Sulfuric acid corrosion-resistant coating member, method for manufacturing a sulfuric acid corrosion-resistant coating member, and hydrogen production IS process apparatus

Abstract

To provide a sulfuric acid corrosion-resistant coating member that is superior in both of resistance to heat and resistance to corrosion due to sulfuric acid.SOLUTION: A sulfuric acid corrosion-resistant coating member includes a steel substrate, and a complex oxide coat provided on the surface of the substrate. The complex oxide coat includes a first coat including aluminum oxide particles, chromium oxide particles and silicon oxide particles, and a chromium oxide phase that fills the gaps among the particles. The chromium oxide phase further includes at least one compound selected from phosphate compounds, borate compounds, and silicate compounds.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a sulfuric acid corrosion-resistant coating member, a method for manufacturing the sulfuric acid corrosion-resistant coating member, and a hydrogen production IS process apparatus.

Background Art

[0002] As materials for components of high-temperature exposure devices such as gas turbines and jet engine components, a thermal shielding coating material having a coating composed of an undercoat made of a heat-resistant alloy containing aluminum, a topcoat made of ZrO2-based ceramics, and an intermediate layer provided between the two has been proposed (see Patent Documents 1 and 2).

[0003] In Patent Document 1, an undercoat made of a heat-resistant alloy containing aluminum is provided on the surface of a substrate, a Cr2O3 layer is provided as an intermediate layer on this undercoat, and a topcoat made of ZrO2-based ceramics is further provided on this intermediate layer. The Cr2O3 layer as the intermediate layer is a chemically densified treatment film with a thickness of 0.2 to 10 μm obtained by applying an aqueous solution in which one or more selected from anhydrous chromic acid, ammonium chromate, and ammonium dichromate are mixed and then firing. A thermal shielding coating material has been proposed.

[0004] In Patent Document 2, an undercoat made of a heat-resistant alloy containing aluminum is provided on the surface of a substrate, an intermediate layer made of SiO2 is provided on this undercoat, and a topcoat made of ZrO2-based ceramics is further provided on this intermediate layer. The intermediate layer is a chemically densified treatment film with a thickness of 0.1 to 15 μm obtained by applying a solution in which one or more selected from silica sol, colloidal silica, and inorganic silicon polymers are mixed and then firing. A thermal shielding coating member has been proposed. These are thermal shielding coating members excellent in corrosion resistance and heat resistance.

[0005] However, when the inventors observed the inside of the coating with an optical microscope, they found that fine pores and cracks were present, and that these pores and cracks sometimes reached the surface of the substrate. These microscopic pores and cracks can prevent some degree of penetration into the base material under various gaseous environments, but in liquid phases, especially in boiling solution environments, the coating itself peels off and the base material is corroded (see, for example, Non-Patent Document 1).

[0006] Incidentally, hydrogen-based energy systems are currently attracting attention in various countries as a means of realizing a carbon-neutral society. In particular, hydrogen is a clean energy source because it does not rely on fossil fuels and does not emit carbon dioxide. However, the currently dominant method of hydrogen production is the water electrolysis process, and renewable energy sources such as solar or wind power alone are nowhere near sufficient to secure the electricity required for this water electrolysis reaction in order to produce large quantities of hydrogen.

[0007] Therefore, in recent years, hydrogen production by pyrolysis reactions using high-temperature gas reactors, which have a higher heat source than conventional light water reactors, has attracted attention. In this method, hydrogen and oxygen can be produced in principle almost indefinitely by combining the reactions of sulfur dioxide and oxygen from the pyrolysis of sulfuric acid, and iodine and hydrogen from the pyrolysis of hydrogen iodide (hereinafter referred to as the IS process). This IS process utilizes only the heat source of a high-temperature gas reactor reaching nearly 850°C, enabling hydrogen production without the use of any electricity, and furthermore, it produces absolutely no carbon dioxide.

[0008] However, the main challenge of this process is that the use of high-temperature acidic solutions such as sulfuric acid and hydrogen iodide causes corrosion of structural components of the apparatus, equipment, and piping. For this reason, SiC ceramics have been used in sulfuric acid decomposition reaction vessels until now (see, for example, Non-Patent Document 2). [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2004-285423 [Patent Document 2] Japanese Patent Publication No. 2005-343107 [Non-patent literature]

[0010] [Non-Patent Document 1] Tanaka, Nobuyuki et al., "Corrosion Resistance of IS Process Equipment Materials in High-Temperature Sulfuric Acid - Corrosion Resistance of Alloy 800, Alloy 600, SUSXM15J1, and SiC -", Materials and Environment, vol. 55, pp. 320-324 (2006). [Non-Patent Document 2] H. Noguchi et al., “R&D status of hydrogen production test using IS process test facility made of industrial structural material in JAEA” Journal of Hydrogen Energy, 44, pp.12583-12592 (2019). [Overview of the Initiative] [Problems that the invention aims to solve]

[0011] When SiC ceramics are used as the material for sulfuric acid decomposition reaction vessels, predicting the remaining lifespan due to crack formation caused by sudden impacts is difficult because SiC is a brittle material. Furthermore, due to the dimensional constraints of the sintering furnaces used to manufacture SiC, it is difficult to enlarge SiC components. [Means for solving the problem]

[0012] Under these circumstances, the inventors conducted extensive research and have completed a sulfuric acid corrosion-resistant coating member that has a coating with excellent heat resistance and corrosion resistance to sulfuric acid.

[0013] The sulfuric acid corrosion-resistant coating member of the present invention is A steel base material, A sulfuric acid corrosion-resistant coating member comprising a composite oxide film provided on the surface of the above-mentioned substrate, The above composite oxide film includes a first film comprising aluminum oxide particles, chromium oxide particles, and silicon oxide particles, and a chromium oxide phase filling the gaps between each of the above particles. The chromium oxide phase further contains at least one compound selected from phosphate compounds, borate compounds, and silicate compounds.

[0014] The above-mentioned sulfuric acid corrosion-resistant coated member has excellent heat resistance and corrosion resistance to sulfuric acid because it is equipped with the above-mentioned composite oxide film. Furthermore, because the sulfuric acid corrosion-resistant coating material is made of steel, it is easier to enlarge and process / form compared to materials made of SiC ceramics.

[0015] In the above sulfuric acid corrosion-resistant coating member, the composite oxide film further includes a second film provided on the surface of the first film. Preferably, the second coating contains chromium oxide and at least one compound selected from phosphate compounds, borate compounds, and silicate compounds. In this case, heat resistance and corrosion resistance to sulfuric acid become better.

[0016] In the above-mentioned sulfuric acid corrosion-resistant coating member, it is preferable that the composition ratio of aluminum oxide, chromium oxide, and silicon oxide contained in the composite oxide film is such that, with a total amount of 100% by mass, aluminum oxide is less than 10% by mass, chromium oxide is 35% or more by mass, and silicon oxide is 50% or more by mass. In this case, corrosion resistance to sulfuric acid becomes particularly good.

[0017] The method for manufacturing the sulfuric acid corrosion-resistant coating member of the present invention is as follows: A method for manufacturing a coated member having a composite oxide film provided on the surface of a steel substrate, (1) A step of applying or spraying a slurry containing aluminum oxide particles, chromium oxide particles, and silicon oxide particles on the surface of the above substrate, or immersing the above substrate in the slurry and then firing at 350 to 600 °C to form a base film; (2) A step of applying or spraying an aqueous chromic acid solution on the surface of the above base film, or immersing the above substrate in the aqueous chromic acid solution and pulling it out, and then holding at a temperature of 350 to 600 °C to fill chromium oxide into the voids of the above base film; It has.

[0018] The method for manufacturing the sulfuric acid corrosion-resistant coating member is as follows. (3) A step of applying or spraying an aqueous chromic acid solution containing at least one compound selected from phosphate compounds, borate compounds, and silicate compounds on the surface of the above base film, or immersing the above substrate in the slurry and pulling it out, and then holding at a temperature of 350 to 600 °C to form a film containing chromium oxide and at least one compound selected from phosphate compounds, borate compounds, and silicate compounds; It is further preferable to have. According to these manufacturing methods, the sulfuric acid corrosion-resistant coating member can be manufactured.

[0019] The device of the present invention is a hydrogen production IS process device provided with the above sulfuric acid corrosion-resistant coating member. The above hydrogen production IS process device includes components having excellent heat resistance and corrosion resistance to sulfuric acid. Examples of the above components include a sulfuric acid decomposition reaction vessel and piping.

Effects of the Invention

[0020] The sulfuric acid corrosion-resistant coating member of the present invention has excellent heat resistance and corrosion resistance to sulfuric acid. (2) A step of applying or spraying an aqueous chromic acid solution on the surface of the above base film, or immersing the above substrate in the aqueous chromic acid solution and pulling it out, and then holding at a temperature of 350 to 600 °C to fill chromium oxide into the voids of the above base film; In addition, the above sulfuric acid corrosion-resistant coating member is easy to scale up and process.

Brief Description of the Drawings

[0021] [Figure 1]This is a partial cross-sectional view of a sulfuric acid corrosion-resistant coating member according to an embodiment of the present invention. [Figure 2] This is a process diagram of a method for manufacturing a sulfuric acid corrosion-resistant coating member according to an embodiment of the present invention. [Modes for carrying out the invention]

[0022] The embodiments of the present invention will be described below. The embodiments of the present invention are not limited to those described below. Figure 1 is a partial cross-sectional view of a sulfuric acid corrosion-resistant coating member 10 according to an embodiment of the present invention. The sulfuric acid corrosion-resistant coating member 10 comprises a stainless steel base material 11 and a composite oxide film 12 provided on the surface of the base material 11.

[0023] The composite oxide film 12 comprises a first film 5 containing aluminum oxide particles, chromium oxide particles, and silicon oxide particles, and a chromium oxide phase filling the gaps between the particles, and a second film 6 provided on the surface of the first film 5, containing chromium oxide and at least one compound selected from phosphate compounds, borate compounds, and silicate compounds.

[0024] The first coating 5 has a base coating 2 formed by applying or spraying a slurry (coating material) containing aluminum oxide (Al2O3) particles, chromium oxide (Cr2O3) particles, and silicon oxide (SiO2) particles onto the surface of the substrate 11, or by immersing the substrate 11 in the slurry and then firing it at 350 to 600°C, and a chromium oxide phase 4 filled in the voids of the base coating 2. The chromium oxide phase 4 contains chromium oxide (Cr2O3) and further contains at least one compound selected from phosphate compounds, borate compounds, and silicate compounds.

[0025] The second coating 6 is a coating provided on the surface of the first coating 5, containing chromium oxide and at least one compound selected from phosphate compounds, borate compounds, and silicate compounds.

[0026] The base film 2 formed on the surface of the stainless steel substrate 11 is a film having a composition of Al2O3-Cr2O3-SiO2, and is formed by coating the film material and firing. The formed base film 2 is very hard and has excellent wear resistance, but fine voids exist within the film, some of which have pathways that reach the substrate 11.

[0027] If such voids remain within the composite oxide film 12, in an environment where sulfuric acid solution is present, the sulfuric acid solution will easily permeate through the composite oxide film 12 and reach the stainless steel substrate 11, causing corrosion of the substrate 11.

[0028] On the other hand, in the sulfuric acid corrosion-resistant coating member 10 according to the embodiment of the present invention, fine voids including pores and cracks in the base film 2 are filled with chromium oxide phase 4. Therefore, the first film 5 of the composite oxide film 12 is in a state in which the gaps between the aluminum oxide particles, chromium oxide particles and silicon oxide particles are filled with chromium oxide phase 4.

[0029] Furthermore, in the composite oxide film 12, a second film 6 is provided on the surface of the base film 2 (first film 5), in which fine voids are filled with chromium oxide phase 4. This second film 6 contains chromium oxide and at least one compound selected from phosphate compounds, borate compounds, and silicate compounds.

[0030] The composite oxide film 12 comprises a first film 5 in which the fine voids of the base film 2 are filled with chromium oxide phase 4, and a second film 6 provided on the surface of the first film, thus exhibiting excellent resistance to sulfuric acid penetration. Therefore, the sulfuric acid corrosion-resistant coated member 10 is a member with excellent corrosion resistance to sulfuric acid. Furthermore, this composite oxide coating 12 is a coating that follows the thermal expansion of the steel material. Therefore, for example, it can suppress the occurrence of cracks even in a thermal shock test at 800°C. Accordingly, the sulfuric acid corrosion-resistant coated member 10 is also a member with excellent heat resistance.

[0031] Preferably, the composition ratio of aluminum oxide, chromium oxide, and silicon oxide contained in the composite oxide film 12 is such that, with a total amount of 100% by mass, aluminum oxide is less than 10% by mass, chromium oxide is 35% or more by mass, and silicon oxide is 50% or more by mass. The composite oxide film 12 having this composition ratio exhibits excellent corrosion resistance to sulfuric acid. Furthermore, having chromium oxide at 35% by mass or more means that there is a relatively large amount of chromium oxide phase filling the voids, resulting in a dense composite oxide film 12, which is suitable for maintaining corrosion resistance.

[0032] In the composition ratio of aluminum oxide, chromium oxide, and silicon oxide contained in the composite oxide film 12, the preferred lower limit for aluminum oxide is 3% by mass. The preferred upper limit for chromium oxide is 50% by mass, and the preferred upper limit for silicon oxide is 65% by mass.

[0033] The thickness of the composite oxide film 12 is preferably 50 to 200 μm. Within this range, it offers excellent resistance to sulfuric acid penetration and is less prone to cracking even at high temperatures.

[0034] Next, a method for manufacturing the sulfuric acid corrosion-resistant coating member 10 will be described. Figure 2 is a process diagram of the manufacturing method for the sulfuric acid corrosion-resistant coating member 10. (a) First, the steel base material 11 is pre-treated as necessary. Specifically, for example, degreasing is performed (see Figure 2(a)).

[0035] (b) A slurry containing aluminum oxide particles, chromium oxide particles, and silicon oxide particles is applied or sprayed onto the surface of the steel substrate 11, or the substrate 11 is immersed in the slurry (see Figure 2(b1)). The slurry described above is a suspension in which aluminum oxide particles, chromium oxide particles, and silicon oxide particles are suspended in purified water or the like. The total content (mass%) of aluminum oxide particles, chromium oxide particles, and silicon oxide particles in the slurry described above is preferably 90 to 98% by mass.

[0036] Subsequently, the slurry is fired at a predetermined temperature within the range of 350 to 600°C for 0.5 to 2 hours to form a base film 2 on the surface of the substrate 11 (see Figure 2(b2)). As described above, the base coating 2 has voids between each particle. Therefore, in the embodiment of the present invention, the voids in the base film 2 are filled by performing the steps described later.

[0037] (c) Apply or spray a chromic acid aqueous solution onto the surface of the base film 2, or immerse the substrate 11 on which the base film 2 is formed in the chromic acid aqueous solution and then remove it (see Figure 2(c1)). Subsequently, the base film 2 is held at a predetermined temperature within the range of 350 to 600°C for 0.5 to 2 hours. This fills the voids in the base film 2 with chromium oxide (see Figure 2(c2)). This process can be performed only once or multiple times.

[0038] (d) A mixture of an aqueous solution containing at least one compound selected from phosphate compounds, borate compounds, and silicate compounds and an aqueous solution of chromic acid is applied or sprayed onto the surface of the base film 2, or the substrate 11 on which the base film 2 is formed is immersed in the mixture and then removed (see Figure 2(d1)). Subsequently, the mixture is held at a temperature of 350-600°C for 0.5-2 hours (see Figure 2(d2)). This forms a first film 5 filled with a chromium oxide phase containing at least one compound selected from phosphate compounds, borate compounds, and silicate compounds, and a second film 6 containing chromium oxide and at least one compound selected from phosphate compounds, borate compounds, and silicate compounds is formed on the surface of the first film 5. This process can be performed only once or multiple times.

[0039] In step (d), a mixture of an aqueous solution containing at least one compound selected from phosphate compounds, borate compounds, and silicate compounds and an aqueous chromic acid solution is applied, sprayed, or immersed in this mixture, followed by a heating step (calcination step). As a result, in step (d), the water contained in the mixture evaporates, chromic acid becomes chromium oxide (Cr2O3) via an intermediate, and at the same time, the aqueous solutions of the phosphate compound, borate compound, and silicate compound release water and become amorphous inorganic substances that partially exhibit a glassy state, thus densifying the entire film.

[0040] In this way, the second film 6 is formed. In this second film 6, the Cr2O3 formed from the aqueous solution is extremely fine and hard, and has excellent wear resistance and corrosion resistance. Furthermore, these amorphous inorganic substances contribute to the adhesion between the constituent particles of the first film 5 (Al2O3 particles, Cr2O3 particles, SiO2 particles) and to strengthening the interparticle bonding force of the Cr2O3 fine particles in the first film 5 and the second film 6. Therefore, by forming the second film 6, the effect of preventing the penetration of sulfuric acid is enhanced, and corrosion resistance to sulfuric acid is ensured.

[0041] Furthermore, during step (d), a mixture of an aqueous solution containing at least one compound selected from phosphate compounds, borate compounds, and silicate compounds and an aqueous chromic acid solution is partially filled into the voids of the base film 2. As a result, Cr2O3 precipitates within the voids of the base film 2, and a portion of it precipitates as an amorphous inorganic substance exhibiting a glassy appearance. This forms the first film 5.

[0042] By going through these processes, a sulfuric acid corrosion-resistant coating member 10 can be manufactured. The construction conditions for the manufacturing method of the sulfuric acid corrosion-resistant coating member 10 are summarized in Table 1.

[0043] [Table 1]

[0044] The above-mentioned sulfuric acid corrosion-resistant coating member 10 can be used as a component of the hydrogen production IS process apparatus in general (for example, a sulfuric acid decomposition reaction vessel). Furthermore, the above-mentioned sulfuric acid corrosion-resistant coating member 10 can also be used as piping in the hydrogen production IS process apparatus. [Examples]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples. Here, evaluation samples were prepared for the examples and comparative examples, and the durability of each sample against boiling sulfuric acid solution was evaluated.

[0046] (Example 1) (1) A slurry containing Al2O3 particles, Cr2O3 particles, and SiO2 particles suspended in purified water was applied to the surface of a degreased substrate (SUS304 steel) 11.

[0047] The substrate coated with slurry was placed in a heating furnace, and the slurry was fired to form a base film 2 on the substrate 11. The heating conditions during firing were a predetermined temperature within the range of 350 to 600°C, held for 0.5 to 2 hours.

[0048] (2) The substrate 11 on which the base film 2 is formed is immersed in a 55% chromic acid aqueous solution, then removed and placed in a heating furnace. The impregnation and firing treatment is repeated multiple times under the conditions of being held at a predetermined temperature in the range of 350 to 600°C for 0.5 to 2 hours, thereby filling the voids in the base film 2 with chromium oxide.

[0049] (3) The substrate 11 that has completed step (2) is immersed in a 55% aqueous chromic acid solution containing a phosphate compound, then removed and placed in a heating furnace. The impregnation and firing treatment is repeated multiple times under the conditions of being held at a predetermined temperature in the range of 350 to 600°C for 0.5 to 2 hours to form a first film having a chromium oxide phase 4 and a second film 6.

[0050] Through this process, an evaluation sample was obtained in which a composite oxide film 12 was formed on the surface of the substrate 11. The thickness of the composite oxide film 12 in the evaluation sample prepared in this example was 58.3 μm. The thickness of the composite oxide film 12 was measured by cutting the evaluation sample and observing the cut surface under magnification.

[0051] (Example 2) An evaluation sample was obtained in the same manner as in Example 1, except that the thickness of the composite oxide film 12 in the evaluation sample was set to 92.5 μm.

[0052] (Example 3) An evaluation sample was obtained in the same manner as in Example 1, except that the thickness of the composite oxide film 12 in the evaluation sample was set to 56.8 μm.

[0053] (Comparative Example 1) (1) A slurry containing Al2O3 particles, Cr2O3 particles, and SiO2 particles suspended in purified water was applied to the surface of a degreased substrate (SUS304 steel) 11.

[0054] The substrate coated with slurry was placed in a heating furnace, and the slurry was fired to form a base film. The heating conditions during firing were set to a predetermined temperature within the range of 350 to 600°C, held for 0.5 to 2 hours.

[0055] (2) The substrate 11 on which the base film has been formed is immersed in a 55% chromic acid aqueous solution containing a phosphate compound, then removed and placed in a heating furnace. The impregnation and firing treatment is repeated multiple times under the conditions of being held at a predetermined temperature in the range of 350 to 600°C for 0.5 to 2 hours to form a film that covers the surface of the base film.

[0056] Through this process, an evaluation sample was obtained in which a composite oxide film was formed on the surface of the substrate 11. In this comparative example, only the surface layer of the composite oxide film in the evaluation sample prepared was densified, and voids remained inside the composite oxide film. The thickness of the composite oxide film in the evaluation sample prepared in this comparative example was 94.3 μm.

[0057] (Comparative Example 2) An evaluation sample was obtained in the same manner as in Comparative Example 1, except that the thickness of the composite oxide film in the evaluation sample was set to 45.7 μm. In the evaluation samples prepared in this comparative example, only the surface layer of the composite oxide film was densified, and voids remained within the composite oxide film.

[0058] (Comparative Example 3) An evaluation sample was obtained by spray-coating the surface of a degreased substrate (SUS304 steel) 11 with a fluororesin layer 28.4 μm thick.

[0059] (Comparative Example 4) An evaluation sample was obtained by forming a 20.7 μm thick alumina layer on the surface of a degreased substrate (SUS304 steel) 11 using a dip treatment.

[0060] (Comparative Example 5) A degreasing treatment was performed on the substrate (SUS304 steel) before use as the evaluation sample.

[0061] (Comparative Example 6) SiC components were used as evaluation samples.

[0062] (component analysis) The composite oxide films in the evaluation samples of Examples 1-3 and Comparative Examples 1 and 2 were subjected to component analysis. Each evaluation sample was cut along its thickness, and cross-sectional observation was performed using a scanning electron microscope (JEOL Ltd., JSM-IT300). The composition ratio was analyzed using EDX. The results are shown in Table 2.

[0063] (Evaluation of durability against sulfuric acid solution) The evaluation samples were immersed in a 96% by mass sulfuric acid solution and held at 328°C (the azeotropic point of sulfuric acid) for 100 hours. The corrosion rate was then calculated based on the weight change before and after immersion. The results are shown in Table 2.

[0064] [Table 2]

[0065] As shown in Table 2, it has become clear that the sulfuric acid corrosion-resistant coating member according to the embodiment of the present invention can exhibit corrosion resistance to boiling sulfuric acid comparable to that of SiC. Furthermore, in Examples 1-3, the sulfuric acid corrosion-resistant coated members showed that the coating remained intact in all evaluation samples after immersion, clearly confirming that they suppressed the progression of corrosion on the SUS304 steel. Furthermore, it has been confirmed that the sulfuric acid corrosion-resistant coating members of Examples 1 to 3 do not undergo cracking or other failures in the temperature range of 800°C or below, even after repeated heating and cooling. [Industrial applicability]

[0066] The above-mentioned sulfuric acid corrosion-resistant coating material is suitable for use as a sulfuric acid decomposition reaction vessel or piping in equipment used in the hydrogen production IS process. Furthermore, the above-mentioned sulfuric acid corrosion-resistant coating material is also suitable for use in geothermal power generation equipment, oil drilling piping, flue gas treatment equipment, and sulfuric acid plants. Furthermore, the above-mentioned sulfuric acid corrosion-resistant coating material can also be used as a substitute for glass lining in applications such as petrochemicals, heat exchangers, and powder drying. [Explanation of symbols]

[0067] 2 Base coating 4. Chromium oxide phase 5. First coating 6. Second Coating 10 Sulfuric acid corrosion resistant coating material 11 Base material 12. Composite oxide film

Claims

1. A method for manufacturing a coated member having a composite oxide film provided on the surface of a steel substrate, (1) A step of forming a base film by applying or spraying a slurry containing aluminum oxide particles, chromium oxide particles, and silicon oxide particles, and not containing any of the compounds of phosphoric acid, phosphate compounds, borate compounds, and silicate compounds, or by immersing the substrate in the slurry and then firing it at 350 to 600°C, (2) A step of filling the voids in the base film with chromium oxide by applying or spraying an aqueous chromic acid solution that does not contain any of the following compounds: phosphoric acid, phosphate compounds, borate compounds, and silicate compounds, to the surface of the base film, or by immersing the substrate in the aqueous chromic acid solution and then holding it at a temperature of 350 to 600°C, A method for manufacturing a sulfuric acid corrosion-resistant coating member having [the specified characteristic].

2. (3) A step of forming a film containing chromium oxide and at least one compound selected from phosphate compounds, borate compounds, and silicate compounds by applying or spraying an aqueous chromic acid solution containing at least one compound selected from phosphate compounds, borate compounds, and silicate compounds onto the surface of the base film, or by immersing the substrate in the slurry and then holding it at a temperature of 350 to 600°C. A method for manufacturing a sulfuric acid corrosion-resistant coating member according to claim 1, further comprising the steps of (1) and (2) above.

3. A method for manufacturing a hydrogen production IS process apparatus, comprising a method for manufacturing a sulfuric acid corrosion-resistant coating member according to claim 1 or 2.

4. The method for manufacturing a hydrogen production IS process apparatus according to claim 3, wherein the sulfuric acid corrosion-resistant coating member is a sulfuric acid decomposition reaction vessel.

5. The method for manufacturing a hydrogen production IS process apparatus according to claim 3, wherein the sulfuric acid corrosion-resistant coating member is a pipe.

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