JP7723942B2 - Salt removal and repainting methods - Google Patents

Description

The present invention relates to a salt removal method that removes salt, including chloride ions that adhere to steel surfaces and cause corrosion of the steel, and a repainting method that applies paint to the steel surface after salt removal.

The steel used in steel bridges and other structures is produced by reducing naturally occurring iron ore, and as it tries to return to its original state, it oxidizes (corrodes). Since steel no longer performs its intended functions once it corrodes, it is common to apply paint or plating to the steel surface to prevent corrosion and cut off the supply of oxygen and moisture.

However, even with such anti-rust treatment, the paint is prone to deterioration and corrosion in environments with high salt content (for example, airborne salt or salt contained in antifreeze).

Steel structures with deteriorated paint can be restored to a healthy state by being repainted. Generally, when repainting, the steel surface is blasted, which can be expected to remove some of the salt. However, salt can sometimes penetrate deep into pitting, making it difficult to remove mechanically.

To reduce the effects of salt, base materials for coatings containing anion adsorbents (such as nitrite ions) or complex hydroxides containing such adsorbents have been developed (Patent Document 1). In recent years, salt-resistant paints have been sold, and salt removal methods using high-pressure water (water jets) have also been tried and tested. However, due to the bridge construction conditions and drainage issues, it is often difficult to carry out sufficient work.

Patent No. 4343570

The present invention was made in light of these circumstances, and its goal is to provide a new salt removal method that differs from conventional methods, and a repainting method in which paint is applied to the steel surface after salt removal.

[Salt removal method]
The salt removal method of the present invention is a method for removing salt from the surface of steel material, and includes the steps of blasting the surface of the steel material, attaching a desalination sheet containing nitrite ions to the surface of the steel material, curing the desalination sheet, and peeling the desalination sheet from the surface of the steel material.

The desalination method may also include a step of applying a solution containing nitrite ions to the blasted steel surface. In the desalination method, a desalination sheet containing a layered double hydroxide may be used as the desalination sheet. The desalination method may also include a step of re-blasting the steel surface after the desalination sheet has been removed.

[Painting and repainting method]
The repainting method of the present invention is a method for repainting the surface of steel material, and includes a step of removing salt from the surface of the steel material using the salt removal method of the present invention, and a step of applying paint to the surface of the steel material after desalting.

The present invention provides high desalination and anti-rust effects through a relatively simple method, thereby improving productivity and coating durability compared to conventional methods.

1 is a flowchart showing an example of a salt removal method of the present invention. 1(a) to 1(c) are explanatory diagrams illustrating the principle of salt removal using the salt removal method of the present invention. (a) shows the gusset plate removed from the actual bridge used in the test construction, and (b) shows the test specimen cut out from the gusset plate in (a). An explanatory diagram of the salinity measurement positions on the test specimen. (a) shows the test specimen after the first blasting, (b) shows the test specimen with the desalination sheet attached, (c) shows the area where the first desalination sheet has been peeled off, (d) shows the area where the second desalination sheet has been peeled off, and (e) shows the test specimen after the final blasting. Graph (a) shows a comparison of the amount of surface salt when the electrical conductivity method is used, and graph (b) shows a comparison of the amount of surface salt when the chloride ion detector tube method is used. A photo of the test specimen 10 days after the test construction. This shows a test specimen cut from a gusset plate and blasted. This shows the test specimen with the desalination sheet attached. Showing the area where the desalination sheet has been peeled off This shows the test specimen after finish blasting. A photograph of the test specimen 30 days after the test construction date. (a) and (b) show test specimens cut out from gusset plates and blasted. (a) and (b) are explanatory diagrams of the salinity measurement positions on the test specimen. (a) is a photograph of the test specimen after the first blasting and high-pressure cleaning of area a1, and (b) shows the state after a solution containing nitrite ions was applied to area a2 and a desalination sheet with nonwoven fabric was then attached. (a) shows the area a1 that has been washed with water, and (b) shows the area a2 after the desalination sheet has been peeled off. (a) shows the area a1 after the finish blasting, and (b) shows the area a2 after the finish blasting. Graph (a) shows a comparison of the amount of surface salt when the electrical conductivity method is used, and graph (b) shows a comparison of the amount of surface salt when the chloride ion detector tube method is used.

(Embodiment)
An example of an embodiment of the present invention will be described with reference to the drawings. As an example, a desalination method shown in Figure 1 is a method including a blasting step S001, a solution application step S002, a desalination sheet application step S003, a curing step S004, a desalination sheet peeling step S005, and a finish blasting step S006.

The blasting process S001 is a process of blasting the surface of the steel material (hereinafter referred to as "primary blasting" for ease of explanation). This process removes paint that has deteriorated due to the primary blasting and rust that has formed on the steel material surface. There are no particular limitations on the method of primary blasting, and it can be a method using power tools, for example. Furthermore, primary blasting can be performed in one go or in multiple rounds.

The solution application step S002 is a step in which a solution containing nitrite ions is applied to the steel surface. In this step, a solution containing nitrite ions is applied to the steel surface that has been subjected to the primary blasting. This step is preferably carried out after the primary blasting and before turning occurs (as a guideline, within 4 hours after the primary blasting; the same applies below).

The solution containing nitrite ions can be a salt containing alkali metal ions, such as an aqueous solution of lithium nitrite ( _LiNO2 ) or sodium nitrite ( _NaNO2 ). The solution can be applied using a sponge roller, a brush, a sprayer, etc. It is preferable to apply the solution in an amount that does not drip.

As shown in Figure 2(a), by applying a solution containing nitrite ions, the solution penetrates into the pitting corrosion on the steel surface, and the diffusion and ion exchange effects of the nitrite ions can be exerted on the salt that has penetrated deep into the pitting corrosion.

Note that the solution application step S002 is not an essential step and can be replaced with ion-free pure water, or can be omitted if not required.

The desalination sheet application step S003 is a step of applying a desalination sheet containing nitrite ions to the surface of the steel material. In this step, a desalination sheet containing nitrite ions is applied to the surface of the steel material to which the solution has been applied.

In order to ensure that the desalination sheet adheres to the steel material with as few gaps as possible, it is preferable to press (press) the desalination sheet against the steel material using a roller or similar tool when applying it. As with the solution application process S002, this process is also preferably carried out after the primary blasting and before turning occurs.

The desalination sheet to be applied can be, for example, a gel sheet (chloride absorbent) based on sodium polyacrylate with nonwoven fabric on the surface (the side facing the steel material) (see Figures 2(b) and (c)). In this embodiment, the desalination sheet used contains nitrite ions in the gel portion.

The term "gel" here generally refers to a state in which colloidal particles have lost their independent mobility and have aggregated together to form a solid, or a sol (colloidal solution) that has solidified into a jelly-like substance.

In addition, desalination sheets can also be made from a gel sheet containing layered double hydroxide (LDH) and sodium polyacrylate as the main component, with a nonwoven fabric on the surface (see Figures 2(b) and (c)).

A typical LDH is a layered inorganic compound with anion exchange capacity, represented by the formula [M ²⁺ _1-x M ³⁺ _x (OH) ₂ ] ^x+ [A ^n- _x/n ·yH ₂ O] ^x- (where M ²⁺ represents a divalent metal cation, M ³⁺ represents a trivalent metal cation, and A ^n- represents an n-valent anion).

Since some of the divalent metal cations (M ²⁺ ) of the hydroxide are replaced by trivalent metal cations (M ³⁺ ) at non-stoichiometric ratios, the material has a positive charge, and can incorporate and retain exchangeable anions (A ^n- ) between its layers for charge compensation.

In this embodiment, a gel sheet is provided with nonwoven fabric on its surface. The purpose of providing the nonwoven fabric is to minimize the amount of gel or other material remaining on the steel material when the desalination sheet is peeled off. The nonwoven fabric can also be attached to the gel sheet on-site rather than being provided during manufacturing. This makes it easier to manufacture the desalination sheet. The nonwoven fabric can be provided as needed, and can be omitted if not required.

The desalination sheet shown in this embodiment is an example, and other desalination sheets can be used.

In this application, "deionizing sheets containing nitrite ions" also include those that do not contain nitrite ions at the time of manufacture, but are later impregnated with a solution containing nitrite ions at the site (those that contain nitrite ions at the time of application).

The curing step S004 is a step of curing the desalination sheet attached to the steel material. In this step, aluminum tape is applied to the periphery of the desalination sheet attached to the steel material surface (including the seams and joints when multiple desalination sheets are attached side by side; the same applies below), and the sheet is cured for a predetermined time in a state where the water contained in the solution and desalination sheet does not evaporate, allowing the nitrite ions contained in the solution and desalination sheet to diffuse. The predetermined time refers to the time required for the nitrite ions to diffuse.

The term "diffusion" used here refers to the change (phenomenon) in which particles move and the concentration distribution becomes uniform when there is a concentration distribution in a mixture of different types of particles, even when the temperature is kept uniform, or the process of change in the concentration distribution that occurs when a mixture of different types of particles approaches thermal equilibrium.

The desalination sheet peeling process S005 is a process in which the desalination sheet is peeled off from the steel surface. The desalination sheet can be peeled off manually. If gel or other substances remain that have protruded from the edges of the nonwoven fabric of the desalination sheet, they can be removed manually or by finish blasting in a subsequent process.

The desalination sheet can be removed at any time after the specified curing time has elapsed after it has been attached to the steel material. It can be removed on the same day as the desalination sheet is attached, or at a later date (for example, the next day).

The finishing blasting process S006 is a process of blasting the surface of the steel material after the desalination process. This process removes any residue left behind after the desalination sheet is removed, and also prepares the steel material's base material to a state suitable for the subsequent paint application process.

There are no particular limitations on the method of finish blasting, and methods such as using power tools can be used.

Next, an example of the repainting method of the present invention will be described. The repainting method of the present invention is a method for repainting the surface of steel material, and includes the steps of removing salt from the steel surface using the salt removal method of the present invention, and applying paint to the desalted steel surface.

As an example, the repainting method shown in Figure 1 is a method that includes a paint application process S007 in which paint is applied to the steel surface from which salt has been removed using the salt removal process. This process is preferably performed after finish blasting and before turning occurs.

In this process, for example, a primer coat of anti-rust material (anti-corrosion base material) is applied, followed by a middle coat of epoxy resin or the like, and a top coat of fluorine-based resin or polyurethane-based resin or the like. The type of paint to be applied and the order in which it is applied can be determined appropriately for each site.

The processes required for salt removal (in the above embodiment, the solution application process S002, the desalting sheet application process S003, the curing process S004, and the desalting sheet removal process S005) can be performed on the entire steel material, but basically they only need to be performed on the corroded areas, and do not need to be performed on the non-corroded areas (areas where the coating remains).

The steps in the above embodiment are merely examples, and the steps of the salt removal method and repainting method of the present invention are not limited to the configuration of this embodiment. The salt removal method and repainting method of the present invention can be modified, such as by adding, omitting, or replacing steps, as appropriate, as long as the intended purpose can be achieved. Examples of modifications include the following:

<Modification 1>
In the above embodiment, an example is given in which a desalination sheet containing nitrite ions is used, but in the salt removal method and repainting method of the present invention, a desalination sheet that does not contain nitrite ions can also be used.

Specifically, a solution containing nitrite ions is applied to the steel surface blasted in the blasting process S001 (solution application process S002), and a desalination sheet that does not contain nitrite ions is then applied on top of the solution. After application, the curing process S004 and the desalination sheet removal process S005 are carried out in the same manner as in the previous embodiment.

<Modification 2>
In the above embodiment, the finish blasting step S006 is performed after the desalination sheet peeling step S005, but if there is a concern that the finish blasting step S006 may cause salt to re-adhere, the desalination sheet may be left attached when the finish blasting is performed, and the finish blasting may not be performed on the area where the desalination sheet is attached. In this case, paint may be applied to the area where the desalination sheet is attached without performing the finish blasting.

Alternatively, if there is a concern that the finishing blasting step S006 may cause salt to re-adhere, the finishing blasting step S006 may be performed first, followed by the desalination sheet application step S003, the curing step S004, and the desalination sheet removal step S005. In this case, there is no need to perform finishing blasting after the desalination sheet removal step S005; paint can be applied directly.

<Test construction 1>
In order to demonstrate the effectiveness of the present invention, the applicant conducted a test (hereinafter referred to as "Test 1") using removed components from an actual bridge that had been replaced due to severe corrosion. Test 1 was a test using a desalination sheet that had been impregnated with nitrite ions during the manufacturing process. The outline of Test 1 is as follows.

[Test specimen]
In test construction 1, a portion of a gusset plate removed from an actual bridge was cut out to serve as a test specimen. A photograph of the gusset plate is shown in Figure 3(a), and a photograph of the cut-out portion of the gusset plate (test specimen) is shown in Figure 3(b).

As shown in Figure 3(b), in test construction 1, areas with similar amounts of corrosion were divided into three regions a1 to a3, and as shown in Figure 4, two locations in region a1 of the test specimen and two locations each in regions a2 and a3 were set as salt measurement locations. The solid circle indicates the measurement location after the primary blasting, the dotted circle indicates the measurement location after the desalination sheet was removed, and the dashed circle indicates the measurement location after the final blasting.

In test construction 1, area a1 was the area where no desalination treatment was performed, area a2 was the area where desalination treatment was performed using a first desalination sheet (labeled "desalination sheet 3" in the graphs of Figures 6(a) and (b)), and area a3 was the area where desalination treatment was performed using a second desalination sheet of a different type than the first desalination sheet (labeled "desalination sheet 6" in the graphs of Figures 6(a) and (b)).

[Desalination sheet]
In test construction 1, the desalination sheet applied to area a2 was a gel sheet containing nitrite ions with nonwoven fabric on the surface, and the desalination sheet applied to area a3 was a gel sheet containing nitrite ions and layered double hydroxide with nonwoven fabric on the surface.

The gel sheet used in Test Construction 1 was manufactured using the method described in JP 2021-066938 A. Its composition was 3 g of sodium polyacrylate, 10 g of glycerin, 0.15 g of aluminum hydroxide, 0.625 g of nickel-aluminum layered double hydroxide, 0.375 g of aluminum oxide, 1.855 g of lithium nitrite, and 83.845 g of water per 100 g of gel. Prior to use, the gel was heated to 50°C under vacuum to remove the water and then dried to an absolutely dry state. A gel sheet with the same composition but without the layered double hydroxide was also used. However, the gel sheet may have a different composition, for example, one that does not contain lithium nitrite.

[Procedure for test construction 1]
Test construction 1 was carried out according to the following steps (1) to (6).
(1) The prepared specimens were subjected to primary blasting (see Fig. 5(a)). The primary blasting was performed using a sandblaster. White fused alumina (grain size #24) was used as the abrasive.
(2) A solution containing nitrite ions was applied to the test specimen after the primary blasting. As the solution containing nitrite ions, a 1 mol/L (69 g/L) aqueous solution of lithium nitrite (LiNO ₂ ) was used.
(3) After applying the solution, the first desalination sheet was attached to the area a2 of the test specimen, and the second desalination sheet was attached to the area a3 (see FIG. 5(b)).
(4) After the desalination sheets were attached, aluminum tape was attached to the periphery of each desalination sheet to prevent evaporation of the water contained in the solution and the desalination sheet.
(5) After a predetermined time had elapsed, the attached desalination sheet was peeled off (see Figures 5(c) and 5(d)).
(6) After the desalination sheet was removed, the test specimen was subjected to finish blasting (see FIG. 5(e)). The finish blasting was carried out in the same manner as in (1) above.

[Measurement and evaluation method]
The desalination effect of test construction 1 was confirmed by measuring the surface salinity at the salinity measurement positions in each of areas a1 to a3. Surface salinity measurements were taken after the primary blasting, after the removal of the desalination sheet (excluding area a1, which was not subjected to desalination treatment), and after the finish blasting.

In addition, since it was expected that nitrite ions would remain on the base material side due to ion exchange where the desalination sheet was installed and that this would affect the electrical conductivity, the measurement using the surface salinity meter was used as a reference value, and the salinity was measured separately using the solution remaining in the measurement cell after the measurement and a chloride ion detection tube. The value [ppm] measured with the detection tube was converted to the surface salinity [mg/ ^m2 ] using the following formula 1 and evaluated.
[Formula 1]

[Measurement results]
FIG. 6(a) is a graph comparing the amount of surface salt measured using the electrical conductivity method, and FIG. 6(b) is a graph comparing the amount of surface salt measured using the chloride ion detector tube method.

After test construction 1, the test specimen was exposed indoors and observed over time. Figure 7 shows a photograph of the test specimen 10 days after test construction.

[Consideration]
The following was confirmed through test construction 1.
(1) No significant difference was observed in the measurement results depending on the type of desalination sheet.
(2) The amount of salt after the primary blasting varied little from site to site, being approximately 80 to 100 mg/ ^m² by the electrical conductivity method and approximately 20 mg/ ^m² by the chloride ion detector tube method.
(3) When electrical conductivity measurements were performed after removing the desalination sheet from the installation site, values exceeding the upper limit of the measuring equipment were measured. This was due to the influence of nitrite ions contained in the desalination sheet.
(4) Measurements using a chloride ion detector tube at the same location showed that the amount of salt was very small.
(5) Measurements after finish blasting at the desalination sheet installation site showed that the electrical conductivity method measured approximately 230 to 290 mg/ ^m2 , while no salt was detected using the chloride ion detection tube method.
(6) Measurements after finish blasting in areas where no desalination sheet was installed showed 85 mg/m ² by the electrical conductivity method and 11 mg/m ² by the chloride ion detector tube method.
(7) In measurements taken after the finishing blasting of the desalting sheet application area, although no salt was detected using the chloride ion detector tube method, a relatively large value was measured using the electrical conductivity method. This indicates that nitrite ions remain even after the finishing blasting, which is thought to indicate good rust prevention effects.
(8) As shown in Figure 7, in the area a1 where no desalination treatment was performed, rust due to turning (numerous tiny black dots in the area a1 in Figure 7) occurred 10 days after the test application date, whereas in the areas a2 and a3 where the desalination sheet was applied, almost no rust due to turning was observed 10 days after the test application date. Note that the yellow rust in the photograph was generated during the process of measuring the surface salt content after the finish blasting, and was not generated by turning.

From the above, it can be seen that in areas where desalting sheets were not installed, a certain amount of salt remained even after finish blasting, but in areas where desalting sheets were installed, higher values were measured using the electrical conductivity method than before the desalting sheets were installed, while no salt was measured using the chloride ion detection tube method, meaning that chloride ions were removed and only nitrite ions remained, indicating good rust prevention effects.

<Test construction 2>
In order to demonstrate the effectiveness of the present invention, the applicant conducted a test (hereinafter referred to as "Test 2") using removed components from an actual bridge that had been replaced due to severe corrosion. Test 2 was a test using a desalination sheet that did not contain nitrite ions at the manufacturing stage but was later impregnated with a solution containing nitrite ions. The outline of Test 2 is as follows.

[Test specimen]
In test construction 2, a portion of a gusset plate removed from an actual bridge was cut out to serve as a test specimen. Figure 8 shows a photograph of the cut-out portion of the gusset plate (test specimen) after blasting.

As shown in Figure 9, in test construction 2, area a1 was the area without desalination treatment, and area a2 was the area where desalination treatment was performed using a desalination sheet.

[Desalination sheet]
In test construction 2, the desalination sheet applied to area a2 was a gel sheet that did not contain nitrite ions, with a nonwoven fabric on the surface and impregnated with a solution containing nitrite ions before application.

The composition of the gel sheet used in Test Construction 2 was 63.25 g of gel, 6 g of sodium polyacrylate, 20 g of glycerin, 0.3 g of aluminum hydroxide, 2 g of magnesium-aluminum layered double hydroxide, 0.3 g of tartaric acid, and 34.65 g of water.

[Procedure for test construction 2]
Test construction 2 was carried out according to the following steps (1) to (4).
(1) The prepared specimens were subjected to primary blasting. The primary blasting was performed using a sandblaster. White fused alumina (grain size #24) was used as the abrasive.
(2) After the primary blasting, a desalination sheet made of nonwoven fabric and impregnated with a solution containing nitrite ions was attached to the test specimen (see Figure 9). A 1 mol/L aqueous solution of sodium nitrite ( _NaNO2 ) was used as the solution containing nitrite ions.
(3) After a predetermined time had elapsed, the attached desalination sheet was peeled off (see FIG. 10).
(4) After the desalination sheet was removed, the test specimen was subjected to finish blasting (see Figure 11).
The finish blasting was carried out in the same manner as in (1) above.

After test construction 2, the test specimen was exposed indoors and observed over time. Figure 12 shows a photograph of the test specimen 30 days after test construction.

[Consideration]
Test construction 2 confirmed the following:
(1) The composition and construction method of the desalination sheet were partially changed, but there were no problems with construction.
(2) As shown in Figure 12, in the area a1 where no desalination treatment was performed, rust due to turning (the black area in area a1 in Figure 12) occurred 30 days after the test application date, whereas in the area a2 where the desalination sheet was applied, almost no rust due to turning was observed 30 days after the test application date.

<Test construction 3>
In order to demonstrate the effectiveness of the present invention, the applicant conducted a test (hereinafter referred to as "Test 3") using removed components from an actual bridge that had been replaced due to severe corrosion. Test 3 was a test using a desalination sheet that does not contain nitrite ions. The outline of Test 3 is as follows.

[Test specimen]
In test construction 3, a portion of a gusset plate removed from an actual bridge was cut out to serve as a test specimen. Photographs of the cut-out portion of the gusset plate (test specimen) after blasting are shown in Figures 13(a) and 13(b).

As shown in Figures 13(a) and (b), in test construction 3, area a1 was the area where desalination treatment was performed by washing with water, and area a2 was the area where desalination treatment was performed using a desalination sheet.

As shown in Figures 14(a) and 14(b), two locations in each of areas a1 and a2 of the test specimen were set as salt measurement locations. The solid circle indicates the measurement location after the primary blasting, and the dashed circle indicates the measurement location after the final blasting.

[Desalination sheet]
In test construction 3, the desalination sheet applied to area a2 was a gel sheet that did not contain nitrite ions, with nonwoven fabric provided on the surface before application.

The composition of the gel sheet used in Test Construction 3 was 63.25 g of gel, 6 g of sodium polyacrylate, 20 g of glycerin, 0.3 g of aluminum hydroxide, 2 g of magnesium-aluminum layered double hydroxide, 0.3 g of tartaric acid, and 34.65 g of water.

[Procedure for test construction 3]
Test construction 3 was carried out according to the following steps (1) to (4).
(1) The prepared specimens were subjected to primary blasting. The primary blasting was performed using a sandblaster. White fused alumina (grain size #24) was used as the abrasive.
(2) After the primary blasting, area a1 of the specimen was washed with high-pressure water (see Fig. 15(a)). Area a2 was coated with a solution containing nitrite ions, and a desalination sheet with nonwoven fabric was attached (see Fig. 15(b)). A 0.1 mol/L aqueous solution of sodium nitrite ( _NaNO2 ) was used as the solution containing nitrite ions.
(3) For the region a2, the attached desalination sheet was peeled off after a predetermined time had elapsed.
(4) After washing the area a1 with water (see FIG. 16(a)), and after peeling off the desalination sheet from the area a2 (see FIG. 16(b)), the specimens were subjected to finish blasting (see FIGS. 17(a) and 17(b)). The finish blasting was performed in the same manner as in (1) above.

[Measurement and evaluation method]
The desalination effect of test construction 3 was confirmed by measuring the surface salinity at the salinity measurement positions in each of the areas a1 to a2. Measurements of the surface salinity were carried out at each stage after the primary blasting and after the finish blasting.

[Measurement results]
FIG. 18(a) is a graph comparing the amount of surface salt measured using the electrical conductivity method, and FIG. 18(b) is a graph comparing the amount of surface salt measured using the chloride ion detector tube method.

[Consideration]
The following was confirmed through test construction 3.
(1) The composition and construction method of the desalination sheet were partially changed, but there were no problems with construction.
(2) In the area a2 where desalination treatment was performed using a desalination sheet, the electrical conductivity method detected approximately 346 mg/ ^m2 of salt, and the chloride ion detector tube method detected no salt. As in test construction 1, chloride ions were removed and nitrite ions remained, which is thought to indicate good rust prevention effects.
(3) In the area a1 that was desalted by washing with water, the electrical conductivity was 72 mg/ ^m2 after the primary blasting and 84 mg/ ^m2 after the final blasting, showing no change.
(4) In the area a1 that was desalted by washing with water, the chloride ion detection tube method showed that the chloride ion concentration was 11 mg/ ^m2 after the primary blasting and 3 mg/ ^m2 after the final blasting, indicating a certain degree of desalting effect, but not as great as when desalting treatment was performed using a desalting sheet.

The salt removal method and repainting method of the present invention can be used for desalination and repainting of various steel structures, and can be particularly suitably used for desalination and repainting of steel structures used as components of existing bridges.

Claims (8)

A desalination method for removing salt from the surface of steel materials,
A step of blasting the surface of the steel material;
A step of attaching a gel sheet containing nitrite ions to the surface of the steel material;
a step of curing the gel sheet in a state where the water contained in the gel sheet does not evaporate ;
Peeling the cured gel sheet from the steel surface,
A salt removal method characterized by: The salt removal method according to claim 1,
Applying a solution containing nitrite ions to the blasted steel surface,
A salt removal method characterized by: The salt removal method according to claim 1,
A gel sheet containing a layered double hydroxide is used as the gel sheet .
A salt removal method characterized by: The salt removal method according to claim 1,
Re-blasting the steel surface after peeling off the gel sheet ;
A salt removal method characterized by: A desalination method for removing salt from the surface of steel materials,
A step of blasting the surface of the steel material;
applying a solution containing nitrite ions to the surface of the steel material;
A step of attaching a gel sheet not containing nitrite ions to the surface of the steel material;
a step of curing the gel sheet in a state where the water contained in the gel sheet does not evaporate ;
Peeling the cured gel sheet from the steel surface,
A salt removal method characterized by: In the salt removal method according to any one of claims 1 to 5,
Tape is applied to the periphery of the gel sheet to prevent the water contained in the gel sheet from evaporating.
A salt removal method characterized by: In the repainting method for repainting the surface of steel materials,
A step of removing salt from a steel material surface by the salt removal method according to any one of claims 1 to 5 ;
This includes a process of applying paint to the surface of the steel after desalting.
A painting repainting method characterized by the following. In the repainting method for repainting the surface of steel materials,
a step of removing salt from the steel surface by the salt removal method according to claim 6;
This includes a process of applying paint to the surface of the steel after desalting.
A painting repainting method characterized by the following.