KR20050075551A - Tungsten-iron alloy electroless plating solution and plating method using the same - Google Patents

Abstract

The present invention relates to an electroless solution, characterized in that the tungsten-iron alloy electroless solution containing tungsten and iron, ammonium sulfate, sodium citrate, and sodium hypophosphite, the iron alone does not form a plated film It is effective to form a plating film having excellent corrosion resistance, chemical resistance, hardness, and abrasion resistance by vacancy with the material.

Description

Tungsten-iron alloy electroless plating solution and plating method using the same

The present invention relates to an electroless solution, and more particularly, to tungsten, which alone does not form a plated film, by vacancy with iron to form a plated film having excellent corrosion resistance, chemical resistance, hardness, and abrasion resistance on the surface of the material. It relates to an alloy electroless solution.

Generally, metals used for electroless plating include copper, nickel, cobalt, cadmium, gold, silver, palladium, platinum, and chromium.

Among them, chromium plating is widely used for decorative plating, but chromic anhydride, which is a raw material, is not only a compound of hexavalent chromium but also addictive, and thus a plating method is required to replace it.

In addition, as a method for improving corrosion resistance, there is a method of improving corrosion by forming an oxide film on the surface by high temperature heat treatment, and a method of forming a passivation film on the surface by immersing it in nitric acid or sulfuric acid solution for a certain time. Many passivation coatings are broken, and the problem of corrosion in chlorine and fluorine environments is not solved.

On the other hand, tungsten has excellent corrosion resistance and heat resistance, so it is an excellent material as a plating material, but because it is a strong material due to its characteristics, it cannot exist in powder form. can not do it. Therefore, in the case of tungsten plating, there is a problem of activating the surface of the base metal with nickel strike or requiring a pretreatment process such as electroless nickel plating in order to improve plating adhesion and wear resistance.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a tungsten-iron alloy electroless solution which replaces chromium plating, which is caused by environmental pollution due to heavy metal emission and restrictions on use.

Another object of the present invention is to provide a tungsten-iron alloy electroless solution which can satisfy the demand for corrosion resistance, heat resistance and wear resistance.

It is still another object of the present invention to provide a tungsten-iron alloy electroless solution that can form a tungsten plated film on the surface of a material without undergoing a ground process.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and preferred embodiments in conjunction with the accompanying drawings.

In order to achieve the above object of the present invention, the present invention provides a tungsten-iron alloy electroless solution containing tungsten, iron and sodium hypophosphite as a reducing agent as a main component, and ammonium sulfate as a complexing agent and sodium citrate as a stabilizer. . The concentration of hydrogen ions in the plating solution is maintained at 8.1 ± 0.5. At this time, sulfuric acid solution or ammonia water is used as a pH regulator.

Tungsten is provided from sodium tungstate, tungsten oxide, tungsten chloride, carbonyl tungsten chloride and the like, preferably from sodium tungstate. As a composition ratio, the vacancy with iron ions was good at 0.024 ~ 0.98mol / l and the hardness, abrasion resistance, corrosion resistance and chemical resistance were the best. When less than 0.024 mol / l is used, the plated film is less than the content, making it difficult to achieve the desired function, and at 0.98 mol / l or more, the plating adhesion is significantly weakened.

In the present invention, iron is a main component of vacancy with tungsten, and is provided from iron sulfate, iron chloride, and the like, and preferably from ferrous sulfate. The composition ratio is different depending on the material and the use of the metal to be plated, but in the present invention was applied within the range of 0.008 ~ 0.92 mol / l. If it is less than 0.008 mol / l, vacancies with tungsten are not formed, and if it is 0.92 mol / l or more, the adhesive strength with a raw material falls remarkably. Iron combines with tungsten to form vacancies and, above all, stabilization to achieve core functionality, hardness, corrosion resistance, abrasion resistance, and chemical resistance.

Sodium hypophosphite is selected as a reducing agent in the range of 0.03 to 0.8 mol / l in the present invention. If it is used in the range of less than 0.03mol / l, it shows the phenomenon that impurities are mixed due to the occurrence of pits or clouding, etc., and when used in excess of 0.8 mol / l, the adhesion strength is weakened to act as a reducing agent. Can not.

Ammonium sulfate is used as a complexing agent in the range of 0.2 to 0.5 mol / l. When less than 0.2 mol / l is used, poor adhesion or swelling occurs, and when 0.5 mol / l or more is used, the adhesion is poor.

Sodium citrate is used as a complexing agent, to extend the life of the plating liquid and as a pH buffer. The range is 0.5 to 0.98 mol / l. If less than 0.5 mol / l is used, poor adhesion or swelling occurs, when using more than 0.98 mol / l adhesion is poor because the reaction driving force is weakened because of electroless plating.

Experimental Example 1

Nickel strikes are performed on stainless steel and general metals to perform uniform and stable activation and then enter tungsten-iron electroless plating according to the present invention. Of course, in the case of food and medical use, nickel strikes are not performed.

In the tungsten-iron of the present invention, many experiments have been conducted in fear that iron ions may be corroded by oxidation. The composition and working conditions of the electroless solution are as follows.

ingredient Sodium tungstate 0.089 mol / l Ferrous sulfate 0.073 mol / l Sodium hypophosphite 0.4 mol / l Sodium citrate 0.95 mol / l Ammonium Sulfate 0.34 mol / l Working condition pH 7.6 to 8.6 Temperature 75 ~ 80 ℃ Plating speed 10-20 μ (30-40 minutes)

As a result of this experiment, there was no fear of rust due to oxidation of iron ions, but rather the structure of the tungsten and iron vacancies became stable and firm. In addition, it is confirmed that economical plating can be performed by not using expensive plating materials such as tungsten and nickel, palladium or ruthenium, rhenium, and gold because of the combination of tungsten and iron in an economic aspect.

Experimental Example 2

As a result of performing corrosion resistance against hydrofluoric acid on the two kinds of stainless steel plates, 18Cr-8Ni, and 18Cr-12Ni-2.5Mo, plated with the electroless solution according to the present invention.

Experimental condition 18Cr-8Ni 18Cr-12Ni-2.5Mo W-Fe Plated 18Cr-8Ni W-Fe Plated 18Cr-12Ni-2.5Mo Hydrofluoric acid (48%) solution is placed in a desiccator and exposed to a gas atmosphere at room temperature for 72 hours. Red rust occurs over the entire surface 20 ~ 30% rust occurrence clear clear

As can be seen from the experimental results, it can be seen that the tungsten-iron alloy plating according to the present invention has a significant improvement in corrosion resistance compared to stainless steel sheets.

[Comparative Example]

This fertilizer is an example in which the aluminum plate plated with the tungsten-iron alloy electroless solution according to the present invention, the aluminum plate plated by the other plating method and the general aluminum plate are compared with the salt resistance.

First, the composition and experimental conditions of the corrosion solution are as follows.

medicine ratio Temperature time Hydrochloric acid One Room temperature 48 hours deposition 72 hours gas atmosphere exposure water 2

That is, hydrochloric acid and water were mixed at 1: 2, and the specimen was deposited at room temperature for 48 hours in the corrosive solution, and placed in a desiccator with corrosive gas, that is, chlorine gas, and exposed for 72 hours. The experimental results are shown in the table below.

Aluminum plate Nickel plating Chrome plated Tungsten-iron plating Corrosive gas Significant erosion with white smoke Swelling, erosion 25%, Corrosion progresses like aluminum sheet after 10 minutes Swelling and erosion 30 minutes after 20 minutes Puffiness, no erosion Corrosive deposition Same as above Same as above Same as above Same as above Gas + deposition shift Same as above Same as above Same as above Same as above

As can be seen from the experimental results, it can be seen that the adhesion to the material and the corrosion resistance are remarkably improved as compared with the conventional nickel or chromium plating.

As described above, according to the present invention, there is provided an electroless solution which can be used where corrosion resistance must be maintained even under corrosion conditions that are difficult to withstand even stainless steel and titanium which are highly corrosion resistant metals.

Conventional nickel plating and chromium plating or surface treatments made of nickel, tungsten and cobalt alloys have caused allergic to the human body due to the release of heavy metal ions. In the present invention, since nickel is not used, corrosion resistance, An electroless solution having various functionalities such as wear resistance and excellent hardness is provided.

Although the present invention has been described with reference to the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will include any modifications or variations that fall within the spirit of the invention.

Claims (5)

Tungsten 0.024 ~ 0.98 mol / l, iron 0.008 ~ 0.92 mol / l, sodium hypophosphite 0.03 ~ 0.8 mol / l, sodium citrate 0.5 ~ 0.98 mol / l, ammonium sulfate 0.2 ~ 0.5 mol / l Tungsten-iron alloy electroless solution. The method of claim 1, The tungsten is tungsten-iron alloy electroless solution, characterized in that provided from any one of sodium tungstate, tungsten oxide, tungsten chloride, carbonyl tungsten chloride. The method according to claim 1 or 2, The iron is tungsten-iron alloy electroless solution, characterized in that provided from iron chloride or iron sulfate. The method of claim 3, wherein A tungsten-iron alloy electroless solution characterized in that it further comprises a sulfuric acid solution or ammonia water as a pH adjuster. Sodium tungstate 0.024 to 0.98 mol / l, ferrous sulfate 0.008 to 0.92 mol / l, sodium hypophosphite 0.03 to 0.8 mol / l, sodium citrate 0.5 to 0.98 mol / l, ammonium sulfate 0.2 to 0.5 mol / l Tungsten-iron alloy electroless plating method characterized in that the liquid composition to be carried out under the operating conditions of pH 8.6 ~ 9.6, temperature 75 ~ 80 ℃.