JPS6233735A - Amorphous alloy having high corrosion resistance - Google Patents

Abstract

PURPOSE:To obtain an amorphous alloy having high corrosion resistance and undergoing no corrosion by the formation of a stable passive film even in a severe corrosive environment, e.g., in boiling concd. hydrochloric acid having no oxidizing power by providing a specified composition contg. Ta and Ni as essential components. CONSTITUTION:The composition of an amorphous alloy is composed of, by atom, 30-80% Ta and the balance Ni, 30-80% in total of >12% Ta and Nb and the balance Ni, 30-80% in total of >25% Ta and one or more among Ti, Zr and Cr and the balance Ni, or 30-80% in total of >12% Ta, Nb (Ta+Nb>25%) and one or more among Ti, Zr and Cr and the balance Ni.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to Futsu II! This invention relates to a highly corrosion-resistant amorphous alloy that can be used in harsh corrosive environments such as concentrated hydrochloric acid.

[Prior Art] Only a small amount of tantalum is used as a metal material in boiling concentrated hydrochloric acid.

[Problems to be solved by the invention] Tantalum is the only metal material that can be used in boiling concentrated hydrochloric acid, but even tantalum inevitably corrodes at a rate of about 501 Lm per year, and often suffers from hydrogen embrittlement fracture. suffer. Therefore, in such an environment where it is extremely difficult to use metal materials, there has been a constant desire for the emergence of new metal materials that can withstand use.

[Means for Solving the Problems] The purpose of the present invention is to provide a material that is non-oxidizing and passivates metals like boiling S concentrated hydrochloric acid, and has high corrosion resistance that can withstand extremely harsh corrosive environments. An object of the present invention is to provide an amorphous alloy having the following properties.

The present invention achieves this object by using an amorphous alloy having a specific composition containing Ta and Ni as essential components.

As is well known, alloys are usually crystallized in the solid state, but by selecting a material with a specific alloy composition and solidifying it by ultra-rapid cooling from a molten state, or by performing solid formation by sputter deposition, etc. If a solid is formed while taking steps to prevent the formation of the long-period order of atoms, or by destroying the long-period order within the solid, such as by ion implantation, and by dissolving the necessary elements in a supersaturated state, it is possible to form a solid even in a solid state. It does not have a crystal structure and has an amorphous structure similar to a liquid. This amorphous alloy is ideally a homogeneous solid solution, and is also characterized in that it remains a homogeneous solid solution even if sufficient alloying elements are added to exhibit predetermined properties.

As a result of research focusing on the excellent properties of such amorphous alloys, the present inventors have discovered a highly corrosion-resistant amorphous alloy that is stable in high-temperature concentrated nitric acid or in high-temperature concentrated nitric acid that further contains an oxidizing agent. A patent application was filed as Japanese Patent Application No. 60-51036.

The highly corrosion-resistant amorphous alloy filed as Japanese Patent Application No. 60-51036 is as follows.

(1) A highly corrosion-resistant amorphous alloy containing 15 to 80 atomic % of Ta, with the balance substantially consisting of Ni.

(2) Contains Ta and one or more elements selected from the group consisting of Ti, Zr, Nb, and W, with the remainder essentially consisting of Ni, and the content is 10 atomic % of Ta.
As mentioned above, one or more elements selected from the above group,
A highly corrosion-resistant amorphous alloy having a Ta content of 15 to 80 atomic %.

(3) Contains Ta, Fe and/or Co, and the remainder is substantially Ni, with a Ta content of 15 to 80
atomic%, Fe and/or Co is 75 atomic% or less, Ni
A highly corrosion-resistant amorphous alloy with 7 atomic % or more.

(4) Contains Ta, one or more elements selected from the group consisting of Ti, Zr, Nb, and W, and Fe and/or Go, with the remainder substantially consisting of Ni, and the content is Ta. and one or more selected from the group consisting of Ti, Zr, Nb, and W in a content of 15 to 8 at%, Ta at 10 at% or more, and Fe and/or Co at 75 at%. A highly corrosion-resistant amorphous alloy containing 7 atomic % or more of Ni.

High-temperature concentrated nitric acid or high-temperature concentrated nitric acid containing an oxidizing agent are both oxidizing environments, so the amorphous alloy described above becomes passivated, forming a passive film with excellent protection.
It exhibits high corrosion resistance, but in contrast, it cannot be passivated in high-temperature concentrated hydrochloric acid, which has weak oxidizing power, unless the alloy itself has a high passivation ability.

As a result of further research while considering various characteristics of amorphous alloys, the present inventors found that
By adding elements that further increase the passivation ability to an alloy with particularly high passivation ability among No. 36 alloys or similar alloys, it can be used even in harsh corrosive environments with weak oxidizing power such as high-temperature concentrated hydrochloric acid. The present invention was completed by discovering that it is possible to create an amorphous alloy with high corrosion resistance by forming a passive film.

The present invention consists of the first to sixteenth inventions shown in claims 1 to 16, and the constituent elements and the constituent elements of these first to sixteenth inventions are shown in Table 1 below. Indicates the content rate.

[Function] Amorphous alloys obtained by various methods for producing amorphous alloys, such as ultra-rapid solidification of a molten alloy having the above composition or sputter deposition, are single-phase alloys in which each of the above-mentioned elements is uniformly dissolved in solid solution. Therefore, a protective film (passive film) that is extremely uniform and has high corrosion resistance is formed on the amorphous alloy of the present invention.

By the way, metal materials easily dissolve in high-temperature concentrated hydrochloric acid solutions that have weak oxidizing power, so in order to use metal materials in such an environment, it is necessary to give them the ability to form a stable protective film. There is a need. This is achieved by creating an alloy containing the required amount of effective elements. However, in the case of crystalline metals, adding a large amount of various alloying elements often results in a multiphase structure with different chemical properties, making it impossible to achieve the desired corrosion resistance. Moreover, the occurrence of chemical non-uniformity is rather detrimental to corrosion resistance.

In contrast, the amorphous alloy of the present invention is a homogeneous solid solution. Therefore, the amorphous alloy of the present invention uniformly contains the necessary amount of effective elements capable of forming a stable protective film, that is, a passive film, and the amorphous alloy has a uniform passivation film and a sufficient amount of active elements. High corrosion resistance is exhibited.

That is, the condition that a metal material that can withstand high-temperature concentrated hydrochloric acid, which has weak oxidizing power, must have is that it has a high passivation ability that allows a stable passive film to uniformly form on the material in a non-oxidizing environment. This is achieved with the alloy composition of the present invention, and the amorphous structure of the alloy allows alloys with complex compositions to be created as single-phase solid solutions, ensuring the formation of a uniform passive film. .

Next, the reason for limiting the composition of each component in the present invention will be described.

Ni is the basic element of the alloy of the present invention, and Ta, N
It is an element that forms an amorphous structure when it coexists with elements such as B, Ti, and Zr. Therefore, in the ninth to twelfth aspects of the present invention, it is necessary to add 20 at % or more of Ni in order to form an amorphous structure.

Ta is an element that forms a stable passive film in high-temperature strong acids, and as mentioned above, it coexists with Ni or a part of Ni replaced with 11a or two of Fe or Co to form an amorphous structure. In the first and fifth aspects of the present invention, it is necessary to add 30 atomic % or more to ensure sufficient corrosion resistance. Further, as described later, even when P is included to help passivate, it is necessary to add 20 at % or more of Ta in the ninth and thirteenth aspects of the present invention. Furthermore, Ni
, Fe, and Co. If the total of the a elements is less than 20 atomic %, it is difficult to form an amorphous structure even if they coexist with Ta. Therefore, in the first and fifth aspects of the present invention, Ta is
The ninth and first aspects of the present invention
In invention No. 3, it is necessary that Ta be less than 80 atomic %.

Nb forms an excellent passive film next to Ta, and Nb
Although it is an element that forms an amorphous structure in coexistence with Nb, the effect of Nb on corrosion resistance is not as good as that of Ta, so it is not possible to completely replace Ta with Nb. In the second and sixth inventions of the present invention, in which a passive film is formed with Nb, Ta
It is necessary to contain 12 atomic % or more of Ta and Nb and 30 atomic % or more of Ta and Nb in total. Furthermore, in the tenth and fourteenth aspects of the present invention, 5P helps form a passive film with Ta and Nb.
In the invention containing 7 atomic % or more of Ta and containing Ta and N
It is necessary to contain 20 atomic % or more of b in total.

Furthermore, if the total amount of Ni, Fe, and Co is less than 20 at%, it is difficult to form an amorphous structure even if Ni, Fe, and Co coexist with Ta and Nb. In the tenth and fourteenth aspects of the present invention, the total of Ta and Nb is 80 atomic % or less, and Ta,
! =The total amount of Nb is less than 80 atomic %.

Both Ti and Zr are elements that coexist with Ni in place of Ta and Nb to form an amorphous structure, and Ti, Zr, and Cr have the ability to form a passive film in high-temperature strong acids. It is an element. However, Ti, Z
The effect of r and Cr on corrosion resistance is inferior to that of Ta and Nb, so in order to guarantee corrosion resistance, it is not possible to completely replace Ta and Nb with these elements. However,
When it contains 25 atomic % or more of Ta as in the third and seventh inventions of the present invention, any one of Ti, Zr and Cr is used.
Sufficient corrosion resistance is guaranteed if the total content of the species or two or more species and Ta is 30 atomic % or more. When both Ta and Nb are included, the content is 12 atomic % as in the fourth and eighth aspects of the present invention.
Corrosion resistance is guaranteed if the total of the above Ta and Nb is 25 atomic % or more, and the total of any one or more of Ti, Zr, and Cr and Ta and Nb is 30 atomic % or more. Ru.

On the other hand, when it contains P that helps passivation, the minimum required amount of each may be low, and when it contains 15 at% or more of Ta as in the eleventh and fifteenth aspects of the present invention, Ti, Z
Corrosion resistance is guaranteed if the total of one or more of r and Cr and Ta is 20 atomic % or more*
When Ta, Nb and P are included, the total of Ta and Nb is 7 at% or more as in the 12th and 16th inventions of the present invention, and the total of Ta and Nb is 16 at% or more, and Ti, Zr and C
Corrosion resistance is guaranteed if the total amount of one or more of r and Ta and Nb is 20 atomic % or more. Furthermore, Ni
, Fe, and Co are less than 20 atomic % in total, Ni,
Even if Fe and Co coexist with Ta, Nb, Ti, Zr and Cr, it is difficult to form an amorphous structure, so in the third and seventh aspects of the present invention, any one or two or more of Ti, Zr and Cr are used. In addition, in the fourth and eighth aspects of the present invention, the total of any one or more of Ti, Zr, and Cr and Ta and Nb is 80 atoms or less. % or less. Similarly, in the eleventh and fifteenth aspects of the present invention, Tf
, one or more of Zr and Cr and Ta
In the 12th and 16th inventions of the present invention, the total of any one or more of Ti, Zr and Cr and Ta and Nb is 80 at%.
less than

P does not constitute a passive film, but Ta, Nb, Ti, Z
It has the effect of significantly promoting the formation of a passive film of r, Cr, etc. This effect is remarkable as long as P is added even in a very small amount. However, in the present invention, Ni (Fe,
In a Co)-valve metal amorphous alloy, adding too much P makes it difficult to make it amorphous, so the P content is set to 7 atomic % or less.

Fe and Co are replaced by Ta, Nb, Ti, Zr
However, if one or both of Fe and Co are substituted until the Ni content is reduced to 2 at %, it becomes difficult to form an amorphous structure. In addition, Ni and Fe containing 2 atomic % or more
If the total amount of one or two of Co and Co is 20 atomic % unvortexed, it becomes difficult to form an amorphous structure. Therefore, in the fifth to eighth and thirteenth to sixteenth aspects of the present invention, it is necessary to contain Ni at 2 at % or more. Further, in the thirteenth to sixteenth aspects of the present invention, Fe and G.

The total of one or two of these and 2 atomic % or more of Ni is 2
It is necessary to make it 0 atomic % or more.

It should be noted that even if the amorphous alloy of the present invention contains 3 atomic % or less of Known as an effective element for forming an amorphous structure. However, in the presence of strong acids at high temperatures, the stability of the passive film of amorphous alloys to which a large amount of metalloid is added decreases. Therefore, it is difficult to specify semimetallic elements as particularly effective elements. However, the addition of semimetallic elements to the extent that they partially replace P is not harmful to corrosion resistance and helps the formation of an amorphous structure, so there is no problem. do not have.

The amorphous alloy of the present invention can be produced by various methods that have already been widely used, such as ultra-rapid solidification of a liquid alloy, various methods of forming an amorphous alloy through a gas phase, and long-period solidification by ion implantation. Any method for producing an amorphous alloy, such as a method for destroying the structure, may be used.

[Example] Raw material metals were mixed to have the compositions shown in Table 2, and raw material alloys were produced by an argon arc melting method. These alloys are remelted in an argon atmosphere and solidified by ultra-rapid solidification using a single roll method to obtain a thickness of 0.01 to 0.05.
An amorphous alloy thin plate having a width of 1 to 3 mm and a length of 3 to 20 m was obtained. The formation of an amorphous structure was confirmed by X-ray diffraction. The surfaces of these alloy samples were polished in cyclohexane to No. 1000 silicon carbide paper.
Next, an alloy sample of a predetermined length was cut out, immersed in a boiling 6N HCl solution for 7 to 10 days, and its weight before and after immersion was measured using a microbalance. If a weight loss was observed due to immersion, this was converted into an annual corrosion rate.

The results obtained are shown in Table 3.

No weight change due to corrosion was detected in most of the amorphous alloys of the present invention. In addition, as a result of surface analysis using X-ray photoelectron spectroscopy after immersion testing of the alloys of the present invention, it was found that the surfaces of these alloys had a tantalum oxyhydroxide passive film consisting of TaO2(OH) or a tantalum oxyhydroxide passive film consisting of TaO2(OH). O
A mixed oxyhydroxide passive film of 2(OH) and NbO2(OH) was formed, which was found to be responsible for the high corrosion resistance of the alloy of the present invention.

Table 3 (Part 1) Side temperature of annual corrosion rate of the alloy of the present invention Table 3 (Part 2) Example of annual corrosion rate of the alloy of the present invention [Effects] As detailed above, the amorphous alloy of the present invention has a It is a highly corrosion-resistant alloy that forms a stable passive film and does not corrode even in highly corrosive environments such as boiling concentrated hydrochloric acid.

Furthermore, since any of the amorphous alloy production techniques that are already widely used can be applied to the production of the alloy of the present invention, there is no need for special equipment, and the alloy of the present invention has excellent practicality. .

Claims (16)

[Claims] (1) Contains 30 to 80 atomic% of Ta, the remainder being substantially Ni
Highly corrosion resistant amorphous alloy. (2) A highly corrosion-resistant amorphous alloy containing 12 atomic % or more of Ta, the total of Ta and Nb being 30 to 80 atomic %, and the balance being substantially Ni. (3) Contains 25 atomic % or more of Ta, Ti, Zr, Cr
A highly corrosion-resistant amorphous alloy in which the total amount of one or more elements selected from the group consisting of Ta and Ta is 30 to 80 atomic %, and the balance is substantially Ni. (4) Contains 12 atomic % or more of Ta, the total of Ta and Nb is 25 atomic % or more, and one or more elements selected from the group of Ti, Zr, and Cr are combined with Ta and Nb. A highly corrosion-resistant amorphous alloy with a total content of 30 to 80 atomic %, the remainder being substantially Ni. (5) A highly corrosion-resistant amorphous alloy containing 30 to 80 atomic % of Ta and 2 atomic % or more of Ni, and substantially consisting of one or both of Fe and Co, with a total of 100 atomic %. (6) Contains 12 atomic % or more of Ta, the total of Ta and Nb is 30 to 80 atomic %, contains 2 atomic % or more of Ni, and the remainder is substantially one of Fe and Co or A highly corrosion-resistant amorphous alloy consisting of two types with a total of 100 atomic %. (7) Contains 25 atomic% or more of Ta, Ti, Zr, Cr
The total of one or more elements selected from the group of 30 to 80 at% of Ta and 2 at% or more of Ni
A highly corrosion-resistant amorphous alloy containing 100 atomic % of the remainder substantially consisting of one or both of Fe and Co. (8) Contains 12 atomic % or more of Ta, the total of Ta and Nb is 25 atomic % or more, and one or more elements selected from the group of Ti, Zr, and Cr and Ta and Nb
Highly corrosion resistant with a total of 30 to 80 atomic % and further containing 2 atomic % or more of Ni, and the remainder substantially consisting of one or two of Fe and Co, making the total 100 atomic %. Amorphous alloy. (9) 20 atomic % or more and less than 80 atomic % Ta and 7 atomic %
Contains the following P, with the remainder being substantially more than 20 at% Ni
A highly corrosion-resistant amorphous alloy with a total of 100 atomic %. (10) Contains 7 atomic % or more of Ta, the total of Ta and Nb is 20 atomic % or more and less than 80 atomic %, contains 7 atomic % or less of P, and the balance is substantially 20 atomic % or more of Ni. A highly corrosion-resistant amorphous alloy with a total of 100 atomic %. (11) Contains 15 atomic % or more of Ta, Ti, Zr, C
The total of one or more elements selected from the group r and Ta is 20 atomic % or more and less than 80 atomic %, contains 7 atomic % or less of P, and the balance is substantially 20 atomic % or more A highly corrosion-resistant amorphous alloy consisting of Ni with a total content of 100 atomic %. (12) Contains 7 atomic % or more of Ta, the total of Ta and Nb is 16 atomic % or more, and contains one or more elements selected from the group of Ti, Zr, and Cr, and Ta and Nb. The total of
Contains the following P, with the remainder being substantially more than 20 at% Ni
A highly corrosion-resistant amorphous alloy with a total of 100 atomic %. (13) The sum of 20 atomic % or more and less than 80 atomic % Ta, 2 atomic % or more Ni, and 7 atomic % or less P, with the substantial balance being one or two of Fe and Co and Ni. is 20 atomic % or more, and the total is 100 atomic %. (14) The total of Ta and Nb of 7 at% or more is 20 at%
or more than 80 atomic % and 2 atomic % or more of Ni and 7
Contains atomic % or less of P, with the substantial balance being Fe and C
A highly corrosion-resistant amorphous alloy in which the total amount of one or two types of o and Ni is 20 atomic % or more, and the total is 100 atomic %. (15) Contains 15 atomic % or more of Ta, Ta, Zr, C
The total of one or more elements selected from the group r and Ta is 20 atomic % or more and less than 80 atomic %, contains 2 atomic % or more Ni, 7 atomic % or less P, and is substantially A highly corrosion-resistant amorphous alloy in which the balance of one or two of Fe and Co and Ni is 20 atomic %, and the total is 100 atomic %. (16) Contains 7 atomic % or more of Ta, the total of Ta and Nb is 16 atomic % or more, and contains one or more elements selected from the group of Ti, Zr, and Cr, and Ta and Nb. The total is 20 at% or more and less than 80 at%, and further 2 at%
Contains the above Ni and 7 atomic % or less of P, and the total of the substantial balance of one or two of Fe and Co and Ni is 20
A highly corrosion-resistant amorphous alloy with a total content of at least 100 at%.