JP2008088455A - Titanium or titanium alloy material subjected to noble metal plating - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a titanium material whose surface can be uniformly subjected to noble metal plating, and which is particularly suitable for application requiring corrosion resistance and low contact resistance, further, to provide a titanium material whose surface is uniformly subjected to noble metal plating, and to provide a method for producing the same. <P>SOLUTION: The titanium material for noble metal plating is characterized in that the average value of C and N detected upon analysis in a depth range of 5 to 30 nm (expressed in terms of SiO<SB>2</SB>) from the outermost surface by XPS (analysis area 800 μmϕ) is ≤5 at.%, respectively. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to titanium or titanium alloy material for precious metal plating (hereinafter, titanium or titanium alloy material is referred to as “titanium material”). The present invention also relates to a titanium material on which noble metal plating has been applied, which is particularly suitable for applications requiring corrosion resistance and low contact resistance. Furthermore, this invention relates to the manufacturing method of the titanium material in which the noble metal plating was given.

Titanium materials are particularly superior in that they have high corrosion resistance, and today, taking advantage of these properties, in addition to civilian fields such as medicine / health, decoration, sports / leisure, aviation / space, chemistry, electricity, architecture / civil engineering, It is used in many industrial fields such as transportation and military. Titanium, on the other hand, has a relatively low contact resistance compared to copper and the like, and further has a property of easily forming an insulating passive film (oxide film) on the surface. For this reason, the titanium material is mainly used for corrosion resistance and has not been used for applications requiring conductivity.
However, in recent years, titanium has been attracting attention as a conductive application in an environment where the corrosion resistance is severe. In order to meet such demands, it is considered to be one of effective means to compensate for the weak point of high contact resistance and to apply precious metal plating such as gold plating on the surface of titanium material for the purpose of further improving corrosion resistance. .

However, as described above, the titanium material has a property that it is easy to form an oxide film on the surface, and this reduces the adhesion to the plating layer. It was difficult to form. Therefore, a pretreatment for improving the adhesion of the plating to the titanium material has been proposed so far.
For example, Japanese Patent Laid-Open No. 3-47991 contains a refractory metal element, characterized in that a nickel layer is subjected to cathode plating on a surface etched in an acidic solution such as nitric acid, hydrochloric acid, or hydrofluoric acid. A method for electroplating a nickel layer on a titanium base alloy is described.
JP-A-6-93494 discloses anodizing a titanium material at a voltage of 10 to 300 V in an electrolytic bath containing at least one of formic acid, acetic acid, or a salt thereof. A plating pretreatment characterized by the following is described: In this document, a copper plating layer is formed by electroplating as a specific example.

Precious metal plating such as gold plating has been used for decoration since ancient times. Today, it is used in various industrial applications for the purpose of imparting electrical conductivity, low contact resistance, corrosion resistance, solderability, wear resistance, smoothness and / or light reflectivity, especially in the field of electronic industry. It is useful. However, a technique for applying gold plating to a titanium material is not so much discovered from the investigation by the present inventor, and the following documents are found.
For example, although a gold plating technique for a titanium material by a plating method is not specifically disclosed, Japanese Patent Laid-Open No. 2001-29777 discloses an anode side for the purpose of improving the durability and cost reduction of a fuel cell separator. Alternatively, a metal plate in which a noble metal element film such as Au is disposed on at least one surface of the cathode-side conductive separator is disclosed, and titanium is disclosed as one of the materials of the metal plate. In this document, Au is formed in an island shape on titanium by rf sputtering, the area of each island-like noble metal element coating is 0.04 mm ^2, and the ratio of the total area is 50% in area ratio. An example is given.
Also, this is not related to the gold plating technique on the titanium material. However, in Japanese Patent Application Laid-Open No. 2004-296281, the surface area of the stainless steel plate is not affected by the gold plating, and the area ratio is 2.3 to 94%. A metal separator for a fuel cell, characterized by being coated, is disclosed. It is described that the gold coating is applied by a plating method.

Japanese Patent Laid-Open No. 3-47991 JP-A-6-93494 JP 2001-29777 A JP 2004-296281 A

  However, in these documents, the relationship between the titanium material and the gold plating is not sufficiently described, and in particular, the relationship between the corrosion resistance and the contact resistance when the titanium material is plated with gold is not yet elucidated in detail. . In addition, the appearance (decoration) is uniformly plated in the past, and even if it is evaluated as good plating, it is considerably mottled by microscopic observation by SEM, and in terms of having high corrosion resistance and low contact resistance, It was found that the plating was not sufficient. In addition to high corrosion resistance, titanium materials have characteristics such as low density and high strength, and are expected to be used in many industrial fields in the future. From the viewpoint of corrosion resistance and contact resistance, titanium materials It is useful to expand the possibilities of titanium material application fields by clarifying the relationship between gold and precious metal plating such as gold plating, and proposing a titanium material with high corrosion resistance and low contact resistance based on this relationship. Let's go.

  Then, this invention makes it a subject to provide the titanium material which can perform a noble metal plating uniformly on the surface especially suitable for the use as which corrosion resistance and low contact resistance are requested | required. Another object of the present invention is to provide a titanium material whose surface is uniformly precious metal plated. Furthermore, this invention makes it another subject to provide the manufacturing method of the titanium material by which the noble metal plating was uniformly given to the surface.

As a result of diligent examination of conditions for a titanium material suitable for noble metal plating, the present inventor directly plated the noble metal on a titanium material from which the above C (carbon) and N (nitrogen) components were removed as much as possible. It has been found that a surprisingly uniform noble metal plating is formed on the surface of the titanium material.
On the other hand, if the C and N concentration on the surface of the titanium material is high, C and N cannot be removed even if the wet pretreatment is sufficiently performed before the noble metal plating, and the noble metal plating is large when microscopically observed by SEM. It adheres as island-shaped unevenness and cannot secure low contact resistance. Particularly in this state, even if the precious metal plating is applied excessively, the precious metal plating is only excessively thickly attached, and the area of the portion where the plating is not attached is not reduced.

  In the case of a titanium cold-rolled material or the like, recrystallization annealing is performed after cold rolling, and since titanium is an active metal, annealing is performed in a non-oxidizing gas or in a vacuum. Therefore, it is considered that N and C components in the air are blocked under normal annealing conditions. However, the rolling oil used in the rolling process adheres to the surface of the titanium material, and if the rolling oil is not completely removed, the remaining oil decomposes and reacts with titanium during annealing, and the surface after annealing. The C and N components remain as certain compounds.

The present invention completed on the basis of the above knowledge, in one aspect, C and N detected when analyzed by XPS (analysis area 800 μmφ) in a depth range (SiO ₂ conversion) of 5 to 30 nm from the outermost surface. The average value is 5 at. % Of noble metal plating titanium material.

In another aspect of the present invention, there is provided a titanium material whose surface is directly plated with a noble metal, and an XPS (analysis area 800 μmφ) in a depth range (SiO ₂ conversion) of 5 to 30 nm from the outermost surface of the noble metal at a plated portion. The average values of C and N detected when analyzed by 2) are 2 at. % Titanium or less.

Further, the present invention, in yet another aspect, is a titanium material whose surface is directly plated with a noble metal, and is 1 μm ² or more in a field of view (15 × 20 μm) of an SEM image (magnification: 5,000 times) of a portion to be plated. This titanium material has no unplated portion forming the square.

  In yet another aspect of the present invention, a titanium material whose surface is directly plated with a noble metal, the noble metal being a titanium material that exists in the form of particles on the surface of the titanium material.

  In one Embodiment of this invention, the average particle diameter of the said particle | grain is 10-400 nm.

  In one embodiment of the present invention, the noble metal is an Au-Pd alloy.

In another aspect of the present invention, the average values of C and N detected when analyzed by XPS (analysis area 800 μmφ) in a depth range of 5 to 30 nm (converted to SiO ₂ ) from the outermost surface are each 2 at. It is a manufacturing method of the titanium material in which the noble metal plating was performed including the process of performing noble metal plating with respect to the surface of the titanium material which is% or less.

  In one embodiment of the present invention, the noble metal plating is performed by electroplating.

  ADVANTAGE OF THE INVENTION According to this invention, the titanium material which can perform a noble metal plating uniformly on the surface suitable for the use by which corrosion resistance and low contact resistance are requested | required especially can be provided.

Titanium material The composition of the titanium material that can be used in the present invention is not particularly limited, and may be appropriately selected depending on the application. For example, pure titanium (for example, JIS 1 to 3 types), corrosion resistance and strength Titanium alloys to which elements for improvement are added can also be used. Among these, pure titanium is preferable from the viewpoint of plating properties, corrosion resistance, and contact resistance.

The shape of the titanium material according to the present invention is not particularly limited. For example, the titanium material can be formed into a plate shape, a fiber shape, or a sponge shape, and can be further processed to be formed into a desired shape.
Moreover, in one Embodiment of this invention, it can also be set as the clad material formed by pinching | interposing another metal material with two plate-shaped titanium materials. Such a clad material is also included in the titanium material in the present invention. In particular, the cost can be reduced by combining with a metal material that is less expensive than a titanium material, such as stainless steel, iron, Al, and Cu.

In one embodiment, the titanium material according to the present invention capable of uniformly precious metal plating on the surface is analyzed by XPS (analysis area 800 μmφ) at a depth range (SiO ₂ conversion) of 5 to 30 nm from the outermost surface. The average values of C and N detected in each are 5 at. % Or less, preferably 5 at. % Or less. When normal pretreatment described later is applied to such a titanium material, the pretreated titanium material is analyzed by XPS (analysis area 800 μmφ) in a depth range (SiO ₂ conversion) of 5 to 30 nm from the outermost surface. The average value of C and N detected is 2 at. % Or less, preferably 1 at. % Or less.

The manufacturing methods C and N of the titanium material are not attached to the surface of the titanium material in the plating process or pretreatment, but are attached to the surface of the titanium material in the previous process. It is important to limit adhesion.
In general, the titanium material after cold rolling is subjected to a degreasing cleaning process in order to remove rolling oil. Then, it enters into an annealing process and is performed in a batch type furnace in non-oxidizing gas or vacuum.
The average value of C and N is 5 at. In order to obtain the titanium material of the present invention that is not more than%, it is necessary to sufficiently remove the rolling oil in the degreasing and washing step before annealing. This is because if not sufficiently removed, the rolling oil decomposes during annealing, and C and N of the rolling oil component react with the titanium material to generate C and N compounds on the surface.
However, the surface of the titanium material generally tends to be rough, and the rolling of titanium tends to generate metal powder during rolling compared to rolling of other metals. When the surface is rough, the rolling oil that has entered the convex portion of the surface, particularly the pit-like portion, cannot be sufficiently removed by simply immersing it in a cleaning solution or the like. In addition, when the degreasing and cleaning process is completed without removing the metal powder, oil remains between the metal powder and the material surface.
Therefore, in the degreasing and cleaning process, by enhancing the cleaning effect by stirring, vibration, brushing, ultrasonic treatment, etc., the oil content accumulated in the convex (pit-shaped) part of the surface, metal powder is removed, titanium material The oil content on the surface can be reduced. As a result, after batch-type annealing in a non-oxidizing gas or in vacuum, the average values of C and N are each 5 at. It is possible to obtain a titanium material having a surface of no more than%. After the degreasing and cleaning step, physical polishing or chemical polishing may be performed. However, since the number of steps increases, it is preferable that the degreasing and cleaning step is performed.
Moreover, even if it is only immersion in the degreasing washing process before annealing and polishing is performed after annealing, the average value of C and N is 5 at. It is possible to obtain a titanium material having a surface of less than or equal to%. However, since the C and N compounds are hard and difficult to dissolve in acids, it is difficult to remove them.
Depending on the application, it is possible to proceed to the next pretreatment step without annealing and with the titanium material after cold rolling.

The pre-treatment pre-treatment is an auxiliary treatment that is usually performed before any plating is performed, and when precious metal plating is applied to titanium, immersion degreasing → water washing → acid washing → water washing → activation treatment → Pre-treat in the order of water washing.
As described above, since C and N are not brought in in the plating process, the average value of C and N in the titanium material immediately before plating is 2 at. % Or less, preferably 1 at. It is important that the titanium material has a surface of less than or equal to%.
Before the pretreatment, the average values of C and N detected when analyzed by XPS (analysis area 800 μmφ) in a depth range (SiO ₂ conversion) of 5 to 30 nm from the outermost surface are 5 at. % Or less, preferably 5 at. In the case of a titanium material that is less than or equal to%, the above requirements can be sufficiently achieved by ordinary pretreatment. On the other hand, the average value of C and N detected when analyzed by XPS (analysis area 800 μmφ) at a depth range (SiO ₂ conversion) of 5 to 30 nm from the outermost surface in the stage before pretreatment is 5 atm. . Even in the case of a titanium material exceeding%, the above requirements can be achieved if the pretreatment is performed under conditions more severe than those of the normal pretreatment.
Examples of such pretreatment include a method of promoting an activation reaction by stirring, vibration, ultrasonic treatment, brushing, or the like in the activation treatment. Stirring includes methods such as stirring with a propeller and stirring with a water flow, but is not limited to these methods. By using ultrasonic waves, stirring is strengthened, and in addition to the C and N components on the surface of the titanium material, oxide films (TiO _{2 and the} like) and impurities are also effectively removed, so ultrasonic treatment is particularly advantageous. In addition, strengthening pickling such as increasing the pickling time is more effective when combined with the promotion of activation treatment.

In the degreasing process, attention should be paid to hydrogen embrittlement in the pretreatment process. From this viewpoint, the degreasing process is preferably performed by immersion degreasing rather than electrolytic degreasing that involves hydrogen generation. For example, it is immersed in a solution having a bath composition containing sodium hydroxide. In pickling, attention should be paid to the neutralization of the specimen after the degreasing treatment. For example, it is immersed in a liquid having a liquid composition containing sulfuric acid. As the activation treatment solution, it is preferable to use a hydrofluoric acid treatment solution in terms of removal of the passive film. For example, it is immersed in a treatment liquid having a bath composition containing ammonium hydrogen fluoride and an anionic surfactant. Washing with water is usually performed between the steps of immersion degreasing, pickling and activation treatment.
By performing the pretreatment, the average values of C and N on the surface of the titanium material can be reduced to about 2% each.

Precious metal plating In the present invention, “precious metal” refers to Au, Ag, and the platinum group (Ru, Rh, Pd, Os, Ir, Pt). In a preferred embodiment of the present invention, Au, Ru, Rh, Pd, Ir And the surface of the titanium material is plated with at least one kind of noble metal selected from the group consisting of Pt and Pt. In an advantageous embodiment of the invention, the plating film contains at least Au, preferably 50-100% by weight of Au, more preferably 80-100% by weight of Au. For example, Au plating or Au—Pd alloy plating in which Au is 90 to 100% by mass and Pd is 0 to 10% by mass. Such a plating film containing two or more elements in a desired weight ratio can be obtained, for example, by appropriately adjusting the ratio of each noble metal ion concentration in the plating bath, current density, stirring conditions, and the like.

  In the present invention, the noble metal is directly plated on the surface of the titanium material. That is, in the present invention, noble metal plating is performed on the titanium material without applying a base plating such as Ni. This is because when base plating lower than that of the noble metal is applied, the corrosion resistance is reduced and the plating is peeled off. For reasons of corrosion resistance. Further, the location where the noble metal plating is applied to the surface of the titanium material can be appropriately selected according to the application, and can be a part or all of the surface of the titanium material. However, the “part or all” as used herein is a concept judged with the naked eye, and is not judged by microscopic observation with an SEM or the like.

  Examples of methods for precious metal plating on titanium materials include vacuum plating, physical vapor deposition (PVD) and chemical vapor deposition (CVD), dry plating such as sputtering and ion plating, and wet plating such as electroplating and electroless plating. However, electroplating is preferred. This is because it is advantageous from the viewpoint of ease of control of the particle size and number of plating particles and cost (particularly, equipment costs). The surface treatment by electroplating has the advantage that the atmosphere does not need to be evacuated unlike dry plating, and the film forming speed is high. Moreover, when forming fine granular plating, electroplating is suitable.

The portion to be plated of the titanium material plated with the noble metal according to the present invention is uniformly formed, and in one embodiment, unplated in the field of view (15 × 20 μm) of the SEM image (magnification: 5,000 times). A square having a portion (that is, a portion to which noble metal is not attached) of 1 μm ² or more is not observed. In a preferred embodiment, a square in which the unplated portion is 0.25 μm ² or more is not observed. In a more preferred embodiment, a square in which the unplated portion is 0.04 μm ² or more is observed. Never happen.

  The initial contact resistance of the titanium material subjected to the noble metal plating according to the present invention, and the rate of increase of the contact resistance when the titanium material is exposed to a corrosive environment is mainly a microscopic area ratio in which the noble metal plating particles cover the titanium material surface. Depending on the (area ratio), the area ratio (theoretically, a range of 0% to 100% can be considered) should be at least 10%, preferably 15% in microscopic observation with an SEM. Is necessary to satisfy the desired corrosion resistance and contact resistance. On the other hand, even if the area ratio is too high, the effect of corrosion resistance tends to saturate and the cost is high, so it is preferably 10 to 95%, more preferably 30 to 95%, and even more preferably 40 to 80. %, Typically 60-70%.

  When the particle size of the plating particles is 340 nm or less, the initial contact resistance of the titanium material subjected to noble metal plating, and the rate of increase of the contact resistance when exposed to a corrosive environment are the particle size of the plating particles. It has been empirically found that it is almost independent of. When the particle size of the plating particles exceeds 340 nm, the adhesion of the plating starts to deteriorate significantly, so that the plating easily peels off under a corrosive environment and the increase in contact resistance is not preferable.

  Thus, if the particle size of the plating particles is 340 nm or less, the contact resistance and corrosion resistance hardly depend on the particle size. Therefore, if the area ratio of the noble metal is the same, the smaller the particle size of the plating particles is required. The amount of the precious metal deposited can be reduced, and the economy can be improved. For example, when the area ratio of the noble metal is the same, if the particle size can be reduced to 1/10, the amount of adhesion can be reduced to 1/10 while maintaining equivalent contact resistance and corrosion resistance.

Therefore, the number of the finest possible plating particles on the surface of the titanium material that can achieve the desired area ratio (for example, about 25,000 / μm ² to achieve the area ratio of 50% with the plating particles having a particle diameter of 5 nm) It is desirable that the particles be generated as uniformly as possible. However, according to the present invention, the average particle size of the plated particles can be 300 nm or less, and more preferably 100 nm or less. Preferably 50 nm or less, and 10 nm in the smallest case.

Specific production conditions of the titanium material subjected to the noble metal plating according to the present invention will be described by taking the case of using an electroplating method as an example. Examples of plating baths that can be used in the present invention include cyan baths (first gold cyanide and second gold cyanide) and non-cyan baths (inorganic gold sulfite and organic gold sulfite). Is preferably a non-cyan bath.
The particle size and number (area ratio) of the plating particles can be controlled by adjusting the distance between the anode and the cathode, the current density, the plating time, the temperature, and the stirring method. The distance between the electrodes is preferably 100 mm or less, and the distance between the electrodes is preferably as short as possible from the viewpoint that there is less unplating and plating particles are uniformly formed. The current density is preferably 0.1 to 0.5 A / dm ^{2 in the} sulfurous acid bath. If it is 0.5 A / dm ² or more, the plating may become rough and brittle. Although the plating time depends on the current density, it is preferably as short as possible from the viewpoint of the amount of plating adhesion, and is usually several seconds to several minutes, for example, 40 seconds or less. The temperature is preferably 50 to 60 ° C. in a sulfurous acid bath. The stirring is preferably performed by controlling the flow rate of the plating solution by changing the circulation flow rate of the plating solution.

In order to adjust the particle size and area ratio, it is necessary to pay particular attention to the distance between the electrodes, the stirring method, and the current density. In order to reduce the particle size, the distance between the electrodes and the current density are important.
In one embodiment of the present invention, for example, the distance between the anode and the cathode is preferably 10 mm to 100 mm. Here, the distance between the electrodes refers to the distance between the anode and the titanium material. Stirring is preferable in terms of increase in the number of particles (or area ratio).

After the post-treatment noble metal plating is applied to the surface of the titanium material, it is preferable from the viewpoint of adhesion to heat-treat in an inert atmosphere such as Ar, He, or Ne. In this heat treatment, it is more advantageous from the viewpoint of adhesion and contact resistance that the temperature is 250 ° C. or higher, preferably 300 to 350 ° C., and the time is several minutes or longer, preferably about 30 to 40 minutes.

  In one embodiment, a titanium material subjected to noble metal plating according to the present invention is a ratio of contact resistance before and after a corrosion test conducted by immersing in a sulfuric acid solution having a pH = 2 at a temperature of 90 ° C. for 168 hours (average contact resistance after the test). / Average contact resistance before the test) is 2.0 or less, preferably 1.5 or less, more preferably 1.3 or less, and most preferably 1.0. A value of 1.0 indicates that no increase in contact resistance is observed after the corrosion resistance test.

  In order to better understand the present invention and its advantages, examples of the present invention will be described below, but the present invention is not limited to these examples.

In all the comparative examples and examples of the test piece material, a plate-like cold rolled material of 0.1 mm thick pure titanium (JIS type 1) was used as the titanium material. About the material, the following three types which changed the degreasing washing conditions after cold rolling were prepared.
(A) The test piece was sufficiently immersed in a commercially available alkaline agent cleaning solution, and the surface was cleaned with a brush during the immersion (immersion time 60 seconds)
(B) The test piece was sufficiently immersed in a commercially available alkaline agent cleaning solution, but the surface was not cleaned with a brush (immersion time 60 seconds)
(C) The test piece was immersed in a commercially available alkaline cleaning solution, but the surface was not cleaned with a brush (immersion time: 10 seconds)
These three kinds of materials were annealed to obtain a titanium material before pretreatment.

For all pretreatment pretreatment before the titanium material according to the conditions described in Table 1, was pretreated in the order of immersion degreasing → water washing → pickling → water washing → activation → water washing.
However, the following three conditions with different conditions were used for the pickling / activation treatment.
(A) For pickling, the immersion time was 15 seconds, and in the activation treatment, the stirring force was increased using ultrasonic waves in the batch tank. (B) For pickling, the immersion time was 7 seconds, (C) Conditions for pickling, with a soaking time of 7 seconds, and with agitation that occurs naturally without forced stirring just by dipping in the batch tank

Table 2 shows a list of titanium materials and pretreatment conditions used in all comparative examples and examples.

Au—Pd alloy plating Next, Au—Pd alloy plating was performed on the surface of each pretreated test piece by electroplating. The plating bath conditions are as follows.
Bath type: sulfurous acid bath Bath composition: Au 4.0 g / L, Pd 2.0 g / L
pH: 9.05 to 9.10
Bath temperature: 50 ° C
Agitation of plating solution: Strong stirring Anode: Pt-Ti
Distance between anode and cathode: 50 mm
Current density: 0.4 A / dm ²
Plating time: 5 seconds

Post-treatment After that, heat treatment was performed at 350 ° C. for 30 minutes in an argon atmosphere on each test piece subjected to Au—Pd alloy plating.

Results FIG. 3 and FIG. 5 and FIG. The SEM image which shows the state of the Au-Pd alloy plating particle | grains of the test piece surface of 8 is shown as an example. For each plated test piece, the electrodeposition distribution, the average particle size [nm], the number of particles per unit area [pieces / μm ² ], the area ratio [%], the adhesion amount [mg / cm ² ] and The adhesion was examined. The results are shown in Table 3.

  SEM observation was performed at 5000 times and 50000 times magnification. The 5000 × photograph was used to observe the electrodeposition distribution of Au—Pd alloy plating. The photo of 50000 times was used to grasp the average particle diameter and the number of particles per unit area.

The electrodeposition distribution was determined as to whether or not there was any unplated portion forming a square of 1 μm ² or more in the field of view (15 × 20 μm) of the SEM image of 5,000 times selected arbitrarily at three locations. The case where the number of the unplated portions was 0 was marked with ◯, and the case where it was 1 or more was marked with x.

  The average particle size was determined by selecting 10 particles considered to be average from the field of view of a 50,000 times SEM image (1.5 × 2.0 μm) arbitrarily selected at three locations, and calculating the arithmetic average thereof.

  The number of particles per unit area was determined by counting the number of particles in a field of view (1.5 × 2.0 μm) of 50,000 times SEM images arbitrarily selected at three locations.

  As for the area ratio, it can be seen from the SEM image that the plating particles are almost spherical. Therefore, assuming that each plating particle is a true sphere, the average particle diameter and the unit area per unit area were determined only for the samples in which the determination of the electrodeposition distribution was ○. Calculated from the number of particles.

  The amount of adhesion was calculated from the value obtained by dissolving each test piece obtained in aqua regia, quantitatively analyzing the weight of Au and Pd contained in the solution using an inductively coupled plasma generation analyzer (ICP).

For adhesion, a tape peeling test was performed by scoring grid marks at 1 mm intervals on the gold-plated surface of each test piece obtained. Further, each test piece was arbitrarily bent by 180 ° to return to the original state, and a tape peeling test of the bent portion was performed. When there was no peeling at all, it was marked with ◯, and when it was partly, it was marked with ×.
In addition, the electrodeposition composition of the plating film is obtained by dissolving a test piece in aqua regia and measuring the weight of Au and Pb contained in the solution using an inductively coupled plasma emission spectrometer (ICP) (model SPS300 manufactured by Seiko Instruments). As a result of investigation, each test piece was found to be about 91 mass% Au and about 9 mass% Pd.

Moreover, in all Examples and Comparative Examples, X-ray photoelectron spectroscopic analysis (XPS, manufactured by ULVAC-PHI Co., Ltd.) of the titanium material surface after each step (before pretreatment and before gold plating (after pretreatment and after treatment)) (Type 5600MC sputtering rate: 1.2 nm / min in terms of SiO ₂ ) The results are shown in Table 4. The amounts of N and C shown in Table 4 are from 5 to 30 nm from the outermost layer for each sample. The average value is calculated by picking up the amount of each element every 1 nm from the XPS data obtained by the analysis.

Furthermore, the corrosion resistance test was performed with respect to each test piece, and the contact resistance before and after the test was examined. The corrosion resistance test was performed by immersing each test piece having a size of 40 × 50 mm in a sulfuric acid aqueous solution having a pH = 2 liquid amount of 350 cc at a temperature of 90 ° C. for 168 hours (one week).
The contact resistance was measured by applying a load to the entire surface of the sample as shown in FIG. A 40 × 50 mm sample was plated from above and below on a copper plate (10 mmt) of the same size with a 1.0 μm Ni underplating, and then a 0.5 μm Au-plated sample was put on and contacted, and 10 kg / cm ² with a load cell. The contact resistance when a current was passed at a current density of 100 mA / cm ² was measured by the 4-terminal method. (In this measurement method, the specific resistance of the copper plate and the titanium plate is also included, but here the value including this is taken as the contact resistance.)

  Moreover, Ti elution amount was measured from the Ti concentration in the sulfuric acid solution used in the corrosion resistance test. Specifically, 200 cc of liquid was collected after the corrosion resistance test, concentrated to 50 cc, and determined by ICP analysis.

The results of the contact resistance and corrosion resistance test are the ratios of the contact resistance before and after the corrosion test conducted by immersing in a sulfuric acid aqueous solution at pH = 2 at a temperature of 90 ° C. for 168 hours (average contact resistance after test / average contact resistance before test). Is 2.0 or less, and the case where there is no elution amount of Ti by the corrosion resistance test is indicated by ◯, and the case other than that is indicated by ×.
Table 5 shows the contact resistance and corrosion resistance test results.

The following can be confirmed from the results of the comparative example and the invention example.
・ If there is N or C on the surface of the titanium material before gold plating, noble metal can be deposited uniformly in all areas of 1 μm, and if the required characteristics (contact resistance, corrosion resistance) are evaluated, the contact resistance after the corrosion resistance test increases. To do.
-N and C on the surface of the titanium material can be almost removed by performing the treatment according to the present invention, and a uniform noble metal film that satisfies the required characteristics is formed.
FIGS. 5 and 6 show sputtering times (4 minutes 10 seconds and 25 minutes 0 seconds correspond to depths of 5 nm and 30 nm, respectively) when XPS analysis was performed on the objects to be plated of Invention Example 1 and Comparative Example 8 from the surface of the noble metal. The relationship between the element concentrations is shown as an example.

  In addition to the low density, high strength, high corrosion resistance, high melting point, etc., which are the original characteristics of the titanium material, the titanium material plated with the noble metal according to the present invention is said to have both high corrosion resistance and low contact resistance. it can. Therefore, the titanium material plated with the noble metal according to the present invention is particularly suitable for applications requiring high corrosion resistance and low contact resistance. For example, it can be used for separators for fuel cells, titanium electrodes, corrosion-resistant grounding bodies, and the like. it can.

No. 3 is a SEM image of 50,000 times and 5,000 times showing the state of the plated particles on the surface of the titanium material in No. 3. No. 5 is a SEM image of 50,000 times and 5,000 times showing the state of the plated particles on the surface of the titanium material in FIG. No. 8 is an SEM image of 50,000 times and 5,000 times showing the plating state of the titanium material surface in FIG. It is the schematic which shows the measuring method of contact resistance. It is a figure which shows a result when XPS analysis is carried out about the test piece of Invention Example 1. It is a figure which shows a result when an XPS analysis is performed on the test piece of Comparative Example 8.

Claims (8)

The average values of C and N detected when analyzed by XPS (analysis area 800 μmφ) in a depth range of 5 to 30 nm from the outermost surface (in terms of SiO ₂ ) are 5 at. % Precious metal plating titanium material. A titanium material whose surface is directly plated with a noble metal, which is detected when analyzed by XPS (analysis area 800 μmφ) in a depth range (SiO ₂ conversion) of 5 to 30 nm from the noble metal outermost surface at a plated portion The average value of N is 2 at. % Titanium material. There is one unplated part that forms a square of 1 μm ² or more in the field of view (15 × 20 μm) of the SEM image (magnification: 5,000 times) of the plated part, which is a titanium material directly plated with a noble metal Not titanium material.   The titanium material according to claim 2 or 3, wherein the surface of the titanium material is directly plated with a noble metal, and the noble metal is present in the form of particles on the surface of the titanium material.   The titanium material according to claim 4, wherein the average particle diameter of the particles is 10 to 400 nm.   The titanium material according to any one of claims 2 to 5, wherein the noble metal is an Au-Pd alloy. The average values of C and N detected when analyzed by XPS (analysis area 800 μmφ) in a depth range of 5 to 30 nm (in terms of SiO ₂ ) from the outermost surface are 2 at. A method for producing a titanium material that has been subjected to noble metal plating, including a step of performing noble metal plating on the surface of a titanium material that is not more than%.   The manufacturing method according to claim 7, wherein the noble metal plating is performed by electroplating.