JP2014133911A - Method for inhibiting hydrogen embrittlement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit the hydrogen embrittlement of a steel material used while being embedded within a concrete.SOLUTION: The surface of a steel material is initially hydrophobicized at the first step S101. The surface of the steel material may be hydrophobicized by modifying the same with a silane coupler, for example. At the next second step S102, a concrete structure is prepared by embedding, within a concrete, the surface-hydrophobicized steel material. It becomes possible to suppress the formation of a water film, etc. in a state of covering the surface of the steel material embedded within the concrete and to inhibit the invasion of hydrogen into the steel material within the concrete structure thus prepared.

Description

  The present invention relates to a method for suppressing hydrogen embrittlement that suppresses hydrogen embrittlement in steel such as a reinforced concrete rebar.

  In structures such as buildings, delayed fracture can be a problem. Delayed fracture is a phenomenon in which steel used under certain conditions under static load suddenly breaks brittlely with almost no plastic deformation after a certain amount of time. is there. Although the mechanism of this delayed fracture has not been fully elucidated, it is thought to be due to hydrogen embrittlement due to the penetration of hydrogen into the metal and loss of ductility. For example, in steel materials embedded in concrete, such as reinforced concrete, there are reports that hydrogen embrittlement occurs and that it does not occur depending on the stress and type of steel in the environment in the concrete that is estimated to be alkaline. Yes, investigation continues (see Non-Patent Document 1).

Hiroyuki Saito, Norihiro Fujimoto, Takashi Sawada, “Hydrogen Penetration Efficiency into High-Strength Steel”, Proceedings of the 79th Annual Meeting of the Electrochemical Society of Japan, 205, 2012.

In order to suppress the hydrogen embrittlement mentioned above, various hydrogen embrittlement countermeasure technologies such as examination of materials that are strongly constrained in the metal structure even if hydrogen invades and do not affect the metal structure, and alloy compositions of steel materials are examined. Is being sought. However, in any case, when steel materials are used, the possibility of hydrogen generation on the surface of the steel materials cannot be denied at this stage even in an environment of concrete. This is adsorbed on the steel material, and depending on the steel type, it can be the starting point for causing hydrogen embrittlement.
Therefore, there is a problem that hydrogen embrittlement may be caused depending on conditions.

  This invention is made | formed in order to eliminate the above problems, and it aims at suppressing the hydrogen embrittlement in the steel materials embed | buried and used for concrete.

  The method for suppressing hydrogen embrittlement according to the present invention includes at least a first step of hydrophobizing the surface of a steel material and a second step of embedding the steel material having a hydrophobized surface in concrete to produce a concrete structure. .

  In the hydrogen embrittlement suppression method, in the first step, the surface of the steel material may be modified with a silane coupler to be hydrophobized.

  As described above, according to the present invention, since the surface of the steel material is made hydrophobic, it is possible to obtain an excellent effect that hydrogen embrittlement in the steel material embedded and used in concrete can be suppressed.

FIG. 1 is a flowchart illustrating a method for suppressing hydrogen embrittlement in an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a partial configuration of the concrete 102 in which the reinforcing bars 101 are embedded. FIG. 3 is a cross-sectional view showing a partial configuration of the concrete 102 in which the reinforcing bars 101 are embedded.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a flowchart illustrating a method for suppressing hydrogen embrittlement in an embodiment of the present invention. In this hydrogen embrittlement suppression method, first, the surface of the steel material is hydrophobized in the first step S101. For example, the surface of the steel material may be hydrophobized by modifying it with a silane coupler (applying a silane coupler agent). Next, in the second step S102, a steel structure having a hydrophobic surface is embedded in the concrete to produce a concrete structure.

  According to the above-described embodiment, in the produced concrete structure, for example, a water film or the like is hardly formed in a state of covering the surface of the steel material embedded in the concrete. Hydrogen intrusion is suppressed.

  In concrete, it can be considered to be alkaline, and in such an environment, water present on the steel surface receives electrons to generate hydrogen and hydroxide ions, and this hydrogen penetrates into the steel material to generate hydrogen. It is considered that brittleness occurs (see Non-Patent Document 1). For this reason, the hydrogen penetration | invasion with respect to the steel material in concrete will be rate-limited by the production | generation reaction mentioned above by presence of water. Therefore, if this reaction can be suppressed, hydrogen intrusion can be suppressed.

  Since the reaction described above occurs because water is in contact with the steel surface, reducing this water is one possible solution. In concrete, bubbles and water are generally present simultaneously. On the other hand, if the surface of the steel material is made hydrophobic, it is considered that the surface area in contact with the air derived from the bubbles becomes larger than the surface area in contact with water because the water becomes poor.

  Therefore, when producing a concrete structure, the steel material surface is hydrophobized before a steel material such as a reinforcing bar is embedded in the concrete. Hydrophobization may be performed by using a well-known existing method. For example, a silane coupler may be modified on the surface of a steel material. If a part or the whole of the steel material surface is modified with a silane coupler, the hydrophobicity of the steel material surface can be improved. For example, by using a silane coupler, the surface of the steel material can be hydrophobized up to a water contact angle of around 120 degrees.

  Concrete can contain water from the absolute dry state (0%) to the fully wet state (100%) (saturation rate), but in normal circumstances it takes an intermediate value between these. In a general outdoor environment, the water saturation rate is around 50 to 70%, although it varies depending on the weather such as rainy weather and fine weather.

  At this time, as shown in FIG. 2, the pores 102a of the concrete 102 in which the reinforcing bars 101 are embedded are, on average, 50 to 70% of the volume filled with water, and the remainder is filled with air. The concrete 102 is a porous body having a plurality of pores 102a. However, normally, since the surface of the reinforcing bar 101 is hydrophilic, it gets wet with water, almost 100% of the pores 102a in the concrete 102 in the vicinity of the reinforcing bar 101 are filled with the water 111, and the layer of the water 111 is the reinforcing bar 101 Covering the surface. In this way, the portion in contact with the water 111 contributes to the electrochemical reaction (charge transfer), and hydrogen is generated by this reaction.

  In this state, as shown in FIG. 3, if the silane coupling layer 103 is formed on the surface of the reinforcing bar 101 and is made hydrophobic, the pores 102 a of the concrete 102 near the surface of the reinforcing bar 101 are also formed. A layer of water 112 and air 113 is produced. When a hydrophobic (water-repellent) surface having a contact angle of 120 degrees is formed, air 113 up to about 50% by volume can enter.

  In such a state, the surface with the air 113 in the reinforcing bar 101 does not contribute to the electrochemical reaction, and only the portion in contact with the water 112 contributes to the electrochemical reaction and hydrogen is generated. In this case, the portion causing the electrochemical reaction of hydrogen generation is reduced.

Resistance due to charge transfer is electrochemically measured as charge transfer resistance (polarization resistance). When exposed to outdoor outdoor for one month with non-hydrophobic rebars embedded in concrete, 0.6 MΩcm ² However, when the surface of the reinforcing bar was made hydrophobic and then buried in concrete and exposed outdoors for one month, it was about 1 MΩcm ² .

When the surface of the reinforcing bar is made hydrophobic, the charge transfer resistance of the electrochemical reaction is increased, so that the hydrogen generation reaction is suppressed. It is known that the concentration p _{H2 of the} hydrogen gas in the vicinity of the reinforcing bar surface and the amount of penetrating hydrogen p _sol are correlated by the relationship of “p _sol ∝p _H2 ^1/2 ” according to the Siebelz rule. If hydrogen generation is suppressed, the amount of intrusion hydrogen to the steel material is also suppressed. Accordingly, the amount of hydrogen entering the steel, which is the cause of hydrogen embrittlement, is reduced, and hydrogen embrittlement is suppressed.

  As described above, in the present invention, since the surface of the steel material embedded in the concrete is made hydrophobic, water on the surface of the steel material receives electrons to generate hydrogen and hydroxide ions. Therefore, hydrogen embrittlement in the steel material can be suppressed.

  The present invention is not limited to the embodiment described above, and many modifications and combinations can be implemented by those having ordinary knowledge in the art within the technical idea of the present invention. It is obvious.

  DESCRIPTION OF SYMBOLS 101 ... Reinforcing bar, 102 ... Concrete, 102a ... Pore, 103 ... Silane coupling layer, 111 ... Water, 112 ... Water, 113 ... Air.

Claims (2)

A first step of hydrophobizing the surface of the steel material;
A method of suppressing hydrogen embrittlement, comprising at least a second step of embedding the steel material having a hydrophobic surface in concrete to produce a concrete structure. The method for suppressing hydrogen embrittlement according to claim 1,
In the first step, a method for suppressing hydrogen embrittlement, wherein the surface of the steel material is modified with a silane coupler to be hydrophobized.

Images