JPH0211794A - Platinum plating method - Google Patents

Abstract

PURPOSE:To form a platinum plating with a good adhesive property on an Nb base material by subjecting the surface of the Nb base material successively to a surface roughening treatment, electrolytic polishing treatment, activating treatment, etc., then to platinum plating. CONSTITUTION:The surface of the Nb or Ta base material is mechanically processed by a sandblasting treatment, etc., to uniformly form a satin rugged surface thereon. The surface is then electrolyzed at about 0.1-10A/dm<2> by using an electrolytic polishing liquid consisting of ethanol, ethylene glycol, silicon fluoride, and water by which the rough rugged surface obtd. by the machining is finished to the much finer ruggedness. After the base material surface is activated by using an alkaline soln. etc., the surface is subjected to the platinum plating by an electroplating, etc. The platinum plating is formed on the base material with the good adhesive property in this way and the current efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a platinum plating method, and more particularly to a pretreatment method for coating platinum on a substrate such as niobium or tantalum.

(Prior art and its problems) Platinum has excellent electrical properties and corrosion resistance, and is used in various products and parts. One of these uses is as an electrode for sensors, electrolysis, and corrosion protection. However, since platinum is an expensive material, using pure platinum for the electrode would be extremely expensive. Therefore, electrodes in which platinum is coated on a composite material such as titanium are sometimes used.

Platinum-plated electrodes gradually consume platinum as they are used, so they must be coated with electrode active material (platinum) glue. However, there are many cases in which corrosion has progressed to the titanium used in the composite material, making it impossible to reuse the composite material. Attempts are being made to solve usage problems.

However, platinum plating has a high internal stress in the precipitates and is prone to cracks and cracks, and since the niobium and tantalum form a strong oxide film, it has poor adhesion with the composite material niobium and tantalum. However, there was a problem that platinum easily peeled off during conventional pretreatment, and a better plating method was desired.

(Objective of the Invention) The present invention was made in view of these problems, and improves the pretreatment method of composite material before platinum plating to form a platinum coating with good adhesion on a niobium or tantalum base material. The purpose is to provide a method that can be used.

(Means for Solving the Problems) The present invention is a method of platinum plating on a niobium or tantalum substrate, firstly, the surface of the niobium or tantalum substrate is mechanically processed to make it rough, and secondly, the surface of the niobium or tantalum substrate is made rough. This platinum plating method is characterized in that the base material is etched by polishing, thirdly activated, and then plated with platinum.

(Function) The method of the present invention includes (I) a step of mechanically processing a niobium or tantalum base material to obtain a rough surface, and (n) a step of further corroding the roughened niobium or tantalum base material by electropolishing. , and (I) activating the surface of the chemically etched niobium or tantalum base material and then depositing platinum plating. Each step will be explained below.

In this process, the composite material of niobium and tantalum is roughened by mechanical processing such as sandblasting to create an uneven surface.

The composite material of niobium and tantalum does not necessarily have to be a pure metal, as long as it has niobium or tantalum as its main component.

To obtain a rough surface by mechanical processing, sandblasting is preferable because it can easily obtain a rough surface with a satin finish. Alternatively, the surface may be roughened using a grinder or sander.

The purpose of this process is to electrolytically polish the uneven surface obtained by the mechanical processing in the vertical direction, using a niobium or tantalum base material as an anode and a suitable cathode such as stainless steel or carbon. By electrolytically polishing by applying electricity in a polishing liquid, finer asperities are formed on the rough uneven surface obtained by mechanical processing.

The electrolytic polishing liquid may be anything as long as it can corrode niobium or tantalum by electrolysis. For example, the following ones are good, but those with a composition in which alcohols such as methanol, ethanol, or ethylene glycol are added to these are suitable. Salts such as sodium chloride, ammonium chloride, and ammonium bromide may also be added.

Fluoride-based products whose main ingredients are hydrofluoric acid or fluoride salts.

Alkaline type: The main ingredient is alkali hydroxide.

Acid-based: Those whose main component is inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid, and in some cases, the above-mentioned fluorides are added.

Electrolysis conditions are usually about 0.1 to IOA/dm' and are selected depending on the composition of the electrolytic solution and the degree of corrosion. The electrolysis voltage varies depending on the current density. Normally, it is only a few volts, but with an electrolytic polishing solution containing a large amount of alcohol, it can be several tens of volts.

In addition, molten salt electropolishing treatment may be performed using an alkali hydroxide or salt as a molten salt.

In this step, the surface of the niobium or tantalum base material is activated immediately before platinum plating, and then a platinum coating is formed by plating.

Activation is performed by an appropriate pretreatment method, but the above step (I)
For the rough surface with unevenness obtained in (n), the intragranular parts within the crystals are further corroded, and the slight remaining oxide coating is thoroughly removed before plating, so that the platinum coating to be formed next is made stronger. This is the process for attaching it to the surface.

Activation methods include treatment with solutions containing inorganic acids such as oxalic acid, hydrochloric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid, and salts such as fluorides, but alkaline solutions or alkaline molten salts The method of treatment is more preferable because it is highly effective in removing the oxidized coating on the substrate, has a simple composition, and is less likely to have an adverse effect on contamination of a platinum plating solution, etc., which will be described later.

Furthermore, it is even better if the activation treatment is followed by an activation treatment using a solution containing a platinum salt, since an extremely thin coating of platinum is formed on the clean rough surface obtained by the activation treatment.

The platinum coating is formed by wet plating, but electroplating is more preferable than electroless plating because it can form a stronger coating, and it is even better to apply the platinum coating through a platinum strike plating process.

According to the method of the present invention, mechanically processing the niobium or tantalum base material to form an uneven surface disperses the internal stress of the platinum deposited in a later step.

In addition, by forming finer irregularities on the irregular surface obtained by the mechanical processing and further activating the surface, platinum is deposited on the fine irregularities, thereby improving the adhesion between the platinum coating and the base material. can be further improved.

However, if these are not combined, internal stress and adhesion problems will occur in the precipitated platinum, making it easy for the platinum to peel off. In addition, when the mechanical processing is performed by sandblasting, the sand that has penetrated during the sandblasting can be removed in the next electrolytic polishing process, and foreign matter on the electrodes can be removed before plating. It's also effective.

The activation treatment is performed for the purpose of removing the oxide film on the base material and corroding the intragranular portion within the crystal. Although the degree of corrosion is weaker than that of the electrolytic polishing, if this step is not performed, the slight oxidized coating remaining on the base material will cause a decrease in adhesion strength.

An example of implementing the present invention will be described below.

(Example 1) A tantalum rod with a diameter of 2 mm and a length of 100 mm was attached to the top of a tantalum plate with a width of 100 mm, a length of 150 mm, and a thickness of 1.5 mm, and a platinum coating was applied to the tantalum base material, which was welded with a width of 5 mm. It was carried out by the method.

The tantalum base material was first sandblasted to roughen the surface and give it a fine satin finish.

Next, an electrolytic polishing treatment was performed with a solution consisting of ethanol: ethylene glycol: fluorosilicic acid: water - 25:40:530 at a current density of 3.0 Δ/dm' for 10 minutes at 25°C, followed by thorough washing with water.

Furthermore, as an activation treatment, heat treatment was performed for 30 minutes in a concentrated solution containing 80% sodium hydroxide at 110°C, followed by 20% sodium hydroxide Am containing 0.05% surfactant.
Immerse it in the solution for 5 minutes, and then add 0.5 dinitrodiaminoplatinum.
% in a 5% potassium hydroxide solution.

Platinum strike plating was performed in this solution at a voltage of 5 V for 20 seconds, followed by washing with running water for 2 minutes, and plating in 5% sulfuric acid solution for 3 minutes.
After 0 seconds of washing with running water, 2 minutes of washing with pure water, and 1 minute of pure water washing, a current density of 0.5A was applied in a sulfuric acid-based platinum plating bath.
A platinum coating of 2 Js was applied at /dm'.

After plating was completed, a beer test using adhesive tape was performed, and the platinum did not peel off and showed good adhesion.

(Example 2) Width 100+nm, length 150mm, thickness 1.5mm
A niobium rod having a diameter of 2 mm and a length of 100 mm was attached to the top of a niobium plate and welded with a thickness of 5+ nm.A platinum coating was carried out by the method of the present invention on a niobium base material.

The tantalum base material was first sandblasted to roughen the surface and give it a fine satin finish.

Next, an electrolytic polishing treatment was carried out at 25°C with a solution consisting of ethanol: ethylene glycol: fluorosilicic acid: water - 25:40:5:30 at a current density of 3. OA/d
m' for 10 minutes and thoroughly washed with water.

Furthermore, as an activation treatment, it was heated for 30 minutes in a concentrated solution containing 80% sodium hydroxide at 110°C, and then immersed in a 20% hydroxide solution containing 0.05% surfactant for 5 minutes. , and further dinitrodiaminoplatinum 0
．． 5% potassium hydroxide solution.

Platinum strike plating was performed in this solution at a voltage of 5 V for 20 seconds, followed by washing with running water for 2 minutes, and plating in 5% sulfuric acid solution for 3 minutes.
After 0 seconds of washing with running water, 2 minutes of washing with pure water, and 1 minute of pure water washing, a current density of 0.5A was applied in a sulfuric acid-based platinum plating bath.
Two females were platinized at /dm'.

After plating was completed, a beer test using adhesive tape was performed, and the platinum did not peel off and showed good adhesion.

(Example 3) Width 100+n+n, length 150 mm, thickness 1.5
2 mm in diameter and 100 mm in length on the top of the tantalum plate.
Platinum coating was carried out by the method of the present invention on a tantalum base material to which a tantalum rod of 5 mm was attached and welded with a clearance of 5 mrrl.

The tantalum base material was first sandblasted to roughen the surface and give it a fine satin finish.

Next, electrolytic polishing treatment was performed using sulfuric acid:hydrofluoric acid:water-50
:5:45 at 40℃, current density is 0.
．． It was carried out for 20 minutes at 5A/dm' and thoroughly washed with water.

Furthermore, as an activation treatment, it was heated for 30 minutes in a concentrated solution containing 80% sodium hydroxide at 110°C, and then immersed in a 20% hydroxide solution containing 0.05% surfactant for 5 minutes. , and further dinitrodiaminoplatinum 0
, 5% in a 5% potassium hydroxide solution.

Platinum strike plating was performed in this solution at a voltage of 5 V for 20 seconds, followed by washing with running water for 2 minutes, and plating in 5% sulfuric acid solution for 3 minutes.
After 0 seconds of washing with running water, 2 minutes of washing with pure water, and 1 minute of pure water washing, a current density of 0.5A was applied in a sulfuric acid-based platinum plating bath.
Two coats of platinum were applied at /dm'.

After plating was completed, a beer test using adhesive tape was performed, and the platinum did not peel off and showed good adhesion.

(Example 4) Width 100mm, length 150mm, thickness 1.5mrI
Two parts of a niobium plate with a diameter of 2 mm and a length of 100 m.
Platinum coating was carried out by the method of the present invention on a niobium base material to which a niobium rod of 5 mm was attached and welded with a clearance of 5 mm.

The niobium base material was first subjected to sandblasting treatment to roughen the surface and give it a fine satin finish.

Next, electropolishing treatment was performed at 25°C with a solution consisting of ammonium bromide: methanol: water - 5:90°.
The test was carried out for 20 minutes with a distance between the electrodes of 50 mm and a voltage not lower than 10 volts, followed by thorough washing with water.

Furthermore, as an activation treatment, it was heated for 30 minutes in a concentrated solution containing 80% sodium hydroxide at 110°C, and then immersed in a 20% hydroxide solution containing 0.05% surfactant for 5 minutes. , and further dinitrodiaminoplatinum 0
．． 5% potassium hydroxide solution.

Platinum strike plating was performed in this solution at a voltage of 5 V for 20 seconds, followed by washing with running water for 2 minutes, and plating in 5% sulfuric acid solution for 3 minutes.
After 0 seconds of washing with running water, 2 minutes of washing with pure water, and 1 minute of pure water washing, a current density of 0.5A was applied in a sulfuric acid-based platinum plating bath.
/ dm' for 2 hours of platinum coating.

After plating was completed, a beer test using adhesive tape was performed, and the platinum did not peel off and showed good adhesion.

(Comparative example 1) Width 100mm, length 150+n+n, thickness 1.5m
On the top of the tantalum plate of rrl, diameter 2 mm, length 10
A tantalum base material (platinum coating method) in which a 0 mm tantalum rod is attached and welded with a clearance of 5 mm+ is shown as an example for comparison with the present invention.

The tantalum base material was first sandblasted to roughen the surface and give it a fine satin finish.

Furthermore, as an activation treatment, it was heated for 30 minutes in a concentrated solution containing 80% sodium hydroxide at 110°C, and then immersed in a 20% hydroxide solution containing 0.05% surfactant for 5 minutes. , and further dinitrodiaminoplatinum 0
．． 5% potassium hydroxide solution.

Platinum strike plating was performed in this solution at a voltage of 5 V for 20 seconds, followed by washing with running water for 2 minutes, and plating in 5% sulfuric acid solution for 3 minutes.
After 0 seconds of washing with running water, 2 minutes of washing with pure water, and 1 minute of pure water washing, a current density of 0.5A was applied in a sulfuric acid-based platinum plating bath.
Two coats of platinum were applied at /dm'.

After plating was completed, when we conducted a beer test using adhesive tape, the entire surface of the platinum coating was attached to the adhesive tape.
The adhesion of platinum to the tantalum base material was extremely poor.

(Comparative example 2) Width 100mm, length 150mm, thickness 1.5mm
2mm in diameter and 100+n in length on the top of the tantalum plate.
The test was carried out in the same manner as in the present invention except that the step of mechanically processing the platinum coating to roughen the tantalum base material to which a tantalum rod of 5 mm was attached and welded with a clearance of 5++ was carried out.

The electrolytic polishing treatment was carried out at 25°C with a solution consisting of ethanol: ethylene glycol: borofluoric acid: water - 25:40:5:30 at a current density of 3. The mixture was washed with OA/dm' for 10 minutes and thoroughly washed with water.

Next, as an activation treatment, it was heated for 30 minutes in a concentrated solution containing 80% sodium hydroxide at 110°C, and then immersed in a 20% hydroxide solution containing 0.05% surfactant for 5 minutes. , and further dinitrodiaminoplatinum 0
．． 5% potassium hydroxide solution.

Platinum strike plating was performed in this solution at a voltage of 5 V for 20 seconds, followed by washing with running water for 2 minutes, and plating in 5% sulfuric acid solution for 3 minutes.
After 0 seconds of washing with running water, 2 minutes of washing with pure water, and 1 minute of pure water washing, a current density of 0.5A was applied in a sulfuric acid-based platinum plating bath.
A platinum coating of 2A1m was applied at /dm'.

After plating was completed, when we conducted a beer test using adhesive tape, some of the platinum coating stuck to the adhesive tape.
The adhesion of platinum to the tantalum base material was poor.

(Effects of the Invention) The present invention provides a method of platinum plating on a niobium or tantalum base material, in which the surface of the niobium or tantalum base material is firstly processed mechanically to make it rough, and secondly, the surface of the niobium or tantalum base material is subjected to electrolytic polishing treatment. The method is characterized in that the base material is corroded, thirdly, an activation treatment is performed, and then platinum plating is performed. A rough surface is created by mechanical processing such as sandblasting, resulting in an uneven surface, and finer unevenness is formed on the rough uneven surface obtained by mechanical processing. After removing the remaining oxide film, the platinum coating is formed by plating, so that the internal stress of platinum can be dispersed and the adhesion between the platinum coating and the base material can be further improved.

In addition to 1, when the present invention is used for electrolytic electrodes, etc., the life of the electrode can be extended by removing foreign matter on the electrode before plating, and the surface area can be increased due to the unevenness of the electrode surface, which can improve the current efficiency. There are other effects as well, such as improved performance.

The present invention provides the following advantages when applying platinum coating to niobium or tantalum.
In addition, considering the reuse of the composite material of electrolytic electrodes and its application to parts that use highly corrosion-resistant materials, it can be said that it will make a great contribution to industry.

(Embodiments) The present invention has the features described in the claims, and examples of embodiments thereof are as follows.

(1) The method according to claim 1, characterized in that the activation treatment is performed with a molten alkali salt and/or an alkaline solution Applicant: Tanaka Kikinzoku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A method of platinum plating on a niobium or tantalum base material, which comprises: a) mechanically processing the surface of the niobium or tantalum base material to make it a rough surface; A platinum plating method characterized by corroding a base material, c) further performing an activation treatment, and then plating with platinum.