JP2012067347A - Method for posttreatment of thermally sprayed film, and posttreatment agent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for posttreatment of a thermally sprayed film, capable of preventing the occurrence of spot rust and early wastage of an aluminum-based thermally sprayed film without enhancing film-thickness control or the time control until sealing treatment, or without conducting excess sealing or coating treatment, and to provide a posttreatment agent.SOLUTION: After the formation of an aluminum-based thermally sprayed film, an aqueous electrolyte solution or a water-based coating material including the aqueous electrolyte solution is applied to the thermally sprayed film to impregnate. The applied electrolyte solution or that contained in the water-based coating material is impregnated through voids 4 of the thermally sprayed film 2, reaches an interface between a steel substrate 1 and the film 2 to form a battery. Since a film 3 comprising magnesium hydroxide as a main component is formed on the surface of the substrate 1 in the case where the electrolyte solution is an aqueous solution of a magnesium compound, a value of electric current flowing between the substrate 1 and the film 2 lessens. Therefore, since oxygen hardly reaches the substrate 1, the occurrences of spot rust and early wastage are prevented.

Description

  The present invention is a steel substrate surface such as bridges, harbor facilities, plants, pipes, advertising towers, indicator lights, carbon steel, iron-based carbon steel, nickel chrome steel and stainless steel used outdoors such as vehicles and ships. TECHNICAL FIELD The present invention relates to a post-treatment method and a post-treatment agent for an aluminum-based thermal spray coating applied for the purpose of preventing rust.

  The anticorrosion spraying method for the anticorrosion of steel used outdoors such as bridges, harbor facilities, plants, piping, advertising towers, indicator lights, vehicles and ships seems to be described in Japanese Industrial Standard (JIS H8300). In addition, the spraying of zinc, aluminum and their alloys is standardized. Among them, spray materials of pure zinc, pure aluminum, zinc aluminum alloy and aluminum / magnesium alloy are particularly recommended.

  Among them, pure aluminum is resistant to acids and has heat resistance, so that it is widely used not only for outdoor environments but also for corrosion protection of plants, tanks and chemical equipment. However, spotted red rust (spot rust) sometimes occurs in the sprayed coating within the initial stage after spraying, particularly within one week after spraying.

  Here, spot rust means that when water or water vapor reaches the interface between the steel substrate and the thermal spray coating and forms a battery, iron ions are generated from the steel substrate and pass through the through-holes of the thermal spray coating to the surface of the thermal spray coating. It is a phenomenon in which spotted red rust is generated on the surface of the sprayed coating by being oxidized by air. Normally, this phenomenon occurs when the thermal potential of the thermal spray coating is higher than that of iron, such as NiCr steel and stainless steel. Polarity reversal occurs and spot rusting may occur. Once spot rust is generated, the wear of the film is accelerated and the life tends to be shortened. In addition, even if thermal spraying is repeated on the film where spot rust has occurred, the adhesion and corrosion resistance will deteriorate, so the only way to repair is to remove the thermal spraying film and re-spray it, resulting in a significant loss in terms of construction and costs. .

  This is a common phenomenon particularly in outdoor environments when the film thickness is thin, it takes time from spraying to sealing treatment, or the sealing treatment is insufficient. Therefore, in the pure aluminum sprayed coating, it is indispensable to reinforce the coating thickness and the time management until the sealing treatment, or to perform the sealing treatment and coating more than necessary.

  On the other hand, aluminum-magnesium (95: 5) alloy, which is another recommended material, has been used extensively for anticorrosion of oil drilling plants in the North Sea oil field, and has a history of showing excellent anticorrosion performance. ) 2063 is also recommended. However, when it is actually used in an outdoor environment, it tends to lack stability due to early consumption due to environmental conditions and thermal spraying, or spot rusting within an initial stage after thermal spraying, particularly within one week after thermal spraying. For this reason, as with pure aluminum spraying, measures are taken by strengthening the film thickness and time management until sealing treatment, or performing sealing treatment and coating more than necessary.

  In addition, as a conventional sealing process, the method of patent documents 1-5 is known, for example. In the method described in Patent Document 1, in order to improve the corrosion resistance in a high-temperature corrosive environment, a high-viscosity or high-molecular material mainly composed of a sulfate having a high melting point is applied to fill the voids of the sprayed coating. In the method described in Patent Document 2, a thermal spray coating is formed on an aluminum substrate with a coating material having high-temperature corrosion resistance against hot water treatment or steam treatment, and the aluminum substrate exposed from the voids of the thermal spray coating by hot water treatment or steam treatment. To form aluminum hydrate and seal it.

  In the method described in Patent Document 3, an alkali silicate aqueous solution is applied to a sprayed coating of zinc, aluminum, or a zinc / aluminum pseudoalloy to form an insoluble complex salt. In the method described in Patent Document 4, a sealing film made of an aqueous sealing agent obtained by mixing colloidal silica and a reactive silicon water repellent in an aqueous polymer emulsion is formed on the surface of a sprayed coating. In the method described in Patent Document 5, in order to improve heat resistance and corrosion resistance in a high temperature environment, vinegar nitrate or acetate is applied to the surface of the sprayed coating and sintered by heat treatment to form a metal oxide.

Japanese Patent Laid-Open No. 11-302820 No. 2005-35829 JP-A-2005-15835 JP 2007-291440 A JP 2009-46765 A

  There are the following problems in the countermeasures against spot rust and premature wear of the aluminum-based sprayed coating as described above. Increasing the thickness of the thermal spray coating is not only a waste of resources, that is, lengthening the construction period, increasing the cost of thermal spraying work, and reducing the competitiveness. On the other hand, performing sealing and painting more than necessary is also a waste of resources, which not only increases construction costs, but also uses a large amount of VOC (volatile organic solvent), which accounts for half of the coating weight. . This is said to be a causative agent of global warming, and there are concerns about adverse environmental effects.

  Further, the thermal spraying for anticorrosion purposes has a film thickness determined according to the life required in each environment. Generally, the larger the film thickness, the longer the life. In the Japanese Industrial Standard (JIS H8300), it is recommended that the zinc-based material pure zinc and zinc-aluminum alloy have a coating thickness of 50 μm or more, whereas the aluminum-based material pure aluminum, and The recommended film thickness of aluminum / magnesium alloy is 100 μm or more. This is considered to be because the aluminum-based material is likely to cause spot rust. If this point rust can be prevented, the film thickness corresponding to the required life can be adopted. That is, when the expected life is short, the coating thickness can be reduced to reduce the construction cost.

  Therefore, in the present invention, it is possible to prevent spot rust and premature wear of the aluminum-based sprayed coating without strengthening the film thickness and time management until the sealing treatment, or performing excessive sealing treatment and coating treatment. It is an object of the present invention to provide a post-treatment method and a post-treatment agent capable of being sprayed.

  In the post-treatment method of the thermal spray coating of the present invention, an aluminum-based material is sprayed on the surface of a steel substrate to form a thermal spray coating, and then an aqueous electrolyte solution or an aqueous paint containing the aqueous electrolyte solution is applied to the thermal spray coating and impregnated. It is characterized by that. Further, the post-treatment agent of the thermal spray coating of the present invention is a sealing treatment agent that is applied and impregnated after a thermal spray coating is formed by spraying an aluminum-based material on the surface of a steel substrate, and an aqueous electrolyte solution, or It is characterized by comprising an aqueous paint containing an aqueous electrolyte solution.

  In order to prevent corrosion of steel substrates, it is necessary for a current of a certain level or more to flow between the steel substrate and the thermal spray coating. However, the current necessary for corrosion protection varies depending on the amount of oxygen supplied to the surface of the steel substrate. . In the thermal spray coating post-treatment method and the thermal spray coating post-treatment agent of the present invention, the applied electrolyte aqueous solution or the aqueous electrolyte solution contained in the aqueous coating is impregnated through the voids of the thermal spray coating, and the interface between the steel substrate and the thermal spray coating. To form a battery.

  Here, when the electrolyte aqueous solution is a magnesium compound aqueous solution, magnesium ions in the magnesium compound aqueous solution are deposited on the surface of the steel substrate to form a film mainly composed of magnesium hydroxide. As a result, the value of current flowing between the steel substrate and the thermal spray coating becomes small, and oxygen hardly reaches the steel substrate, so that the occurrence of spot rust is prevented and early consumption is prevented. In addition, as a magnesium compound aqueous solution, aqueous solutions, such as magnesium sulfate, magnesium nitrate, and magnesium chloride, can be used.

  When the electrolyte aqueous solution is a chloride aqueous solution, the battery reaction is activated by chloride ions in the chloride aqueous solution, and the aluminum in the thermal spray coating hardly forms a passive film. Thereby, the electric potential of a thermal spray coating can be kept low, generation | occurrence | production of spot rust is prevented, and early consumption is prevented. In addition, as a chloride aqueous solution, aqueous solutions, such as sodium chloride, ammonium chloride, and magnesium chloride, can be used.

  In particular, when the sprayed coating is an aluminum / magnesium alloy, in addition to the above, elution of magnesium ions from the sprayed coating or to the steel substrate due to chloride ions, sulfate ions, nitrate ions, etc. contained in the electrolyte aqueous solution. Since the reaction such as precipitation is activated and the film of the magnesium compound covering the steel substrate becomes thick, the occurrence of spot rust and early consumption are further prevented.

  Furthermore, in this case, since the amount of magnesium ions inevitably increases when the magnesium ions eluted from the thermal spray coating are impregnated with the magnesium compound aqueous solution, the amount of magnesium hydroxide precipitated increases, and the magnesium compound coating covering the steel substrate It gets thicker. Therefore, the occurrence of spot rust and early consumption are prevented.

  Further, the post-treatment method of the thermal spray coating of the present invention is the method of spraying an aluminum-based material onto the surface of a steel substrate to form a thermal spray coating, and then applying an aqueous electrolyte solution to the thermal spray coating, impregnating, drying, and then applying an aqueous paint. It is characterized by applying. As mentioned above, after spraying an aluminum-based material on the surface of a steel substrate to form a sprayed coating, an aqueous electrolyte solution is applied to the sprayed coating and impregnated to prevent the occurrence of spot rust. Can be used for heavy anticorrosion purposes.

(1) According to the present invention, the applied electrolyte aqueous solution or the electrolyte aqueous solution contained in the aqueous paint is impregnated through the voids of the thermal spray coating, reaches the interface between the steel substrate and the thermal spray coating, and forms a battery. Thus, when the electrolyte aqueous solution is a magnesium compound aqueous solution, a film mainly composed of magnesium hydroxide is formed on the surface of the steel substrate, so that the current value flowing between the steel substrate and the sprayed coating is reduced, Oxygen is difficult to reach the steel substrate, so that the occurrence of spot rust is prevented and early consumption is prevented. Thereby, it becomes possible to employ a sprayed coating thickness according to the required life. When the expected life is short, it is possible to reduce the coating cost by reducing the thickness of the sprayed coating. In addition, by using an aqueous paint containing an aqueous electrolyte solution, it is possible to use an aqueous paint excellent in environmental measures for the purpose of heavy corrosion protection.

(2) Also, when the aqueous electrolyte solution is a chloride aqueous solution, the cell reaction is activated by chloride ions in the chloride aqueous solution, and it becomes difficult for aluminum in the sprayed coating to form a passive coating. Can be kept low, the occurrence of spot rust is prevented, and premature wear is prevented.

(3) In particular, when the sprayed coating is an aluminum / magnesium alloy, in addition to the above, elution of magnesium ions from the sprayed coating or steel by the chloride ions, sulfate ions, nitrate ions, etc. contained in the electrolyte aqueous solution. Reactions such as precipitation on the base material are activated, and the magnesium compound film covering the steel base material becomes thick, so that the occurrence of spot rust and early consumption are further prevented. Furthermore, in this case, since the amount of magnesium ions inevitably increases when the magnesium ions eluted from the thermal spray coating are impregnated with the magnesium compound aqueous solution, the amount of magnesium hydroxide precipitated increases, and the magnesium compound coating covering the steel substrate It gets thicker. Therefore, the occurrence of spot rust and early consumption are prevented.

(4) After spraying an aluminum-based material on the surface of a steel substrate to form a sprayed coating, an aqueous electrolyte solution is applied to the sprayed coating, impregnated, dried, and then applied with an aqueous paint to provide an excellent aqueous solution. The paint can be used for heavy corrosion prevention purposes.

It is a flowchart of the antirust process in 1st Embodiment of this invention. It is an expanded sectional view of the steel base material surface which gave the antirust process in 1st Embodiment of this invention. It is a flowchart of the antirust process in 2nd Embodiment of this invention.

(Embodiment 1)
The rust prevention process in 1st Embodiment of this invention is demonstrated. FIG. 1 is a flow chart of rust prevention treatment in the first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of the steel base surface subjected to rust prevention treatment in the first embodiment of the present invention.

  As shown in FIG. 1, in the rust prevention treatment according to the first embodiment of the present invention, first, a steel base of a steel material is blasted (S1) to form an aluminum-based sprayed coating (S2). The blast treatment is Sa2 to Sa3, and the film thickness of the sprayed coating is 50 μm to 500 μm, preferably 100 μm to 200 μm recommended by the Japanese Industrial Standard (JIS H8300). The aluminum-based thermal spray coating is formed by plasma spraying of a thermal spray material such as pure aluminum, zinc aluminum alloy or aluminum / magnesium alloy, gas flame spraying or arc spraying.

  Then, a post-treatment of the thermal spray coating is performed on the thermal spray coating (S3). The post-treatment of the thermal spray coating is performed by applying and impregnating an aqueous electrolyte solution as a post-treatment agent for the thermal spray coating on the thermal spray coating shortly after spraying. As the aqueous electrolyte solution applied here, an aqueous solution of chloride or magnesium compound is used. As the chloride, sodium chloride, ammonium chloride, magnesium chloride or the like is used. As the magnesium compound, magnesium sulfate, magnesium nitrate, magnesium chloride or the like is used. The concentration of the aqueous electrolyte solution is in the range of 0.1 mol / L to solubility in water. Even if it is 0.1 mol / L or less, it is considered that there is a certain effect, but if it is 0.1 mol / L or more, the potential is stabilized. Moreover, it is desirable to make it below the maximum solubility of 0 ° C. so as not to recrystallize when the temperature of the aqueous solution decreases. Further, the method for applying the electrolyte aqueous solution may be water jet or spray, in addition to application with a brush or a roller.

  After application of these water or aqueous electrolyte solution, it is dried and cured. The drying time may be up to finger touch drying. As the drying method, natural drying is sufficient, but forced drying with hot air or the like is also possible. Even if it remains as it is, sufficient rust prevention is exhibited, but generally, after drying, a sealing treatment is performed (S4). For the sealing treatment, for example, water-based or solvent-based paints can be used.

  According to such a rust prevention treatment, the aqueous electrolyte solution applied in the post-treatment (S3) of the thermal spray coating is impregnated through the gaps 4 between the constituent particles 2a of the thermal spray coating 2 shown in FIG. And reaches the interface of the thermal spray coating 2 to form a battery.

  At this time, when the electrolyte aqueous solution is a magnesium compound aqueous solution, the pH rises to about 13 by a chemical reaction. Then, magnesium ions in the aqueous electrolyte solution are deposited on the surface of the steel substrate 1 to form a film 3 containing magnesium hydroxide, which is hardly soluble in alkali, as a main component. This coating 3 reduces the value of the current flowing between the steel substrate 1 and the thermal spray coating 2, and makes it difficult for oxygen to reach the steel substrate 1, thereby preventing the occurrence of spot rust and preventing premature wear. Is done.

  On the other hand, when the electrolyte aqueous solution is a chloride aqueous solution, since chloride ions are present, the battery reaction is activated, and it becomes difficult for the aluminum of the thermal spray coating 2 to form a passive coating, and the potential of the thermal spray coating 2 is increased. To keep it low. Therefore, as in the case of the magnesium compound aqueous solution, the occurrence of spot rust is prevented and early consumption is prevented.

  In particular, in the case where the sprayed coating 2 is an aluminum / magnesium alloy, in addition to the above-described effects, elution of magnesium ions from the sprayed coating 2 or steel due to chloride ions, sulfate ions, nitrate ions, etc. contained in the aqueous electrolyte solution. There is also an effect of activating reactions such as precipitation on the base material 1, and since the magnesium compound film covering the steel base material 1 becomes thick, the occurrence of spot rust and early consumption are further prevented.

  Further, when magnesium ions eluted from the thermal spray coating 2 are impregnated with a magnesium compound aqueous solution, the amount of magnesium ions inevitably increases, so the amount of precipitated magnesium hydroxide is increased and the magnesium compound coating covering the steel substrate 1 is also produced. Becomes thicker. Therefore, the occurrence of spot rust and early consumption are prevented. In this reaction, the aluminum of the sprayed coating 2 is also ionized, but the aluminum compound mainly composed of aluminum hydroxide is dissolved in water in an environment having a high pH, so that it does not precipitate on the surface of the steel substrate 1.

(Embodiment 2)
Next, the rust prevention process in 2nd Embodiment of this invention is demonstrated. FIG. 3 is a flowchart of the antirust treatment in the second embodiment of the present invention.

  As shown in FIG. 3, the rust prevention treatment in the second embodiment of the present invention is the same as that in the first embodiment in the blast treatment (S1) and the thermal spray coating formation (S2). In the second embodiment, an aqueous paint as a post-treatment agent for the thermal spray coating is applied to the thermal spray coating with a brush or a roller and dried (S5).

  In order to make the water-based paint easy to apply, usually about 10% tap water is added to the water-based paint and applied. However, the water-based paint in the present embodiment is replaced with the tap water in the first embodiment. The aqueous chloride solution or aqueous magnesium compound described in 1) is used. The mixing ratio of the water-based paint and the chloride or magnesium compound solution is set to solutions 1 to 3 with respect to the water-based paint 10 in terms of mass ratio. Moreover, the density | concentration of a solution shall be the range of the solubility with respect to 0.1 mol / L-water.

  Water-based paints are expected to be environmentally friendly because they do not contain VOC (volatile organic compound), which is one of the substances that cause global warming, but they have been used for heavy anti-corrosion purposes because of their low anticorrosion properties. Not. Thus, it has been considered to be used in combination with a sprayed coating. However, when a water-based coating is actually applied to the sprayed coating, complete drying is delayed by the resin component, so that spot rust is likely to occur. Moreover, although a battery is formed between the steel base material 1 and the thermal spray coating 2 only with a water-based paint, there exists an effect | action which raises the electric potential of the thermal spray coating 2, and the antirust effect with respect to the steel base material 1 is small.

  However, in the aqueous paint containing the aqueous electrolyte solution in the present embodiment, the aqueous electrolyte solution contained in the applied aqueous paint is impregnated through the gaps 4 between the constituent particles 2a of the thermal spray coating 2, and the steel substrate 1 and the thermal spray coating 2 are impregnated. Since the potential of the thermal spray coating 2 is lowered while the battery is formed and the potential of the thermal spray coating 2 is lowered, the same effect as the first embodiment can be obtained, and the water-based paint excellent in environmental measures can be used for the purpose of heavy corrosion prevention. Become.

  A corrosion test by outdoor exposure was performed using the test piece of the aluminum-based sprayed coating in the above embodiment. The accelerated corrosion test is usually conducted by a salt spray test or a combined cycle test, but the salt water used in these tests is mainly composed of sodium chloride, which is a chloride. When used in a corrosion test, it has a function of prolonging the life, and an acceleration effect cannot be obtained. Therefore, it was confirmed in a prior test that an acceleration effect was obtained by using distilled water or fresh water having a high electric resistance value. Therefore, in this example, an accelerated corrosion test using rainwater was performed in order to approximate the actual environment.

  Table 1 shows a list of test piece specifications. In this example, as shown in Table 1, Al-5% Mg and 99.7% Al were used as the aluminum-based spray material.

  Outdoor exposure was performed in a sunny place (room temperature). Rain water was sprayed on each test piece every 24 hours from the start of outdoor exposure, and the number of days of outdoor exposure until it rusted by visual judgment was evaluated. Rainwater is considered to be the most ideal fresh air environment in the atmosphere. Moreover, the corrosion test of rusting at an early stage was made by making the sprayed coating thickness half of the normal construction film thickness. Table 2 shows the rusting situation in outdoor exposure. As can be seen from Table 2, it was confirmed that the sample subjected to the pretreatment of the sealing treatment was dramatically extended in rusting time as compared with the sample not subjected to the pretreatment. The concentration of the aqueous solution was 0.1 mol / L and 1 mol / L, and magnesium chloride was also tested at 2.5 mol / L, which is the solubility in water at 0 ° C.

  The above corrosion test was performed with a test piece having a sprayed coating thickness thinner than usual in order to evaluate the appearance change in a short period of time. The natural potential was measured, and the potential difference between the iron material and the sprayed coating was evaluated. Table 3 shows a list of test pieces.

  First, as a comparative example, the potential difference between an iron material and an Al-5% Mg sprayed coating (without impregnating solution) in rainwater and salt water environments is shown in Table 4, and the potential difference between the iron material and 99.7% Al sprayed coating (without impregnating solution). Are shown in Table 5, respectively. In the table below, the potential difference from the iron material is represented by ◎ for −101 mV or less, ◯ for -100 mV to −51 mV, Δ for -50 mV to −1 mV, and × for 0 mV or more (polarity reversal). As can be seen from Tables 4 and 5, in the conventional method in which no pretreatment is performed, a good potential difference can be maintained with respect to salt water, but it becomes unstable with respect to rainwater and the polarity may be reversed. When the polarity is reversed, the steel substrate is more easily eluted than the aluminum-based spray coating, and the eluted iron ions reach the surface of the spray coating and oxidize, which is one of the major causes of spot rust.

  Next, as an example, the potential difference between the Al-5% Mg film impregnated with various solutions and the iron material in the rainwater environment and the 99.7% Al film impregnated with various solutions and the iron material in the rainwater environment. The potential difference is shown in Table 6. As can be seen from Table 6, those subjected to the pretreatment of the sealing treatment were able to maintain a good potential difference against rainwater, and it was confirmed that the life of the sprayed coating against rainwater was prolonged.

  Next, a water-based paint in which an electrolyte aqueous solution of each drug was mixed was applied to the Al-5% Mg coating, and a corrosion test by outdoor exposure was performed. Table 7 shows the specifications of the test piece.

  Outdoor exposure was performed in a sunny place (room temperature). Rain water was sprayed on each test piece every 14 hours from the start of outdoor exposure, and the number of days of outdoor exposure until it rusted by visual judgment was evaluated. Rainwater seems to be the most ideal fresh air environment in the atmosphere. Moreover, the corrosion test of rusting at an early stage was made by making the sprayed coating thickness half of the normal construction film thickness. Table 8 shows the rusting situation after outdoor exposure. As can be seen from Table 8, it was confirmed that the sample subjected to the pretreatment of the sealing treatment was dramatically extended in rusting time as compared with the sample not subjected to the pretreatment.

  The present invention relates to steels such as bridges, harbor facilities, plants, piping, advertising towers, indicator lamps, carbon steels mainly composed of iron used outdoors such as vehicles and ships, steels such as nickel chrome steels and stainless steels. It is useful as a post-treatment method and a post-treatment agent for a thermal spray coating of an aluminum-based thermal spray coating applied for the purpose of preventing rust on the substrate surface. In particular, the post-treatment method and post-treatment agent of the thermal spray coating of the present invention are suitable for those used in an outdoor environment exposed to rainwater or the like.

DESCRIPTION OF SYMBOLS 1 Steel base material 2 Thermal spray coating 2a Constituent particle 3 Metal compound 4 Cavity

Claims (7)

  After thermal spraying an aluminum-based material on the surface of a steel substrate to form a thermal spray coating, an aqueous electrolyte solution or an aqueous paint containing an aqueous electrolyte solution is applied to the thermal spray coating and impregnated with the thermal spray coating. Method.   2. The thermal spray coating according to claim 1, wherein the electrolyte aqueous solution reaches the surface of the steel substrate through a void portion of the thermal spray coating and forms a battery between the steel substrate and the thermal spray coating. Post-processing method.   3. The electrolyte aqueous solution is a magnesium compound aqueous solution, and magnesium ions in the magnesium compound aqueous solution are deposited on the surface of the steel base material to form a film mainly composed of magnesium hydroxide. The post-treatment method of the thermal spray coating as described in 2.   The aqueous electrolyte solution is an aqueous chloride solution, and the cell reaction is activated by chloride ions in the aqueous chloride solution, so that the aluminum in the thermal spray coating makes it difficult to form a passive coating, and the potential of the thermal spray coating is kept low. The post-processing method of the thermal spray coating of Claim 1 or 2 characterized by the above-mentioned.   The post-treatment method according to claim 1, wherein the thermal spray coating is an aluminum-magnesium alloy.   After spraying an aluminum-based material on the surface of a steel substrate to form a sprayed coating, an aqueous electrolyte solution is applied to the sprayed coating, impregnated, dried, and then coated with an aqueous paint. Method.   A sealing agent that is applied to and impregnated after a thermal spray coating is formed by spraying an aluminum-based material on the surface of a steel substrate, and is a post-treatment of a thermal spray coating comprising an aqueous electrolyte solution or an aqueous paint containing an aqueous electrolyte solution. Agent.

Images