JP5903239B2 - Aluminum material with excellent resistance to alcohol corrosion - Google Patents

Description

The present invention is alcohol-resistant corrosion excellent aluminum material relates to A aluminum alloy material especially excellent in resistance to alcohol-corrosion.

  Aluminum materials are lightweight and have a relatively high strength, that is, they have a relatively high specific strength and are relatively inexpensive, so they can be used in automobile parts, electrical / electronic parts, low-temperature and cryogenic equipment. It is used in a very wide range of fields, including various equipment parts and various structures including low-temperature tanks.

  As one of such fields, there are fuel system parts used for automobile parts, particularly fuel parts from fuel tanks to engines, and many aluminum materials are used.

  The term “aluminum material” used in this specification means “pure aluminum material” in which no additive element is intentionally added, and “aluminum alloy material in which an element is intentionally added for the purpose of improving desired characteristics” Is a concept that includes both.

In recent years, as one countermeasure against global warming, an alcohol such as ethanol (for example, bioethanol) is frequently used as a fuel for automobiles. When alcohol such as ethanol is used as fuel, it may be used alone or mixed with other fuels. When mixing, it is mixed with gasoline and mixed with ethanol (alcohol mixed gasoline). Often used as
Further, even in the next generation of fuel cell vehicles, the use of alcohol have been studied as a fuel, opportunities for contact between the aluminum component and the alcohol automobile has been increasing.

  Alcohol such as ethanol dissolves and corrodes the aluminum material. For this reason, when the fuel is a liquid containing alcohol, such as ethanol and ethanol-mixed gasoline, there is a concern that the aluminum material used for the fuel system parts may corrode and dissolve on the surface in contact with the fuel.

  Patent Document 1 discloses that corrosion resistance can be improved by performing honing and high-temperature water treatment. However, it is an improvement of the conventional boehmite treatment, and it is expected that film defects will occur due to the influence of impurities in the material. Corrosion due to alcohol may occur due to the film defects.

JP 2004-277784 A

Such a problem also occurs in oxide films other than boehmite, plating or paint films.
For this reason, there has been a demand for an aluminum material that is resistant to corrosion even when it comes into contact with a liquid containing alcohol, and that has excellent alcohol corrosion resistance.

This onset bright, in order to meet such demands, and to provide an excellent aluminum material resistance to alcohol-corrosion.

The present inventors made of aluminum or an aluminum alloy, at least one of iron and silicon, an impurity element, and an aluminum material concentration is below 0.01% by mass, in contact with a liquid containing alcohol It was found that even if it was used , corrosion hardly occurred .

One aspect of this aluminum material, iron is the impurity element, and its concentration is the case of 0.01 mass% or less.

Aspect 1 of the present invention comprises an aluminum alloy , the aluminum alloy contains 0.15% by mass to 12.0% by mass of magnesium, at least one of iron and silicon is an impurity element, and the concentration thereof is An aluminum material used in contact with a liquid containing alcohol , characterized by being 0.01% by mass or less.

Aspect 2 of the present invention is the aluminum material according to aspect 1, wherein the total of the iron concentration and the silicon concentration is 0.01% by mass or less.

Aspect 3 of the present invention is the aluminum material according to aspect 1, wherein the total of the concentration of iron, the concentration of silicon, and the concentration of copper as an impurity element is 0.01% by mass or less. is there.

  According to the present invention, by controlling the concentration of at least one of iron (Fe) and silicon (Si), which are impurity elements, it is possible to provide an aluminum material excellent in alcohol corrosion resistance.

This onset inventor et al., Details are given below, which is an impurity element contained in the aluminum material, of iron and silicon, by at least one below 0.01 wt%, aluminum material (pure aluminum and It has been found that the alcohol corrosion resistance of an aluminum alloy can be improved.
The details are shown below.

  In general, since aluminum is produced by an electrolysis method such as the Hall-Eleu method, the purity of pure aluminum generally used industrially is about 99% or more (mass ratio, the same applies hereinafter. “2N” (2 Similarly, for example, a purity of 99.999% by mass or more is represented by “5N” (5 nines), and in the mass percentage notation indicating purity, N is added after the consecutive 9 numbers from the top. In some cases, it contains impurities close to 1%.

Among the impurity elements contained in the aluminum material, the main elements having a large amount are three types of iron (Fe), silicon (Si), and copper (Cu).
Therefore, in order to examine the purity of pure aluminum, it is widely used to measure the concentrations of these three impurity elements, iron, silicon, and copper, and use the remainder obtained by subtracting the total concentration of these three elements from 100% by mass. Has been done.

Among these three types of impurity elements, there are many iron and silicon, and even pure aluminum of 2N class purity is usually about 0.1 mass% or more of iron and about 0.05 mass% or more of silicon. Is contained as an impurity.
The present onset inventor has focused on the iron and silicon, at least one of the concentrations of iron and silicon as an impurity element in alcohol resistance corrosion by 0.01 mass% or less (100 ppm by mass or less) It has been found that an excellent aluminum material can be obtained.
Respect corrosion by an alcohol, such knowledge is not in the prior art, in which the onset inventor et al. First found.

Mechanism of Alcohol-resistant corrosion improvement the onset inventor guess is as follows. It should be noted that the following mechanism is for the onset inventor has estimated from knowledge have been obtained at the present time, it should be noted that it is not intended to limit the present onset bright range.

  Corrosion caused by a liquid containing an alcohol such as ethanol and ethanol-mixed gasoline tends to be slow or hardly progressed with alcohol alone, as shown in Examples described later. And when trace amount elements or compounds, such as chlorine (or chlorine ion) which exist in use environment, are contained in the liquid containing alcohol, there exists a tendency for corrosion to advance.

Moreover, among iron, copper, and silicon which are main impurities contained in the above-described aluminum material, copper is relatively small, and silicon and iron are large.
When both iron and silicon are present in the aluminum, forming an Al-Fe-Si ternary intermetallic compound. However, when the concentration of at least one of iron and silicon is 0.01% by mass or less, this ternary intermetallic compound is hardly formed.

From the above events, if both the iron and silicon concentrations are high (the iron concentration is higher than 0.01% by mass and the silicon concentration is higher than 0.01% by mass), chlorine that promotes corrosion, etc. substances, in the portion where the intermetallic compound of the ternary Al-Fe-Si is present, to act catalytically, seems to corrosion of the aluminum with an alcohol proceeds.
In contrast, (when at least one of the concentrations of iron and silicon is less than 0.01 wt%) is low, at least one of the density of iron and silicon, intermetallic compounds ternary Al-Fe-Si is almost Therefore, it is considered that local corrosion by alcohol does not proceed, and excellent alcohol corrosion resistance is exhibited.

Preferably, in the aluminum material according to the present invention , the concentration of iron is 0.01% by mass or less among iron and silicon which are impurity elements. This is because silicon may be intentionally added as an additive element for the purpose of, for example, suppressing thermal expansion or improving wear resistance. More preferably, the concentration of iron as an impurity element is 0.001% by mass or less. More reliably, and suppress the formation of Al-Fe-Si ternary intermetallic compound, which is possible to improve resistance to alcohol corrosion.

Further, the aluminum material according to the present onset Ming, preferably the total concentration of the concentration and silicon iron is less than 0.01 wt%, thus, to reduce the amount of both the iron and silicon as an impurity element it is because the more reliably can suppress the formation of Al-Fe-Si ternary intermetallic compounds, thus it is possible to obtain a reliable high alcohol resistance corrosion.

Aluminum material according to the present onset Ming, more preferably the total concentration and the silicon concentration and the concentration of copper iron is not more than 0.01 mass%. By reducing the iron and the amount of silicon which is an impurity element, more reliably in addition to the Al-Fe-Si ternary effect of suppressing the formation of intermetallic compounds of copper, which is one of the main impurity elements of aluminum This is because by reducing the amount, the effect of more reliably suppressing the occurrence of local corrosion by alcohol. Thereby, high alcohol corrosion resistance can be obtained more reliably.

  Note that the measurement of the concentration of the impurity element in aluminum containing iron, silicon, and copper can be performed by, for example, solid-state emission spectroscopy. It can also be measured by mass spectrometry such as glow discharge mass spectrometry.

Aluminum material you disclosed herein, as described above, including any of pure aluminum and aluminum alloys.
That is, it may be pure aluminum composed of aluminum and unavoidable impurities (the unavoidable impurities include iron, silicon, and copper), and may be an alloy including other elements (additive elements) in addition to aluminum and unavoidable impurities. .

Such is the additive elements aluminum material may include, for example, copper (Cu), manganese (Mn), silicon (Si), magnesium (Mg) and zinc (Zn) 1 or more selected from the group consisting of These elements can be exemplified.
These are examples of additive elements, and may contain other additive elements as appropriate.

  When the additive elements exemplified above are added, preferred concentrations (compositions) for copper, manganese, silicon, magnesium and zinc are copper (Cu): 0.5 to 7.0% by mass, manganese (Mn), respectively. : 0.3 to 1.5 mass%, silicon (Si): 0.5 to 24.0 mass%, magnesium (Mg): 0.15 to 12.0 mass%, zinc (Zn): 4.0 It is 8.4% by mass.

Preferred elements from among these are magnesium, for not forming an intermetallic compound in the aluminum alloy, i.e. Al-Fe-Si also absent intermetallic compounds other than the intermetallic compound of the ternary, more reliably This is because high alcohol corrosion resistance can be obtained.
In particular, if the magnesium concentration is 0.15 to 12.0% by mass, this effect can be obtained more reliably. A more preferable magnesium concentration at which this effect can be obtained even more reliably is 0.2 to 5.6% by mass.

Moreover, as long as the concentration of at least one of iron and silicon is 0.01% by mass or less, for example, an aluminum alloy defined in Japanese Industrial Standards (JIS) H4000, H4040, H4080, H4100 and H4140, so-called 1000 series (1000 series), 2000 series (2000 series), 3000 series (3000 series), 4000 series (4000 series), 5000 series (5000 series), 6000 series (6000 series) or 7000 series (7000 series) alloy It may be.
Of these, 1000 series alloys and 5000 series alloys are preferred. This is because the intermetallic compound hardly precipitates and the alcohol corrosion resistance can be improved more reliably.

Incidentally, as can be seen from the above description, the aluminum material according to the present onset Ming is a major impurity element in pure aluminum, iron, silicon, either one or two additional elements of copper (deliberately added Element). However, in this case, as a matter of course, since the concentration of at least one of iron and silicon needs to be 0.01% by mass or less, both iron and silicon are not included as additive elements. That is, when one of iron and silicon is included as an additive element, the other is an impurity element, and the concentration thereof is 0.01% by mass or less.

Further, in Honmyo Saisho, "alcohol", for example ethanol, n-propanol, isopropanol, n-butanol, including isobutanol and methanol may be of various types of alcohol.

Next, a method for manufacturing A aluminum material.
When the aluminum material is pure aluminum, for example, the aluminum material can be obtained by processing into a desired shape using high-purity aluminum having a purity of 99.99 mass% or more (4N).

An example of such a high-purity aluminum production method is a three-layer electrolysis method.
In the three-layer electrolysis method, commercially available relatively low-purity aluminum (for example, a special grade of JIS-H2102 having a purity of 99.9%) is added to an Al—Cu alloy layer and used as an anode in a molten state. For example, an electrolytic bath containing, for example, aluminum fluoride and barium fluoride is arranged on the cathode, and high-purity aluminum is deposited on the cathode.
The three-layer electrolysis, it is possible to obtain a purity of 99.999 mass% or more purity aluminum. Moreover, the iron concentration in aluminum can be suppressed to 10 mass ppm (0.001 mass%) or less relatively easily.

The high purity aluminum obtained by three-layer electrolysis method or the like, to suppress intrusion of impurities, rolling, extruding, die casting, by performing desired processing of pulling or bending or the like, having a predetermined shape luer A ruminium material can be obtained.

On the other hand, when the aluminum material is an aluminum alloy, for example, high purity aluminum having a purity of 99.99% by mass or more is used as a raw material, and this is melted (dissolved), and a desired additive element is added and cast. after obtaining an aluminum alloy ingot having a composition, in the in-cum DOO, for example, forging, rolling, extruding, die casting, by performing desired processing of pulling or bending or the like, Rua aluminum to have a predetermined shape A material can be obtained.

Since the amount of the impurity element in the molten high purity Aluminum is sometimes increased, purity 99 as a high purity Aluminum used for melting, for example, high purity Aluminum obtained in three-layer electrolysis it is preferable to use a high-purity aluminum of .999 wt% or more (5N).

Moreover, it is preferable to melt the high-purity aluminum in an inert atmosphere such as argon gas using a graphite crucible so as to suppress the intrusion of impurity elements.
Furthermore, it goes without saying that it is preferable to use a high-purity material having a purity of, for example, 99.9% by mass or more, in which the impurity level of the additive element is controlled.

Incidentally, the purity of the high purity aluminum is used in the exemplified manufacturing method above, in general, as described above, it is often determined by subtracting the concentration of iron and silicon and copper from 100 wt%. However, for example, metal 35 elements (Li, Be, B, Na, Mg, Si, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Co, Cu, Zn, Ga, Ge, As, Se, Zr , Mo, Ag, Cd, In, Sn, Sb, Ba, La, Ce, Pt, Hg, Pb, Bi), and the concentration of more impurity elements is measured, and the total concentration is 100 mass. High-purity aluminum whose purity is obtained by subtracting from% may be used.

(1) Sample Preparation Example 1 and for the sample of Reference Example, to prepare a high purity Aluminum obtained in three-layer electrolysis (5N), purity 99.86% of the samples of Comparative Examples 1 and 2 Commercially available pure aluminum (a widely available aluminum) was prepared.

The sample of Example 1 was produced as follows.
High purity Aluminum above was melted by using a graphite crucible in an argon atmosphere to obtain an ingot by adding magnesium purity 3N5 (99.95 wt%) as an additive element. Next, the said ingot was rolled and the board | plate material was cut out from the obtained rolling material. Thereafter, the surface of the obtained plate material was washed with ethanol.
The size of the obtained sample was 20 mm long × 20 mm wide × 0.5 mm thick.

Samples of reference example, rolling a high purity Aluminum above, cut out a plate material from the obtained rolled material, the surface obtained by ethanol washing. The size of the obtained sample was 20 mm long × 20 mm wide × 0.5 mm thick.

Samples of Comparative Example 1, except for using pure aluminum described above in place of high purity Aluminum, was obtained in the same manner as the samples of Example 1. The size of the obtained sample was also the same as the sample of Example 1.

Samples of Comparative Example 2, except for using pure aluminum described above in place of high purity Aluminum, was obtained in the same manner as the samples of Reference Example. The size of the obtained sample was also the same as the sample of the reference example .

  Table 1 shows the result of measuring the composition of the obtained sample by solid-state emission spectroscopy.

(2) Evaluation of alcohol corrosion resistance Evaluation of alcohol corrosion resistance was performed as follows.
300 g of absolute ethanol (water: 50 ppm or less) manufactured by Wako Pure Chemical Industries, Ltd. was heated to 78.4 ° C. (boiling point), and 4 samples of Example 1, Reference Example and Comparative Examples 1 and 2 were added to the heated absolute ethanol. Soaked for hours.
The weight of the sample before and after the immersion was measured, and the ratio of the weight reduced by the immersion to the weight of the sample before the immersion was taken as the dissolution rate. The smaller the rate, the better the resistance to alcohol corrosion.)

In order to accelerate the corrosion by alcohol, anhydrous aluminum chloride (AlCl ₃₎ and 0.001 mol / L of absolute ethanol was added, anhydrous aluminum chloride (AlCl ₃₎ and 0.01 mol / L of absolute ethanol was added anhydrous aluminum chloride Anhydrous ethanol added with 0.1 mol / L of (AlCl ₃ ) was prepared, and the dissolution rate was determined by immersing the sample in each of these three types of absolute ethanol under the same conditions.
The obtained dissolution rate (%) is shown in Table 2.

The blank part in Table 2 indicates that the evaluation is not performed under this condition.
When no AlCl ₃ was added, all the samples evaluated had a dissolution rate of 0, and no corrosion by alcohol occurred under the above conditions.

In the case where the AlCl ₃ concentration is 0.001 mol / L, that is, when chlorine as a catalyst is introduced and the catalyst concentration is considered to be the closest to the environment in which corrosion by alcohol actually occurs, the sample of Example 1 Compared with the sample of the comparative example 1, the remarkable alcohol-corrosion resistance was shown.

When the AlCl ₃ concentration was 0.01 mol / L, the sample of Example 1 showed remarkable alcohol corrosion resistance as compared with the sample of Comparative Example 1.

Even in the extremely severe environment where corrosion is considerably accelerated compared with the actual environment, the AlCl ₃ concentration is 0.1 mol / L, the sample of Example 1 and the reference example are compared with the samples of Comparative Examples 1 and 2. Remarkable alcohol corrosion resistance.

Claims (3)

It consists of 1000 series or 5000 series aluminum alloy, this aluminum alloy contains 0.15 mass%-12.0 mass% magnesium, and at least one of iron and silicon is an impurity element, and the density | concentration is 0. An aluminum material used in contact with a liquid containing alcohol, characterized by being 0.01 mass% or less.   The aluminum material according to claim 1, wherein the total of the iron concentration and the silicon concentration is 0.01 mass% or less.   2. The aluminum material according to claim 1, wherein the total of the iron concentration, the silicon concentration, and the impurity element copper concentration is 0.01 mass% or less.