JPH0440438B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for plating the surfaces of titanium and titanium alloys.

<Prior art> Titanium and titanium alloys are lightweight, have strength and fracture toughness, and have been rapidly used in recent years because they have excellent corrosion resistance against various acids, alkalis, and other chemicals. It's starting to look like this. However, when the surfaces of titanium and titanium alloys come into contact with air or water, a thin oxide film is formed, making it difficult to plate them using conventional methods.

Many studies have been conducted and published on plating methods for titanium and titanium alloys, but there are problems such as insufficient adhesion, lack of reproducibility in manufacturing methods, and the need for high processing temperatures. Due to problems such as changes in physical properties, it has not been possible to use it in various industries.

Therefore, it has been difficult to apply plating with strong adhesion to the surfaces of titanium and titanium alloys without damaging the physical properties. To date, electroplating has been performed by immersion in a mineral acid bath containing hydrofluoric acid or a chromic acid bath containing hydrofluoric acid as a pretreatment.
Furthermore, high-temperature heat treatments have been announced, but all of them have drawbacks in adhesion and reproducibility that can withstand industrial machining, and no satisfactory plating method has been developed.

A review of past plating methods for titanium and titanium alloys is provided by Martin Thoma in Plating Surf Ace Finishing 70, 5, 96-98 (1983), and more recently, A method for surface treatment of titanium or titanium alloy is disclosed in Japanese Patent No. -48586.

However, all of these known techniques have a minimum of 450
℃ or 880-1023℃, which requires long-term high-temperature heat treatment that changes the physical properties of titanium and titanium alloys, so it was considered extremely difficult to put it into practical use.

<Problems to be Solved by the Invention> The present invention was developed in view of these conventional drawbacks, and is particularly capable of being carried out extremely simply and reliably, and with heat treatment at low temperatures and in a short time. The present invention relates to a method for plating titanium and titanium alloys.

<Means for Solving the Problems> The material processing method in the plating process in the present invention is not limited to conventional concepts, but involves etching and forming an active oxide film using direct current anodic electrolysis in an acidic solution. , a plating method in which nickel plating is applied to titanium and titanium alloys, and the adhesion is extremely improved through low-temperature heat treatment.The characteristics of this method are its degree of industrial use and the need for adhesion. Depending on the nature of the process, low-temperature heat treatment can be omitted, shortening the process.

In addition, heat treatment in the range of 150°C to 200°C is sufficient for a short time and does not damage the physical properties of the material in any way, making it possible to re-machine materials that were previously unavailable and sticky. . Materials obtained by nickel plating titanium and titanium alloy wires using the method of the present invention can be easily drawn, making it extremely easy to plate various metal films on the drawn thin wires and to perform various surface treatments. It has become easy to use, has been put into practical use, and has a wide range of applications in other industrial fields. In addition, titanium alloys, both a-alloy and α-β alloy, undergo phase transformation when heat treated, and this is used to improve strength and toughness, and many of them undergo heat treatment corresponding to the purpose before processing. ,
Processing at such high temperatures as to cause phase decomposition again may significantly impair physical properties, and the method of the present invention is considered to be extremely effective in solving this problem.

Next, the plating method according to the present invention will be specifically described as follows.

That is, the present invention uses an electrolytic solution prepared by adding 5 to 100 ml of 47% hydrofluoric acid to a solution of 5 to 50 ωt% of 98% concentrated sulfuric acid, and uses an insoluble electrode plate such as lead or carbon as a cathode to produce titanium and titanium alloys. A method of further applying nickel plating to the surface of titanium and titanium alloys that have been pretreated by direct current anodic electrolysis, and further applying a nickel plating film on titanium and titanium alloys treated as described above to 150 to 200 This method further improves the adhesion of the plating film without impairing the physical properties of the material by performing a low-temperature heat treatment at ℃.

Therefore, the method of the present invention involves direct current anodic electrolysis of titanium and titanium alloys in a sulfuric acid electrolytic solution containing hydrofluoric acid to form an anodized film having active micropores, and then nickel plating is performed on the anodic oxide film having active micropores. 150~200℃
This is a method of producing nickel plating with extremely good adhesion on titanium and titanium alloys by subjecting it to a relatively low temperature heat treatment. Furthermore, it is a method of surface treatment for plating that allows many metal coatings and processing treatments to be performed using the nickel plating film as a base, and the nickel plating method used is not limited to an electrolytic bath or an electroless bath.

<Function> The above-described method for plating titanium and titanium alloy according to the present invention has various functions as detailed below.

Although titanium and titanium alloys have very different general properties, they share a common feature of large passivated areas. Therefore, the metallic titanium on the surface of both is easily oxidized to form an oxide film. Titanium undergoes allotropic transformation at 885℃ to form Cr,
Contains elements such as Ni, Co, Cu, and Si, as well as V,
Mn etc. are added and alloyed. Also, many of these alloys contain several percent Al. When titanium, titanium alloys, and each metal on the surface are electrolyzed with an electrolytic solution of sulfuric acid and hydrofluoric acid, the original oxide film is dissolved and a new barrier type film is formed. This barrier type film is selectively dissolved by hydrofluoric acid, creating micropores.
A highly active light brown oxide film with a porous structure is formed. Next, when nickel plating is performed on the porous anodic oxide film, adhesive plating can be obtained because the nickel particles are influenced by the porous structure and its activation. Further heat treatment causes diffusion between the porous oxide film and the metal nickel, creating an anchor effect and forming a plating film with good adhesion. The reason for this is that hydrofluoric acid acts on the oxide film formed in the early stage of electrolysis and redissolves it in the electrolyte, leaving a small amount of hydrofluoric acid in the micropores when creating micropores, and the final low-temperature heat treatment removes the titanium. It is presumed that the reaction occurs and titanium fluoride (TiF ₄ ) is produced, further improving the anchoring effect. Since the generation temperature of this titanium fluoride is said to be 150°C or higher, it is considered that titanium fluoride was definitely generated during the above process.

<Example> Example 1 100ml of concentrated sulfuric acid/10ml of hydrofluoric acid (47%)/
JIS H2151, TW35 titanium wire 2 using a lead plate as an electrolyte and a voltage of 5 volts at room temperature.
Ni is deposited on a titanium wire that has been anodically electrolyzed for 1 minute.
( _NH2SO3 ) _{24H2O350 ~} 450g/, _NiCl ,
6H ₂ O 5g/, H ₃ BO ₃ 30~40g/, temperature 40~
60℃, cathode current density 1~10A/ ^dm2 , PH4.0~4.5,
Electrolytic nickel plating was performed for 10 minutes using a depolarized nickel anode, and nickel plated wires on titanium were compared with and without low-temperature heat treatment. Heat treatment: 150℃ for 10 minutes, 200℃ for 5 minutes
They were subjected to the same adhesion test at 250°C for 1 minute, 300°C, and 400°C for 1 minute.

The heat treatment was the same as above, the nickel plating was the same, and the sulfuric acid concentration was kept constant.
%) was varied from 5 to 100 ml/piece to prepare specimens. Adopting practical methods for evaluation,
JIS H2151, TW35 titanium 5mmφ wire is electrodeposited with nickel at a rate of 10μ, and drawn with a die to 1mm
Appearance and cracks were measured and evaluated to see if the nickel coating on the φ was uniformly coated to a thickness of 0.5 to 2.5μ. Items with poor adhesion cannot be drawn, and can be clearly determined by peeling off into powder.

Example 2 The conditions of the activation electrolytic bath were changed in the same manner as in Example 1, and the heating conditions were changed in the same manner as in Example 1,
NiSO ₄ 7H ₂ O 250g/,
NiCl ₂ 6H ₂ O 40g/, H ₃ BO ₃ 30g/, PH4.0~
4.5, temperature 40~60℃, cathode current density 1~10A/d
m ² and plating time was performed for 10 minutes to determine the adhesion of nickel plating, and good results were obtained in all cases.

Example 3 The conditions of the activation electrolytic bath were changed in the same manner as in Example 1, and the heating conditions were changed in the same manner as in Example 1,
SnCl ₂ 5H ₂ O30g/, PdCl ₂ 0.1g/, HCl100
Activated with 10% sulfuric acid solution and sensitized with 30g of NiCl ₂ 6H ₂ O, NaPH ₂ O ₂ ,
Nickel plating was performed using an electroless nickel plating solution containing 10 g of H ₂ O and 10 g of citric acid at a pH of 4 to 6 and a temperature of 80° C. to determine adhesion, and good results were obtained in all cases.

Example 4 The conditions of the activation electrolytic bath were changed in the same manner as in Example 1, and the heating conditions were changed in the same manner as in Example 1.
NiCl ₂ 6H ₂ O 100-150g/,
H ₃ BO ₃ 30g/, PH3.5~4.0, temperature 40℃~60℃,
Cathode current density 1~10A/ ^dm2 , plating time 5~
The adhesion of the nickel plating was evaluated after 10 minutes, and good results were obtained in all cases.

Example 5 The conditions of the activation electrolytic bath were changed in the same manner as in Example 1, the heating conditions were changed in the same manner as in Example 1, and the titanium material was also used for type 1 and type 3 wires of JIS H2151, TW28, and TW49. Similarly, we tested the adhesion of electrolytic nickel plating films using a nickel sulfamic acid plating bath, and good results were obtained in all cases.

Example 6 The conditions of the activation electrolytic bath were changed in the same manner as in Example 1, and the heating conditions were changed in the same manner as in Example 1,
The adhesion of the electrolytic nickel plating film was tested using a nickel sulfamic acid plating bath using titanium plates of α alloy Ti-5Al-2.5Sn and the most representative α-β alloy, Ti-6Al-4V. .

A 180 degree bending test, an Erichsen test, and a thermal cycle test were performed as methods for evaluating and judging the plate materials. In the thermal cycle test, the specimen was heated to 300-400°C in an electric furnace and cooled with 20°C water, repeated 10 times, and the state of swelling was observed.

In addition, the heat cycle test described above was carried out by applying glossy nickel, chrome plating, copper sulfate plating, bright nickel, chrome plating, etc.
It was proven that the material that was heat-treated at 150°C to 200°C for 10 minutes can withstand practical use even if any metal is plated on the top.

<Effects of the Invention> Since the plating method according to the present invention has the above-mentioned configuration, when the method of the present invention is carried out, titanium and titanium alloys, which were conventionally considered extremely difficult, can be plated easily, in large quantities, and at low cost. can be carried out,
Moreover, it has features such as being able to provide plating with extremely good adhesion.

Therefore, by employing the method of the present invention, titanium can be used in a wide variety of other applications such as aircraft structural materials, chemical equipment parts, seawater utilization industries, electrolytic electrode materials, communication equipment, engineering equipment, medical equipment, etc. It has the characteristics that titanium alloy products can be manufactured in extremely large quantities at low cost, and titanium products can increasingly be used in place of conventionally commonly used stainless steel, aluminum, and alloy products. It is something.

Claims (1)

[Claims] 1. Lead,
Forming a nickel plating film by applying nickel plating to titanium and titanium alloys that have been pretreated by subjecting titanium and titanium alloys to direct current anodic electrolysis using an insoluble electrode plate such as carbon as a cathode, A method for plating titanium and titanium alloys, further comprising subjecting the nickel plating film to a low-temperature heat treatment at 150 to 200°C.