Al-plated ferritic stainless steel sheet

Abstract

This Al-plated ferritic stainless steel sheet comprises a base steel sheet, an Al-based plating layer, and a coating, wherein: the chemical composition of the base steel sheet consists of C, Si, Mn, P, S, Cr, Ti, and B, with the remainder comprising Fe and impurities; the chemical composition of the Al-based plating layer consists of 0-20.0% Si, and 0-10.0% Fe, with the remainder comprising Al and impurities; the plating adhesion amount of the Al-based plating layer is 10-200 g / m2; the coating contains Si, V, Zr, and P; the maximum value of the cation fraction of Si in the surface layer portion of the coating is 10 at% or more, the maximum value of the cation fraction of V in the surface layer portion of the coating is 10 at% or more, the maximum value of the cation fraction of Zr in the surface layer portion of the coating is 10 at% or more, and the maximum value of the cation fraction of P in the surface layer portion of the coating is 30 at% or less; and the thickness of the coating is 10 to 200 nm.

Description

Al-plated ferritic stainless steel sheet

[0001] This disclosure relates to an Al-plated ferritic stainless steel sheet. This application claims priority under Japanese Patent Application No. 2025-050929, filed in Japan on March 26, 2025, the contents of which are incorporated herein by reference.

[0002] Automotive components such as fuel tanks, fuel pipes, battery cases, battery coolers, and battery covers require extended lifespan. Applying plated steel or stainless steel sheets to these components can be a means of achieving this extended lifespan. Furthermore, in these applications, paint or adhesives may be applied to the surface.

[0003] However, plated steel sheets or stainless steel sheets are not considered to have sufficient corrosion resistance in salt-damaged environments when applied alone to fuel tanks, fuel pipes, etc.

[0004] Regarding stainless steel sheets, ferritic stainless steel sheets such as SUS436L have a problem in accelerated laboratory testing simulating exposure to snowmelt salts, where crevice corrosion occurs in crevice structures or welded structures. Austenitic stainless steel sheets such as SUS304L have a problem in the aforementioned accelerated laboratory testing, where stress corrosion cracking occurs in welds and other areas.

[0005] Therefore, ferritic stainless steel sheets are used in automotive parts from a cost perspective. Furthermore, to improve crevice corrosion resistance, plated ferritic stainless steel sheets are sometimes used in automotive parts. In particular, among platings, aluminum plating has excellent corrosion resistance, so applying aluminum plating to the surface of ferritic stainless steel sheets used in the above parts can be expected to significantly improve their properties.

[0006] Patent Document 1 discloses a hot-stamping plated stainless steel sheet that can obtain sufficient corrosion resistance even when the steel sheet beneath the paint or plating is exposed. The sheet comprises a martensitic stainless steel sheet containing C, Si, Mn, P, S, Cr, Ni, Cu, Mo, Al, N, and O, with a γP value of 80 or more and 200 or less represented by the following formula (1), and a C + 0.5N content of 0.04% or more and 0.37% or less, and a plating layer on the surface of the martensitic stainless steel sheet made of aluminum or an aluminum alloy with a thickness of 10 μm or more and 100 μm or less. γp = 420C + 470N + 23Ni + 9Cu + 7Mn - 11.5Cr - 11.5Si - 12Mo - 52Al + 189 …(1)

[0007] Patent Document 2 describes an Al-plated stainless steel sheet having a plated substrate and a molten Al-based plating layer on the surface of the plated substrate, wherein the plated substrate contains, by mass%, C: 0.030% or less, Si: 1.50% or less, Mn: 1.00% or less, P: 0.040% or less, S: 0.010% or less, Cr: 11.0 to 30.0%, Al: 1.00% or less, Ni: 0.05 to 0.50%, and N: 0.030% or less, and Mo: A ferritic stainless steel sheet is disclosed having a compositional composition in which at least one selected from 2.5 to 6.0% and W: 2.5 to 6.0%, and at least one selected from Zr: 0.01 to 0.20%, Hf: 0.01 to 0.20%, and REM: 0.01 to 0.20%, with the remainder being Fe and unavoidable impurities, and satisfying the following relationships (1) and (2): 2.5 ≤ ΔAl ≤ 7.0 ... (1) Mo + W - (ΔAl / 12 + 2.3) ≥ 0 ... (2) where ΔAl = 30 × t / T ... (3). Furthermore, in formulas (1) to (3) above, Mo: Mo content in the composition of the plated substrate (mass%) W: W content in the composition of the plated substrate (mass%) T: plate thickness of the plated substrate (μm) t: thickness of the molten Al-based plating layer (total thickness of the molten Al-based plating layers on both sides of the plated substrate if the plated substrate has molten Al-based plating layers on both sides) (μm).

[0008] Patent Document 3 discloses a ferritic stainless steel sheet having a composition in which, by mass%, C: 0.030% or less, Si: 3.0% or less, Mn: 1.0% or less, P: 0.040% or less, S: 0.010% or less, Cr: 11.0 to 30.0%, Al: 8.0 to 20.0%, Ni: 0.05 to 0.50%, and N: 0.020% or less, and also contains at least one selected from Zr: 0.01 to 0.20% and Hf: 0.01 to 0.20%, with the remainder being Fe and unavoidable impurities.

[0009] Patent Document 4 describes a ferritic stainless steel material without plating, which contains, by mass%, C: ≤0.015%, N: ≤0.015%, Cr: 10.5-18.0%, Si: 0.01-0.80%, Mn: 0.01-0.80%, P ≤0.050%, S: ≤0.010%, Mo: 0.6% or less, Al: 0.010-0.100%, and further satisfies Ti ≤0.30%, Nb ≤0.30%, with one or both of 0.03% ≤ Ti and 0.03% ≤ Nb being satisfied, with the remainder being Fe and unavoidable impurities. Between this member and a metal fitting made from a sacrificial corrosion-resistant plated steel sheet attached to the member, there is a gap structure exposed to a salt-damaged environment, and the amount of plating adhesion on the surface of the metal fitting that contacts the gap of the gap structure is 20 g / m². ２ 150g / m or more ２ The following conditions apply, and the surface of members other than the gap structure and metal parts is covered with a coating, and the cathode current value when -0.8V vs SSE is applied to the surface of the member without plating after painting is 10 -7 A / cm ２ An automotive component characterized by the above is disclosed.

[0010] Patent Document 5 discloses, in mass%, C: ≤ 0.015%, N: ≤ 0.015%, Cr: 13.0 to 18.0%, Si: 0.01 to 0.80%, Mn: 0.01 to 0.80%, P: ≤ 0.050%, S: ≤ 0.010%, Mo: ≤ 1.5%, Al: 0.010 to 0.100%, further satisfies Ti ≤ 0.30%, Nb ≤ 0.30% and one or both of 0.03% ≤ Ti and 0.03% ≤ Nb, with the balance consisting of Fe and unavoidable impurities. Between an unplated member made of ferritic stainless steel as a raw material and a metal fitting component molded from a steel plate attached to said member, a gap structure portion exposed to a salt damage environment is formed, and the coating adhesion amount of said metal fitting component on the surface corresponding to the gap portion of said gap structure portion is 20 g / m ２ or more and 150 g / m ２ or less, plating having a sacrificial anticorrosive effect is applied, and the entire surface is not coated; an automobile fuel supply pipe characterized by the above is disclosed.

[0011] Patent Document 6 discloses, in mass%, C: ≤ 0.015%, N: ≤ 0.015%, Cr: 10.5 to 18.0%, Si: 0.01 to 0.80%, Mn: 0.01 to 0.80%, P: ≤ 0.050%, S: ≤ 0.010%, Al: 0.010 to 0.100%, further satisfies Ti ≤ 0.30%, Nb ≤ 0.30% and one or both of 0.03% ≤ Ti and 0.03% ≤ Nb, with the balance consisting of Fe and unavoidable impurities. For an unAl-plated member made of ferritic stainless steel as a raw material, the Al plating adhesion amount is 20 g / m ２ or more and 150 g / m ２ or less, a metal fitting component molded from an Al-plated stainless steel plate is attached by welding or brazing, a gap structure portion exposed to a salt damage environment is formed between said member and said metal fitting component molded from an Al-plated stainless steel plate attached to said member, and then, the surfaces of the metal fitting component and the member are coated with a cationic electrodeposition coating film having a thickness of 5 to 35 µm; an automobile member characterized by the above is disclosed.

[0012] Patent Document 7 discloses that the elongation at break when processed by uniaxial tension is 50% or more, and the work hardening rate is 400 N / mm ２The following vehicle fuel tank is disclosed, which is manufactured by forming a hot-dip aluminum plated stainless steel sheet, on which an austenitic stainless steel is used as the base material and a hot-dip aluminum plated layer is formed on the surface of the base material.

[0013] Patent Document 8 discloses an Al-plated stainless steel sheet with excellent high-temperature oxidation resistance, which is obtained by plating a ferritic stainless steel sheet with aluminum or an aluminum-based alloy, comprising, by weight percent, C: 0.05% or less, Si: 1.0% or less, Mn: 1.0% or less, Cr: 10-30%, N: 0.05% or less, Mo: 0.1-4.0%, a total of one or more elements selected from the group consisting of rare earth elements and Y: 0.01-0.2%, and the remainder being iron and unavoidable impurities.

[0014] Patent Document 9 discloses a method for producing a hot-dip ferritic stainless steel with good bendability, characterized in that a ferritic stainless steel containing Cr: 11% to 25% and Nb: 0.1% to 1.5% by weight is used as the plating base, and in the manufacturing process of a hot-dip galvanized stainless steel in which Zn or Al or an alloy thereof is the main component, the annealing temperature after cold rolling of the plating base is 1000°C or less, the cooling is performed at a cooling rate of 5°C / s to 50°C / s up to at least 500°C, and the preheating temperature before plating is 650°C to 780°C.

[0015] Patent document 10 discloses a hot-dip aluminum plated stainless steel sheet having a hot-dip aluminum plating layer formed on a base material made of ferritic stainless steel containing 16 to 25% by weight of Cr, followed by a coating film of an organic resin that does not contain pigment.

[0016] Patent Document 11 discloses an aluminum-plated stainless steel for automotive exhaust systems with excellent corrosion resistance, characterized in that a stainless steel material consisting of C; 0.05% or less, Si; 0.2% or less, Mn; 1.0% or less, Cr; 10% to 20%, Mo; 0.5% to 6.0%, P; 0.025% or less, S; 0.010% or less, with the remainder being Fe and unavoidable impurities is coated with an Al plating layer of 80 to 120 microns in thickness by hot-dip Al plating treatment.

[0017] Japanese Patent Publication No. 2023-044342 International Publication No. 2020 / 255563 International Publication No. 2020 / 054384 Japanese Patent Publication No. 2016-169418 Publication Japanese Patent Publication No. 2016-169417 International Publication No. 2 015 / 037707 Japanese Unexamined Patent Publication No. 2003-221660 Japanese Unexamined Patent Publication No. 7-233451 Japanese Unexamined Patent Application No. 8-49050 Japanese Unexamined Patent Application No. 7-188941 Japanese Unexamined Patent Application No. 5-112859

[0018] However, in corrosive environments, ferritic stainless steel sheets with aluminum plating are susceptible to preferential corrosion of the aluminum layer. This raises concerns that if paint or adhesive is applied to the surface of the plating layer, the paint or adhesive may peel off prematurely. If the paint or adhesive peels off, crevice corrosion may occur in the peeled areas, potentially leading to premature deterioration such as holes occurring before the initially expected product lifespan.

[0019] This disclosure is made in view of the above circumstances and aims to provide an Al-plated ferritic stainless steel sheet that has excellent adhesion to paints and adhesives, as well as excellent corrosion resistance.

[0020] To address the above issues, this disclosure adopts the following configuration. [1] A base steel sheet, an Al-based plating layer located on the surface of the base steel sheet, and a film located on the surface of the Al-based plating layer, wherein the chemical composition of the base steel sheet is, in mass%, C: 0.010% or less, Si: 0.01 to 0.80%, Mn: 0.01 to 0.50%, P: 0.050% or less, S: 0.0050% or less, Cr: 10.5 to 30.0%, Ti: 0.01 to 0.30%, B: 0.0001 to 0.0010%, Ni: 0 to 0.50%, Mo: 0 to 3.00%, Al: 0 to 0.20%, N: 0 to 0.100%, Nb: 0 to 0.50%, Cu: 0 to 3.00%, V The composition of the Al-based plating layer is, in mass%, Si: 0-1.00%, Sn: 0-1.00%, W: 0-1.00%, Co: 0-1.00%, Sb: 0-1.00%, Ca: 0-0.010%, Mg: 0-0.010%, Ga: 0-0.010%, Zr: 0-0.050%, Hf: 0-0.050%, REM: 0-0.050%, the remainder being Fe and impurities. The chemical composition of the Al-based plating layer is, in mass%, Si: 0-20.0%, Fe: 0-10.0%, the remainder being Al and impurities. The plating adhesion amount of the Al-based plating layer is 10-200 g / m². ２Al-plated ferritic stainless steel sheet, characterized in that the film contains Si, V, Zr, and P, and when the thickness of the film is t, and the surface layer of the film is defined as the range from the surface of the film to a depth of (1 / 2)t, the maximum value of the cation fraction of Si in the surface layer of the film is 10 atomic percent or more, the maximum value of the cation fraction of V in the surface layer of the film is 10 atomic percent or more, the maximum value of the cation fraction of Zr in the surface layer of the film is 10 atomic percent or more, the maximum value of the cation fraction of P in the surface layer of the film is 30 atomic percent or less, and the thickness of the film is 10 nm or more and 200 nm or less. [2] The chemical composition of the base steel sheet is, in mass%, Ni: 0.01 to 0.50%, Mo: 0.01 to 3.00%, Al: 0.001 to 0.20%, N: 0.001 to 0.100%, Nb: 0.001 to 0.50%, Cu: 0.01 to 3.00%, V: 0.01 to 1.00%, Sn: 0.01 to 1.00%, W: 0.01 to 1.00%, Co: 0.01 to 1.00%, Sb: 0.01 to 1.00%, Ca: 0.0001 to 0.010%, Mg: 0.0001 to 0.010%, Ga: 0.0001 to 0.010%, [1] The Al-plated ferritic stainless steel sheet according to [1], containing one or more of the following: Zr: 0.0001 to 0.050%, Hf: 0.0001 to 0.050%, and REM: 0.0001 to 0.050%. [3] The Al-plated ferritic stainless steel sheet according to [1] or [2], wherein the maximum value of the Si cation fraction in the surface layer of the film is 23 atomic percent or more, the maximum value of the V cation fraction in the surface layer of the film is 18 atomic percent or more, and the maximum value of the Zr cation fraction in the surface layer of the film is 30 atomic percent or more.

[0021] According to this disclosure, it is possible to provide an Al-plated ferritic stainless steel sheet that has excellent adhesion to paints and adhesives, as well as excellent corrosion resistance.

[0022] The present inventors have found that by optimizing the chemical composition of a coating, such as a chemical conversion coating, formed on the surface of the plating layer of an Al-plated ferritic stainless steel sheet, adhesion to paints and adhesives can be improved, as well as corrosion resistance. An embodiment of the Al-plated ferritic stainless steel sheet described herein will be explained below.

[0023] In this disclosure, "excellent adhesion" means that the adhesive applied to the surface of an Al-plated ferritic stainless steel sheet is difficult to peel off even after a combined cycle corrosion test (CCT) has been performed.

[0024] Furthermore, in this disclosure, "excellent corrosion resistance" means that even after conducting a combined cycle corrosion test (CCT), the maximum pitting depth on the steel plate surface is small.

[0025] The specific conditions for the above test will be described in the examples.

[0026] The Al-plated ferritic stainless steel sheet of this embodiment comprises a base steel sheet, an Al-based plating layer located on the surface of the base steel sheet, and a film located on the surface of the Al-based plating layer. The base steel sheet is made of ferritic stainless steel.

[0027] <Chemical Composition of Base Steel Sheet> The chemical composition of the base steel sheet specified in this embodiment will be described in more detail below. The reasons for limiting each element are as follows. In the following description, "%" for content means "mass%".

[0028] C: 0.010% or less. Carbon (C) reduces workability, corrosion resistance, and intergranular corrosion resistance. For this reason, the C content is 0.010% or less. However, excessive reduction of the C content increases refining costs, so it is preferable that the C content be 0.001% or more. The C content may also be 0.002% or more and 0.009% or less, or 0.003% or more and 0.008% or less.

[0029] Si: 0.01-0.80% Silicon (Si) is an element that improves oxidation resistance. For this reason, the Si content is 0.01% or more. However, if Si is present in excess, it can cause non-plating and reduce corrosion resistance. For this reason, the Si content is 0.80% or less. The Si content may also be 0.03% or more and 0.70% or less, or 0.05% or more and 0.60% or less.

[0030] Mn: 0.01-0.50% Manganese (Mn) is used as a deoxidizing element. Therefore, the Mn content is 0.01% or more. However, if Mn is present in excess, it can cause non-plating and reduce corrosion resistance. Therefore, the Mn content is 0.50% or less. The Mn content may also be 0.03% or more and 0.40% or less, or 0.05% or more and 0.30% or less.

[0031] P: 0.050% or less. Phosphorus (P) is an element contained as an impurity in steel, and it reduces corrosion resistance, workability, and weldability. For this reason, the P content should be 0.050% or less. However, excessive reduction of P increases refining costs. For this reason, a P content of 0.010% or more is acceptable. The P content may also be 0.015% or more and 0.045% or less, or 0.020% or more and 0.040% or less.

[0032] S: 0.0050% or less. S (sulfur) is an element contained as an impurity in steel and reduces corrosion resistance. For this reason, the S content should be 0.0050% or less. However, excessive reduction of S increases refining costs, so an S content of 0.0001% or more is acceptable. The S content may also be 0.0005% or more and 0.0040% or less, or 0.0008% or more and 0.0030% or less.

[0033] Cr: 10.5 to 30.0% Cr (chromium) has the effect of improving corrosion resistance. Therefore, the Cr content is 10.5% or more. However, excessive Cr content reduces workability and manufacturability. In addition, the formation of a dense passive film reduces plating adhesion. Therefore, the Cr content is 30.0% or less. The Cr content may be 13.0% or more and 27.0% or less, or may be 15.0% or more and 25.0% or less.

[0034] Ti: 0.01 to 0.30% Ti (titanium) has the effect of suppressing sensitization of stainless steel. Therefore, the Ti content is 0.01% or more. However, excessive Ti content reduces workability. In addition, the formation of a dense passive film reduces plating adhesion. Therefore, the Ti content is 0.30% or less. The Ti content may be 0.03% or more and 0.28% or less, or may be 0.05% or more and 0.25% or less.

[0035] B: 0.0001 to 0.0010% B (boron) has the effect of improving secondary workability. Therefore, the B content is 0.0001% or more. However, excessive B content reduces corrosion resistance. Therefore, the B content is 0.0010% or less. The B content may be 0.0002% or more and 0.0008% or less, or may be 0.0003% or more and 0.0005% or less.

[0036] In addition to the above elements, one or more selected from the group consisting of Ni, Mo, Al, N, Nb, Cu, V, Sn, W, Co, Sb, Ca, Mg, Ga, Zr, Hf and REM may be contained within the range shown below. That is, the lower limit of the above elements is 0%. The reasons for the limitation of each element are described below.

[0037] Ni: 0 to 0.50%  Ni (nickel) has an effect of improving corrosion resistance. Therefore, Ni may be contained as required. However, when Ni is contained excessively, hot workability and weldability are reduced. Therefore, the Ni content is 0.50% or less. On the other hand, in order to obtain the above effect, the Ni content is preferably 0.01% or more. The Ni content may be 0.03% or more and 0.40% or less, or may be 0.05% or more and 0.30% or less.

[0038] Mo: 0 to 3.00%  Mo (molybdenum) has an effect of improving corrosion resistance. Therefore, Mo may be contained as required. However, when Mo is contained excessively, workability is reduced. In addition, since it is an expensive element, manufacturing cost increases. Therefore, the Mo content is 3.00% or less. On the other hand, in order to obtain the above effect, the Mo content is preferably 0.01% or more. The Mo content may be 0.03% or more and 2.50% or less, or may be 0.05% or more and 2.00% or less.

[0039] Al: 0 to 0.20%  Al (aluminum) has an effect of improving the oxidation resistance of stainless steel. Therefore, Al may be contained as required. However, when Al is contained excessively, workability is reduced. Therefore, the Al content is 0.20% or less. On the other hand, in order to obtain the above effect, the Al content is desirably 0.001% or more. The Al content may be 0.003% or more and 0.18% or less, or may be 0.005% or more and 0.15% or less.

[0040] N: 0 to 0.100%  N (nitrogen) has an effect of improving hardness. However, when N is contained excessively, workability is reduced. Therefore, the N content is 0.100% or less. On the other hand, in order to obtain the above effect, the N content is preferably 0.001% or more. The N content may be 0.005% or more and 0.080% or less, or may be 0.008% or more and 0.050% or less.

[0041] Nb: 0-0.50% Niobium (Nb) has the effect of improving high-temperature strength. In addition, Nb has the effect of improving the intergranular corrosion resistance of welded joints. However, if Nb is present in excess, the workability decreases. For this reason, the Nb content is 0.50% or less. On the other hand, in order to obtain the above effect, it is preferable that the Nb content is 0.001% or more. The Nb content may also be 0.002% or more and 0.40% or less, or 0.003% or more and 0.30% or less.

[0042] Cu: 0-3.00% Cu (copper) has the effect of improving corrosion resistance. For this reason, Cu may be included as needed. However, if Cu is included in excess, the hot workability will decrease. For this reason, the Cu content is 3.00% or less. On the other hand, in order to obtain the above effect, it is preferable that the Cu content be 0.01% or more. The Cu content may also be 0.03% or more and 2.50% or less, or 0.05% or more and 2.00% or less.

[0043] V: 0-1.00% V (vanadium) has the effect of improving corrosion resistance. For this reason, V may be included as needed. However, if V is included in excess, the processability will decrease. For this reason, the V content is 1.00% or less. On the other hand, in order to obtain the above effect, it is preferable that the V content be 0.01% or more. The V content may also be 0.03% or more and 0.80% or less, or 0.05% or more and 0.50% or less.

[0044] Sn: 0-1.00% Sn (tin) has the effect of improving corrosion resistance. For this reason, Sn may be included as needed. However, if Sn is included in excess, the processability will decrease. For this reason, the Sn content should be 1.00% or less. On the other hand, in order to obtain the above effect, it is preferable that the Sn content be 0.01% or more. The Sn content may also be 0.02% or more and 0.80% or less, or 0.03% or more and 0.50% or less.

[0045] W: 0-1.00% W (tungsten) has the effect of improving corrosion resistance. For this reason, W may be included as needed. However, if W is included in excess, the processability will decrease. For this reason, the W content should be 1.00% or less. On the other hand, in order to obtain the above effect, it is preferable that the W content be 0.01% or more. The W content may also be 0.02% or more and 0.80% or less, or 0.03% or more and 0.50% or less.

[0046] Co: 0-1.00% Co (cobalt) has the effect of improving secondary processability and toughness. For this reason, Co may be included as needed. However, if Co is included in excess, processability will decrease. The Co content should be 1.00% or less. On the other hand, in order to obtain the above effect, the Co content should preferably be 0.01% or more. The Co content may also be 0.02% or more and 0.80% or less, or 0.03% or more and 0.50% or less.

[0047] Sb: 0-1.00% Sb (antimony) has the effect of improving corrosion resistance. For this reason, Sb may be included as needed. However, if Sb is included in excess, the processability will decrease. For this reason, the Sb content should be 1.00% or less. On the other hand, in order to obtain the above effect, it is preferable that the Sb content be 0.01% or more. The Sb content may also be 0.02% or more and 0.80% or less, or 0.03% or more and 0.50% or less.

[0048] Ca: 0-0.010% Ca (calcium) has a desulfurization effect. For this reason, Ca may be included as needed. However, if Ca is included in excess, corrosion resistance will decrease. For this reason, the Ca content should be 0.010% or less. On the other hand, in order to obtain the above effect, it is preferable that the Ca content be 0.0001% or more. The Ca content may also be 0.0005% or more and 0.008% or less, or 0.001% or more and 0.005% or less.

[0049] Mg: 0-0.010% Magnesium (Mg) has the effect of refining the structure and improving processability and toughness. For this reason, Mg may be included as needed. However, if Mg is included in excess, processability will decrease. For this reason, the Mg content should be 0.010% or less. On the other hand, in order to obtain the above effect, it is preferable that the Mg content be 0.0001% or more. The Mg content may also be 0.0005% or more and 0.008% or less, or 0.001% or more and 0.005% or less.

[0050] Ga: 0-0.010% Ga (gallium) has the effect of improving corrosion resistance and hydrogen embrittlement resistance. For this reason, Ga may be included as needed. However, if Ga is included in excess, the processability will decrease. For this reason, the Ga content is 0.010% or less. On the other hand, in order to obtain the above effect, it is preferable that the Ga content be 0.0001% or more. The Ga content may also be 0.0005% or more and 0.008% or less, or 0.001% or more and 0.005% or less.

[0051] Zr: 0-0.050% Zr (zirconium) has the effect of improving corrosion resistance. For this reason, Zr may be included as needed. However, if Zr is included in excess, the processability will decrease. For this reason, the Zr content is 0.050% or less. On the other hand, in order to obtain the above effect, it is preferable that the Zr content be 0.0001% or more. The Zr content may also be 0.0005% or more and 0.010% or less, or 0.001% or more and 0.005% or less.

[0052] Hf: 0-0.050% Hf (hafnium) has corrosion resistance. For this reason, Hf may be included as needed. However, if Hf is included in excess, the manufacturability will decrease. For this reason, the Hf content is 0.050% or less. On the other hand, in order to obtain the above effect, it is preferable that the Hf content be 0.0001% or more. The Hf content may also be 0.0005% or more and 0.010% or less, or 0.001% or more and 0.005% or less.

[0053] REM: 0-0.050% REM (rare earth elements) has a deoxidizing effect. Therefore, REM may be included as needed. However, if REM is included in excess, the processability will decrease. For this reason, the REM content should be 0.050% or less. On the other hand, in order to obtain the above effect, it is preferable that the REM content be 0.0001% or more. The REM content may also be 0.0005% or more and 0.010% or less, or 0.001% or more and 0.005% or less.

[0054] REM refers to the total of 17 elements including Sc, Y, and lanthanides, and the REM content mentioned above refers to the total content of these elements. REM may also be added in the form of mischmetal.

[0055] In the chemical composition of the base steel sheet of this embodiment, the remainder consists of Fe and impurities. Here, "impurities" refers to components that are mixed in during the industrial production of stainless steel sheets due to various factors in the raw materials such as ore and scrap, and the manufacturing process, and which are acceptable as long as they do not adversely affect this embodiment.

[0056] <Al-based plating layer> The Al-based plating layer is placed on the base steel sheet. The chemical composition of the Al-based plating layer is, in mass%, Si: 0-20.0%, Fe: 0-10.0%, and the remainder: Al and impurities. If the Si content in the Al-based plating layer exceeds 20.0%, the sacrificial corrosion protection effect of Al decreases, and the corrosion resistance decreases. Similarly, if the Fe content in the Al-based plating layer exceeds 10.0%, the sacrificial corrosion protection effect of Al decreases, and the corrosion resistance decreases. The Si and Fe content in the Al-based plating layer may each be 0%. In addition, the Al-based plating layer may contain Mg. The Mg content may be 0-3.0%. By including Mg, the corrosion resistance of the Al-based plating layer can be further improved.

[0057] The aluminum-based plating layer may be either an electroplated layer or a hot-dip galvanized layer.

[0058] [Plating adhesion amount: 10-200 g / m per side] ２To achieve the required corrosion protection life for an Al-plated ferritic stainless steel sheet, the amount of Al-plated layer applied should be 10 g / m² per side. ２ The above is necessary. Considering the exposed cut edges of the base steel plate and damage to the Al-based plating layer due to chipping, the amount of Al-based plating layer should be 10 g / m². ２ Preferably 15 g / m² ２ The above is good. On the other hand, if the thickness of the Al-based plating layer becomes too thick, defects such as peeling of the plating layer will occur during the formation of the Al-based plating layer. Therefore, the amount of Al-based plating layer to adhere to is 200 g / m² per side. ２ The following applies: Considering weldability, the amount of Al-based plating layer to adhere is 70 g / m². ２ The following is preferable.

[0059] <Coating> Over time, an oxide film is formed on the surface of the Al-based plating layer due to air oxidation, which deteriorates its adhesion to paints and adhesives. Therefore, a coating containing Si, V, Zr, and P is formed on the outermost surface of the Al-based plating layer.

[0060] The Si and Zr contained in the coating have the effect of improving the adhesion between the coating and the coating when a coating or adhesive is formed on the coating. In addition, the V, Zr, and P contained in the coating have the effect of improving the corrosion resistance of the coating. However, P reduces adhesion. For this reason, in the coating of this embodiment, the concentrations of Si, V, and Zr in the surface layer of the coating are set to be above a predetermined concentration. On the other hand, the concentration of P in the surface layer of the coating is set to be below a predetermined concentration.

[0061] In other words, if the thickness of the film is t, and the area from the surface of the film to a depth of (1 / 2)t is defined as the surface layer of the film, then the maximum value of the Si cation fraction in the surface layer of the film shall be 10 atomic percent or more, the maximum value of the V cation fraction in the surface layer of the film shall be 10 atomic percent or more, the maximum value of the Zr cation fraction in the surface layer of the film shall be 10 atomic percent or more, and the maximum value of the P cation fraction in the surface layer of the film shall be 30 atomic percent or less. The maximum value of the cation fraction in the surface layer of the film means the cation fraction that is the maximum value in the surface layer of the film when the cation fraction of a specific element is measured along the thickness direction of the film and the distribution of the cation fraction of that element in the depth direction is obtained.

[0062] [Maximum Si cation fraction in the surface layer of the film is 10 atomic percent or more] Increasing the Si concentration in the film increases the proportion of SiOH (silanol groups) exposed on the outermost surface. Consequently, the number of bonds with paints and adhesives increases, improving adhesion. Therefore, Si in the film is an important element. This effect can be obtained if the maximum Si cation fraction in the surface layer of the film is 10 atomic percent or more, so the maximum Si cation fraction in the surface layer is set to 10 atomic percent or more. In other words, the Si cation fraction in the film may fluctuate along the thickness direction of the film, but if the maximum Si cation fraction in the surface layer is 10 atomic percent or more, adhesion to paints and adhesives placed on the surface of the film can be improved. More preferably, it is 23 atomic percent or more.

[0063] The maximum value of the Si cation fraction in the surface layer of the film may be, for example, 70 atomic percent or less.

[0064] [Maximum cation fraction of V in the surface layer of the film is 10 atomic percent or more] Corrosion resistance is improved by increasing the concentration of V in the film. This effect is obtained when the maximum cation fraction of V in the surface layer of the film is 10 atomic percent or more. In other words, the cation fraction of V contained in the film may fluctuate along the thickness direction of the film, but it is sufficient that the maximum cation fraction in the surface layer of the film is 10 atomic percent or more. More preferably, it is 18 atomic percent or more.

[0065] The maximum value of the cation fraction of the V concentration may be, for example, 70 atomic percent or less.

[0066] [Maximum Zr cation fraction in the surface layer of the film is 10 atomic percent or more] Increasing the Zr concentration in the film improves corrosion resistance and adhesion to paints and adhesives. This effect is achieved when the maximum Zr cation fraction in the surface layer of the film is 10 atomic percent or more. In other words, the Zr cation fraction in the film may fluctuate along the thickness direction of the film, but it is sufficient if the maximum cation fraction in the surface layer of the film is 10 atomic percent or more. More preferably, it is 30 atomic percent or more.

[0067] The maximum value of the cation fraction of the Zr concentration may be, for example, 70 atomic percent or less.

[0068] [Maximum cation fraction of P in the surface layer of the film is 30 atomic percent or less] Although phosphorus in the film improves corrosion resistance, it reduces the adhesion of paints and adhesives, so it is desirable for phosphorus to be present in low concentrations and trace amounts. For this reason, the maximum cation fraction of P in the surface layer of the film is set to 30 atomic percent or less. In other words, although the cation fraction of P contained in the film may fluctuate along the thickness direction of the film, it is sufficient if the maximum cation fraction in the surface layer of the film is 30 atomic percent or less.

[0069] Furthermore, the maximum value of the cation fraction of the P concentration may be 10 atomic percent or more from the viewpoint of improving corrosion resistance.

[0070] [Coating Thickness] The coating thickness shall be between 10 nm and 200 nm. If the coating thickness is less than 10 nm, the amount of adhesion is too small, making it difficult to obtain coating effects such as improved adhesion. On the other hand, if the coating thickness exceeds 200 nm, the thickness is too large, for example, increasing resistance during spot welding and reducing spot weldability. Therefore, the coating thickness shall be between 10 nm and 200 nm.

[0071] [Method for measuring the concentration of Si, V, Zr, and P in the coating, and method for measuring the thickness of the coating] The concentration of each element Si, V, Zr, and P in the coating and the thickness of the coating are measured using Auger electron spectroscopy. Using an Auger electron spectrometer, the coating is sputtered with Ar ions, and the analysis is performed continuously along the depth direction of the coating to measure the energy spectrum of Auger electrons. The cation fraction of each element is determined at the depth position where the intensity of each element is maximum in the surface layer of the coating, i.e., from the surface of the coating to a depth of (1 / 2)t, and this is taken as the maximum value of the cation fraction of each element. The cation fraction is the proportion of each element when the total amount of Si, V, Zr, P, and the remainder is set to 100 atomic percent. Si, V, Zr, P, and the remainder refers to all types of cation elements contained in the coating and detected by Auger electron spectroscopy.

[0072] Specifically, for example, a JEOL JAMP-9510f Auger electron spectrometer can be used. The Auger electron spectrometer is used in conjunction with Ar ion sputtering to analyze the film along its depth. The LMM peaks of Si, V, and Zr, the KLL peak of P, and the peak intensities of all other elements detected by the Auger electron spectrometer are measured, and the composition of each element is determined using a relative sensitivity factor. When calculating the cation fraction, the sum of the cation elements obtained by subtracting the values ​​of O (oxygen), C (carbon), and N (nitrogen) from the obtained composition value is used as the denominator, and the composition values ​​of Si, V, Zr, and P are used as the numerators.

[0073] Furthermore, the film thickness is determined by defining the boundary between the film and the Al-based plating layer as the depth at which the maximum concentration of O (oxygen) obtained by Auger electron spectroscopy becomes half, and the distance from the surface of the film to the boundary is defined as the film thickness.

[0074] The vacuum level inside the Auger electron spectrometer is 5 × 10⁻⁶. －７ The pressure is set to Pa or less, the electron gun acceleration voltage is set to 10 kV, and the sample current is set to 10 nA. For Ar ion sputtering, the ion gun acceleration voltage is set to 1 kV and the ion current is set to approximately 650 nA. The sputtering rate under these conditions is SiO ２ Converted to 0.09 nm －１That is the case.

[0075] <Manufacturing Method> [Manufacturing Process of Base Steel Sheet] In the manufacturing method of aluminum-plated ferritic stainless steel sheet of this embodiment, the manufacturing method of the base steel sheet is basically the general method for manufacturing ferritic stainless steel sheets. For example, molten steel having the above chemical composition is produced in a converter or electric furnace and refined in an AOD furnace or VOD furnace, etc. Then, steel billets are made by continuous casting or ingot forming, and then the base steel sheet of this embodiment is manufactured through the processes of hot rolling - pickling - cold rolling - finish annealing - pickling. If necessary, annealing of the hot-rolled sheet may be performed, or cold rolling - finish annealing - pickling may be repeated. Surface grinding may be performed between each process.

[0076] [Al Plating Process] The method for Al plating the base steel sheet is not particularly limited, and various methods such as hot-dip plating, electroplating, vacuum deposition, and cladding are possible, but hot-dip plating is particularly preferred. The Al plating bath for hot-dip plating should, for example, have a bath temperature of 650 to 700°C. The plating bath can contain 0 to 20.0% by mass of Si and 0 to 3.0% by mass of Fe as minor components other than Al. More preferably, a plating bath containing about 10% Si and about 1% Fe should be used. The Al plating bath may also contain impurities such as Fe, Cr, and Mn eluted from the base steel sheet. Small amounts of other elements such as Mg and Zn can also be included. The plating amount is reduced to 10 to 200 g / m² per side by gas wiping after plating. ２ This is preferable in order to ensure rust prevention.

[0077] [Film Formation Process] Next, after Al plating, a chemical conversion treatment is performed to form a film on the surface of the Al-based plating layer. The chemical conversion treatment solution used is, for example, an aqueous solution containing colloidal silica, vanadium pentoxide, ammonium zr carbonate, and phosphoric acid, which is prepared so that after drying, the maximum cation fraction of Si is 10% or more, the maximum cation fraction of V is 10% or more, the maximum cation fraction of Zr is 10% or more, and the maximum cation fraction of P is 30% or less.

[0078] More specifically, when the components remaining after removing water (solvent) from the chemical treatment solution are considered as solids, the elements contained in the solids should be prepared such that the total amount of elements excluding O (oxygen), C (carbon), and N (nitrogen) is used as the denominator, and the total amount of Si, V, Zr, and P is used as the numerator, resulting in the following elemental percentages (atomic %): Si: 10% or more, V: 10% or more, Zr: 10% or more, and P: 30% or less.

[0079] The shorter the waiting time between applying the chemical treatment solution and starting drying in the hot air drying oven, for example, if the waiting time is less than 5 seconds, the closer the maximum value (atomic %) of the cation fraction of each element in the surface layer of the film will be to the content (atomic %) of each element in the chemical treatment solution.

[0080] On the other hand, if the waiting time is long, for example, more than 5 seconds, the maximum value (atomic %) of the cation fractions of Si, V, and Zr in the surface layer of the film will be higher than the content (atomic %) of each element in the chemical conversion solution. On the other hand, the maximum value (atomic %) of the cation fraction of P in the surface layer of the film will be lower than the content (atomic %) of P in the chemical conversion solution. Therefore, the composition of the chemical conversion solution should be set appropriately according to the desired film composition and waiting time. The waiting time will be discussed later.

[0081] As a source of Si among the solid components in the chemical treatment solution, colloidal silica and silane coupling agents are desirable. Furthermore, as a source of V, phosphates, carbonates, acetates, nitrates, oxides, hydroxides, and ammonium salts of V (including their complex compounds) are desirable. Furthermore, as a source of Zr, phosphates, oxides, and hydroxides of Zr (including their complex compounds) are desirable. Moreover, as a source of P, phosphoric acid, polyphosphate, phosphonic acid, phosphinic acid and their salts, in addition to phosphon oxide and phosphine are desirable.

[0082] The chemical conversion solution may contain trivalent Cr compounds, V (vanadium) compounds, Mg compounds, Zr compounds, and Ti compounds. Furthermore, to improve corrosion resistance and paintability, it is desirable to add a water-soluble resin as an additional component of the chemical conversion solution. While there are no particular limitations on the water-soluble resin, a water-soluble acrylic resin is preferred.

[0083] Although there are no specific regulations regarding the application method of the chemical conversion treatment solution, an aqueous solution containing the above reagents is applied to the surface of the Al-based plating layer using a roll coater method, and then baked in a hot air drying oven to a final plate temperature of 60 to 180°C. The thickness of the film is adjusted to a range of 10 to 200 nm by adjusting the nip pressure between the rolls and between the roll plates.

[0084] By setting the target plate temperature to 60-180°C, a film containing an appropriate amount of moisture can be formed on the surface of the Al-based plating layer. Furthermore, the reaction between the phosphoric acid contained in the chemical conversion treatment solution and the Al contained in the Al-based plating layer can be promoted, facilitating the formation of aluminum phosphate and improving the adhesion of the film to the Al-based plating layer. If the target plate temperature exceeds 180°C, the moisture content in the film decreases excessively, leading to excessive volume shrinkage of the film, cracking of the film, and a decrease in adhesive adhesion and corrosion resistance. Conversely, if the target plate temperature is below 60°C, the moisture content in the chemical conversion treatment film is too high, making it easier for moisture from the environment to penetrate and reducing corrosion resistance.

[0085] The waiting time from the application of the chemical treatment solution to the start of drying in the hot air drying oven shall be 1 second or more. More preferably, it shall be 5 seconds or more.

[0086] By allowing a waiting time of one second or more after applying the chemical conversion treatment solution, the thickness of the coating can be made uniform. Furthermore, a waiting time of one second or more promotes the formation of aluminum phosphate through the reaction between the phosphoric acid contained in the chemical conversion treatment solution and the Al contained in the aluminum-based plating layer, thereby improving the adhesion between the coating and the paint or adhesive.

[0087] Furthermore, by setting the waiting time to 5 seconds or more, the formation of aluminum phosphate can be further promoted, and the maximum cation fraction of Si on the surface of the film can be set to 23 atomic percent or more, the maximum cation fraction of V on the surface of the film can be set to 18 atomic percent or more, and the maximum cation fraction of Zr on the surface of the film can be set to 30 atomic percent or more, thereby further improving adhesion.

[0088] Furthermore, waiting times should be limited to, for example, 60 seconds, 30 seconds, 20 seconds, or 10 seconds, in order to increase productivity.

[0089] As described above, the Al-plated ferritic stainless steel sheet of this embodiment, when applied to Al-plated ferritic stainless steel sheets used in applications requiring high corrosion resistance where paint or adhesive is applied, can delay the occurrence of crevice corrosion by improving the adhesion between the paint or adhesive and the chemical conversion treatment film. Furthermore, by using a ferritic stainless steel sheet as the base steel sheet, the presence of a passive film increases the natural potential of the underlying steel, enabling sacrificial corrosion protection even in crevice corrosion environments and slowing the progression of crevice corrosion. This ensures corrosion resistance over a very long period.

[0090] A base steel sheet (0.6 mm thick) with the steel composition shown in Table 1 was produced through hot rolling and cold rolling processes. The obtained base steel sheet was plated with an aluminum alloy using a non-oxidizing furnace - reducing furnace type line under the conditions shown in Table 2A. After Al plating, the plating thickness was adjusted by the gas wiping method and the sheet was wound up. In this way, an Al-based plating layer was formed on the surface of the base steel sheet (ferritic stainless steel sheet). The chemical composition of the Al-based plating layer was as shown in Table 3.

[0091] Subsequently, an aqueous solution containing colloidal silica, vanadium pentoxide, ammonium zr carbonate, and phosphoric acid was prepared to create a chemical conversion solution. The concentrations of Si, V, Zr, and P in the chemical conversion solution were as shown in Tables 2B and 2C. Note that the concentrations of each element shown in Tables 2B and 2C are the converted concentrations of each element contained in colloidal silica, vanadium pentoxide, ammonium zr carbonate, and phosphoric acid. The prepared chemical conversion solution was applied to the surface of the Al-based plating layer using a roll coater method, and then baked in a hot air drying oven to a final plate temperature of 60 to 180°C to form a film on the surface of the Al-based plating layer. The final plate temperature and the waiting time from application of the chemical conversion solution to introduction into the hot air drying oven were as shown in Table 2C. In this way, Al-plated ferritic stainless steel sheets No. C1 to C23 and c1 to c16 shown in Table 3 were manufactured. The method for measuring the maximum cation fraction and the film thickness was as described above.

[0092]

[0093]

[0094]

[0095]

[0096] The performance of the Al-plated ferritic stainless steel sheet manufactured as described above was evaluated using the following tests.

[0097] <Characteristic Evaluation> [Adhesion and Corrosion Resistance] Flat plates measuring 70 mm in width and 150 mm in length were cut from aluminum-plated ferritic stainless steel sheet. A 10 mm wide urethane resin adhesive was applied to the center of each plate along its length, and the plate was dried for 10 days to prepare corrosion test specimens. The edges and back surfaces of the 70 mm x 150 mm flat plates were sealed. These corrosion test specimens were evaluated using JASO (Japan Automotive Standards Organization) M610-92 "Automotive Parts Appearance Corrosion Test Method" over a 360-cycle test period.

[0098] As an evaluation of adhesion after the test, after 360 cycles, specimens were judged as passing (○) if 90% or more of the applied urethane resin adhesive remained adhered to the surface of the corrosion test specimen, passing (◎) if 95% or more of the applied urethane resin adhesive remained adhered, and failing (×) if less than 90% of the applied urethane resin adhesive remained adhered.

[0099] As part of the post-test corrosion resistance evaluation, the remaining urethane resin adhesive was removed using a spatula, and the entire surface of the 70 mm x 150 mm flat plate (including areas where the adhesive was not applied) was observed. The depth of pitting corrosion at all corrosion sites was examined using the depth of focus method of microscopy. A Hisomet microscope manufactured by Union Optical Co., Ltd. was used. The observation magnification was set to 200x. A maximum pitting corrosion depth of less than 0.6 mm was considered a pass (○), and a maximum pitting corrosion depth of 0.6 mm or more (penetration) was considered a fail (×).

[0100] As shown in Table 3, the inventive examples C1 to C18 passed both the adhesion and corrosion resistance evaluations (○). Furthermore, in the inventive examples C19 to C23, by increasing the waiting time to 5 seconds or more, the maximum value of the Si cation fraction in the surface layer of the film was 23 atomic percent or more, the maximum value of the V cation fraction was 18 atomic percent or more, and the maximum value of the Zr cation fraction was 30 atomic percent or more, resulting in a passing grade (◎) for adhesion and further improvement in adhesion. On the other hand, the comparative examples c1 to c16 all failed the corrosion resistance evaluation (×), and in some cases also failed the adhesion evaluation (×).

[0101] Comparative Examples c1 to c8 failed the corrosion resistance test (×) because the components affecting the corrosion resistance of the base steel sheet were outside the specified range. Comparative Example c9 failed the corrosion resistance test (×) because the Si content in the Al-based plating layer was outside the upper limit. Comparative Example c10 failed the corrosion resistance test (×) because the Fe content in the Al-based plating layer was outside the upper limit. Comparative Example c11 failed the corrosion resistance test (×) because the amount of Al-based plating layer attached was outside the lower limit. Comparative Example c12 failed the corrosion resistance test (×) because the film thickness was outside the lower limit. Comparative Example c13 failed the corrosion resistance test (×) because the maximum value of the Si cation fraction in the surface layer of the film was outside the lower limit. Comparative Example c14 failed the corrosion resistance test (×) because the maximum value of the V cation fraction in the surface layer of the film was outside the lower limit. Comparative Example c15 failed to pass (×) in terms of corrosion resistance and adhesion because the maximum value of the Zr cation fraction in the surface layer of the film was outside the lower limit range. Comparative Example c16 failed to pass (×) in terms of corrosion resistance and adhesion because the maximum value of the P cation fraction in the surface layer of the film was outside the upper limit range.

[0102] Furthermore, in the adhesion evaluation, the test pieces that failed (×) all failed the corrosion resistance evaluation because the adhesive remained on the surface even after partial peeling, promoting crevice corrosion.

[0103]

[0104] According to this disclosure, in Al-plated ferritic stainless steel sheets used in applications requiring high corrosion resistance where paints or adhesives are applied, the occurrence of crevice corrosion can be delayed by improving the adhesion between the paint or adhesive and the chemical conversion coating. Furthermore, by using a ferritic stainless steel sheet as the base material, the presence of a passive film increases the natural potential of the underlying steel, enabling sacrificial corrosion protection even in crevice corrosion environments and slowing the progression of crevice corrosion. As a result, it is possible to provide an Al-plated ferritic stainless steel sheet that can guarantee corrosion resistance for a very long period of time.

Claims

1. The material comprises a base steel sheet, an Al-based plating layer located on the surface of the base steel sheet, and a film located on the surface of the Al-based plating layer, wherein the chemical composition of the base steel sheet is, in mass%, C: 0.010% or less, Si: 0.01 to 0.80%, Mn: 0.01 to 0.50%, P: 0.050% or less, S: 0.0050% or less, Cr: 10.5 to 30.0%, Ti: 0.01 to 0.30%, B: 0.0001 to 0.0010%, Ni: 0 to 0.50%, Mo: 0 to 3.00%, Al: 0 to 0.20%, N: 0 to 0.100%, Nb: 0 to 0.50%, Cu: 0 to 3.00%, V The composition of the Al-based plating layer is, in mass%, Si: 0-1.00%, Sn: 0-1.00%, W: 0-1.00%, Co: 0-1.00%, Sb: 0-1.00%, Ca: 0-0.010%, Mg: 0-0.010%, Ga: 0-0.010%, Zr: 0-0.050%, Hf: 0-0.050%, REM: 0-0.050%, the remainder being Fe and impurities. The chemical composition of the Al-based plating layer is, in mass%, Si: 0-20.0%, Fe: 0-10.0%, the remainder being Al and impurities. The plating adhesion amount of the Al-based plating layer is 10-200 g / m². ２ Al-plated ferritic stainless steel sheet, characterized in that the film contains Si, V, Zr, and P, and when the thickness of the film is t, and the surface layer of the film is defined as the range from the surface of the film to a depth of (1 / 2)t, the maximum value of the cation fraction of Si in the surface layer of the film is 10 atomic percent or more, the maximum value of the cation fraction of V in the surface layer of the film is 10 atomic percent or more, the maximum value of the cation fraction of Zr in the surface layer of the film is 10 atomic percent or more, the maximum value of the cation fraction of P in the surface layer of the film is 30 atomic percent or less, and the thickness of the film is 10 nm or more and 200 nm or less.

2. The chemical composition of the base steel sheet is, in mass%, Ni: 0.01-0.50%, Mo: 0.01-3.00%, Al: 0.001-0.20%, N: 0.001-0.100%, Nb: 0.001-0.50%, Cu: 0.01-3.00%, V: 0.01-1.00%, Sn: 0.01-1.00%, W: 0.01-1.00%, Co: 0.01-1.00%, Sb: 0.01-1.00%, Ca: 0.0001-0.010%, Mg: 0.0001-0.010%, Ga: 0.0001-0.010%, An Al-plated ferritic stainless steel sheet according to claim 1, containing one or more of the following: Zr: 0.0001 to 0.050%, Hf: 0.0001 to 0.050%, and REM: 0.0001 to 0.050%.

3. The Al-plated ferritic stainless steel sheet according to claim 1 or claim 2, wherein the maximum value of the Si cation fraction in the surface layer of the film is 23 atomic percent or more, the maximum value of the V cation fraction in the surface layer of the film is 18 atomic percent or more, and the maximum value of the Zr cation fraction in the surface layer of the film is 30 atomic percent or more.

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