KR100725644B1 - Method of preventing corrosion of bolt and nut connection of steel structure by corrosion inhibitor and gel type sacrificial anode sealing agent - Google Patents

Abstract

A corrosion protection method of connecting parts of bolts and nuts in a steel structure by sealing the crevices with a gel type sacrificial anode sealant after coating inner surfaces or crevices of the connecting parts of bolts and nuts with a corrosion inhibitor or injecting the corrosion inhibitor onto the inner surfaces or the crevices thereof, and a gel type sacrificial anode sealant that contains a high purity Zn anode powder, or a Zn- or Al-based alloy anode powder and is used conveniently in the same are provided. As a gel type sacrificial anode sealant of a Zn- or Al-based alloy, the sealant is prepared by mixing a high purity(99.99% or more) Zn anode powder of -1.05 volt(SCE) or less, or a fine powder of a Zn- or Al-based alloy anode with a liquid phase organic or inorganic binder at a mixing ratio of 1:1 to 1:1.5, wherein the Zn-based ally comprises 99.3% of Zn, 0.6% of Al and 0.1% of other components, the Al-based alloy comprises 95% of Al, 4.5% of Zn and 0.5% of other components, the other components are one or more elements selected from the group consisting of In, Si, Mg and Ca, and the sealant is a gel type sealant that can be conveniently used in corrosion protection of connecting parts of bolts and nuts in a steel structure and maintains a surface electric potential of -1,000 mV SCE or less during hardening.

Description

Corrosion protection method of bolt-nut-connected parts in a steel construction by inhibitor and gel type anode sealant}

1A is a view schematically showing a state of a bolt-nut connection portion of a steel structure.

Figure 1b is a view schematically showing the state of the bolt-nut connection of the steel structure of the road facility.

2A to 2D are photographs showing corrosion of existing bridges and bolt and nut connections of the bridges.

3A and 3B are photographs showing the results of the salt immersion test of the bolt nut connection specimen and the control bolt nut connection treated by the corrosion protection method according to the present invention.

<Description of Symbols for Main Parts of Drawings>

1-structural material, 20-bolt, 21-nut,

30-gap, 31-crevice, 32-splice,

33-bolt holes, 40-washers

50-Road Facility

The present invention relates to a method for preventing corrosion of bolt and nut connections of steel structures, and more particularly, after applying or injecting a corrosion inhibitor comprising a mixed aqueous solution of potassium silicate and sodium silicate to the inner surface and the gap of the bolt and nut connections, (99.99% or more) The present invention relates to a method for preventing corrosion (corrosion) consisting of sealing a gap with a gel-type sacrificial anode sealing agent containing a Zn anode powder or a Zn or Al-based alloy anode powder.

As shown in Figures 1a, 1b and 2b-2d, the bolt connection of the steel structure is formed between the bolt and the leaflet, the leaflet and the structural member, and the leaflet and the nut into the gap in the presence of moisture As water enters and becomes watered on the inner surface of the gap, corrosion occurs. Corrosion of the inner surface and gap of bolted connections of steel structures can be divided into three types according to the mechanism. First, because the bolts, washers, leaflets, structural members, and nuts of steel structures have different surface potentials, they form galvanic cells in the presence of water (water film) on the surface or gap, and dissimilar metals in which the relative anode part is corroded. There is cell structure corrosion. Second, when water is present in the crevice between bolts and washers, washers and leaflets, leaflets and structural nuts and washers of steel castings, an oxygen shade cell is formed between the outside and the inside of the gap, so that the anode is deficient in oxygen. There is an oxygen concentration cell type corrosion that causes local corrosion by reaction. Third, there is stress corrosion in bolt struts that are partially stressed and corroded in the presence of non-tightening bolts, bending of members, deflection of loads, etc. of steel structures.

In spite of this situation, in Korea, unlike the developed countries, the anticorrosive treatment of the bolted joints of steel structures such as bridges and road facilities is not properly performed at the construction stage. It is severely corroded and is a major cause of extremely shortening the safety life of steel structures. Until recently, in the construction of domestic bridges, there was a lack of sealing treatment for gapless joints and gaps between joints, and the heavy-duty coating method was applied to external surfaces after high-tight bolts were tightened. Moisture was introduced, and the corrosion damage of the bolt caused by the formation of the corrosion battery on the inner surface of the bolt connection was severe. As such, corrosion of the inner surface of the bolt connection part of the existing steel structure in the state where structural disassembly is impossible cannot be solved by the existing coating method.

In developed countries, zinc-rich primers are applied to the joints of the bolted joints of bridges to prevent corrosion, and the gaps are sealed with organic sealing agents such as epoxy or urethane, and then coated in a heavy manner to prevent corrosion.

In addition, after applying the anti-corrosion method to the outer surface of the bolt connection part of the steel structure recently, by supplying the anticorrosive current by the external power method to suppress the corrosion of the outer surface, and also by supplying the anticorrosive current to the inner surface of the gap partially corrosion method Cathodic protection method has been developed, but it is not actually applied due to economic problems.

In addition, a method of injecting a corrosion inhibitor into the bolt connection part and applying a modified epoxy to the outside has been developed, but there is a problem in that the corrosion protection function is limited because the waterproof function against the gap is absolutely insufficient.

The inventors of the present invention continue to study the corrosion prevention method of the bolt connection of the steel structure that can be put to practical use and excellent anticorrosive effect compared to the conventional techniques, and developed and used a corrosion inhibitor and a gel type sacrificial anode sealing agent according to the present invention. By confirming that it is possible to completely prevent the corrosion of the bolted connection of the steel structure to complete the present invention.

An object of the present invention is a high purity (99.99% or more to maintain a surface potential of -1,000mV SCE or less after applying or injecting a corrosion inhibitor composed of a mixed aqueous solution of potassium silicate and sodium silicate on the inner surface and the gap of the bolt-nut connection portion; The present invention provides a method for preventing corrosion of bolt and nut connections of steel structures comprising sealing a gap with a gel-type sacrificial anode sealing agent containing Zn anode powder or Zn or Al-based alloy anode powder.

In addition, it is an object of the present invention is a high purity (more than 99.99%) Zn anode powder, or Zn or Al-based alloy anode powder that can be conveniently used to prevent corrosion of the bolt-nut connection of the steel structure and maintain the surface potential of less than -1,000mV SCE It is to provide a gel-type sacrificial anode sealing agent containing.

In order to achieve the object of the present invention, after applying or injecting a corrosion inhibitor composed of a mixed aqueous solution of potassium silicate and sodium silicate on the inner surface and the gap of the bolt-nut connection, high purity (99.99% or more) Zn anode powder, or Zn Alternatively, there is provided a method for preventing corrosion of bolt and nut connections of a steel structure comprising sealing a gap with a gel-type sacrificial anode sealing agent containing Al-based alloy anode powder.

A corrosion inhibitor for use in the present invention the water resistance is excellent potassium silicate _{(K 2 O · SiO 2 ·} nH 2 O) and the adhesion is excellent sodium silicate _{(Na 2 O · SiO 2 ·} nH 2 O) is a preferably a weight ratio A 5-30% aqueous solution, mixed and dissolved in water, is used at a ratio of about 1.5: 1 to 1: 1, most preferably at a ratio of 58:42. If the ratio of potassium silicate and sodium silicate is 1.5: 1 or more, the adhesion may be inferior, and if it is 1: 1 or less, the water resistance may be inferior. If the concentration of the aqueous solution is 5% or less, the corrosion effect is not effective, and if it is 30% or more, the economic efficiency is poor. When applied to existing steel structures, the concentration of the aqueous solution is adjusted according to the thickness of the rust layer. That is, when a thick rust layer is formed, it is preferable to use a dilute aqueous solution in order to increase penetration.

In addition, you may mix potassium silicate and sodium silicate after making them into aqueous solution, respectively.

When the corrosion inhibitor is injected into the inner surface of the bolt connection part, it has strong alkalinity and passivates the iron surface, and acts as a rust film on the iron surface to form a highly adhesive glass protective film. Catalytic polarization of the potential about 100mV (Cathodic polarization) acts.

Gel-type sacrificial anode sealing agent used in the present invention is a high-purity (99.99% or more) Zn anode powder having a potential of -1.05 volts (SCE) or less, or a fine powder of a Zn-based or Al-based alloy anode with 1: 1 in a liquid binder. It is prepared in a gel state by mixing at a weight ratio of ˜1: 1.5. The fine powder of the Zn-based or Al-based alloy anode can be obtained by melting the sacrificial anode alloyed with a specific component / component ratio as shown in the following table, and then spraying it in a vacuum tank through a nozzle.

Table 1: Composition and Composition of Alloys

 Zn-based alloy  Zn (99.3%)  Al (0.6%)  In, Si, Mg, and / or Ca (0.1%)  Al-based alloy  Al (95%)  Zn (4.5%)  In, Si, Mg, and / or Ca (0.5%)

The liquid binder uses an inorganic binder in which silicate and zinc oxide are mixed at 9: 1, or an organic binder in which modified epoxy and zinc-based curing agents are mixed at 5: 1, and has excellent adhesion with iron.

Viscosity of the sacrificial anode sealing agent can be adjusted by controlling the addition amount of the high purity (more than 99.99%) Zn anode powder or Zn-based or Al-based alloy anode added to the liquid binder.

The gel type sacrificial anode sealing agent of the present invention is dried and cured after 24 to 48 hours after sealing or sealing the bolt connection gap of the steel structure after the coating or injection treatment of the corrosion inhibitor, and the surface potential is lower than -1,000 mV SCE. By acting as a sacrificial anode against iron, it inhibits the corrosion of iron when water is introduced into the gap. As described above, the gel type sacrificial anode used in the present invention, unlike the sacrificial anode of a conventional metal piece that is attached to a steel structure by welding or bolted joint, is easily applied to the gap between the bolt connection part as a sealing agent, and seals the gap until the waterproof effect. Can be exercised. As such, a gel type sacrificial anode sealant with excellent ease of application and anti-corrosion effect is a new anticorrosive technology that has never been developed.

The corrosion prevention method of the present invention can completely prevent corrosion of the bolt-nut connection portion of the steel structure by using a corrosion inhibitor and a gel type sacrificial anode sealing agent together.

The application of corrosion inhibitors and gel type sacrificial anode sealants used in the corrosion protection method according to the invention to the steel structure bolt and nut connections can be as follows:

(A) In case of newly constructed steel structures, corrosion inhibitor is applied to the bolted joints and bolt nuts, and the gap is sealed with gel-type sacrificial anode sealant.

(B) In the case of existing steel structures, corrosion inhibitors are injected into the inner surface of the bolted joint (gap injection, upper bolt injection, plate injection), and the gap is sealed with sacrificial anode sealant. Corrosion inhibitor injection is applied according to the bolt connection. For the gap injection, it is better to use 'I' shaped injection nozzle. The upper injection of bolt is used for bolt injection, and the plate injection is made by drilling holes in splice. It is installed and injected under the pressure of 0.5 ~ 2.0Kg / ㎠.

Through the following examples, the method of preventing corrosion of the bolt-nut connection portion of the steel structure of the present invention has been described in more detail, but the present invention is not limited thereto.

Example

Production Example  1: Preparation of corrosion inhibitor

Potassium silicate (Youngil Chemical Co., Ltd.): Sodium silicate (Youngil Chemical Co., Ltd.) was mixed in a weight ratio of 58:42 and dissolved in water to obtain 10 kg of a 30% aqueous solution corrosion inhibitor of the present invention.

pH: 12.5 to 13

Polarization function for iron: -100 mV

Production Example  2: gel type Al Sacrificial anode  Sealant Manufacturing

Al: Zn: In is mixed at a weight ratio of 95: 4.5: 0.5 to make a sacrificial anode that maintains a surface potential of -1.0 V SCE or less. 15 kg of alloy anode powder was obtained.

The sealing agent manufacturing binder was prepared by mixing a liquid Zn-based or Li-silicate (Donghae Chemical Co., Ltd.) with zinc oxide in a weight ratio of 9: 1 to prepare a 15 kg inorganic binder.

The prepared liquid inorganic binder and the Al-based alloy sacrificial anode powder were blended in a ratio of 1: 1.5 by weight to obtain a gel-type sacrificial anode sealing agent.

The resulting gel-type sacrificial anode sealing agent maintained a surface potential of −1,000 mV SCE or lower upon dry curing.

Production Example  3: gel type Zn system Sacrificial anode  Sealant Manufacturing

Zn: Al: In is mixed at a weight ratio of 99.3: 0.6: 0.1 to make a sacrificial anode that maintains a surface potential of -1.0 V SCE or less, and after making it melted again, Zn-based injecting from a vacuum tank through a nozzle 15 kg of alloy anode powder was obtained.

The binder for sealing agent manufacture 15 kg of the organic binder which mixed the modified epoxy (Donghae Chemical Co., Ltd.) and an amine hardening agent by 5: 1 by weight ratio.

The prepared organic binder and the Zn-based alloy sacrificial anode powder were combined at a weight ratio of 1: 1 to obtain a gel-type sacrificial cathode sealing agent.

The resulting gel-type sacrificial anode sealing agent maintained a surface potential of −1,000 mV SCE or lower upon dry curing.

Production Example  4: Gel type  High purity Zn Sacrificial anode  Sealant Manufacturing

High purity Zn (99.99%) was heated to 450 ° C. to evaporate to cool the vapor to prepare 15 kg of high purity Zn powder.

The binder for sealing agent manufacture 15 kg of the organic binder which mixed the modified epoxy (Donghae Chemical Co., Ltd.) and an amine hardening agent by 5: 1 by weight ratio.

The prepared organic binder and high purity Zn powder were blended in a ratio of 1: 1 by weight to obtain a gel type sacrificial anode sealing agent.

The resulting gel-type sacrificial anode sealing agent maintained a surface potential of −1,000 mV SCE or lower upon dry curing.

Test Example  1: Brine spray test on iron specimens, brine Immersion  Test result

A 30% aqueous solution of the corrosion inhibitor of Preparation Example 1 was applied to the iron specimens and subjected to an air exposure test (3 years) or saline immersion (3 years) after the salt spray. Control iron specimens were applied in the same way without corrosion inhibitor.

Table 2: Salt Spray

  Test specimen  Control specimen  Corrosion rate: 5% or less Corrosion rate: 0.0001mm / Year  Corrosion rate: 100% Corrosion rate: 1.0 to 1.5mm / Year

Table 3: brine Immersion

Test specimen  Control specimen Callout rate: 0%  Corrosion rate: 100% Corrosion rate: 1.0mm / Year or more

Test Example  2. Corrosion suppression effect of bolt and nut connection of steel structure

The corrosion inhibitor according to Preparation Example 1 was injected into the inner surface and the gap of the bolt connection part of the steel structure, and the gel type sacrificial anode sealing agent according to Preparation Example 2 was sealed and cured as if sealing a gap around the bolt, and then the surface potential of the sacrificial anode was first hardened. The measured value was -1.01 ~ -1.05V SCE. The specimens were eroded after 1 year immersion in saline. As control specimens, the bolted connections of the steel structures not subjected to the anticorrosion treatment according to the invention were also immersed in saline for one year.

Test results are shown in FIGS. 3A and 3B. In the anti-corrosion treated specimens according to the present invention, the rust resistance of the inner surface of the bolt connection was 5% or less (FIG. 3a), but the rust resistance was 95% or more in the control specimen.

According to the corrosion prevention method of this invention, corrosion of the bolt and nut connection part of a steel structure can be completely prevented. In particular, steel structures such as bridges, which are already installed, can prevent corrosion of bolt and nut joints and internal surfaces without dismantling the structure.

In addition, the new material gel type sacrificial anode sealing agent used in the corrosion prevention method of the present invention is a gel type, which is not only easy to seal the gap between the bolt and nut connection part of the steel structure, but also the sealing is perfect so that the gap is in addition to the action of the sacrificial anode. It also serves as a waterproofing effect that prevents water from entering, resulting in a perfect corrosion protection effect. Therefore, the corrosion prevention method of the bolt-nut connection portion of the steel structure according to the present invention is immediately applicable commercially with excellent applicability and economy.

Claims (2)

delete Gel type sacrificial anode sealing agent of Zn or Al-based alloy, It is prepared by mixing the fine powder of the high purity (more than 99.99%) Zn anode powder, Zn-based or Al-based alloy anode of less than -1.05volt (SCE) with a liquid organic or inorganic binder in a weight ratio of 1: 1 ~ 1: 1.5, Wherein the Zn-based alloy consists of 99.3% Zn, 0.6% Al and 0.1% other components, and the Al-based alloy consists of 95% Al, 4.5% Zn and 0.5% other components. At least one selected from the group consisting of In, Si, Mg, and Ca, A gel type that can be conveniently used to prevent corrosion of bolt and nut connections of steel structures, and is a sealing agent characterized by maintaining a surface potential of -1,000 mV SCE or less upon curing.

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