JPH0445292A - Electric corrosion protection for reinforcing bar - Google Patents

Abstract

PURPOSE:To prevent corrosion of reinforcing bars for a reinforced concrete structure by directly coating the surface of a reinforcing bar with base metal having higher ionization tendency than the reinforcing bar to make a sacrifice anode and then bringing this anode into contact with the objective reinforcing bar to be protected from corrosion. CONSTITUTION:A reinforcing bar 1 is directly coated with base metal having higher ionization tendency such as aluminum, zinc, magnesium, etc., to form an anode metal layer. Figure 1 shows one example of arrangement of reinforcing bars, in which the metal-coated bar 1 is used as a distributing bar to form a lattice with the main reinforcing bar 3. In this arrangement, the anode metal layer comes into contact with the reinforcing member 3 and the crossing part is fixed as shown in the figure 2. In this state, at the crossing part of the main reinforcing bar 3 and the bar 1, a galvanic cell is formed with the bars 1 as an anode and the main bar 3 as a cathode, and the main bar 3 is given the corrosion preventive effect by galvanic anode system. The reinforcing bar 1 is used as a sacrifice anode, however, the bar 1 itself is covered with the anode metal layer 2 and thereby, it has corrosion resistance.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a galvanic anode cathodic protection method for preventing corrosion of reinforcing bars in reinforced concrete structures.

[Conventional technology]

Corrosion reactions of metals in an environment containing moisture are electrochemical reactions in which an oxidation reaction in which the metal releases electrons (anode reaction) and a reduction reaction in which the metal receives electrons (cathode reaction) proceed simultaneously.Therefore, the metal potential changes. Corrosion prevention is possible if
Cathodic protection methods are broadly divided into galvanic anode methods that utilize the natural potential difference of metals, and external power supply methods that supply power from outside. The conventional method for cathodic protection of reinforcing steel in concrete involves installing an electrode as an anode on the surface of the concrete, and using the reinforcing steel as a cathode between this electrode and the anode on the concrete surface, an external force is applied via the concrete. An external power supply method that passed current through the was common.

[Problem to be solved by the invention]

However, the external power supply method has the following problems. (1) Electrodes must be installed over a wide area on the concrete surface, and installation requires a great deal of effort and construction cost. (2) Compared to normal cathodic protection for metals, the electrical resistance of concrete is high, so a large power supply is required. (3) The electrical resistance of concrete changes depending on the environment in which the concrete structure is installed, and it is necessary to adjust the amount of electricity supplied accordingly, making the equipment complex and increasing equipment costs and running costs. The costs including this will be enormous. On the other hand, in the case of the conventional galvanic anode method in which the sacrificial anode is placed away from the reinforcing steel that serves as the cathode, the electrical resistance of concrete is high, so in order to achieve the desired corrosion protection effect, the sacrificial anode must be placed closely together. However, there were some construction difficulties. An object of the present invention is to provide a method for electrolytic corrosion protection of reinforcing bars that does not have such problems despite using a galvanic anode method and can eliminate the above-mentioned drawbacks caused by an external power supply method.

[Means to solve the problem]

In the present invention, the surface of the reinforcing bar is directly coated with a metal whose natural potential series is more base than this, and this is used as a sacrificial anode in contact with the reinforcing bar to be protected against corrosion.

[For production]

A metal-coated reinforcing bar serves as a sacrificial anode and is placed close to the reinforcing bars that require corrosion protection, and these reinforcing bars directly constitute a cathodic protection circuit network. Therefore, although it is a galvanic anode method, it has a good corrosion prevention effect, and moreover, cathodic corrosion protection can be achieved economically without requiring any special work other than conventional reinforced concrete construction. Additionally, metal-coated reinforcing bars can be protected by the coating layer.

【Example】

An embodiment of the present invention will be described below. The reinforcing bars of reinforced concrete structures generally include main reinforcing bars whose required sectional force is determined from the design sectional force and the tensile strength of the reinforcing bars, and distribution bars, stirrup bars, and hoop reinforcing bars that evenly distribute the stress acting on the main reinforcing bars. It is divided into auxiliary reinforcing bars such as There are also assembly bars to secure the position of reinforcing bars. Therefore, when the main reinforcing bar is the reinforcing bar to be protected against corrosion, the surface of the other reinforcing bar 1 is directly coated with a metal whose natural potential series is baser than that, such as aluminum, zinc, magnesium, etc., as shown in Figure 3. Then, the anode metal layer 2 is formed. The thickness of the anode metal layer 2 is appropriately set depending on the thickness of the reinforcing bar 1 and the installation environment. 11] shows an example of reinforcing bar arrangement, and metal-coated reinforcing bar 1
The main reinforcing bars 3 are arranged in a lattice pattern as distribution bars, and the anode metal layer 2
are brought into contact with the surface of the main reinforcing bars 3, and the intersections are tied together as shown in FIG. 2, for example. In this case, a galvano cell is formed in which the reinforcing bar 1 serves as an anode and the main reinforcing bar 3 serves as a cathode through the intersection of the reinforcing bar 1 used as a distribution bar and the main reinforcing bar 3, and the main reinforcing bar 3 is protected against corrosion by the galvanic anode method. Ru. Further, the reinforcing bar 1 becomes a so-called sacrificial reinforcing bar, but since it is covered with the anode metal layer 2, it is protected against corrosion. Figures 4(A) and 4(B) show an example in which the method is applied to a column 4 of a reinforced concrete structure. When reinforcing hoops 6 are arranged around and in contact with the main reinforcing bars 5, an anode metal layer as shown in FIG. 2 is formed on the hoop reinforcing bars 6, and this is used as a sacrificial anode to protect the main reinforcing bars 5 from corrosion. do. Fig. 5 shows an example in which the application is applied to the slab part 7 and beam part 8 of a reinforced concrete structure.For the slab part 7, an anode metal layer is formed on the distribution bar 9 to prevent corrosion of the main reinforcing bar 10, and for the beam part 8, the anode metal layer is formed on the distribution bar 9. An anode metal layer is formed on the stirrup bar 11 to protect the main reinforcing bar 2 from corrosion. In particular, in the case of beams and slabs, the lower side is difficult to dry, and moisture and salt from seawater droplets are concentrated here (see Section 6 [21]).
. Furthermore, as shown in FIG. 7, the quality of the concrete on the lower side of the reinforcing bars 13 is inferior to other parts due to breathing water 15 caused by water separation in the concrete 14, so this part is particularly susceptible to rust. Therefore, if sacrificial reinforcing bars as described above are placed in such places, effective corrosion prevention can be achieved.

【Effect of the invention】

According to the present invention, there are the following effects. ■ By simply assembling the reinforcing bars as usual, a cathodic protection circuit using the galvanic anode method is formed, significantly reducing costs and construction time compared to conventional methods. ■ No running costs required. ■ It is particularly effective in preventing corrosion of reinforcing bars in areas such as beams and slabs that are susceptible to moisture and salt. ■ Metal-coated reinforcing bars can be protected by the coating layer.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an example of reinforcement according to the present invention, FIG. 2 is an enlarged plan view of a part thereof, FIG. 3 is an enlarged sectional view of reinforcing bars on which an anode metal layer is formed, and FIGS. B) is a vertical cross-sectional view and a cross-sectional view of an example applied to a column part of a reinforced concrete structure, Figure 5 is a cross-sectional view of an example applied to a slab part and a beam part, and Figures 6 and 7 are a cross-sectional view of an example applied to a column part of a reinforced concrete structure. FIG. 2 is an explanatory diagram for explaining that reinforcing bars are susceptible to rust. 1...Reinforcement bar, 2...Anode metal layer, 3,
5.10... Main reinforcing bar, 6... Hoop reinforcing bar,
9... Distribution muscle, 11... Star lamp muscle. Figure Figure A Figure Figure Figure (A) Figure <8) Figure Figure Salt Moisture Figure Concrete Placement Direction

Claims (1)

[Claims] 1. A method for electrolytic corrosion protection of reinforcing bars, which is characterized in that the surface of reinforcing bars is directly coated with a metal whose natural potential series is baser than this, and this is used as a sacrificial anode to contact the reinforcing bars to be protected against corrosion.