JP6663601B2 - Backfill structure of galvanic anode and method for producing the same - Google Patents

Description

  The present invention relates to a backfill structure of a galvanic anode used for cathodic protection and a method for producing the same.

  In the case of reinforced concrete structures, the internal reinforcing steel is corroded due to the neutralization of the concrete, the salt content of the concrete material, the salt coming from outside, the effect of antifreezing materials, etc. (salt damage), leading to deterioration of the concrete. There is.

  Therefore, in order to prevent such corrosion of reinforcing steel, a galvanic anode made of zinc, aluminum, etc., which has a lower oxidation-reduction potential than a reinforcing steel, is installed on the concrete surface or inside the concrete, and the galvanic anode and the inside of the reinforcing steel are used. A corrosion suppression structure that electrically connects steel and generates a potential difference between the galvanic anode and the internal steel, and supplies anticorrosion current to the internal steel to prevent and control corrosion of the internal steel It is known (see, for example, Patent Document 1).

  In addition, this type of corrosion suppression structure includes a backfill formed by impregnating a liquid retaining member made of a porous material with an electrolyte solution, surrounds the galvanic anode with the backfill, and fills a gap between the galvanic anode and concrete. There is also known a method in which the electrode potential of the galvanic anode is stabilized by an electrolyte solution to prevent local dissolution of the galvanic anode (for example, see Patent Document 1).

  In this corrosion suppression structure, an anode atom such as a zinc atom forms a complex ion with one Na ion (or Li ion) and four OH ions in the electrolyte solution and elutes into the electrolyte solution, thereby increasing the electrode potential of the anode. Has stabilized.

  Further, when a passivation film is formed on the anode, the anticorrosion effect is reduced. However, in order to suppress such passivation of the anode, an electrolyte such as sodium hydroxide (NaOH) or lithium hydroxide (LiOH) is used. It is known that the use of a solution is effective, and in suppressing passivation, it is desirable that the pH of the electrolyte solution is high, for example, in the case of a zinc anode, the pH is 13.3 or more. It is also known that when the initial pH is high, for example, when it is 13.5 to 14.0 or more, the durability of the anode is improved.

Japanese Patent No. 3099830

  However, in the conventional techniques as described above, the volume of the electrolyte solution that can be impregnated into the liquid retaining member is limited, and it is necessary to form complex ions in order for the anode atoms to elute into the electrolyte solution. Since four OH ions are consumed, there has been a problem that the OH ions in the electrolyte solution decrease over time, and the performance of the galvanic anode decreases accordingly.

  In view of such a conventional problem, the present invention has been made with the object of providing a backfill structure of a galvanic anode capable of extending the life of the galvanic anode and a method of generating a backfill used therein. Things.

  The feature of the invention according to claim 1 for solving the conventional problem as described above is that a liquid retaining member made of a porous material covering the galvanic anode and an electrolyte solution retained in the liquid retaining member are provided. In the backfill structure of a galvanic anode provided, the liquid retaining member contains a powdery anode passivation suppressing material in an amount exceeding the solubility of the electrolyte solution. It is in.

  A feature of the present invention according to claim 2 is the method for producing a backfill used in the backfill structure of a galvanic anode according to claim 1, wherein the powdery anode material is added to the fine particulate porous material. A passivation inhibitor is added, water is added to the mixture, and the mixture is kneaded to retain the electrolyte solution in the porous material, and the anode passivation inhibitor in excess of the solubility of the electrolyte solution is solidified. In the state described above.

  As described above, the backfill structure of a galvanic anode according to the present invention includes a liquid retaining member made of a porous material covering the galvanic anode, and an electrolyte solution retained in the liquid retaining member. In the backfill structure of the electroanode, the liquid retaining member contains a powdery anode passivation inhibitor in an amount exceeding the solubility of the electrolyte solution, so that time elapses, and Even if the amount of hydroxide ions in the solution decreases, hydroxide ions are supplied by the elution of the anode passivation suppressing member contained in the liquid retaining member into the solution, so that the durability of the galvanic anode is improved. Can be improved.

  In the present invention, the powdery anode passivation inhibitor is added to the fine-particle porous material, and water is added to the mixture, followed by mixing and kneading, thereby keeping the electrolyte solution in the porous material. By containing the anode passivation inhibitor in a solid state in an amount exceeding the solubility of the electrolyte solution, the powder anode passivation inhibitor is contained in a state of being uniformly dispersed in the liquid retaining member. Can be done.

It is a schematic sectional drawing which shows an example of the electrical corrosion suppression method using the backfill structure of the galvanic anode which concerns on this invention. 4 is a graph comparing the off-potential with respect to the energizing time in the backfill structure according to the present invention and the conventional example in the same test. 4 is a graph comparing the off-potential with respect to the energizing time in the backfill structure according to the present invention and the conventional example in the same test.

  Next, an embodiment of the backfill structure of the galvanic anode according to the present invention will be described based on the embodiment shown in FIGS.

  FIG. 1 shows an example of a method for suppressing electric corrosion using a backfill structure according to the present invention, in which a galvanic anode 2 installed in concrete 1 is electrically connected to an internal steel material 3 such as a reinforcing bar. An anticorrosion current is supplied to the internal steel material 3 by utilizing a potential difference between the electroanode 2 and the internal steel material 3 to suppress corrosion of the internal steel material 3.

  The backfill structure 4 includes a liquid retaining member 5 surrounding the galvanic anode 2 and an electrolyte solution impregnated in the liquid retaining member 5, and the electrolyte solution impregnated in the liquid retaining member 5 contacts the galvanic anode 2. This causes the galvanic anode 2 to corrode and suppresses the formation of a passive film on the galvanic anode 2.

  The galvanic anode 2 is formed of a metal such as zinc or aluminum having a low oxidation-reduction potential with respect to the internal steel material 3 such as a reinforcing bar, and is electrically connected to the internal steel material 3 such as a reinforcing bar via a lead wire 6 or the like. It has become.

  The electrolyte solution is a sodium hydroxide solution, a lithium hydroxide solution or the like adjusted to a pH of 13.5 or more, and an electrolyte having an effect of suppressing passivation of the galvanic anode 2 is dissolved in a solvent such as water. It is a solution.

  The liquid retaining member 5 is made of a porous material such as cement mortar, bentonite, gypsum, etc., so that the aqueous solution can be impregnated and retained in the gaps.

  The porous material is not limited to the examples described above, and may be any material that is porous and can impregnate and retain an electrolyte solution, and may be made of, for example, a phenol continuous foaming resin.

  The liquid retaining member 5 has an anode passivation made of an electrolyte similar to the electrolyte used in the electrolyte solution such as powdery (solid) sodium hydroxide and lithium hydroxide in an amount exceeding the solubility of the electrolyte solution. Are contained in an evenly dispersed state.

  In order to generate this backfill, a predetermined amount of a powdery anode passivation inhibitor 7, 7,... Is added to a predetermined amount of a particulate porous material, and water is added thereto and kneaded. As a result, the porous material exhibits a certain shape-retaining property, and the anode activating agent 7 dissolves in water retained in the gaps between the porous materials to form an electrolyte solution. Are uniformly dispersed and contained in a solid state.

  Then, a liquid retaining member made of a porous material is molded, cured in that state, and cured, and then impregnated with an electrolyte solution as necessary to adjust the electrolyte concentration and pH.

  In the backfill structure 4 configured as described above, the liquid retaining member 5 contains an amount of the anode passivation suppressing materials 7, 7,... Therefore, the electrolyte solution is in a state in which more than a certain amount of electrolyte cannot be dissolved, that is, in a saturated state, and the anode passivation suppressing material 7, 7,... The liquid is held in the liquid retaining member 5 in an ionic crystal state.

  Next, when the galvanic anode 2 and the internal steel material 3 such as a reinforcing bar are electrically connected to form a corrosion suppression circuit, the anode atom becomes one cation such as a sodium ion and four hydroxide ions and a complex ion. Is formed and eluted into the solution, and as time passes, hydroxide ions in the electrolyte solution decrease.

  On the other hand, since the liquid retaining member 5 contains the anode passivation suppressing materials 7, 7,... In the state of ionic crystals, the anode passivation suppressing materials 7, 7,. Are eluted into the electrolyte solution, hydroxide ions are supplied, and the concentration of the anode passivation inhibitor in the electrolyte solution is kept constant for a long time.

  FIGS. 2 and 3 are graphs comparing the relationship between the number of days elapsed from the start of energization when the current-carrying anode 2 is energized and the off-current and instant-off potential of the current-carrying anode (zinc).

  In the case of using the conventional backfill structure, as shown in FIGS. 3 and 4, the off-potential and the instant-off potential sharply increase shortly after the start of energization, whereas the backfill structure 4 according to the present invention has A rapid increase in the off-potential and the instant-off potential over a long period can be suppressed, and a stable state can be maintained.

  Note that, in the above-described embodiment, an example in which the backfill structure according to the present invention is applied to corrosion prevention of the internal steel material of a concrete structure has been described. However, the internal steel material is not limited to a reinforcing bar, and may be, for example, a PC steel wire or the like. Alternatively, the present invention can be applied to a backfill for a galvanic anode attached to the outside of a target to be protected.

DESCRIPTION OF SYMBOLS 1 Concrete 2 Galvanic anode 3 Inner steel material 4 Backfill structure 5 Liquid retention member 6 Lead wire 7 Anode passivation suppressing material

Claims (2)

In the backfill structure of the flowing anode comprising a liquid retaining member made of a porous material covering the galvanic anode and an electrolyte solution retained in the liquid retaining member,
The backfill structure of a galvanic anode, wherein the liquid retaining member contains a powdery anode passivation inhibitor in an amount exceeding the solubility of the electrolyte solution. A method for generating a backfill used in the backfill structure of the galvano anode according to claim 1,
A powdery anode passivation inhibitor is added to the fine-particled porous material, and water is added thereto and kneaded to keep the electrolyte solution in the porous material and to dissolve the electrolyte solution. A method for producing a backfill, comprising: adding a part of the anode passivation inhibitor in a solid state, the amount of which exceeds the limit.

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