JPS61246378A - Surface-treated steel plate for fuel container - Google Patents

Abstract

PURPOSE:To obtain a surface-treated steel plate for a fuel container having excellent corrosion resistance and formability by forming a diffusion coating layer of Ni and Co and Pd-Sn alloy coating layer at suitable thicknesses on the steel plate consisting of specifically composed C, sclAl, Cr and Fe. CONSTITUTION:The diffusion coating layer consisting of Ni, Co or the alloy thereof is formed to >=0.01mu, more preferably about >=0.05mu on the side corresponding to the outside surface of the fuel container made of the steel plate contg. <=0.1% C, 0.005-0.1% solAl and 3-20% Cr, contg. 0.03-0.50%>=1 kinds among Ti, Nb, Zr and V if necessary and consisting of the balance Fe and inevitable impurities. The coating layer consisting of >=1 kinds among Ni, Co, Sn and Cu is formed thereon to 0.01-1mu thickness if necessary and thereafter th Pb-Sn alloy coating layer is foemd thereon to 1-10mu thickness. The surface- treated steel plate for teh container which is highly resistant to corrosion by alcohol fuel, gasoline, etc., and snow-melting salt corrosion on the outside surface and has the good formability and weldability is thus obtd.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention provides surface treatment for fuel containers that has excellent corrosion resistance and moldability as a container material for alcohol fuel, alcohol-containing gasoline, and fuels such as gasoline. This relates to steel plates.

(Prior Art) With the recent deterioration of the oil situation (rise in oil costs and decrease in production), alcohol fuels such as methyl alcohol and ethyl alcohol, or methyl alcohol and methyl alcohol in gasoline, have been replaced with gasoline as automobile fuel. Ethyl alcohol, methyl tert-butyl alcohol (MT
The use of fuel mixed with alcohol (so-called gasohol), such as Inglobil alcohol, etc., has been proposed and is being put into practice.

Automotive fuel container materials for these alcohol fuels or alcohol-added gasoline (gasohol) are disclosed in Japanese Patent Application Laid-Open No. 1986-
Although pb-Sn alloy coated steel sheets disclosed in many patent publications such as No. 23345 and Japanese Unexamined Patent Publication No. 51-115240 have been used, there has been a problem in that the corrosion resistance of the steel sheets is significantly deteriorated.

This is because the Pb-Sn alloy coated steel sheet is composed mainly of Pb.
For example, (a) the Pb metal layer of the coating layer is easily corroded because it is severely corroded by (a) Pb gold metal methyl alcohol. (
b) The PB gold metal is severely corroded by acetaldehyde, sulfuric acid (oxidation product of ethyl alcohol), formaldehyde, and formic acid (oxidation product of methyl alcohol) produced when alcohol fuel or alcohol-added gasoline is oxidized, and the coating layer is The PB metal layer inside is easily corroded. (The water contained in Cl alcohol or the oxidation products of alcohol increase corrosion from the pinholes formed in the coating layer.) Due to these reasons, the corrosion resistance of Pb-Sn alloy coated steel sheets is significantly reduced. be made to deteriorate.

For this reason, as a container steel plate for storing such fuel,
A material with high corrosion resistance is required, which 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 Nil Cot Sn or alloys thereof, 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.
Due to defects that reached the base steel due to scratches in the coating layer caused by this phenomenon, and scratches that reached the base steel during handling, red rust phenomena were observed that occurred from these defects.

In addition, the problem of snowmelt salt corrosion, especially on the outer surface of tanks, has become more severe in recent years.
Due to the occurrence of flaws reaching the base steel due to the so-called chipping phenomenon, there was a concern that corrosion due to CA- ions, especially perforation corrosion that would lead to perforation, would occur.

(Problems to be Solved by the Invention) The present invention has been made in response to these circumstances, and is made by making ultra-low carbon steel contain 3 to 20% Cr, so that it can be used in applications such as gasoline alcohol or alcohol-containing gasoline. Improve corrosion resistance to fuel, or even Ti+Nb
+ Zr + One or more types of V from 0.03 to 0.
In order to improve workability and improve the corrosion resistance of the outer surface, the corrosion resistance of the Cr-containing steel sheet is utilized. This product has a Pb-Sn alloy coating layer, which solves the problem of corrosion resistance against alcohol fuels, alcohol-containing fuels, gasoline fuels, etc., as well as the corrosion problems of snowmelt salt on the outer surface of the tank, and improves formability and weldability. The present invention provides a surface-treated steel sheet for containers with excellent properties.

The present invention will be explained in detail below.

Alcohol, alcohol-containing fuel, gasoline, alcohol oxides (aldehydes, organic acids such as formic acid, saccharic acid, etc.) The Cr content is 3 compared to the water contained in these.
% or more, particularly steel sheets containing 5% or more of Cr, exhibit 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 during manufacturing. Therefore, from the viewpoint of corrosion resistance, workability, and weldability in the above-mentioned corrosive atmosphere, the Cr content should be 3 to 3.
It was set at 20%. Preferably it is 5 to 11%.

In particular, compositions with a Cr content of 11% or less are in the two-phase coexistence region of γ phase and α phase, and coarse graining during the heat treatment process during the production of Cr-containing steel sheets is unlikely to occur, resulting in a phenomenon called ridging during forming. This is advantageous in terms of molding process because it does not cause roughness.

As mentioned above, Cr has the greatest effect in terms of corrosion resistance, but in the present invention, from the viewpoint of targeting materials for fuel tanks for automobiles and other storage, the content of C, acid-soluble M, and other steel components is also reduced. limit.

As C content increases, the workability of the steel sheet deteriorates, and a large amount of cementite precipitates scattered on the surface of the steel sheet, resulting in many pinholes after the base coating treatment or coating treatment (painting treatment). cause it to occur. Therefore, the C component is a harmful element that completely deteriorates the corrosion resistance, so it is preferable to have a small amount of the C component, and its upper limit k O,l is 0%, and preferably 0.02% or less.

Al is acid-soluble Ajt (sol Aj
? ) If the content is less than 0.005%, it is difficult to completely prevent the generation of bubbles due to oxidizing gas, which significantly increases the incidence of surface defects in steel and becomes the starting point for deterioration of the corrosion resistance of steel materials. Also, excess acid-soluble AA exceeding 0.10%'
In this method, Al-based oxides are scattered on the steel surface, which can be the starting point for deterioration of corrosion resistance, or cause unplatedness, pinholes, etc. on the plated surface applied to the steel sheet, impairing the integrity of the plated layer. .

Furthermore, in the present invention, in addition to the above-mentioned steel components, Ti,
Nb, Zr, Vk 1 type or 2 or more types 0.0
The total content of C is 3 to 0.50%, which combines with C in the steel to make the carbon contained in the steel more effective, thereby further improving formability and corrosion resistance.

If the total content of steel components such as Ti and Nb is less than 0.03%, the effect of preventing precipitation of chromium carbide and improving overall formability and corrosion resistance is small, and the content is less than 0.50%. If it exceeds this, the effect reaches saturation and becomes uneconomical, and the precipitation of these components tends to cause the material to become hard and deteriorate moldability. The preferred content is 0.075 to 0.20.

When a steel plate having the above-mentioned composition is used as it is as a material for alcohol or an alcohol-containing fuel container, the corrosion resistance against alcohol-containing fuel is good, but the corrosion resistance against the outer surface of the fuel container is insufficient. Particularly, in a sea breeze atmosphere where CI'''' ions or C6- ions caused by road-sprayed salt are present, red rust develops on the outer surface of the fuel container, and furthermore, the red rust develops into pitting corrosion, resulting in a significant deterioration of the corrosion resistance life.

Therefore, in the present invention, only one side of the steel plate corresponding to the outer surface of the fuel container is provided with a diffusion coating layer of one or two types of Ni and Co, and optionally Ti, Ne&.

A coating layer of one or more of Zr and V is applied to provide an alloy coating layer having a thickness of 1 to 10 μm and mainly composed of Pl and Sn. This has extremely excellent corrosion resistance against Cr- ions, moisture, etc., and can provide an excellent effect of improving the corrosion resistance of the outer surface of the fuel container even when exposed to the above-mentioned corrosive atmosphere.

In particular, the couple corrosion current between the Cr-containing steel plate and the Pb-Sn alloy coating layer becomes extremely small compared to when a steel plate that does not contain Cr is used as the original plate to be plated, or depending on the Cr content, pb + Since the Sn alloy coating layer is anodic, corrosion of the plated original plate from pinholes in the alloy coating layer or flawed areas during forming processing is significantly reduced, resulting in an extremely excellent corrosion-resistant life extension effect. can get.

Further, since the Pb-Sn alloy coating layer is a soft metal with rich lubricity, when it is formed into a fuel container, the coating layer has a lubricating effect.

Furthermore, since the Pb-Sn alloy coating layer is a solder alloy, many parts of piping such as the fuel feed pipe of a fuel container are joined by solder, so the steel sheet of the present invention has extremely excellent solderability. , is particularly advantageous as a steel plate for fuel containers.

The composition of this Pb-Sn alloy coating layer is not particularly defined, but from the viewpoint of solderability, the Sn content is 3.
% or more, preferably 5% or more, and the upper limit of the Sn content is not specified, but from an economical point of view, an alloy with a composition of less than 50%, preferably 30% or less is used. be done.

The thickness of this coating layer is important for achieving the objectives of the invention, and its thickness ranges from 1 to 10 microns.

That is, if the thickness is less than 1 μm, the uniform coating on the surface of the Cr-containing steel plate is insufficient, a large amount of pinholes are generated, the corrosion resistance is insufficient, and the coating layer is too thin. The lubricating effect and solderability improvement effect of the coating layer cannot be obtained. In addition, if the thickness exceeds 10μ, the effect becomes saturated and becomes uneconomical, and the smoothness of the coating layer increases, resulting in an increase in contact resistance during molding, resulting in poor moldability and This is undesirable because weldability deteriorates, such as increased contamination of the electrode by the coating layer metal during welding for fuel container fabrication.

Therefore, the thickness of the Pb-Sn alloy coating layer is 1 to 10μ,
Preferably it is 3-7μ.

The method of providing the Pb-Sn alloy coating layer only on one side of the Cr-containing steel plate may be any of electroplating, hot-dip plating, and vapor deposition plating. Cr
After the surface of the containing steel plate is subjected to surface cleaning such as degreasing and pickling, and activation treatment, a Pb-Sn alloy coating treatment is performed. For example, in the case of the electroplating method, a fluoride bath containing PB ions and Sn ions corresponding to a predetermined alloy composition is used to apply an amount of electricity to obtain a predetermined thickness on only one side of the steel plate by energizing electrolysis. Obtained by processing.

In addition, in the case of hot-dip plating, a masking agent, such as a Cr2O3-based compound or a silicate compound, is applied to the non-plated surface of the Cr-containing steel sheet to prevent the reaction with the hot-dip Pb-Sn alloy plating bath. By immersion treatment,
Molten Pb- containing a predetermined amount of Sn on only one plated surface
A Sn alloy plated coating layer can be obtained. Regarding the vapor phase deposition plating method, molten P is applied in a vacuum to only one side of the plating surface.
This can be achieved by heating and evaporating a b-Sn alloy plating bath and providing a Pb-an alloy vapor deposited layer only on one side of the steel plate.

In the present invention, the Pb-Sn alloy coating layer may be provided on only one side of the Cr-containing steel plate by any method, but it is necessary to provide the coating layer with a thickness of 1 to 10 μm from the viewpoint of performance. be.

Therefore, this Pb-Sn alloy coating layer is free from moisture, C7-
Although it exhibits excellent corrosion resistance against ions, so<-2 ions, etc., it has extremely poor corrosion resistance against alcohol, alcohol oxides, etc., and its dissolution is significant. As a result, if the Pb-Sn alloy coating layer is present on the surface in contact with alcohol fuel, there is a problem in that corrosion products caused by the alcohol fuel cause clogging of tank piping. Therefore, Pk with
)-Sn alloy coating layer must be limited to only one side corresponding to the outer surface of the fuel container.

Furthermore, in the present invention, as an intermediate layer between the Pb-Sn alloy coating layer on one side corresponding to the outer surface of the fuel container and the Cr-containing steel plate, 0. Ni+Co+Ni-C with a thickness of O1μ or more
o alloy diffusion layer or further 0. A two-layer intermediate coating layer consisting of a base coating layer of Ni+Con Sn+Cu having a thickness of 01 to 1μ or a coating layer made of an alloy of two or more of these is applied. When these coating layers are provided as intermediate coating layers between the Cr-containing steel sheet and the Pb-Sn alloy coating layer, the following advantages can be obtained. That is, compared to providing a Pb-Sn alloy coating layer directly on the surface of a Cr-containing steel sheet, Ni+ Con Ni-
By applying a Co alloy diffusion layer to a Cr-containing steel plate,
It is possible to bring the potential of the Cr-containing steel sheet in a corrosion atmosphere in the presence of C1- ions closer to the positive direction, further reducing the coupled corrosion current with the Pb-Sn alloy coating layer, and as a result, P
The combined effect with the b-Sn alloy coating layer further improves its corrosion resistance life.

Furthermore, Cr-containing steel sheets are generally easily oxidized during the annealing process to ensure the quality of the material, so strict atmospheric control of the annealing conditions is required, and when providing a Pb-Sn alloy plating layer after annealing, degreasing, pickling, etc. Pretreatment and activation treatment are required.

Therefore, unlike Nr + Co + Ni-Co alloys, they are difficult to oxidize during the heat annealing process and are relatively easily activated during pre-treatment pickling, etc. Uniform coverage of the layer, plating adhesion of the coating layer, etc. are improved, and effects such as improved corrosion resistance and reduced peeling of the coating layer (so-called powdering) during molding can be obtained.

The diffusion layer of Ni, Co/Ni-Co alloy as an intermediate coating layer between the Cr-containing steel plate and the Pb-Sn alloy coating layer has a thickness of 0.
A thickness of 0.01μ or more is required, and the thicker the better. The thickness of this diffusion layer is 0
．． If it is less than 0.01μ, a diffusion layer will not be uniformly formed on the surface of the Cr-containing steel plate, and the above objective will not be achieved. Preferably it is 0.05μ or more.

Although the method for obtaining this diffusion layer is not particularly limited, it can be achieved, for example, by the following method. That is, after degreasing and pickling the surface of a cold-rolled material (As Cold material), a preliminary coating layer of a predetermined thickness is formed by electroplating a Ni+ Car Ni-Co alloy or by applying an aqueous solution containing these metal salts. For example, 700~
A diffusion coating layer is provided by heat treatment in a temperature range of 950° C. for 30 to 180 seconds.

Of course, Ni + CO is added to the annealed material (full finish material).
・Although it is possible to provide a pre-coating layer of Ni-Co and perform heat diffusion treatment, it is better to use the cold-rolled material as described above because of the processing strain that the cold-rolled material has, so that the pre-coating layer and the steel plate do not interact with each other. Since diffusion is further promoted, the desired diffusion layer can be generated with a short heat treatment, and there is also the advantage that surface oxidation of the Cr-containing steel sheet can be prevented during the annealing process, which is advantageous in terms of the process.

Ni+ Car NlI in the diffusion coating layer of N1-Co alloy
Apply a base coating layer of one or more types of C0ISn+Cu. When a two-layer intermediate layer is applied, a first-order effect can be obtained in addition to the effect of the diffusion coating layer. That is, N
When a base coating layer of t+ Cot Sn+ Cu or an alloy of two or more of these is provided, Pb-
The effect of improving corrosion resistance is obtained by reducing pinholes due to the superimposed effect of the Sn alloy coating layer and these base coating layers.

Furthermore, the metals or alloys constituting these base coating layers have a fast diffusion rate with the Sn metal in the Pb-Sn alloy coating layer and have excellent wetting reactivity. A uniform and dense alloy layer containing Sn is generated, and the effect of reducing pinholes in the Pb-Sn alloy coating layer is obtained.In addition, when the coating layer is affected by heat such as welding or soldering, the Sn between the coating layer and the underlying metal is The alloying reaction containing the heat-affected zone easily occurs, thereby providing advantages such as preventing deterioration of the corrosion resistance of these heat-affected zones and enhancing solder bondability.

In other words, the two-layer intermediate layer improves the corrosion resistance of the outer surface of the fuel container.
Further performance improvement effects can be obtained in moldability and solderability. Therefore, in order to obtain the effect of improving the performance of the base coating of Ni+Car Sn+Cu and alloys containing two or more of these, a base coating layer with a thickness of 0.01 to 1 μm is required. If the thickness of the base coating layer is less than 0.01μ, the uniform coverage of the base coat layer will be insufficient, a large amount of pinholes will be formed, and the desired effects of the present invention as explained above may not be achieved. do not have.

On the other hand, if the thickness of this base coating layer exceeds 1μ, the performance improvement effect is saturated and it becomes uneconomical, and the effect of the base coating layer during processing may cause the Pb-Sn alloy coating layer to peel off or the base coating to occur. This results in drawbacks such as the fact that cracks originating from the layer tend to reach the surface of the Pb-Sn alloy coating layer on the surface. Therefore, the thickness of these base coating layers is
0. It is in the range of O1 to 1μ, preferably 0.05 to 0.3μ. The method for providing this base coating layer is not particularly specified, but it may be applied by a normal electroplating method after degreasing and pickling a Cr-containing steel plate treated with a diffusion coating such as Ni + Go (1° as described above). Further performance improvement is possible by providing a two-layer intermediate coating layer consisting of a diffusion layer and a coating layer between the Pb-Sn alloy coating layer and the Cr-containing steel plate.

Note that as the intermediate layer of the present invention, the diffusion layer contains N 11 Co.
*Ni-Co alloy, and the coating layer contains Ni, Co,
The reason why Sn/Cu and alloys made of two or more of these were selected is as follows.

First, we limited the Ni+Co+Ni-Co alloy to the diffusion coating layer because Sn+Cu and alloys containing these have a low melting point, making it difficult for Sn to diffuse uniformly through heat diffusion treatment. In the case of Cu, the diffusion treatment hardens the material of the Cr-containing steel plate, which is undesirable because it deteriorates the formability and makes the fuel container more likely to crack during the forming process.

In addition, the reason why Ni+Co+Sn+Cu and alloys consisting of two or more of these are used in the coating layer is that the diffusion rate with Sn in the Pb-Sn alloy coating layer is fast, the wetting reactivity is excellent, and the C1- Excellent corrosion resistance against ions, moisture, etc. Therefore, as mentioned above, in heat-affected zones such as welds and solder zones, an alloy layer is likely to be formed due to the reaction with Sn in the Pb-Sn coating layer, which improves the corrosion resistance of these heat-affected zones and improves solder joints. Bondability can be improved.

In addition, since the Pb-Sn alloy coating layer is extremely soft, it is easily damaged during handling or molding, reaching the base metal.
Often causes deterioration of corrosion resistance. However, the presence of such a base coating layer prevents damage from reaching the base metal, and these base coating layers with good corrosion resistance can prevent deterioration of corrosion resistance.

Similarly, in the present invention, Zn+ is added in the Pb-Sn alloy coating layer.
When Sb and the like are contained, they may be contained in an amount of about 5% or less since they do not have any adverse effect on the performance of the present invention. Furthermore, another dud E! NirM, an element that improves corrosion resistance, is added to Cr-containing steel sheets used in AK.
o * Even if Co or the like is contained in an amount of 10% or less, the object of the present invention is not hindered in any way.

Next, Pb-Sn alloy targeted at the outer surface of the fuel container.
``For the purpose of further chemically treating the defective parts of the coating layer on the surface of the coating layer to improve corrosion resistance, or to improve the coating performance when used as a coating,
Aqueous solution containing phosphate ions or cr+6・C
Chemical treatment may be performed with an aqueous solution containing r+3 ions.

For example, using a 0.1 to 5% phosphoric acid aqueous solution,
It is possible to improve the corrosion resistance or paint adhesion by dipping or spraying at a temperature of 80° C. for 1 to 10 seconds.

Although the present invention has been mainly described above with respect to alcohol or a fuel tank containing alcohol, there is no problem in applying or sharing the present invention to a fuel tank intended for ordinary gasoline as its corrosion resistance is good.

(Example) Using steel sheets with steel components whose Cr content was changed as shown in Table 1, after pretreatment such as degreasing and pickling, and activation treatment, one side of the Cr-containing steel sheet was coated. The results of performance evaluations of the outer and inner surfaces (non-plated surfaces) of fuel containers of the products of the present invention, which have undergone a predetermined amount of treatment, are shown.

Furthermore, the results of performance evaluation of the product of the present invention in terms of moldability and solderability assuming the formation of a fuel container are also shown. In addition, the surface of the Pb-Sn alloy layer is 0.5
% phosphoric acid aqueous solution at 70° C. for 7.5 seconds, ringer roll squeezing and drying.

As a result, the product of the present invention has extremely superior properties as a steel plate for alcohol or alcohol-containing fuel containers compared to comparative materials.

The evaluation test was conducted in the following manner.

1. Corrosion resistance evaluation for the outer surface of the fuel container (A) Corrosion resistance by salt spray test External surface of the fuel container (coating layer surface) after 500 hours of salt spray test
? The target corrosion resistance was evaluated, and the evaluation criteria were as follows.

◎・・・Number of red rust in 100X300111B test piece size 5 or less O... 6 to 12 △
... 13-20 pieces×・
... 21 or more (B)C,
Corrosion resistance by C, T test Cyclic Corrosion/Test (C, C, T test) ■ Salt spray (5% NaC635'CX 4 hours) → ■ Drying (70
C humidity 60% for 2 hours) → Humidity (49C humidity 98C for 2 hours) → Cooling (-20CX 2 hours) → Salt water spray Using a test piece with a thickness of .8'urn, corrosion resistance was evaluated by measuring the amount of reduction in the thickness of the corroded area where red rust occurred.

◎・・・ Plate thickness reduction less than 0.25 ○・・・
0.25 or more to less than 0.45 Δ...-
0.45on or more - less than 0.75m5×...
0.75 an or more (C) 0.8 X 10
0 x 150 seagull test piece? Using 1 to 2 diameter alundum, apply 1.5 to 1.5 cm of alundum per 1 crn2 to the surface of the coating layer of the test piece for 10 seconds at a pressure of 1 kfl/cm2. ? After collision and chipping, the C, C, and T tests described above were carried out for 45 cycles, and the amount of plate thickness reduction in the red rusted area was measured.
) was evaluated based on the evaluation criteria.

2. Test blank size for fuel container inner surface 0.8×15 (from a 1 mφ test piece, punch diameter 75IIsφ, wrinkle pressing force 1t, 75nnφ×
A cylindrical container with a height of 40IIIB? Created, filled with corrosion accelerating solution for alcohol fuels below 100 cc,
It was sealed and an evaluation test was conducted.

) gasohol target test (10% methanol + 3% inglovir alcohol + 0
．． Conducted 3t monthly evaluation test using 01% formic acid + 0.25% distilled water + residual gasoline) solution (E) Gasohol target test (20% ethanol + 0.03% succinic acid + 0.50% distilled water + residual gasoline) solution Conducted 3t monthly evaluation test using
solution? (G) Gasoline target test (99% gasoline + 1% distilled water) solution was used to conduct a 3 ton monthly evaluation test. All evaluations were conducted using the following evaluation criteria.

◎・・・ Number of red rust occurrences inside the cylindrical container (both the solution immersion part and the steam contact part) 0 to 3 ○...
3-10 pieces △...
10 to 20 pieces...-21 pieces to many occurrences 3. Evaluate the external bonding of this evaluation material with the Sn Zn alloy (80 to 90% in Sn) plated steel plate used for solderable fuel container piping. In order to do so, we measured the solder climbability between the Sn-Zn alloy plated surface and the coating layer surface (and the strength of the solder joint) using ZnC1t HC6-based flux and 60%5N40%PB solder, and then comprehensively evaluated and compared the materials. All relative evaluations of materials were carried out.

◎...Very good○...Comparatively goodΔ...Slightly poor ×...Very poor4, Formability Blank size 0.8x 500X 500+111.
After applying lubricating oil, apply 150X under wrinkle presser pressure of 30t.
Square cylinder drawing was performed using a 150 m square punch, and evaluation was made based on the limit of the drawing depth and the occurrence of galling on the outer surface of the square cylinder drawing material.

◎...No damage due to galling of the coating layer or the outer surface of the steel plate, and very good formability ○...No damage due to galling of the coating layer or the outer surface of the steel plate, and fairly good formability △...Depending on the degree of processing Slight damage caused by galling of the coating layer or the outer surface of the steel plate X...Extremely poor formability

Claims (1)

[Claims] 1. The outer surface of a fuel container made of a steel plate containing C: 0.1% or less, solAl: 0.005 to 0.1%, Cr: 3 to 20%, and the balance being iron and inevitable impurities. Thickness 0.
1. A surface-treated steel sheet for a fuel container, comprising a diffusion coating layer made of one or both of Ni and Co with a thickness of 0.01μ or more, and further a Pb-Sn alloy coating layer with a thickness of 1 to 10μ. 2. Contains C: 0.1% or less solAl: 0.005-0.1% Cr: 3-20%, and further contains Ti, Nb, ZrV
Ni or Co with a thickness of 0.01μ or more is applied to the outer surface of the fuel container of a steel plate containing 0.03 to 0.50% of one or more of the following, with the remainder being iron and unavoidable impurities. A surface-treated steel sheet for a fuel container, comprising a diffusion coating layer consisting of one or two types, and a Pb-Sn alloy coating layer having a thickness of 1 to 10 microns thereon. 3.C: 0.1% or less solAl: 0.005-0.1% Cr: 3-20%, the balance is iron and unavoidable impurities on the outer surface of the fuel container. 0.
A diffusion coating layer made of one or both of Ni and Co with a thickness of 0.01 to 1μ, and a diffusion coating layer of Ni, Co, and Sn with a thickness of 0.01 to 1μ.
, Cu, and a Pb-Sn alloy coating layer having a thickness of 1 to 10 microns thereon. 4. Contains C: 0.1% or less solAl: 0.005-0.1% Cr: 3-20%, and further contains Ti, Nb, Zr,
A steel plate containing 0.03 to 0.50% of one or more types of V, with the remainder being iron and unavoidable impurities, is coated on the outer surface of the fuel container with a thickness of 0.01μ or more.
A diffusion coating layer consisting of one or two of the above, and further has a thickness of 0.
01-1μ of one or two of Ni, Co, Sn, aCu
A coating layer consisting of seeds or more, and a thickness of 1 to 10 μm on top of the coating layer.
A surface-treated steel sheet for a fuel container, characterized in that it is coated with a Pb-Sn alloy coating layer.