JPS62230988A - Rust preventing steel sheet for fuel tank - Google Patents

Abstract

PURPOSE:To obtain a material for a tank having superior resistance to corrosion by lower alcohols and superior solderability by coating a steel sheet as a material for a tank for fuel contg. a lower alcohol with an Al-Si alloy having a specified composition by hot dipping and by plating one side of the coated steel sheet with specified metals. CONSTITUTION:A steel sheet as a material for a tank for a lower alcohol such as methanol or ethanol or fuel for an automobile prepd. by mixing a lower alchol with gasoline is coated with an Al-Si alloy contg. <13% Si or further contg. one or more among 0.03-1.0% Mg, 0.05-0.5% Ti and 0.03-1.0% Cr by hot dipping. One side of the coated steel sheet is plated with one ore more among Ni, Cu and Fe to form an underlayer of >=0.1mum thickness and it is further plated with Sn and/or Zn to 0.2mum thickness. The Al-Si alloy coated side has superior resistance to corrosion by lower alcohols and the coated and plated side has superior solderability, so the resulting steel sheet has superior properties as a material for a tank for fuel contg. a lower alcohol.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a rust-preventing steel sheet suitable for use as a material for fuel tanks of automobiles, etc., and in particular, a lower alcohol or a mixture thereof is suitable for use as a material for fuel tanks such as pudding or gasoline.

(U.S.-based technology) In recent years, lower alcohols such as methanol and ethanol can be produced domestically, are inexpensive, and do not produce harmful fumes when burned, so they have gained worldwide attention as automobile fuels but also as alternative fuels for pudding. Neat ethanol (pure ethanol) is already being used in large quantities as automobile fuel in Brazil, and in some parts of the United States and Europe, alcohol blends made by mixing methanol or ethanol with gasoline have been put into practical use for pudding. There is.

However, when lower alcohols or gasoline mixtures thereof are used as automobile fuels, if the fuel tank is made of conventional gasoline materials, there is a problem in that the materials corrode.

In general, materials for fuel tanks such as those for automobiles are required to have common properties on both the inside and outside of the tank, such as press formability and weldability, and different properties are also required on the inside and outside of the tank (for example, inside the tank) Since it is always in contact with fuel, the inner surface must be resistant to corrosion against the fuel. It is required that no floating corrosion products occur. On the other hand, since the side with a hanger is used to connect fuel transport pipes and the like to the tank on the outside surface, durability is required for the side with a hanger. Conventionally, a Pb-Sn alloy plated steel plate called turn plate (VF Kosho 57-6
No. 1833) and electrogalvanized steel sheets subjected to thick chromate treatment (Japanese Patent Publication No. 19981/1981) are used.

However, these steel plates have a problem in that they are easily corroded by lower alcohols and gasoline mixtures thereof. For this reason, in the case of Pb-Sn alloy coated steel sheets, the Pb-Sn alloy generates a large amount of floating corrosion products, and in the case of electrogalvanized steel sheets with thick chromate treatment, pitting corrosion and white rust occur. There was a problem that occurred.

(Problems to be Solved by the Invention) The present invention solves the problem of corrosion caused by lower alcohols and their mixtures due to pudding, and provides a novel rust-proof steel plate for fuel tanks that has excellent hanging properties. It is something.

(Means for Solving the Problems) As a result of various studies to develop the above-mentioned rust-proof steel plate, the present inventors found that the rust-proof steel plate was made by using Al or S on both sides of the steel plate.
It is coated with an Al-Si alloy with an i content of 13% or less and the remainder is AI and unavoidable impurities, and one side is coated with one or more of Sn, Cu%Zn, and old overlay Fe to a thickness. The steel plate coated with a thickness of 0.3 to 5 μm or the Al-Si alloy of the steel plate has a Si content of 13% or less, 0.03
-1.0%Hg10,05-0.5%Ti and 10
．． Contains one or more types of 03 to 1.0% Cr,
If the steel sheet is made with the remainder consisting of Al and unavoidable impurities, the Al or ^l-5iPS alloy coating layer side will exhibit excellent corrosion resistance against lower alcohols and gasoline mixtures thereof, and will also exhibit excellent corrosion resistance against lower alcohols and gasoline mixtures thereof. F
They discovered that the coated side of e was excellent in hang spreadability, and completed the present invention.

The present invention will be explained in detail below.

The present inventors investigated the corrosion resistance of surface-treated steel sheets against lower alcohols and gasoline mixtures thereof, and found that Al or Al-Si alloy coated steel sheets exhibit excellent corrosion resistance. When we examined the Si content of Al-Si alloy coated steel sheets, we found that since these steel sheets are usually manufactured by hot-dip plating, it is necessary to keep the Si content below 13% in order to suppress the Fe-Al alloy layer, which has poor workability. It turned out to be good. The reason why these steel sheets exhibit excellent corrosion resistance against lower alcohols and gasoline mixtures is presumed to be because a stable oxide film is formed on the surface of the coating layer.

However, when such stable oxide films exist on both sides,
It was found that when attaching fuel transport pipes to the outside of the tank, the hang type had poor performance and was unable to form a perfect seal.

Therefore, the present inventors investigated to solve the conflicting problem of corrosion resistance and hanging property, and found that Al or ^, l-
It has been found that it is sufficient to coat one side of a 5ii alloy-coated steel sheet with a metal having excellent hang spreadability, that is, one or more of Sns Cus Zn, Ni, and Fe to a thickness of 0.3 to 5 μm. The reason why the steel plate coating is made of a metal with excellent hangability on one side is because when installing oil pipes, etc., hangs are usually only attached to one side, so it is only necessary to attach hangs on that side as long as the hangability is ensured. The reason why the coating thickness is 6
This is because even if it is coated beyond the ring, no further hang spreadability can be expected, and it becomes economically expensive, which is undesirable.

Among metal coatings with excellent hang spreading properties, Sn or Zn is particularly excellent in hang spreading properties. This Sn or Zn coating may be used alone, but if stronger adhesion strength is required for the hang, a metal that is difficult to dissolve in the molten hang, such as Cu, Ni, or Fe, is used as an undercoat, and then the Sn or Zn coating is applied. Alternatively, it is preferable to coat with Zn. In this case, the coating thickness of any metal in the case of the base coating is 0.1 μm or more, preferably 0.3 to 1 μIII, from the viewpoint of hang adhesion and economical efficiency. Further, the coating thickness of Sn or Zn is preferably 0.2 to 4 μm in consideration of hang spreadability and economical efficiency.

By the way, Al-coated steel sheets exhibit excellent corrosion resistance against lower alcohols and their mixtures, but
It has been found that pitting-like corrosion occurs, albeit slightly, in pure lower alcohol on copper plates coated with ^l-5i alloys.

Therefore, the inventors of the present invention further conducted various studies to solve this problem. As a result, the coating layer was formed with a Si content of 13% or less and a Si content of 0.5%.
They discovered that it is sufficient to use one or more of the following: 03 to 1.0% M, 10.05 to 0.5% Ti, and 0.03 to 1.0% Cr. . Here A
Corrosion resistance is improved by containing one or more of Mg, Ti and C in the l-8i alloy coating layer.
This is presumed to be because a more stable oxide film is formed on the surface of the coating layer.

817, the reason why the content of Ti and C is set as above is that if the content of Mg and Cr is less than 0.03%, pitting corrosion will occur when the steel plate is immersed in pure lower alcohol, such as pure methanol. This is because some corrosion occurs, making it impossible to obtain sufficient corrosion resistance as a fuel tank material, and on the other hand, even if the content exceeds 1.0%, the corrosion resistance improvement effect is saturated and no further effect can be obtained. .

The same is true for Ti, if it is less than 0.05%, a sufficient corrosion resistance improvement effect cannot be obtained, and if it is contained in more than 0.5%, the corrosion resistance improvement effect is saturated.

Examples of methods for coating the rust-proof steel sheet of the present invention with Al or ^l-5i alloy include hot-dip plating, vapor deposition plating, powder plating, molten salt plating, non-aqueous electroplating,
Examples include thermal spraying and cladding methods, but it has been confirmed that coatings coated with either of these methods exhibit excellent corrosion resistance against lower alcohols and gasoline mixtures thereof, regardless of the coating method.

However, considering the processability when processing into fuel tanks,
It is preferable that the Al coating be applied by a method other than hot-dip plating, and conversely, it is preferable that the ^l-5i alloy coating be applied by hot-dip plating. This is because in the case of Δ1-coated steel sheets, when coated by hot-dip plating, a thick Fe-Al alloy layer with poor workability is formed at the interface between the coating layer and the steel sheet, and when processed, cracks occur in the coating layer and The corrosion resistance of the oil-covered steel sheet is reduced, so Si is added to the plating bath during hot-dip plating.
This is because the growth of the Fe-Al alloy layer, which has poor workability, is suppressed, and cracks are less likely to occur in the coating layer due to processing.

^I When coating a Si-based alloy by hot-dip plating, it is preferable that the coating layer contains 3 to 13% Si. The growth of the Fe-Al alloy layer cannot be sufficiently suppressed, and even if the content exceeds 13%, the effect of suppressing the alloy layer is 13%.
This is because it becomes saturated.

Examples of coating with 5nSCuSZn, Ni and Fe include electroplating, vapor deposition plating, displacement plating and electroless plating, but the present invention is not particularly limited to the coating method.

Next, the present invention will be explained with reference to examples.

(Example) Using an Al-killed low carbon steel plate having a thickness of 0.81111 as a raw material, various coated steel plates were manufactured as follows.

(1) Hot-dip ^l-5ii alloy plated steel sheet After degreasing the steel sheet, it was annealed for 30 seconds in a 50% 112-N2 atmosphere at a temperature of 700°C, and then in the same atmosphere at a temperature of 660°C. The plating thickness is 10% by immersing it in the following alloy plating bath.
The sea urchin was hot-dipped to a thickness of μm.

(,) Al-Si plated steel sheet Si 8.5% Residual Al and unavoidable impurities (b)^l-5i-HB plated steel sheet Si 8.5% Mg 0.01%, 0.03% and 1.0% Residual ΔI unavoidable impurities (c)^l-5i-Ti plated steel sheet Si 8.5% TiO, 01%, 0.05% and 0.5% residual Al and unavoidable impurities (d) 8l- 5i-Cr plated steel plate Si 8.5% Cr O, 01%, 0.03% and 1.0% Residual Al and inevitable impurities (2) Vapor deposition plated steel plate After degreasing the steel plate, 50% at a temperature of 700°C 11□-N
Annealing for 60 seconds in a 2 atmosphere, followed by annealing at a vacuum pressure of 3
Al was vapor-deposited and plated under the conditions of 10-' Torr, substrate temperature (plate temperature) of 250° C., and vapor deposition rate of 1 μs/win.

(3) ^I clad steel plate 1100 () 12 with steel plate as core material, plate thickness 1.0II1m
4) Use Al plate as the skin material, and after degreasing both, the total thickness is 25
Heating to 0℃, first cold rolling with a reduction rate of 70%, then 3
Diffusion annealing for 151 ki at 50°C, further reduction rate of 20%
The steel sheet was subjected to secondary cold rolling to obtain an Al-clad steel sheet.

Next, after degreasing, alkaline etching, and pickling the AI-coated steel sheets, ^l-5iP, and alloy-coated steel sheets manufactured as described in (1) to (3) above, 5nSCLI was applied to one side by a known electroplating method. % Zns or Fe to produce a rust-proof steel sheet for a fuel tank of the present invention and a plated plate outside the scope of the present invention.

Thereafter, we investigated the corrosion resistance of the coating layer of the 1-Si or 1-Si alloy of these steel sheets against lower alcohols and gasoline mixtures, and investigated the corrosion resistance of the coating layer of Sn and Cu.

The hang spreadability of the Zn sNi and Fe coating layers was investigated.

Table 1 shows the Al or ^l-5i alloy coating layer side of these steel plates and the pb-8%, which is a conventional rust-proof steel plate for fuel tanks.
31 alloy plated steel sheet (single side plating coating weight 459/Ia2
) and methanol and methanol mixture with electrogalvanized steel sheet (single side plating adhesion fi 409/m") having a chromate film with a film amount of 45 tag's2 in terms of chromium. Shows corrosion resistance against solin etc. .

In addition, the corrosion resistance investigation was conducted using a conventional Mura plate with a thickness of 0.8Il1m.
A test piece with a width of 50 mm and a length of 100 mm was subjected to 51 overhang processing using an Erichsen tester, and then soaked in methanol, water-containing methanol, or methanol-mixed gasoline shown in Table 1 at room temperature. The corrosion conditions of the processed parts and their surroundings were investigated by immersing them in water for 11 months.

As is clear from Table ptS1, the AI-coated steel sheet of the present invention exhibits excellent corrosion resistance against both methanol, water-containing methanol, and pudding mixed therewith.
In the case of -5ii alloy coated steel sheets, some pitting corrosion occurs due to pure methanol and water-containing methanol. But ^l-
5i alloy coated steel sheet also contains Mg, 'ri or C in the coating layer.
Those containing 0.03% or more of ``3'' exhibit excellent corrosion resistance even to methanol containing pure methanol and water.

On the other hand, the M or Ti content of the coating layer is 0.0
If the C content is less than 3% or less than 0.05%, it will have good corrosion resistance against mixed gasoline, similar to the case of Al-Si alloy coated steel sheets that do not contain them. However, against pure methanol and water-containing methanol, pitting corrosion occurs, albeit mildly, resulting in corrosion.

In addition, Pb-8%Sn, which is a conventional rust-proof steel plate for fuel tanks.
In the case of alloy-plated steel sheets, the methanol mixture that rises from the methanol mixture is severely corroded by the pudding, producing a large amount of corrosion products. Similarly, in the case of electrogalvanized steel sheets, Pb-8
Although not as bad as %Sn+gold-plated steel plate, it corrodes considerably.

Next, Figure 1 shows the relationship between the hang spread area on the side where Sn or Zn is plated on one side of the Al* or Al-Si alloy coating layer and the Sn or Zn plating thickness. However, when the Sn or Zn plating thickness is set to 0.3 μm or more, the hang spread property is comparable to that of the conventional Pb-8% Sn alloy plated steel sheet. On the other hand, if the Sn or Zn plating thickness is less than 0.3 μm, sufficient solder spreadability cannot be obtained. Although not shown, C
Those plated with U, Ni, and Fe to a thickness of 0.3 μm or more also had the same hang spreading properties as those plated with Sn or Zn. The hang spreadability test was conducted using Blacks (ZnCl, system) 0.39.
40% Pb) 0.59 ht 300'C (n) Five test pieces were measured by the method of measuring the area that spreads when a steel plate is heated for 30 seconds in a hot water bath, and the average value and variation are illustrated.

Figure 2 shows C on one side of the Al or Al-Si alloy coating layer.
The solder spread area on the surface side of which U, Ni or Fe is plated with 0.1μ of each undercoat and Zn plated thereon is measured in the same manner as in Figure 1, and the relationship between the spread area and the Zn plating thickness is determined. However, regardless of the type of base plating, if the Zn plating thickness is 0.2 μm or more, sufficient hang spreadability can be obtained, whereas if the Zn plating is less than 0.2 μm, Therefore, sufficient hanging spreadability cannot be obtained. Similarly, apply 0.2% of Sn plating on top of the base plating.
Although not shown in the drawings, those to which more than μw was applied also had sufficient hang spreadability.

Table 2 shows the solder adhesion on the side where one of Cu, old or Fe is underplated and Sn or Zn is plated at 1 μm on top of it, but the thickness of the underlayer plating is similar to the above. If it is less than 0.1 μm, solder adhesion will decrease. The solder adhesion test was carried out by bending the test piece used for the solder spreadability test in an Ott-adhesive manner and then opening it again to visually judge the degree of solder peeling.

Table 2 (Note) Adhesion evaluation criteria ○... No peeling Δ... Slight peeling is observed (effect) As described above, the rust-proof steel plate for fuel tanks of the present invention is made of Al or ^l-5ii alloy. The coated surface side exhibits excellent corrosion resistance against lower alcohols and gasoline mixtures thereof, and one or more of Sn, Cu, ZnsNi, and Fe is applied on the coating layer. Since the surface coated with the above material has excellent hanging properties, it is suitable as a material for fuel tanks for lower alcohols and mixed gasolines.

[Brief explanation of drawings]

Figure 1 shows the rust-preventive steel plate according to the present invention, in which one side of an Al or Al-Si alloy limb-covered steel plate is plated with Sn or Zn.
This shows the relationship between the hang spread area on the n or Zn plating side and the Sn or Zn plating thickness, and pt&
Figure 2 shows C on one side of an Al or Al-31 alloy coated steel plate.
The hanging spread area on the Zn-plated side of the rust-proof steel sheet according to the present invention, which is plated with one type of u, Ni or Fe, and then plated with Zn, and the Zn plating J! This shows the relationship with L.

Claims (4)

[Claims] (1) Both sides of the steel plate are made of Al or have a Si content of 13%
In the following, the remainder consists of layers and unavoidable impurities.
It is coated with Si-based alloy, and one side is coated with Sn, Cu, Zn,
One or more of Ni and Fe, thickness 0.3 to 5
A rust-proof steel plate for fuel tanks characterized by μm coating. (2) One side is first coated with one or both of Sn, Cu, Zn, Ni and Fe.
A seed or two or more kinds are applied to a thickness of 0.1 μm or more, and then Sn
The rust-proof steel plate for a fuel tank according to claim 1, characterized in that it is made of Zn or Zn to a thickness of 0.2 μm or more. (3) Both sides of the steel plate are made of Al or have a Si content of 13%
Below, 0.03-1.0% Mg, 0.05-0.5
% of Ti and 0.03 to 1.0% of Cr, and the remainder is Al and inevitable impurities, and one side is coated with Sn, C.
A rust-proof steel sheet for a fuel tank, characterized in that it is coated with one or more of U, Zn, Ni, and Fe to a thickness of 0.3 to 5 μm. (4) One side is first coated with one or both of Sn, Cu, Zn, Ni and Fe.
A seed or two or more kinds are applied to a thickness of 0.1 μm or more, and then Sn
The rust-proof steel plate for a fuel tank according to claim 3, characterized in that it is made of Zn or Zn to a thickness of 0.2 μm or more.