of the underground part directly above the embedded part of the steel structure An anticorrosion structure for a steel structure, characterized in that the anticorrosion hollow material composed of is wound, and the anticorrosion hollow material and the steel structure are electrically connected.

  [2] The steel structure according to item 1, wherein both ends of the anticorrosion hollow member wound around the steel structure are connected via a connecting member made of a material having a corrosion potential higher than that of the anticorrosion hollow member. Anti-corrosion structure of things.

  [3] The connecting member is provided with an insertion portion that is inserted into the opening end of the anticorrosion hollow material on both surfaces of the flange portion, and the insertion portion has a conical shape whose cross-sectional area decreases from the proximal end side toward the distal end side. The anticorrosion structure for a steel structure according to item 2, wherein a plurality of trapezoidal nodes are stacked.

  [4] The anticorrosion structure for a steel structure according to any one of items 1 to 3, wherein the steel structure and the anticorrosion hollow material are connected to each other through a conduction means.

  [5] The anticorrosion structure for a steel structure according to item 2 or 3, wherein the steel structure and the connection member are connected via a conduction means.

  [6] The anticorrosion structure for a steel structure according to any one of items 1 to 5, wherein a water retaining portion is provided between the anticorrosion hollow material and the steel structure.

  [7] The anticorrosion structure for a steel structure according to any one of [1] to [6], wherein 0.01 to 0.5% by mass of Sn is contained in the aluminum alloy composition.

  [8] The anticorrosion structure for a steel structure according to any one of items 1 to 7, wherein an outer diameter of the anticorrosion hollow material is 6 to 20 mm and a thickness is 0.3 to 2 mm.

  [9] Zn: 2 to 20% by mass, and Cu concentration restricted to 0.1% by mass or less, on the outer peripheral surface of the underground part directly above the embedded part of the steel structure partly embedded in the foundation And winding the anticorrosion hollow material made of an aluminum alloy, the balance of which is made of Al and impurities, having a lower corrosion potential than that of the steel structure, while making the anticorrosion hollow material and the steel structure conductive. An anticorrosion method for steel structures characterized by

  [10] An anticorrosion tool to be attached to the outer peripheral surface of the submerged portion directly above the embedded portion of the steel structure, a portion of which is embedded in the base, containing 2 to 20% by mass of Zn and having a Cu concentration of 0.1. An anticorrosive tool characterized by being a hollow material made of an aluminum alloy that is regulated to 1% by mass or less, the remainder is made of Al and impurities, and has a lower corrosion potential than the steel structure.

[11] A connecting member for connecting the both opening ends of the anticorrosive tool according to the previous item 10 to form the anticorrosive tool in an annular shape,
Insertion parts for inserting into the opening end of the anticorrosive tool protrude from both sides of the flange part, and the insertion part is provided with a plurality of frustum-shaped nodes having a cross-sectional area that decreases from the proximal end side toward the distal end side. The connection member for anticorrosives characterized by comprising.

  In the anticorrosion structure for a steel structure according to the invention described in [1] above, the anticorrosion hollow material is wound around the ground portion of the steel structure to form a sacrificial anode. Since the anticorrosion hollow material can be easily bent, it can be attached to steel structures having various shapes. Moreover, since the anticorrosion hollow material is an aluminum alloy, anticorrosion performance can be obtained over a longer period than zinc or a zinc-based alloy.

  According to the invention described in [2] above, the end portion of the anticorrosion hollow material can be easily processed. Moreover, by making the steel structure and the anticorrosion hollow material conductive through the connecting member, the anticorrosion hollow material can be stably sacrificed and corroded.

  According to the invention described in [3] above, the end treatment of the anticorrosion hollow material can be easily performed, and the retaining state can be maintained.

  According to the inventions described in [4] and [5] above, the steel structure and the anticorrosion hollow material can be reliably conducted.

  According to the invention described in [6] above, the sacrificial hollow material can be stably sacrificed.

  According to the invention described in [7] above, preferential corrosion of the anticorrosion hollow material is promoted.

  According to the invention described in [8] above, the anticorrosion hollow material is easy to bend and long-term anticorrosion performance can be reliably obtained.

  According to the corrosion prevention method for a steel structure according to the invention described in [9] above, a sacrificial anode is attached to a steel structure having various shapes to form the corrosion prevention structure. Can be given.

  Since the anticorrosive tool according to the invention described in [10] can be easily bent, the sacrificial anode can be formed by wrapping around the ground portion of various shaped steel structures.

  According to the connecting member according to the invention described in [11], the anticorrosive tool is easily connected in an annular shape by inserting both open ends of the hollow anticorrosive tool described in [10] into the insertion portion. be able to. In addition, after the connection, the maximum diameter portion of the node bites into the inner wall of the anticorrosion tool and is prevented from coming off.

  FIG. 1 shows one embodiment of the corrosion prevention structure of a steel structure of the present invention, and FIGS. 2A and 2B are a sectional view taken along line 2A-2A and a sectional view taken along line 2B-2B in FIG. In FIG. 1, a steel pipe (1) having a circular cross section has its lower part embedded in concrete (2) and its upper part exposed to the atmosphere. The steel pipe (1) and the concrete (2) correspond to the steel structure and the base in the present invention.

  On the outer peripheral surface of the submerged portion immediately above the buried portion of the steel pipe (1), a hollow anticorrosive material (10) having a circular cross section serving as a sacrificial anode is wound in contact with the surface of the concrete (2), and both ends thereof Are connected via a connecting member (20) to form an annular shape. Further, a water retaining part (30) is interposed between the steel pipe (1) and the anticorrosion hollow material (10). The connecting member (20) is made of a conductive material, and the connecting member (30) and the steel pipe (1) are connected via the lead wire (3), and thus the anticorrosion hollow material (10) and the steel pipe (1) Connected to a conductive state.

  The anticorrosion hollow material (10) contains Zn: 2 to 20% by mass, the Cu concentration is regulated to 0.1% by mass or less, and the balance is made of an aluminum alloy composed of Al and impurities. The aluminum alloy having the above composition has a lower corrosion potential than the steel pipe (1) and forms a sacrificial anode for the steel pipe (1). Further, by using an aluminum alloy as the sacrificial anode, the corrosion is slower than that of a sacrificial anode made of zinc or a zinc-based alloy, and an anticorrosive effect can be achieved over a long period of time.

  In the aluminum alloy composition, Zn is an element that lowers the corrosion potential of the alloy. If the Zn concentration is less than 2% by mass, the effect of sacrificial corrosion is poor. On the other hand, if it exceeds 20% by mass, it will corrode early and the replacement cycle of the anticorrosion hollow material (10) will be shortened. A preferable Zn concentration is 3.5% by mass or more, and a particularly preferable Zn concentration is 4 to 8% by mass.

  Cu is an element that promotes corrosion, and it is necessary to regulate the Cu concentration to 0.1 mass% or less in order to prevent early corrosion. A particularly preferable Cu concentration is 0.05% by mass or less.

  Sn is also an element whose base is the corrosion potential of the alloy. Preferential corrosion can be promoted by arbitrarily containing Sn in the range of 0.01 to 0.5% by mass. If the Sn concentration is less than 0.01% by mass, the preferential corrosion promoting effect is small, and if it exceeds 0.5% by mass, the corrosion is excessively early. A particularly preferable Sn concentration is 0.05 to 0.2% by mass.

  Since the anticorrosion hollow material (10) is hollow, it can be easily bent. For this reason, the hollow material of a straight pipe can be bent and wound around various shapes of steel structures, and sacrificial anodes can be formed on various shapes of steel structures. For example, in addition to a simple steel pipe (1) having a circular cross section as shown in FIG. 1, a plurality of outer peripheral surfaces such as H-shaped steel (4), I-shaped steel, and U-shaped structures shown in FIG. A sacrificial anode can also be formed by winding a complex-shaped steel structure having corners. Moreover, since the hollow material can be easily bent, it can be wound while being bent along the outer peripheral surface of the steel structure at the time of attachment. Of course, the hollow material can be bent in advance according to the outer peripheral shape of the steel structure. Since the hollow material is easier to bend than the solid material having the same diameter, a sacrificial anode having a larger surface area than the solid material can be formed. Further, when the attached anticorrosion hollow material (10) is corroded to some extent, it can be replaced before the corrosion reaches the steel structure, but it can be easily removed, so the replacement work is also simple.

  The dimension of the anticorrosion hollow material (10) is easier to bend as the outer diameter is smaller and the wall thickness is thinner, but on the other hand, since the corrosion allowance is reduced, the corrosion is reduced early, making it difficult to obtain long-term anticorrosion performance. From this viewpoint, the outer diameter of the anticorrosion hollow material (10) is preferably in the range of 6 to 20 mm, and the wall thickness is preferably in the range of 0.3 to 2 mm. The particularly preferable outer diameter of the anticorrosion hollow material (1) is 6 to 16 mm, and the particularly preferable thickness is 0.3 to 1.5 mm. Further, the cross-sectional shape of the anticorrosion hollow material (10) is not necessarily circular, and may be elliptical, rectangular, or other shapes.

  The connecting member (20) is provided with insertion portions (22) and (22) projecting on both surfaces of a plate-like flange portion (21), and the insertion portions (22) and (22) and the flange portion (21) are formed at the center. A cylindrical member having a through-hole. The insertion portion (22) is a so-called bamboo shoot joint in which a plurality of frustoconical nodes (23) whose cross-sectional area decreases from the proximal end side toward the distal end side are overlapped. The diameter of the maximum diameter portion (24) of the node (23) is slightly larger than the inner diameter of the anticorrosion hollow material (10). For this reason, when the opening end of the anticorrosion hollow material (10) is inserted into the insertion portion (22) of the connection member (20), the inner wall of the anticorrosion hollow material (10) advances while contacting the maximum diameter portion (24). However, if it is going to advance in the pulling direction, the corner portion of the maximum diameter portion (24) bites into the inner wall and is prevented from coming off. By using such a bamboo shoot joint, it is possible to easily process the end portion of the hollow material (10) and maintain the retaining state. In addition, the connecting member (20) in the illustrated example has a frustum shape in the node (23) of the insertion portion (33) in order to connect the hollow material having a circular cross section, but the shape of the node corresponds to the cross-sectional shape of the hollow material. It may be formed into various truncated cone shapes such as an elliptical truncated cone shape and a truncated pyramid shape. Further, although the connecting member (10) in the illustrated example is a hollow material, the connecting member in the present invention may be either a hollow material or a solid material.

  In addition, it is preferable to use a material having a corrosive potential more noble than the anticorrosion hollow material (10) as the material of the connecting member (20). The reason is that when the steel pipe (1) described later and the anticorrosion hollow material (10) are conducted through the conduction means, the conduction means is connected to the steel pipe (1) and the connection member (20), thereby the steel pipe. This is because (1) and the anticorrosion hollow material (10) can be electrically connected to each other, and the anticorrosion hollow material (10) can be surely sacrificed and corroded. In the above embodiment, the lead wire (3) which is a conduction means is welded to the steel pipe (1) and the flange (21) of the connecting member (20). Examples of the material of the connection member (20) having a corrosion potential higher than that of the anticorrosion hollow material (10) include steel and stainless steel.

  Furthermore, it is not necessary to wind the entire circumference of the steel structure with one anticorrosion hollow material (10), and it is also possible to wind a plurality of hollow materials around the entire circumference while connecting them.

  In the present invention, the shape of the connecting member is not limited to the illustrated example, and a structure in which both ends of the wound anticorrosion hollow material (10) are directly connected without using the connecting member is also included in the present invention.

  The water retaining part (30) is formed in a gap between the concrete (2), the steel pipe (1), and the anticorrosion hollow material (10), and interposes water to interpose the wound anticorrosion hollow material (10) to the concrete ( 2) and the steel pipe (1) are securely brought into contact with each other, and the anticorrosion hollow material (10) is stably sacrificed. If the gap between the concrete (2), the steel pipe (1), and the anticorrosion hollow material (10) is small, water (rainwater, etc.) is retained in the gap due to the interfacial tension of water, but it is actively used with water-retaining members Alternatively, water may be retained. In this case, concretely, we recommend water with foamed metal pores such as foamed synthetic resin and foamed aluminum, water absorbent resin with water, mortar with water, etc. It is preferable that it can be freely deformed according to the shape of the gap. Although it is difficult to contact the anticorrosion hollow material (10) bent at the corner between the steel pipe (1) and the concrete (2) without any gaps, a substantially large area can be obtained by interposing the water retention part (30). Can be contacted reliably.

  In addition, the height that the water retaining part (30) can keep in the space surrounded by the steel structure (1), the base (2), and the anticorrosion hollow material (10) is called the immediately above ground part, The base (2) and the anticorrosion hollow material (10) may not be in direct contact as long as the water retaining part (30) can be maintained.

  The anticorrosion hollow material (10) is brought into direct electrical contact by being wound around the steel pipe (1) or indirectly through water in the water retaining part (30), thereby preventing electrical corrosion. The edible hollow material (10) is a sacrificial anode. In this embodiment, both ends of the lead wire (3) are welded to the steel pipe (1) and the anticorrosion hollow material (10), thereby further ensuring the conduction state. The lead wire (3) is an example of a conduction means in the present invention, and can be reliably conducted if connected using the conduction means, and the corrosion prevention hollow material (10) is deformed due to progress of corrosion. The connection state can be reliably maintained. In addition, the conduction means can be directly connected to the anticorrosion hollow material (10), but when the connection member (20) is used for fixing in an annular shape, the connection member (20) and the steel pipe (1) are connected. It is preferable to do. This is because the connection member (20) is made of a material having a corrosion potential more precious than the anticorrosion hollow material (10), so that the conductive state is maintained even if the anticorrosion hollow material (10) is preferentially corroded. . The connecting means for the lead wire (3) is not limited to welding, and any means such as screwing or caulking can be adopted.

  Furthermore, in the present invention, the conduction means is not limited to the lead wire (3), and examples of other conduction means include those shown in FIGS. 4A to 4C. In these connection examples, the conduction means is connected to the flange portion (21) of the connection member (20), but it can be directly connected to the anticorrosion hollow material (10) by the same method.

  In FIG. 4A, the connecting member (20) and the steel pipe (1) are directly welded, and the weld portion (25) serves as a conduction means. FIG. 4B shows a connection member (20) wound with a conductive belt (26), and both ends thereof are overlapped and welded or screwed (not shown) to the steel pipe (1). (27) is a weld portion. FIG. 4C shows that the end portion of the belt-like body (28) is bent to form an arc portion (28a) corresponding to the shape of the connecting member, and the connecting member (20) is fitted and brought into contact with the arc portion (28a). The other end is fixed to the steel pipe (1) with a screw (28) or welded (not shown).

  In this invention, the foundation | substrate which embeds a steel structure is not limited, In addition to the concrete of the said embodiment, soil, asphalt, resin, rubber | gum, etc. can be illustrated.

  As shown in FIG. 1, the anticorrosion structure was formed by winding each anticorrosion tool shown in Table 1 around a steel pipe (1) having a circular cross section installed in concrete (2).

  The steel pipe (1) has an outer diameter of 115 mm and a wall thickness of 4.5 mm.

[Examples 1-12, Comparative Examples 21-23]
The anticorrosion hollow material (10) having an aluminum alloy composition shown in Table 1 and having an outer diameter and a wall thickness shown in Table 1 was extruded. This straight pipe anticorrosion hollow material (1) is bent around the steel pipe (1) while being bent, and both open ends are inserted into the insertion part (22) of the tacho joint (20) to form an annular shape. . Further, the gap at the corner between the steel pipe (1) and the concrete (2) was filled with a water retaining part (20) in which water was contained in the foaming synthetic resin. Furthermore, both ends of the lead wire (3) were welded to the flange portion (21) of the steel bamboo shoot joint (20) and the outer peripheral surface of the steel pipe (1).

[Comparative Example 24]
The anticorrosion tool was changed to a solid material in Table 1, and it was tried to bend along the steel pipe (1) into a circle. However, because of its strength, it could not be bent easily. I could not.

  The anticorrosion structure was evaluated by conducting the following test. The evaluation results are also shown in Table 1.

[Bending performance of corrosion protection equipment]
The breaking load of each anticorrosive tool was measured, and the bending performance was relatively evaluated in three stages based on the breaking load. That is, the smaller the breaking load, the easier it is to bend and the easier attachment by winding. In Table 1, the most easily bendable is “◎”, and it becomes difficult to bend in the order of “○” and “x”.

[Anti-corrosion performance]
The steel pipe (1) with the anticorrosion tool was exposed in the atmosphere for half a year, and the anticorrosion performance was evaluated according to the following criteria.

○: Only the anticorrosion tool was corroded, and the steel pipe was not corroded. ×: Corrosion reached the steel pipe.

  From the results in Table 1, it was confirmed that the anticorrosion structure of each example had long-term anticorrosion performance. Further, the anticorrosion hollow material was easy to bend and could be easily attached.

  The corrosion prevention structure of the steel structure of the present invention is formed by winding the sacrificial anode with a hollow material made of an aluminum alloy, and can be used for corrosion prevention of steel structures having various shapes.

It is a perspective view showing typically one embodiment of the corrosion prevention structure of the steel structure of the present invention. It is the 2A-2A sectional view taken on the line of FIG. FIG. 2 is a cross-sectional view taken along line 2B-2B in FIG. 1, showing connection portions at both ends of the anticorrosion hollow material. It is a perspective view which shows typically other embodiment of the anticorrosion structure of the steel structure of this invention. It is sectional drawing which shows other embodiment of the conduction | electrical_connection means in this invention. It is sectional drawing which shows other embodiment of the conduction | electrical_connection means in this invention. It is sectional drawing which shows other embodiment of the conduction | electrical_connection means in this invention.

Explanation of symbols

1 ... Steel pipe (steel structure)
2… Concrete (base)
3 ... Lead wire (conduction means)
4 ... H-shaped steel (steel structure)
10 ... Corrosion-resistant hollow material
20… Connecting member (Bamboo joint)
30 ... Water retention part

Claims (11)

A part of the anti-corrosion structure of a steel structure embedded in the ground,
Aluminum alloy containing Zn: 2 to 20% by mass, Cu concentration is regulated to 0.1% by mass or less, and the balance is made of Al and impurities on the outer peripheral surface of the underground part directly above the embedded part of the steel structure An anticorrosion structure for a steel structure, characterized in that the anticorrosion hollow material composed of is wound, and the anticorrosion hollow material and the steel structure are electrically connected.   2. The steel structure according to claim 1, wherein both ends of the anticorrosion hollow member wound around the steel structure are connected via a connecting member made of a noble material having a corrosion potential higher than that of the anticorrosion hollow member. Anti-corrosion structure.   The connecting member has a truncated cone shape in which insertion portions that are inserted into the opening ends of the anticorrosion hollow material project on both surfaces of the flange portion, and the insertion portion has a cross-sectional area that decreases from the proximal end side toward the distal end side. The anticorrosion structure for a steel structure according to claim 2, wherein a plurality of nodes are overlapped.   The anticorrosion structure of the steel structure according to any one of claims 1 to 3, wherein the steel structure and the anticorrosion hollow material are connected via a conduction means.   The anticorrosion structure for a steel structure according to claim 2 or 3, wherein the steel structure and the connection member are connected via a conduction means.   The anticorrosion structure for a steel structure according to any one of claims 1 to 5, wherein a water retaining portion is provided between the anticorrosion hollow material and the steel structure.   The corrosion prevention structure of the steel structure in any one of Claims 1-6 which contains 0.01-0.5 mass% Sn in the said aluminum alloy composition.   The anticorrosion structure for a steel structure according to any one of claims 1 to 7, wherein an outer diameter of the anticorrosion hollow material is 6 to 20 mm and a wall thickness is 0.3 to 2 mm.   Zn: 2-20% by mass is contained on the outer peripheral surface of the underground part directly above the embedded part of the steel structure partly embedded in the base, the Cu concentration is regulated to 0.1% by mass or less, and the remainder Wrapping the anticorrosion hollow material made of an aluminum alloy composed of Al and impurities and having a lower corrosion potential than the steel structure while bending it, and electrically connecting the anticorrosion hollow material and the steel structure To prevent corrosion of steel structures.   An anticorrosion tool to be attached to the outer peripheral surface of a submerged portion directly above an embedded portion of a steel structure, a portion of which is embedded in the base, containing 2 to 20 mass% of Zn and having a Cu concentration of 0.1 mass% An anticorrosive tool characterized in that it is a hollow material made of an aluminum alloy that is regulated as follows and the balance is made of Al and impurities, and has a lower corrosion potential than the steel structure. A connecting member for connecting the both open ends of the corrosion protection device according to claim 10 to form the corrosion protection device in an annular shape,
Insertion parts for inserting into the opening end of the anticorrosive tool protrude from both sides of the flange part, and the insertion part is provided with a plurality of frustum-shaped nodes having a cross-sectional area that decreases from the proximal end side toward the distal end side. The connection member for anticorrosives characterized by comprising.

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