JPS61246058A - High corrosion-resistant coated steel plate for fuel vessel - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides a container material for storing gasoline, alcohol fuel, and fuel such as gasoline containing alcohol.
This invention relates to a painted steel sheet for fuel containers that has excellent corrosion resistance.

(Prior art) With the recent deterioration of the petroleum situation (rise in petroleum costs and decrease in production), alcohol fuels such as methyl alcohol and ethyl alcohol or petroleum alcohol are being used instead of gasoline as automobile fuels. Fuels mixed with alcohols such as methyl alcohol, ethyl alcohol, methyl tertiary-butyl alcohol (MTBA), etc. (so-called gasohol) are being used as alternative fuels.

The material for automobile fuel containers for these alcohol fuels or alcohol-added gasoline (gasohol) is
Pb-Sn alloy coated steel sheets, which have been published in many patent publications such as JP-A-23345 and JP-A-51-115240, have been used, but there has been a problem in that the corrosion resistance of the steel sheets is significantly deteriorated.

The reason for this is that Pb-Sn alloy steel sheets have a coating layer composed of a eutectic alloy of Pb and Sn, with Pb as the main component. The PB metal layer part of the coating layer is easily corroded (acetaldehyde produced when BL alcohol fuel or alcohol-added gasoline is oxidized,
Pb metal is severely corroded by citric acid (an oxidation product of ethyl alcohol), formaldehyde, and formic acid (an oxidation product of methyl alcohol), and the portion of the Pb metal layer in the coating layer is likely to be corroded. (Moisture contained in Cl alcohol or oxidation products of alcohol increase corrosion from pinholes formed in the coating layer.

Due to these reasons, the corrosion resistance of Pb-Sn alloy plated steel sheets is significantly deteriorated.

For this reason, as a container steel plate for storing such fuel,
A highly corrosion-resistant material is required that has fewer pinholes in the coating layer and has excellent corrosion resistance against alcohol and alcohol oxidation products (formaldehyde, acetaldehyde, formic acid, citric acid).

Materials that meet these requirements include surface Ni plating, Ni-Co alloy plating, Ni-8n alloy plating, and S
Steel sheets coated with Ni+C4, Sn, or their alloys, such as n-plating, have been developed and have relatively good corrosion resistance.

Furthermore, due to the processed shape of the fuel container or high-speed molding process, the pinholes in the coating layer may be enlarged, and the surface may become hard to press.
A red rust phenomenon was observed that occurred from these defects due to defects that reached the base steel due to scratches in the coating layer due to this phenomenon, or scratches that reached the base steel during handling.

In particular, C4- ions mixed in from gasoline or the outside,
Corrosion progressed and pitting corrosion was also observed when there was a lot of moisture or due to moisture separated from the mixed fuel of alcohol and gasoline. On the other hand, the problem of snowmelt salt corrosion on the outer surface of tanks has become more severe in recent years, and corrosion due to C1- ions occurs due to defects in the coating layer or damage to the base metal caused by collisions with road sprayed salt (so-called chipping phenomenon). There was also particular concern about perforation corrosion that could lead to perforation.

(Problems to be Solved by the Invention) The present invention has been made in response to these circumstances, and solves the problem of corrosion resistance to alcohol fuel, alcohol-containing fuel, gasoline fuel, etc., and the problem of snow melting salt corrosion on the outer surface of the tank. The object of the present invention is to provide a painted steel sheet for fuel containers that has excellent formability and weldability.

(Means for solving the problems) The gist of the present invention is that C: 0.10% or less, 5olAl:
0.005 to 0.10%, Cr: 3 to 20% or, if necessary, one or more of Ti, Nb, Zr, and V, containing 0.03 to 0.50%, and the remainder being A mixture of aluminum powder and one or more of nickel, stainless steel, cobalt, tin, chromium, graphite, iron phosphide powders or their alloy powders on one or both sides of a steel plate consisting of iron and inevitable impurities. The powder is coated with a corrosion-resistant paint containing 30% (wt%) or more based on the non-volatile content of the paint, or one side is coated with the corrosion-resistant paint and the other side is coated with a plating layer of Zn or Zn-based alloy or a layer of Zn powder and Zn. One or two types of alloy powders and aluminum, nickel,
Any corrosion-resistant paint containing 60% (wt%) or more of the nonvolatile paint powder of cobalt, tin, chromium, iron, iron phosphide powder, or a mixture of one or more of their alloy powders. This is a highly corrosion-resistant coated steel sheet for fuel containers that is coated on one side.

The present invention will be explained in detail below.

Steel sheets containing 3% or more Cr exhibit good corrosion resistance against alcohol, alcohol-containing fuels, gasoline, and alcohol oxides (aldehydes, organic acids such as formic acid, saccharic acid, etc.), and these fuels Even when a small amount of water and Cl- ions are contained therein, a steel sheet containing 5% or more of Cr exhibits excellent corrosion resistance.

However, if the Cr content exceeds 20%, the workability and weldability deteriorate, making it difficult to form or weld the fuel container. Therefore, from the viewpoint of corrosion resistance against the above-mentioned corrosive atmosphere, workability, and weldability, the Cr content is defined to be in the range of 3 to 20%, preferably 5 to 15%.

As mentioned above, from the point of view of corrosion resistance, as mentioned above (Cr has the greatest effect, but in this invention, from the viewpoint of targeting fuel tank materials for automobiles and other storage), C, acid-soluble A4, and other steel components are also used. Limit its content.

Increased carbon content deteriorates the workability of steel sheets, and the large amount of cementite precipitated scattered on the steel sheet surface causes many pinholes to occur after base coating treatment or coating treatment (painting treatment). Become.

Therefore, the C component is a harmful element that deteriorates corrosion resistance and is preferably as small as possible, with the upper limit being 0.10% and preferably 0.02% or less.

Al is the acid-soluble Al (Sol!Al) remaining in the steel. If the amount of Al is less than 0.005%, it is difficult to prevent the generation of bubbles due to oxidizing gas, and the surface defects of the steel. This significantly increases the occurrence rate and becomes the starting point for deterioration of the corrosion resistance of steel materials.

In addition, excessive acid-soluble AA exceeding 0.10% causes Al-based oxides to be scattered on the steel surface, which may be the starting point for deterioration of corrosion resistance or the coating film applied to the steel sheet. It becomes the starting point of poor adhesion or the starting point of defective parts of the coating film, impairing the integrity of the coating film.

In addition to the above-mentioned steel components, the present invention also includes Ti, Nb+Zr.
By containing one or more types of +V at 0.03 to 0.50%, it combines with C in the steel to make the contained Cr more effective, further improving formability and corrosion resistance. It is something that forces you to do something.

If the total content of steel components such as Ti + Nb is less than 0.03%, there is little effect in preventing the precipitation of chromium carbide and improving formability and corrosion resistance, and if the content exceeds 0.50%, The effect reaches saturation and becomes uneconomical, and the precipitation of these components tends to harden the material and deteriorate moldability. In particular, the preferable content is 0.075 to 0.20%.

If a steel plate with the above composition is used as a material for various fuel containers, there will be a lot of moisture in the fuel.
If c7- ions or the like are contained, or if the outer surface of the fuel container comes into contact with road-sprayed salt, its corrosion resistance will be insufficient.

Therefore, in the present invention, one or more of aluminum powder, stainless steel, nickel, cobalt, tin, chromium, graphite, iron phosphide powder, or alloy powder thereof is coated on one or both sides of the steel plate. A corrosion-resistant paint containing 30% by weight or more based on nonvolatile content is coated using a roll coater, a curtain 70-coater, or the like.

When coating a Cr-containing steel plate with this corrosion-resistant paint, the following pre-painting treatment is performed. The surface of the steel plate is roughened by brushing, or H2SO4, HCl
After surface activation with an aqueous solution of nitric-fluoric acid or sulfuric-fluoric acid, surface roughening treatment is performed by brushing treatment, and painting treatment is performed.

Alternatively, chromic acid-sulfuric acid, chromic acid-silicon fluoride,
It is painted after being subjected to a chromate coating using a chromic acid-silifluoride-sulfuric acid bath or a chromic acid-phosphoric acid bath.

In particular, when this pre-painting treatment is applied to fuel containers that undergo severe molding, after various studies, the following chromate treatment conditions and chromate treatment film were formed. In some cases, it has been found that the adhesion of the coating film is excellent, especially when exposed to a corrosive solution for a long period of time (so-called secondary adhesion).

That is, after cleaning and activating the surface of a Cr-containing steel plate using the above acid solution, using an aqueous solution containing sulfate ions, fluoride containing fluoride ions, or both of these in an aqueous chromic acid solution, Through cathodic electrolytic treatment, metal C
The amount of Cr deposited per one side of the metal Cr layer 1 to 150 m97 m2 in terms of r amount, and the amount of oxidized C mainly composed of water-use oxidized Cr
The r layer is 5 to 501 ng/2m.

It is desirable to provide a chromate-based treated coating layer having an amount of Cr deposited on one side.

This is believed to be because the following advantages can be obtained by applying a chromate coating having the above structure using a chromate treatment bath containing the above (r+6 ions and anions).

Even if the stable oxide film on the surface of the steel sheet is not sufficiently removed during pre-treatments such as degreasing and pickling, the oxide film can be reduced and removed by cathodic electrolysis treatment in a chromic acid bath containing anions. Perhaps because of this, a chromate treatment film consisting of a metal Cr layer and a chromium oxide layer is uniformly formed on the steel surface.

As a result, sufficient adhesion between the chromium oxide layer and the paint is ensured, and even when exposed to a corrosive aqueous solution for a long period of time, the infiltration of the corrosive aqueous solution through the paint film or coating film defects is prevented. These chromate-treated coatings prevent corrosion products from reaching the steel base, preventing corrosion products from forming on the steel surface, and the paint adhesion is extremely good.

In addition, in the above-mentioned chromate treatment, the Cr layer content on the surface of the steel sheet becomes low due to the dechromization phenomenon, which causes deterioration of corrosion resistance, but since a metallic Cr layer is generated, the Cr concentration on the surface is increased. can be maintained. Therefore,
It prevents deterioration of the corrosion resistance of the steel plate itself, and in fact improves its corrosion resistance, thereby significantly improving the corrosion resistance after painting.

In order to ensure the adhesion of the secondary paint after painting and the effect of improving the corrosion resistance after painting, a chromate-based treatment film having the above-mentioned structure is provided.
If the thickness of the layer is less than 1 m97 m'', it is difficult to uniformly form the chromate-based treated film, which is the object of the present invention, and the desired effect of improving coating performance cannot be obtained.

On the other hand, if the metal Cr layer exceeds 150 m97 m'', the workability deteriorates and the metal Cr layer generates a crank due to processing, and this crack becomes the starting point and the crank reaches the surface of the coating layer. This is undesirable because it makes it more likely to occur, and it may actually cause deterioration of coating performance.Therefore,
The metal Cr layer is 1-150mg/m2, preferably 3
~60m9/rrL2.

On the other hand, if the chromium oxide layer is less than 5m97m2, the uniform coverage by the chromium oxide layer will be poor, and the coating performance, especially the effect of improving paint adhesion, which is the objective of the present invention, will not be obtained. If it exceeds m2, the coating performance improvement effect will be saturated and the processing will reduce oxidized C.
There is a tendency for cranks to easily occur in the r layer.

Therefore, the Cr oxide layer has a thickness of 5 to 50 mg/m2, preferably 7.5 to 30 m97 m2.

Powders of aluminum, stainless steel, nickel, etc. or their alloy powders are pigments that have good corrosion resistance against alcohol, alcohol-containing fuels, alcohol oxides, gasoline, etc., and also have electrical conductivity. It has the effect of improving weldability. However, this effect is due to the non-volatile components of resin-based paints (with good corrosion resistance) in which pigments such as aluminum, stainless steel, and nickel are difficult to dissolve in alcohol, alcohol oxides, and gasoline. Native ethylene globylene copolymer, polyfluoroalkoxy resin, polychlorotrifluoroethylene, ethylene chlorotrifluoroethylene copolymer, ethylene tetrafluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride, polyether sal 7on , polymethylbatene, polysal7one, polyamide, polyimide, and epoxy phenoxy resin in a coating vehicle of 30% or more by weight.

In addition, if there are restrictions on the use of alcohol fuel, such as ethyl alcohol fuel or gasoline fuel (gasohol) mixed with 20% or less alcohol,
In addition to the above resins, 1 of phenol and polyester resins
The species or species may be used as a coating vehicle. In addition, the coating thickness of the corrosion-resistant paint in this case is 3 to 3
0μ is good.

When the coating thickness is less than 3 μm, it is excellent in terms of weldability and workability, but it is difficult to coat the coating layer uniformly enough, and when the coating layer is not sufficient, depending on the corrosive environment, the base material may be removed from the coating defect. Partial melting may occur and the desired corrosion resistance may not be achieved. In addition, if the coating thickness exceeds 30μ,
In some cases, defects such as partial peeling of the coating layer (so-called powdering) or difficulty in welding may occur during molding. Among them, 5 to 20μ is the most stable and causes no problems.

(Operations and Effects of the Invention) According to the present invention as described above, when a container is manufactured and used with the steel plate coated with a corrosion-resistant paint or the paint-coated surface facing the fuel contact side such as alcohol fuel, gasoline, etc., the following will occur. It has excellent effects.

Compared to general cold-rolled steel sheets and other surface-treated steel sheets that do not contain Cr, steel sheets containing Cr are less susceptible to the oxidation of a small amount of water, C7- ions, or alcohol contained in fuel. Extremely good corrosion resistance against objects, etc. Therefore, when exposed to a corrosive environment, moisture penetrating through the coating layer of the corrosion-resistant paint, CI! -Even if ions, alcohol or alcohol oxidation products reach the surface of the Cr-containing steel sheet, very few corrosion products are generated on the surface, so the coating film (coating) caused by the corrosion products is very small. There is no blistering (so-called pre-stern), and the paint adhesion (so-called secondary paint adhesion) is ensured even when exposed to corrosive conditions containing moisture such as alcohol-based fuels and gasoline for a long time, extending corrosion-resistant life. do.

In this way, the present invention has the advantage that alcohol,
It is an excellent material for fuel containers for fuels such as alcohol-containing fuels and gasoline.

Furthermore, the present invention provides that one side of the above-mentioned steel sheet of the present invention is coated with a corrosion-resistant paint made of aluminum, stainless steel, nickel, etc., and the other side of the present invention is coated with a plating layer of Zn or a Zn-based alloy, or a coating layer of Zn powder and a Zn-based alloy. One or two types of alloy powder
Seeds and aluminum, nickel, cobalt, tin, chromium, iron,
One or two of each powder of iron phosphide or its alloy powder
This is a steel plate coated with one of the corrosion-resistant paints, which is a mixture of two or more types of paint and non-volatile matter contained in the paint.

In particular, when a fuel container is manufactured using a surface plated with Zn or a Zn-based alloy as the outer surface of the fuel container, the outer surface has an anti-corrosion effect and the outer surface corrosion resistance of the container is significantly improved.

Although the Cr-containing steel plate used in the present invention has superior corrosion resistance compared to general steel plates that do not contain Cr, C4 is an important cause of corrosion, particularly from the outer surface of the fuel container. - In a corrosive environment where a large amount of ions, moisture, etc. are present, its corrosion resistance is not necessarily sufficient.

In particular, the occurrence of red rust is significant in processed parts or flawed parts of Cr-containing steel sheets, and there is a great risk of perforation corrosion from these parts. Therefore, Zn or Zn-Ni+ has relatively good corrosion resistance against C1- ions, moisture, etc., and is less potent in potential than these coating layers.
Plating layer of Zn-based alloy such as Zn-Fe, or Zn
Alternatively, a Cr-containing steel plate can be protected against corrosion by coating it with a corrosion-resistant paint containing non-volatile matter by arbitrarily mixing a Zn-based alloy with aluminum, nickel, or the like.

It significantly increases the corrosion resistance life against corrosion from the outside of the fuel container.

This is because weldability is important in the present invention.

The amount of Zn powder or Zn alloy powder contained in the paint non-volatile components such as aluminum and nickel is limited. In other words, in order to ensure the welding performance required for fuel containers,
It is necessary that the content of Zn powder or Zn alloy powder is 60% by weight or more, preferably 80% by weight or more, based on the nonvolatile content of the paint.

Regarding the thickness of the coating layer, which has a corrosion-preventing effect on the outer surface of the container and has a remarkable effect of extending the corrosion-resistant life, if it is less than 3 μm, C
Uncoated areas tend to occur on the surface of the r-containing steel plate, and a sufficient anticorrosion effect may not be obtained.

On the other hand, if the thickness exceeds 30 μm, the anticorrosive effect is saturated, and depending on the conditions, it may be unfavorable in terms of weldability and workability.

Further, the paint vehicle is not particularly specified, and the non-volatile components of the paint described above may be used, and acrylic resin,
One or a mixture of two or more resins such as melamine resin and alkyd resin may be used ().

In addition, as a pretreatment method for coating, similar to the above, brushing treatment or surface activation treatment using an acid aqueous solution such as HCl, H2SO<, nitric-fluoric acid aqueous solution, CrO3 + CrO3
-5O4-2+ Paint adhesion is improved by performing a chemical conversion treatment using an aqueous CrO3-F- solution or the like.

In particular, in order to improve the adhesion of the secondary paint and the corrosion resistance after painting, it is desirable to provide a chromate-based treated film containing the above-mentioned anions. There is no need to limit the coating method,
Any commonly used method such as a roll coater or a curtain flow coater may be used.

Similarly, the conditions for painting (coating) baking are 100~
Depending on the type of paint, the type of curing agent added to the paint, and the coating thickness, it can be applied to the inner surface of the fuel container or the outer surface of the fuel container, depending on the type of paint, the type of curing agent added to the paint, and the coating thickness. , is arbitrarily selected and applied within the above conditions.

The coating thickness of the zinc plating layer or Zn alloy plating layer is desirably 0.5 to 10 microns, preferably 1 to 6 microns, from the viewpoint of anticorrosive effect, formability, and weldability. Z in this case
n-alloy plating is Zn~(8~20%) Ni-based, zn~
(8 to 20%) Fe-based, Zn to (8 to 20%) Co
It is best to use an alloy plating composition of

Furthermore, the Zn or Zn alloy plating method is not particularly specified, but electroplating is advantageous.

That is, compared to hot-dip plating, the plating work is easier when plating only one side, and the uniformity of the coating thickness is excellent, which is advantageous for molding. Zn or Z
By applying an n-based alloy plating layer to the top surface of the Cr-containing steel plate, it is extremely effective in preventing corrosion of the Cr-containing steel plate from flow areas during machining due to sprayed salt for road anti-icing, moisture, etc. .

As mentioned above, the present invention coats aluminum, stainless steel, etc. with a corrosion-resistant paint that exhibits excellent corrosion resistance, especially against alcohol, alcohol oxides, and gasoline! By using the - surface on the inner surface of the fuel container, the corrosion resistance of the same surface is ensured, and at the same time, a Zn plating layer, a Zn alloy plating layer, a Zn powder, or a Zn alloy having sacrificial corrosion protection ability is applied to the Cr-containing steel plate. By using a surface coated with a corrosion-resistant paint containing powder and pigments such as aluminum and nickel on the outer surface of the fuel container, the corrosion-resistant life of the container itself is extended.

That is, the present invention provides extremely excellent characteristics as a material for fuel containers. During the seam welding process in the fuel container manufacturing process, if the surface corresponding to the outer surface of the fuel container that comes into contact with the electrode is made of a metal plating layer, it has better electrical conductivity than if it is made of an organic ruptured membrane layer. Therefore, a wide welding range can be used, and since the amount of deposits on the electrode is smaller than that of an organic film, the electrode has a long life span and continuous welding workability is improved, which is particularly preferable.

The present invention may be used with a coating structure as described above, and for decoration of the outer surface of the fuel container, a coating treatment may be further applied after the fuel container is formed, and the outer surface layer may be made of zinc or In the case of a zinc alloy plating layer, the chromel-based treatment or phosphate-based treatment as a base treatment for the above-mentioned coating may be applied in advance to the present invention, or may be applied after the fuel container is formed.

The present invention provides a coated steel sheet for the purpose of improving the corrosion resistance on both sides, that is, improving the corrosion resistance on the inner surface of the fuel container and the outer surface of the fuel container. However, in an environment where corrosion from the outside surface is mild, It is also possible to use a steel plate that has only been painted.

The Cr-containing steel sheet used in the present invention has a Cr content within the scope of the present invention as an essential component, and other corrosion resistance improving elements such as N r r Mo + Cu (. There is no problem in obtaining the effects of the product of the present invention, and N s +Mo+ is added to the Cr-containing steel plate.
It may contain Cu.

(Example) Examples of the present invention will be described below.

After electrolytically degreasing a cold rolled steel sheet having a predetermined Cr content, the first
Pretreatment was performed under the painting pretreatment conditions shown in the table, and the treatment of the present invention (painting or electroplating) shown in Table 1 was performed, and then the performance evaluation test shown below was conducted.

■ Evaluation test for the outer surface of the fuel container Using evaluation materials of 0.8 MN, a cylindrical drawing process with an inner diameter of 75 φ and a drawing depth of 4 QmrA was carried out, and each of the following accelerated corrosive liquids was filled inside.
00cc was filled and sealed, and the corrosion resistance was evaluated by a static test after renewing the corrosion metallization once a week.

■ Alcohol-containing fuel acceleration test Methanol (10%)-formic acid (0.01%)-1%N
a Rust occurrence status after 3 months evaluation test at 50C using a solution consisting of Cl water (0.15%) and residual gasoline;
The corrosion resistance was completely evaluated based on the observation status of the coating film.

■ Alcohol-containing fuel acceleration test After evaluation test at 60C for 3 months using a solution consisting of ethyl alcohol (30%) - succinic acid (0.03%) - 1.5% NaCl water (1%) - residual gasoline The corrosion resistance was completely evaluated based on the rust occurrence and the observation status of the paint film.

■ Alcohol-containing fuel acceleration test Methanol (60%) - Formic acid (0.01%) - 1T Na
Using a solution consisting of C6 water (0.3 g) and residual gasoline, the corrosion resistance was determined from the rust occurrence and coating film observation after an evaluation test at room temperature for 6 months. evaluated.

Note that the evaluation criteria were based on the method ν below.

◎...-No red rust, and no blisters on the paint surface○...No red rust, and very few blisters on the paint surface (0
, less than 5%) △... Several spots of red rust are observed or blisters on the paint surface 0.5% or more to less than 1%
■ Corrosion resistance for fuel container outer surface metal ■ Corrosion resistance evaluation by cyclic corrosion test Under the cyclic corrosion test conditions shown in Figure 1, the amount of plate thickness reduction in the area where red rust occurred after 120 cycles The corrosion resistance was evaluated.

The evaluation criteria were based on the following method.

◎... Amount of plate thickness reduction Q, 5 mln or less ○... Amount of plate thickness reduction 0.6 ms or less △... 3 or less occurrences of drilling corrosion ×... 3 or more occurrences of drilling corrosion, A large number of occurrences ■ Corrosion resistance by salt spray test Red rust occurrence after 240 hours of salt spray test and after salt spray test, the coating surface was subjected to base grain → sellotape peeling test) Th, and its corrosion resistance and after being exposed to a corrosive environment The paint adhesion (secondary paint adhesion) was also evaluated.

◎...Red rust occurrence rate less than 1%, no paint film peeling by base grain test○...Red rust occurrence rate less than 1%, paint film peeling by base grain test less than 5 inchesΔ...Red rust occurrence rate 1% or more Less than 10%, less than 5 inches of paint film peeling by base grain test ×... Red rust occurrence rate of 10 inches or more, or paint film peeling of 5 inches or more by base grain test ■ Molding workability Blank size 0.8 x 480 x 4801 m + 1. After applying lubricating oil, 150 x 15
A rectangular tube was drawn using a 0IIIm square punch, and evaluation was made based on the limit of the drawing depth and the occurrence of coating peeling on the outer surface of the rectangular tube drawing material.

◎...Excellent molding processability with no peeling of the paint film○...Relatively good molding processability with no peeling of the paint film△...-Significant peeling of the paint layer due to molding process×...Significant peeling of the paint film mosquito,
Or cannot be formed ■ Seam weldability Using a sample with a plate thickness of 0.8 tsuru, a trapezoidal electrode with a width of 4 ass, a pressure of 400 kl-f, and a welding speed of 2.5 m/m1M
.

Welding time was 2 to 200 seconds, and the weldability of each evaluation material was relatively evaluated based on the welding range, the formation of naked, and the appearance of the welded part.

Welding was carried out to weld fuel containers, and weldability was investigated by joining the inner surfaces of the products of the present invention to each other, and by making a small indentation at the welding point for current diversion.

◎...Very good ○...Good Δ...Slightly inferior ×...Very poor As is clear from the above experimental results, the present invention has better fuel corrosion resistance and formability during processing than the comparative materials. and has excellent weldability.

[Brief explanation of the drawing]

FIG. 1 shows a diagram of the conditions of a cyclic corrosion test in an example of the present invention. Yaik 1 hour Chr)

Claims (1)

[Claims] 1. C: 0.10% or less, solAl: 0.005-0
．． 10%. A Cr-containing steel plate containing 3 to 20% Cr, the balance being iron and unavoidable impurities, is coated with aluminum powder and powders of nickel, stainless steel, cobalt, tin, chromium, graphite, iron phosphide, or A highly corrosion-resistant coated steel sheet for a fuel container, characterized in that it is coated with a corrosion-resistant paint containing at least 30% (weight ratio) of one or more of the alloy powders based on the non-volatile content of the paint. 2, C: 0.10% or less, solAl: 0.005-0
．． 10%, Cr: 3-20%, Ti, Nb, Zr, V
Contains 0.03 to 0.50% of one or more of the following,
Aluminum powder, nickel, stainless steel,
30% (weight ratio) of cobalt, tin, chromium, graphite, iron phosphide powder or a powder mixed with one or more of their alloy powders based on the non-volatile content of the paint.
A highly corrosion-resistant coated steel sheet for fuel containers, characterized in that it is coated with a corrosion-resistant paint containing the above. 3, C: 0.10% or less, solAl: 0.005-0
．． Aluminum powder and powders of nickel, stainless steel, cobalt, tin, chromium, graphite, and iron phosphide are applied to one side of a Cr-containing steel plate containing 10% Cr, 3 to 20% Cr, and the balance consisting of iron and unavoidable impurities. Alternatively, a corrosion-resistant paint containing at least 30% (weight ratio) of the non-volatile content of the paint is coated with a mixed powder of one or more of these alloy powders, and a plating layer of Zn or Zn-based alloy is coated on the other side. Alternatively, one or more of Zn powder and Zn-based alloy powder may be mixed with one or more of aluminum, nickel, cobalt, tin, chromium, iron, iron phosphide powder, or their alloy powder to form a paint. A highly corrosion-resistant coated steel sheet for a fuel container, characterized in that it is coated with either one of corrosion-resistant paints containing at least 60% (weight ratio) of non-volatile content. 4, C: 0.10% or less, solAl: 0.005-0
．． 10%, Cr: 3 to 20%, containing 0.03 to 0.50% of one or more of Ti, Nb, Zr, and V,
Mixing aluminum powder with one or more of nickel, stainless steel, cobalt, tin, chromium, graphite, iron phosphide powder, or alloy powder thereof on one side of a Cr-containing steel plate, the balance of which is iron and unavoidable impurities. The powder is coated with a corrosion-resistant paint containing 30% or more (weight ratio) of the non-volatile content of the paint, and the other side is coated with a plating layer of Zn or Zn-based alloy, or one or both of Zn powder and Zn-based alloy powder. A powder that is a mixture of seeds and one or more of aluminum, nickel, cobalt, tin, chromium, iron, iron phosphide powders or their alloy powders is added to the non-volatile content of the paint.
A highly corrosion-resistant coated steel sheet for a fuel container, characterized in that it is coated with either one of corrosion-resistant paints containing 0% (weight ratio) or more.