JP2016113647A - Production method of stainless material coated with metal plating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of a stainless material coated with metal plating, which forms a thin and uniform metal plating layer having excellent adhesion on a stainless steel material, independently on individual difference and variation of thickness of an oxide film formed on the surface of the stainless steel material, and can improve corrosion resistance, conductivity, smoothness or the like of the stainless material coated with metal plating.SOLUTION: A production method of a stainless material 1 coated with metal plating includes an acidification step for treating a stainless steel material 10 with an acidic solution, an etching step for treating the stainless steel material 10 with an etching agent after the acidification step, and a modification step for modifying the surface of the stainless steel material 10 to a surface suitable for metal plating after the etching step.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing a metal plating coated stainless steel material.

  Conventionally, as an electrical contact material used for a connector, a switch, a printed wiring board, or the like, a metal plating coated stainless steel material in which a metal plating layer such as a gold plating layer is coated on the surface of a stainless steel material, or a surface-treated stainless steel material is used. ing.

  In order to improve the adhesion of the metal plating layer on the surface, the stainless steel material with the metal plating layer formed on the surface (hereinafter also referred to as a metal plating coated stainless steel material) is formed on the stainless steel material before forming the metal plating layer. In addition to forming a base nickel plating layer by applying a base nickel plating to the substrate, for example, as described in Patent Document 1, a technique for directly forming a metal plating layer on a stainless steel material without applying the base nickel plating Is also known. Further, as a surface-treated stainless steel material, for example, a stainless steel material in which a predetermined oxide film is formed on the surface is known as in Patent Document 2.

Japanese Patent Laid-Open No. 2008-4498 JP 2007-280664 A

  In the metal plating coated stainless steel, if the thickness of the metal plating layer on the surface is made too thin, the coverage of the metal plating layer is remarkably lowered, and the characteristics required for the metal plating layer cannot be obtained. On the other hand, the corrosion resistance is lowered due to exposure, but if the thickness of the metal plating layer on the surface is too thick, it is disadvantageous in terms of cost. Therefore, in the metal plating coated stainless steel material, in order to solve these problems, the metal plating layer formed on the surface is required to have a thin and uniform thickness.

However, the technique disclosed in Patent Document 1 has a problem that the thickness of the metal plating layer formed on the stainless steel material becomes non-uniform, and the adhesion and corrosion resistance of the metal plating layer are lowered. That is, the surface of the stainless steel material is exposed to an air atmosphere, and a natural oxide film is generated. This oxide film has a different thickness for each individual stainless steel material, and even within the same surface of one stainless steel material. There are variations. In the technique of the above-mentioned patent document 1, since the variation of the oxide film generated on the surface of the stainless steel material used as the substrate is not considered, the metal plating layer formed on the stainless steel material has a thickness corresponding to the variation of the thickness of the oxide film. Becomes non-uniform, and a portion where plating does not precipitate occurs, or peeling of the metal plating layer occurs. As a result, the coverage of the metal plating layer is lowered, and there is a problem that characteristics required for the metal plating layer such as corrosion resistance, conductivity and smoothness are lowered.
Moreover, in the technique disclosed in the above-mentioned Patent Document 2, as a surface treatment to the stainless steel material, a cathodic electrolytic treatment is performed on the stainless steel material, thereby forming a predetermined oxide film on the stainless steel material, thereby preventing the corrosion resistance of the stainless steel material. However, when using a stainless steel material that is complex in shape and cannot be energized uniformly, or a stainless steel material that is difficult to energize due to the high electrical resistance of the base material, the energization of the stainless steel material becomes uneven and formed. There is a problem that the thickness of the oxide film is non-uniform.

  The present invention relates to a metal plating layer formed on a stainless steel material, regardless of individual differences and variations in the thickness of the oxide film formed on the surface of the stainless steel material. It aims at providing the manufacturing method of the metal plating coating stainless steel material which can improve the corrosion resistance, electroconductivity, smoothness, etc. of plating coating stainless steel material.

  In order to complete the present invention, the present inventors have found that the above object can be achieved by treating a stainless steel material with an acid solution, then treating with an etching solution, and then performing a treatment for modifying the surface. It came.

  That is, according to the present invention, an acid treatment step of treating a stainless steel material with an acidic solution, an etching step of treating the stainless steel material after the acid treatment step with an etching treatment agent, and a stainless steel material after the etching step. There is provided a method for producing a metal plating-coated stainless steel material, which has a modification step for modifying the surface to a state suitable for metal plating treatment.

In the production method of the present invention, by treating the stainless steel material with the acidic solution, an oxide film having a lower density than the passive film before the treatment with the acidic solution is formed on the surface of the stainless steel material. preferable.
In the production method of the present invention, by treating the stainless steel material with the acidic solution, the oxide film including the passive film on the surface of the stainless steel material may be thickened compared to before the acid treatment step. preferable.
In the production method of the present invention, it is preferable to use a solution containing any one of hydrochloric acid, ammonium hydrogen fluoride, sulfuric acid and nitric acid, or a mixture thereof as the acidic solution.
In the production method of the present invention, it is preferable to use any one of nitric acid and sulfuric acid or a mixture thereof as the etching treatment agent.
In the modification step of the production method of the present invention, it is preferable to perform a treatment of immersing the stainless steel material in a sulfuric acid aqueous solution having a sulfuric acid concentration of 20 to 25% by volume at a temperature of 50 to 70 ° C. for 5 to 600 seconds. .
In the manufacturing method of this invention, it is preferable to further have the metal plating process which performs a metal plating process to the said stainless steel material after the said modification | reformation process.

  According to the present invention, the stainless steel material is treated with an acidic solution, then intentionally etched with an etching treatment agent, and then subjected to a treatment for modifying the surface. As a result, the surface of the stainless steel material to be used The thickness of the oxide film can be made uniform, and the metal plating layer formed on the stainless steel material can be excellent in adhesion, thin and uniform in thickness. Thereby, the manufacturing method of the metal plating coating | cover stainless steel material excellent in the characteristic requested | required of metal plating layers, such as corrosion resistance, electroconductivity, and smoothness, can be provided.

FIG. 1 is a cross-sectional view of a metal plating coated stainless steel material according to an embodiment of the present invention. Drawing 2 is a figure for explaining each process for manufacturing a metal plating covering stainless steel material. FIG. 3 is a diagram for explaining a method of measuring the contact resistance of the metal plating-coated stainless steel material 1 obtained in Examples and Comparative Examples.

Hereinafter, the manufacturing method of the metal plating coating | cover stainless steel material 1 of this embodiment is demonstrated.
The metal plating-coated stainless steel material 1 of the present embodiment includes an acid treatment process for treating a stainless steel material with an acid solution, an etching process for treating the stainless steel material after the acid treatment process with an etching treatment agent, and after the etching process. The surface of the stainless steel material is formed by subjecting the surface of the stainless steel material to a state suitable for metal plating treatment, and the metal plating is performed on the oxide film 11 covering the stainless steel material 10 as shown in FIG. Layer 20 is formed.

<Acid treatment process>
First, in this embodiment, the stainless steel material 10 used as the board | substrate of the metal plating coating | cover stainless steel material 1 is prepared. It does not specifically limit as a board | substrate, Stainless steel materials, such as SUS316L, SUS316, SUS304, are mentioned. In addition, examples of the stainless steel material include martensite, ferrite, and austenite, and austenitic stainless steel is particularly preferable. The shape of the stainless steel material 10 is not particularly limited and can be appropriately selected depending on the intended use. For example, a conductive metal part or plate processed into a linear shape or plate shape is processed into an uneven shape. It is possible to use a material that has been processed into a necessary shape according to the application such as a conductive member, a part of an electronic device that has been processed into a spring shape or a cylindrical shape. Further, the length (width), thickness (diameter) and thickness (plate thickness) of the stainless steel material 10 are not particularly limited, and can be appropriately selected according to the intended use.

In this embodiment, about the stainless steel material 10 prepared in this way, the acid treatment process processed with an acidic solution is managed and managed on predetermined conditions. In the present embodiment, by performing an acid treatment step, an oxide film 11 having a lower density than the passive film existing on the surface of the stainless steel material 10 before the treatment with the acidic solution is formed on the surface of the stainless steel material 10. Can do. As a method for forming such a low-density oxide film 11, the stainless steel material 10 is treated with an acidic solution, so that the surface of the stainless steel material 10 is identified from the passive film existing before the treatment with the acidic treatment liquid. There is a method of removing the above components and forming the oxide film 11. As the specific component is not particularly limited, iron oxide in the passivation film (FeO, _Fe 2 _{O 3),} and the like. Alternatively, as a method of forming the low-density oxide film 11, the stainless steel material 10 is treated with an acidic solution, so that at least one of the passive films existing on the surface of the stainless steel material 10 before the treatment with the acidic solution is performed. There is a method of removing the portion and forming the oxide film 11 as a new oxide film on the surface of the stainless steel material 10.
In the present embodiment, by forming such an oxide film 11, as shown in FIG. 2, an oxide film 11 thicker than an oxide film including a passivated film existing before the treatment with an acidic solution is formed. In this case, as a result, most of the oxide film on the surface of the stainless steel material 10 is increased. FIG. 2 shows that the untreated stainless steel material 10 is subjected to an acid treatment process in which it is treated with an acidic solution, an etching process, a reforming process in which the metal plating process is modified to a state suitable for metal plating treatment, and a metal plating process. It is a figure which shows an example of a mode that is formed. In addition, in FIG. 2, about the stainless steel material 10 which passed through the acid treatment process processed with an acidic solution, the stainless steel material 10 which passed through the etching process, and the stainless steel material 10 which passed through the modification process modified to a state suitable for metal plating treatment, Each graph was measured with a scanning Auger electron spectrometer (AES), and a graph showing changes in atomic concentrations (at%) of oxygen (O) and iron (Fe) is shown. In FIG. 2, the vertical axis indicates the atomic concentration of oxygen (O) or iron (Fe), and the horizontal axis indicates the depth measured from the surface of the stainless steel material 10 using a scanning Auger electron spectrometer (AES).

  In the present embodiment, the prepared stainless steel material 10 (described as “untreated” in FIG. 2) is treated on the surface as shown in FIG. An oxide film 11 can be formed. That is, in the example of FIG. 2, referring to the graph obtained by measurement with a scanning Auger electron spectrometer (AES), the atomic concentration of oxygen (O) from the surface of the stainless steel material 10 is an atom of iron (Fe). When the thickness of the oxide film 11 is set to a depth smaller than the concentration, the thickness of the oxide film 11 is 4.6 nm in an unprocessed state, but becomes 19 nm through a process with an acidic solution. Increase the film thickness.

  In the present embodiment, as described above, the oxide film 11 can be made uniform by forming the oxide film 11 using an acidic solution. That is, the untreated stainless steel material 10 has a non-uniform thickness of the passive film, as shown in FIG. The portion where the dynamic membrane is thick is difficult to oxidize. In contrast, when the above-described oxide film 11 is formed by intentionally oxidizing the surface of the stainless steel material 10 using an acidic solution, a portion of the stainless steel material 10 that is easily oxidized (passive film is While the increase in the thickness of the oxide film 11 formed in the thin portion proceeds, the increase in the thickness of the oxide film 11 formed in the portion that is difficult to oxidize (the portion where the passive film is thick) is suppressed. As a result, the entire surface of the stainless steel material 10 is oxidized to the same extent, and the thickness of the oxide film 11 on the stainless steel material 10 is considered to be uniform.

  In this embodiment, the oxide film 11 formed by the acid treatment process treated with an acidic solution has a characteristic that it can be removed relatively easily by an etching agent in an etching process described later. This is considered to be because the oxide film 11 formed by the acid treatment step of treating with an acidic solution has a low density to the extent that it can be peeled off with a cellophane tape. In this embodiment, the thickness of the oxide film 11 on the surface of the stainless steel material 10 can be intentionally made uniform by performing the acid treatment step and the etching step for treating with such an acidic solution. Thereby, according to this embodiment, it becomes possible to form a good metal plating layer 20 on the obtained coated stainless steel material 1, and the corrosion resistance, conductivity, smoothness, and the like required for the metal plating layer 20. An excellent metal plating coated stainless steel material 1 can be manufactured.

  The acid solution used in the acid treatment step treated with the acid solution is not particularly limited as long as the oxide film 11 can be reduced in density to the extent that it can be peeled off with a cellophane tape. It is preferable to use any one of ammonium hydrogen fluoride, sulfuric acid, and nitric acid, or a mixture thereof, and hydrochloric acid is particularly preferable.

  In the acid treatment step of treating with an acidic solution, the surface of the stainless steel material 10 can be oxidized by bringing the aqueous solution of the acidic solution into contact with the stainless steel material 10, but the concentration of the acidic solution in the aqueous solution is preferably 1 It may be adjusted to a concentration suitable for use depending on the kind of acidic solution. The concentration when treating with a hydrochloric acid solution is preferably 10 to 35 wt%, more preferably 15 to 25 wt%. By setting the concentration of the acidic solution in the above range, the surface of the stainless steel material 10 can be appropriately oxidized.

  As a method of bringing the stainless steel material 10 into contact with the acidic solution, any method can be used as long as the oxide film 11 can be appropriately formed with a uniform thickness as much as possible. The method of immersing the stainless steel material 10 in the aqueous solution of the acidic solution, A method of spraying an aqueous solution of an acidic solution can be used.

  When the stainless steel material 10 is immersed in an aqueous solution of an acidic solution, the temperature of the aqueous solution is preferably 40 to 80 ° C, more preferably 50 to 65 ° C. Furthermore, the time for immersing the stainless steel material 10 in the aqueous solution of the acidic solution is preferably 5 to 120 seconds, more preferably 10 to 60 seconds.

<Etching process>
Next, an etching agent is brought into contact with the stainless steel material 10 on which the oxide film 11 has been formed by the acid treatment process, whereby the etching process for reducing the oxide film 11 is performed as shown in FIG.

  In the present embodiment, the stainless steel material 10 that has been subjected to the acid treatment step is managed by performing the treatment in contact with the etching agent under predetermined conditions as described above, so that the oxide film 11 on the surface as shown in FIG. Can be uniformly reduced. That is, in the example shown in FIG. 2, referring to the graph obtained by measurement with a scanning Auger electron spectrometer (AES), the atomic concentration of oxygen (O) is iron (Fe) from the surface of the stainless steel material 10. When the thickness of the oxide film 11 is set to a depth smaller than the atomic concentration, the thickness of the oxide film 11 is 19 nm in the state after the acid treatment process, but is reduced to 9.2 nm through the etching process. Film.

  Although it does not specifically limit as an etching agent used at an etching process, It is preferable to use any 1 type or a mixture thereof among nitric acid and a sulfuric acid, and nitric acid is especially preferable.

  In the etching step, a part of the oxide film 11 on the surface of the stainless steel material 10 can be removed by bringing the aqueous solution of the etching agent into contact with the stainless steel material 10, but the concentration of the etching agent in the aqueous solution is preferably 5 to 30 wt. %, More preferably 10 to 25 wt%. By setting the concentration of the etching agent in the above range, the oxide film 11 of the stainless steel material 10 can be appropriately reduced, and the thickness of the oxide film 11 remaining on the stainless steel material 10 can be made uniform.

  As a method of bringing the stainless steel material 10 into contact with the etching agent, any method can be used as long as the oxide film 11 can be appropriately reduced in thickness as uniform as possible. The method of immersing the stainless steel material 10 in the aqueous solution of the etching agent, the stainless steel material 10 For example, a method of spraying an aqueous solution of an etching agent can be used.

  When the stainless steel material 10 is immersed in an aqueous solution of an etching agent, the temperature of the aqueous solution is preferably 20 to 60 ° C, more preferably 25 to 40 ° C. Furthermore, the time for immersing the stainless steel material 10 in the aqueous solution of the etching agent is preferably 1 to 30 seconds, more preferably 2 to 15 seconds.

  In the present embodiment, when a part of the oxide film 11 is removed in the etching process, the ground iron of the stainless steel material 10 (the base portion that is not oxidized and does not become the oxide film 11 in the stainless steel material 10) is exposed. It is desirable not to do so. That is, when the ground iron of the stainless steel material 10 is exposed, the exposed portion comes into contact with oxygen in the air or oxygen in the water, and a new oxide film 11 is naturally generated. In this embodiment, the oxide film 11 that is naturally generated is likely to have a non-uniform thickness. Therefore, in the present embodiment, the oxide film 11 is reduced in the etching process to such an extent that the ground iron of the stainless steel material 10 is not exposed. The new oxide film 11 is prevented from being naturally generated on the stainless steel material 10, and the thickness of the oxide film 11 can be made uniform.

<Reforming process>
Next, the stainless steel material 10 in which the oxide film 11 is reduced by the etching process is subjected to a modification process for modifying the surface oxide film 11 to a state suitable for metal plating. In the present embodiment, a stainless steel material 10 covered with an oxide film 11 as shown in FIGS.

  As a state suitable for metal plating treatment, Cr / O value (Cr / O molar ratio) and Cr / Fe value (Cr / Fe molar ratio) by Auger electron spectroscopy analysis on the surface of the oxide film 11 are as follows. The state adjusted to the range is mentioned. That is, the Cr / O value is preferably in the range of 0.05 to 0.2, more preferably 0.05 to 0.15. The Cr / Fe value is preferably in the range of 0.5 to 0.8, more preferably 0.5 to 0.7.

  In the present embodiment, the metal plating layer formed on the oxide film 11 by controlling the Cr / O value and the Cr / Fe value by Auger electron spectroscopy analysis of the surface of the oxide film 11 in the stainless steel material 10 to the above ranges. 20 (that is, the ratio of the area covered with the metal plating layer 20 on the surface on which the metal plating layer 20 is formed on the oxide film 11) is improved, and the adhesion and corrosion resistance are excellent. .

  In the present embodiment, the Cr / O value and the Cr / Fe value by Auger electron spectroscopy can be measured, for example, by the following method. That is, first, the surface of the oxide film 11 is measured using a scanning Auger electron spectrometer (AES), and the atomic% of Cr, O, and Fe on the surface of the oxide film 11 is calculated. Then, the surface of the oxide film 11 is subjected to measurement with a scanning Auger electron spectrometer at five locations, and the obtained results are averaged to obtain a Cr / O value (Cr atomic% / O atomic%). ) And Cr / Fe value (atomic% of Cr / atomic% of Fe). In this embodiment, among peaks obtained by measurement using a scanning Auger electron spectrometer, a peak at 510 to 535 eV is a Cr peak, a peak at 485 to 520 eV is an O peak, and 570 The atomic% of Cr, O, and Fe is measured by setting the peak at ˜600 eV as the peak of Fe and the total of these Cr, O, and Fe as 100 atomic%.

  In the reforming step for reforming to a state suitable for the metal plating treatment of the present embodiment, as a method of setting the Cr / O value and the Cr / Fe value by Auger electron spectroscopy analysis in the oxide film 11 of the stainless steel material 10 as the above ranges. For example, a method of immersing the stainless steel material 10 that has undergone the etching step in an aqueous sulfuric acid solution can be mentioned.

  When the stainless steel material 10 is immersed in the sulfuric acid aqueous solution in the modification step for modifying the metal plating to a state suitable for the metal plating treatment, the sulfuric acid concentration of the sulfuric acid aqueous solution is preferably 20 to 25% by volume. Moreover, the temperature at the time of immersing the stainless steel material 10 becomes like this. Preferably it is 50-70 degreeC, More preferably, it is 60-70 degreeC. Furthermore, the time for immersing the stainless steel material 10 in the sulfuric acid aqueous solution is preferably 3 to 600 seconds, more preferably 5 to 300 seconds.

  According to the present embodiment, when the method of immersing the stainless steel material 10 in the sulfuric acid aqueous solution is used in the reforming step for reforming to a state suitable for the metal plating treatment, the conditions for the sulfuric acid concentration, temperature, and immersion time are as described above. By setting the range, a part of the oxide film 11 on the surface of the stainless steel material 10 is removed, and the Cr / O value and the Cr / Fe value by the Auger electron spectroscopic analysis of the surface on the stainless steel material 10 are the ranges described above. It is possible to obtain a controlled stainless steel material surface.

  In the present embodiment, the stainless steel material 10 having the oxide film 11 reduced by the etching process is usually subjected to a reforming process for reforming it into a state suitable for the metal plating process described above, so that the oxide film 11 is usually further reduced. Reduce the film thickness. For example, in the example shown in FIG. 2, referring to a graph obtained by measurement with a scanning Auger electron spectrometer (AES), the atomic concentration of oxygen (O) is iron (Fe) from the surface of the stainless steel material 10. When the thickness of the oxide film 11 is set to a depth smaller than the atomic concentration, the thickness of the oxide film 11 is 9.2 nm after the etching process, but is changed to a state suitable for the metal plating process. The film thickness is reduced to 6.7 nm through a modification process.

<Metal plating process>
Next, the stainless steel material 10 that has been modified by a modification process that is modified to a state suitable for the metal plating process is subjected to metal plating to perform a metal plating process that forms a metal plating layer 20 on the surface.

  The metal constituting the metal plating layer 20 is not limited to the following, but is gold (Au), silver (Ag), palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium ( Ru), copper (Cu), tin (Sn), chromium (Cr), nickel (Ni), cobalt (Co), iron (Fe), phosphorus (P), boron (B), any one metal, Or the alloy containing at least 2 or more metals among these is mentioned, Among these, Au, Ag, Pd, or Pt is especially preferable. Moreover, the plating method for forming the metal plating layer 20 is not particularly limited, but plating including a salt such as Au, Ag, Pd, Pt, Rh, Ru, Cu, Sn, Cr, Ni, Co, Fe, P, B, etc. It is preferable to form by electroless plating using a bath.

  All of Au, Ag, Pd, Pt, Rh, Ru, Cu, Sn, Cr, and Ni mentioned here are noble metals having a large standard electrode potential and a common property that their contact resistance is low. have. Therefore, even when any of the above metals is used as the metal constituting the metal plating layer 20, the obtained metal plating coated stainless steel material 1 has the plating property, adhesion, corrosion resistance, and conductivity of the metal plating layer 20. Etc.

  The coverage of the metal plating layer 20, that is, the ratio of the area covered with the metal plating layer 20 on the surface of the oxide film 11 on which the metal plating layer 20 is formed is preferably 95% or more. . By setting the coverage of the metal plating layer 20 to 95% or more, pinholes in the metal plating layer 20 can be reduced, thereby preventing peeling of the metal plating layer 20 triggered by the pinholes. In addition, the corrosion resistance and conductivity of the obtained metal plating-coated stainless steel material 1 can be further improved.

  When gold is used as the main metal constituting the metal plating layer 20, the thickness of the metal plating layer 20 to be formed is preferably 2 to 20 nm, more preferably 2 to 10 nm. If the thickness of the metal plating layer 20 mainly made of gold is too thin, the uniform metal plating layer 20 is not formed on the oxide film 11 of the stainless steel material 10, and the corrosion resistance and conductivity of the metal plating coated stainless steel material 1 are lowered. There is a fear. On the other hand, if the thickness of the metal plating layer 20 mainly made of gold is too thick, it is disadvantageous in terms of cost.

  Moreover, when using silver as a main metal which comprises the metal plating layer 20, the thickness of the metal plating layer 20 to form becomes like this. Preferably it is 10-200 nm, More preferably, it is 20-100 nm. If the thickness of the metal plating layer 20 mainly made of silver is too thin, the uniform metal plating layer 20 is not formed on the oxide film 11 of the stainless steel material 10, and the corrosion resistance and conductivity of the metal plating coated stainless steel material 1 are lowered. There is a fear. On the other hand, when the thickness of the metal plating layer 20 mainly made of silver is too thick, it is disadvantageous in terms of cost.

  Alternatively, when a metal other than gold and silver is used as the main metal constituting the metal plating layer 20, the thickness of the metal plating layer 20 to be formed is preferably 2 to 20 nm, more preferably 2 to 10 nm. is there. If the thickness of the metal plating layer 20 made of such a metal is too thin, the uniform metal plating layer 20 is not formed on the oxide film 11 of the stainless steel material 10, and the corrosion resistance and conductivity of the metal plating coated stainless steel material 1 are lowered. There is a risk. On the other hand, when the thickness of the metal plating layer 20 made of such a metal is too thick, it is disadvantageous in terms of cost.

  As described above, the metal plating-coated stainless steel material 1 can be obtained by subjecting the stainless steel material 10 to metal plating by the metal plating step and forming the metal plating layer 20 on the oxide film 11.

  According to the present embodiment, for the stainless steel material 10 prepared as the base material, the thickness variation of the oxide film 11 naturally formed on the surface (that is, the thickness variation of the oxide film 11 based on the individual difference of the stainless steel material, Regardless of the thickness variation of the oxide film 11 in the same plane of the stainless steel material, the thickness of the oxide film 11 can be made uniform by the acid treatment step and the etching step performed with the acidic solution described above. Specifically, even if the thickness of the oxide film 11 varies with respect to the untreated stainless steel material 10, the oxide film 11 of the stainless steel material 10 is formed by an acid treatment process that is treated with an acidic solution, and then etched. By reducing the film thickness in the process, the thickness is adjusted to be uniform regardless of individual differences or variations in the thickness of the oxide film 11 formed on the surface of the stainless steel material 10.

  And in this embodiment, the oxide film 11 is metal-plated by performing the modification | reformation process reformed to the state suitable for the metal plating process mentioned above with respect to the oxide film 11 in which thickness was equalized in this way. It can be in a state suitable for processing, and the metal plating layer 20 having a thin and uniform thickness can be formed in the subsequent metal plating step.

  Thereby, in this embodiment, the oxide film 11 having a uniform thickness and suitable for the metal plating process is formed regardless of the variation of the oxide film 11 generated on the surface of the stainless steel material 10. A thin and uniform metal plating layer 20 is formed. As a result, according to this embodiment, the metal plating coated stainless steel material 1 excellent in the adhesion and corrosion resistance of the metal plating layer 20 can be manufactured.

  Further, as described above, the metal plating-coated stainless steel material 1 of the present embodiment can be used as an electrical contact material used for a connector, a switch, a printed wiring board, or the like, but can also be used as a fuel cell separator. . A fuel cell separator is used as a member of a fuel cell constituting a fuel cell stack, and has a function of supplying fuel gas and air to an electrode through a gas flow path, and a function of collecting electrons generated at the electrode It is. When the metal plating coated stainless steel material 1 is used as a fuel cell separator, the stainless steel material 10 has a surface on which irregularities (gas flow paths) that function as fuel gas or air flow paths are formed in advance. The stainless steel material 10 is prepared and subjected to each of the acid treatment step, the etching step, the reforming step, and the metal plating step, which are modified to a state suitable for the metal plating treatment. preferable. A method for forming the gas flow path is not particularly limited, and for example, a method of forming by a press working can be mentioned.

  Normally, when a stainless steel material having a metal plating layer formed on the surface is used as a fuel cell separator, the fuel cell separator is exposed to a high-temperature and acidic atmosphere in the fuel cell. When the coverage of the plating layer is low, the corrosion of the stainless steel material that is the base material progresses early, which increases the electrical resistance value due to the corrosion products generated on the surface of the stainless steel material, and causes the electrons generated at the electrodes. There is a problem that the function as a fuel cell separator that collects the current is reduced.

  On the other hand, according to the metal plating coated stainless steel material 1 of the present embodiment, as described above, the metal plating layer 20 having excellent coverage and adhesion is formed. Can also be suitably used.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.
In addition, the evaluation method of the metal plating coating | cover stainless steel material 1 obtained in the Example and the comparative example is as follows.

<Measurement of contact resistance value>
About the metal plating coating | cover stainless steel material 1, the contact resistance value was measured using the measuring system shown in FIG. The measuring system shown in FIG. 3 includes two metal plating coated stainless steel materials 1, a copper electrode 2 coated with gold plating, a voltmeter 3, and an ammeter 4. Specifically, the contact resistance value is measured by first processing the metal plating coated stainless steel material 1 into a size of 20 mm in width, 20 mm in length, and 0.1 mm in thickness, and as shown in FIG. A stack of two stainless steel materials 1 was sandwiched and fixed from both sides by a copper electrode 2 coated with gold plating to obtain a measurement system shown in FIG. Next, the contact resistance value of the test piece was measured using a resistance meter (manufactured by Hioki Electric Co., Ltd., milliohm high tester 3540) while applying a constant load to the copper electrode 2 coated with gold plating.

Example 1
First, a SUS316L plate was prepared as the stainless steel material 10. Next, the prepared stainless steel material 10 was washed with water and degreased, and then immersed in an aqueous hydrochloric acid solution having a hydrochloric acid concentration of 20 wt% under conditions of a temperature of 60 ° C. and an immersion time of 60 seconds (acid treatment step of treating with an acidic solution). Treatment), an oxide film 11 was formed on the surface of the stainless steel material 10.

  Next, after the stainless steel material 10 on which the oxide film 11 is formed is washed with water, a treatment (etching treatment) is performed in which the nitric acid concentration is immersed in an aqueous nitric acid solution having a concentration of 20 wt% at a temperature of 30 ° C. and an immersion time of 3 seconds. Thus, the oxide film 11 on the surface of the stainless steel material 10 was reduced.

  Thereafter, the stainless steel material 10 with the oxide film 11 reduced is washed with water, and then immersed in a sulfuric acid aqueous solution having a sulfuric acid concentration of 25% by volume at a temperature of 70 ° C. and an immersion time of 5 seconds (suitable for metal plating treatment). The oxide film 11 on the surface of the stainless steel material 10 was reformed by performing a reforming process for reforming it to a new state.

  Then, after washing the stainless steel material 10 with the modified oxide film 11 with water, using an electroless palladium alloy plating bath, electroless plating is performed under conditions of 38 ° C., pH 5.5, and 4 minutes (metal plating process). ), A metal plating layer 20 having a thickness of about 40 nm was formed on the oxide film 11 to obtain a metal plating coated stainless steel material 1.

  Next, contact resistance of the obtained metal plating coated stainless steel material 1 was measured according to the method described above. Furthermore, the metal plating-coated stainless steel material 1 was subjected to a heat treatment for 1 hour in an environment at a temperature of 250 ° C., and the contact resistance was measured again. The results are shown in Table 1.

<< Comparative Example 1 >>
A metal-plated coated stainless steel material was prepared in the same manner as in Example 1 except that the treatment for immersing the stainless steel material 10 in an aqueous hydrochloric acid solution (treatment in the acid treatment step using an acidic solution) was not performed. Measurements were made. The results are shown in Table 1.

  From the results of Table 1, in Example 1 in which the metal plating coated stainless steel material 1 was manufactured through the acid treatment step treated with the acid solution described above, the etching step, and the modification step modified to a state suitable for the metal plating treatment. The contact resistance value before heat treatment and the contact resistance value after heat treatment were both 4.1 mΩ, and it was confirmed that the contact resistance value did not change even when heat treatment was applied. In addition, in the metal plating coated stainless steel material 1, when the metal plating layer 20 is not sufficiently formed and a part of the stainless steel material 10 is exposed, the exposed portion of the stainless steel material 10 is treated with chromium oxide by heat treatment. Or, iron oxide is formed, and the contact resistance value of the metal plating coated stainless steel material 1 is increased. On the other hand, in the metal plating coated stainless steel material 1 of Example 1, even when heat treatment was applied, the contact resistance value did not increase, so that the gold plating layer was well formed without exposing the stainless steel material 10. It has been confirmed.

  On the other hand, from the results of Table 1, in Comparative Example 1 in which the metal plating coated stainless steel material was produced without passing through the acid treatment step of treating with an acidic solution, the contact resistance value before the heat treatment was 5.8 mΩ, The contact resistance value after the heat treatment was 60.1 mΩ, and it was confirmed that the contact resistance value was increased by the heat treatment. Thereby, since the metal plating coating stainless steel material 1 produced without passing through the process processed with an acidic solution raises the contact resistance value resulting from exposure of the stainless steel material 10, formation of an alloy plating layer is insufficient. It was confirmed that.

DESCRIPTION OF SYMBOLS 1 ... Metal plating coating stainless steel 10 ... Stainless steel material 11 ... Oxide film 20 ... Metal plating layer

Claims (7)

An acid treatment step of treating stainless steel with an acidic solution;
Etching step of treating the stainless steel material after the acid treatment step with an etching treatment agent,
A method for producing a metal-plated coated stainless steel material, comprising: a modifying step of modifying the surface of the stainless steel material after the etching step into a state suitable for metal plating treatment.   The said acid treatment process WHEREIN: By processing the said stainless steel material with the said acidic solution, a low density oxide film is formed on the surface of a stainless steel material from the passive film which exists before the process with the said acidic solution. The manufacturing method of the metal plating coating | cover stainless steel material of description.   3. In the acid treatment step, the stainless steel material is treated with the acidic solution, thereby increasing the thickness of the oxide film including the passive film on the surface of the stainless steel material as compared with that before the acid treatment step. The manufacturing method of the metal plating coating | cover stainless steel material of description.   The metal plating-coated stainless steel production according to any one of claims 1 to 3, wherein a solution containing any one of hydrochloric acid, ammonium hydrogen fluoride, sulfuric acid and nitric acid or a mixture thereof is used as the acidic solution. Method.   The method for producing a metal-plated coated stainless steel according to any one of claims 1 to 4, wherein any one of nitric acid and sulfuric acid or a mixture thereof is used as the etching treatment agent.   The said modification | reformation process WHEREIN: The process which immerses the said stainless steel material in the sulfuric acid aqueous solution whose sulfuric acid concentration is 20-25 volume% at the temperature of 50-70 degreeC for 5 to 600 second is performed. The manufacturing method of the metal plating coating | cover stainless steel material as described in a term.   The method for producing a metal-plated coated stainless steel according to any one of claims 1 to 6, further comprising a metal plating step of performing a metal plating process on the stainless steel material after the reforming step.

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