KR100431125B1 - Double electroless nikel plating method by pre-treatment process of magnesium and magnesium alloy - Google Patents

Abstract

The present invention relates to a double electroless nickel plating method through a pretreatment process of magnesium and magnesium alloy to improve the corrosion resistance of molded articles of magnesium and magnesium alloy used in electrical, electronic devices and various mechanical parts. And alkali degreasing of the object to be molded of magnesium alloy and the acidic aqueous solution of hydrofluoric acid and fluoride; and an insoluble hydroxide film on the surface of the magnesium and magnesium alloy-formed coating in an aqueous solution containing calcium pyrophosphate as a water-soluble compound. Alkali etching step of conversion and removal; Acid etch of fluoride and alkali etching process are carried out twice in sequence, and then nickel sulfate and ammonium ammonium ammonium are composed of fluoride, lactic acid, succinic acid and sodium hypophosphite (pH). 5-8% phosphorus with an alkali electroless nickel plating of 7.8-8.2 7-3 micron thick nickel coating containing 10-12% phosphorus by electroless nickel plating with pH 4.8-5.2 after forming a 2-3 micron thick nickel coating containing It is a double electroless nickel plating method that forms a metal, which is chemically unstable such as magnesium and magnesium alloy, is easily oxidized and corroded, and is subjected to anticorrosive treatment for structural metal materials having fine surface defects generated during molding. Washing with water three times by immersing a metal emulsifier to be used at pH 9-10 in a 60 ° C. aqueous solution having a concentration of 60-70 g / L for 5-7 minutes; Immersing for 2 minutes in an aqueous solution at room temperature mixed with 100 g / L ammonium and 20 cc / L hydrofluoric acid and washing with water twice; 40 ° C. of pH 9-10 (pH) 9-10 dissolved in potassium pyrophosphate hydrate through the above steps 5 minutes in aqueous solution Washing with water three times; and immersing for two minutes in an aqueous solution at room temperature mixed with ammonium fluoride hydrate 100 g / L and 200 cc / L hydrofluoric acid through the above process, and washing twice with water; Immersing in a 40 ° C. aqueous solution of 10 g / L potassium hydrate (pH) 9-10 for 2 minutes and washing it three times; nickel sulfate 10-15 g / L, ammonia water 5 mL / L, ammonium difluoride 0.5 g / L, lactic acid 25 g / L, zucchini acid 2 g / L, sodium hypophosphite 25-45 g / L and mixed for 20 minutes in an electroless nickel plating solution adjusted to pH 7.8-8.2 with ammonia water at a temperature of 75-80 ° C. Immersion process; Nickel sulfate 10-15g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, pumpkin acid 2g / L, sodium hypophosphite 50-60g / L And electroless nickel plating for 40 minutes in an electroless nickel plating solution adjusted to pH 4.8-5.2 with ammonia water at a temperature of 75-80 ℃. Electroless nickel plating process of the two through the pre-treatment process of the magnesium and magnesium alloys, characterized in that.

Description

Double electroless nikel plating method by pre-treatment process of magnesium and magnesium alloy}

The present invention relates to a double electroless nickel plating method through a pretreatment process of magnesium and magnesium alloy to improve the corrosion resistance of molded articles of magnesium and magnesium alloy used in electrical, electronic devices and various mechanical parts. And alkali degreasing of the object to be molded of magnesium alloy and the acidic aqueous solution of hydrofluoric acid and fluoride; and an insoluble hydroxide film on the surface of the magnesium and magnesium alloy-formed coating in an aqueous solution containing calcium pyrophosphate as a water-soluble compound. Alkali etching step of conversion and removal; Acid etch of fluoride and alkali etching process are carried out twice in sequence, and then nickel sulfate and ammonium ammonium ammonium are composed of fluoride, lactic acid, succinic acid and sodium hypophosphite (pH). 5-8% phosphorus with an alkali electroless nickel plating of 7.8-8.2 7-3 micron thick nickel coating containing 10-12% phosphorus by electroless nickel plating with pH 4.8-5.2 after forming a 2-3 micron thick nickel coating containing It is a double electroless nickel plating method to form a.

In general, magnesium is the lightest metal with the highest specific strength among practical metals, and has excellent recycling properties. Therefore, the demand for magnesium and plastics is rapidly increasing in many applications such as automobiles and aerospace industries. Corrosive properties have limited use.

Conventionally, in order to solve the problem of low corrosion resistance of magnesium and magnesium alloy, chromate, anodization, chemical treatment and electroplating are used to improve the corrosion resistance by using surface treatment methods such as plating, coating, and chemical treatment. have.

The chromate is regulated due to chromium's adverse effects on the environment and is gradually prohibited from use.Anodic oxidation and chemical conversion have low yields due to complexity and difficulty in reproducibility due to complexity. The strength of the coating film is weak and its corrosion resistance is significantly lower than that of a strong metal such as nickel, so it is easily damaged by the impact from the outside, so that it does not sufficiently function as a protective film and an anti-corrosion film, and additional coating treatment is required to improve the corrosion resistance even after the coating film is formed. In many cases, there is a problem that the excellent productivity by the wet process is offset by painting, and electroplating is applied to complex shapes and galvanic corrosion is caused by the contact between the rack and magnesium molded parts, and the coating film is completely coated. Er It has been used in a limited way due to luck problems. Due to the difference in current density distribution in the bath during plating and the formation of electric fields according to complex shapes, it is not possible to maintain a uniform current density in deep and complex shaped parts. It is impractical to apply electroplating immediately after melting or other oxidizing corrosion, so to solve this problem, obtain uniform coating by substitution plating such as jincate and suppress the occurrence of pinhole Although additional plating treatments such as plating have been performed, the thickness of the coating film formed by substitution plating is too thin and not dense enough to sufficiently compensate for minute irregularities and pinholes on the surface of the substrate formed during the pretreatment before plating and during molding. Not enough adhesion There was a problem that swelling often occurs.

In addition, the existing electroless nickel plating method, which forms a protective and anticorrosive film on the surface of magnesium base by using acid nickel plating in the range of pH 4.4-4.8, is partially used for mechanical parts, but electroless nickel generated during plating is used. It is not economical and has an extremely low yield of 30-40% due to problems such as liquid decomposition due to instability of the plating bath, excessive occurrence of pinholes and poor adhesion. It was difficult to form a low and uniform coating film and there was an uneconomical problem such as extremely low yield due to low reproducibility.

Accordingly, the present invention has been made for the purpose of solving the above-mentioned conventional problems, and it is chemically unstable compared to mechanical properties such as magnesium and magnesium alloy and is easily oxidized and corroded to structural metal materials having fine surface defects generated during molding. Eliminates the microscopic defects of molded products by forming a nickel plated film in double layers that provides corrosion resistance and ensures durability and reliability over time, and applies industrially-produced and environmentally friendly wet plating method It is to provide an electroless plating method through a pretreatment process.

In order to provide the above plating method, a metal emulsifier using a magnesium and magnesium alloy which is introduced into a mold from a die casting or a similar molten state at a pH of 9-10 at a concentration of 60-70 g / L is used. Immersing in an aqueous solution at 60 ° C. for 5-7 minutes for alkali degreasing and Desmut treatment and washing with water three times;

Immersing, activating and washing with water twice for 2 minutes in an aqueous solution at room temperature mixed with ammonium fluoride hydrate 100g / L and 200 cc / L hydrofluoric acid through the above steps;

5 minutes of immersion alkali etching treatment in a 40 ° C. aqueous solution of Peh (pH) 9-10 in which 10 g / L of potassium pyrophosphate hydrate is dissolved;

Washing with water three times after the homogenization process of repeating the alkali degreasing, activation, and alkali etching processes;

Nickel sulfate 10-15g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, zucchini acid 2g / L, sodium hypophosphite 25-45g / L and mixed with ammonia water at 75-80 ℃ Immersing for 20 minutes in an electroless nickel plating solution adjusted to pH 7.8-8.2 to form a nickel plating layer having a thickness of 2-3 microns and washing with water three times;

Nickel sulfate 10-15g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, pumpkin acid 2g / L, sodium hypophosphite 50-60g / L and mixed with ammonia water at 75-80 ℃ 2 to improve the corrosion resistance of the molded product of magnesium and magnesium alloy by immersing for 40 minutes in an electroless nickel plating solution set to pH 4.8-5.2, forming a nickel plating layer with a thickness of 7-8 microns, and washing with water three times. It is possible to provide an electroless nickel plating method.

Hereinafter, the gist of the present invention will be described in detail with reference to the manufacturing process and examples.

In anticorrosive treatment of structural metal materials such as magnesium and magnesium alloy, which are chemically unstable, easily oxidized and corroded, and have fine surface defects generated during molding,

Washing with water three times by immersing a metal and a magnesium alloy coated product at a pH of 9-10 in a 60 ° C. aqueous solution having a concentration of 60-70 g / L for 5-7 minutes;

Immersing for two minutes in an aqueous solution at room temperature mixed with ammonium fluoride 100g / L of hydrate and 200cc / L of hydrofluoric acid through the above steps;

Washing with water three times by immersing for 5 minutes in a 40 ° C. aqueous solution of Peh (pH) 9-10 in which 10 g / L of potassium pyrophosphate hydrate was dissolved through the above steps;

Immersing for two minutes in an aqueous solution at room temperature, in which ammonium fluoride hydrate 100g / L and 200 cc / L hydrofluoric acid are mixed through the above steps and washed twice;

Washing with water three times by immersing for 5 minutes in a 40 ° C. aqueous solution of pH 9-10 in which 10 g / L of potassium pyrophosphate hydrate was dissolved through the above steps;

Nickel sulfate 10-15g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, zucchini acid 2g / L, sodium hypophosphite 25-45g / L and mixed 75-80 ℃ Immersing for 20 minutes in an electroless nickel plating solution adjusted to pH 7.8-8.2 with ammonia water at a temperature; Nickel sulfate 10-15g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, zucchini acid 2g / L, sodium hypophosphite 50-60g / L and mixed 75-80 ℃ The process consists of electroless nickel plating for 40 minutes in an electroless nickel plating solution adjusted to pH 4.8-5.2 with ammonia water at a temperature.

Referring to the manufacturing process of the present invention thus applied to the embodiment as follows.

In the first process,

Aqueous solutions of magnesium and magnesium alloy dissolved in an emulsifier for metal at a concentration of 65 g / L are heated at 60 ° C. for 6 minutes, and then washed three times.

In the second process,

After immersing for 2 minutes in an aqueous solution at room temperature mixed with the ammonium fluoride 100g / L and 200cc / L of the hydrate through the first step and washed twice.

With the third process,

After immersing 10 g / L of potassium pyrophosphate hydrate 10g / L through the second process in a 40 ° C aqueous solution of pH 9.5 (pH) for 5 minutes, washing with water is performed three times.

With the fourth process,

In the same manner as in the second step through the third step, the solution is immersed for 2 minutes in an aqueous solution at room temperature mixed with 100 g / L ammonium fluoride and 200 cc / L of hydrate and washed twice.

With the fifth process,

In the same manner as in the third step, the fourth step is followed by immersion for 5 minutes in a 40 ° C aqueous solution of pH 9.5 in which 10 g / L of potassium pyrophosphate hydrate is dissolved.

In the sixth process,

Nickel sulfate 12.5g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, pumpkin acid 2g / L, sodium hypophosphite 33g / L through the fifth process Immerse in electroless nickel plating solution adjusted to pH 8.0 and rinse three times.

In the seventh process,

Through the sixth step, nickel sulfate 12.5 g / L, ammonia water 5 mL / L, ammonium difluoride 0.5 g / L, lactic acid 25 g / L, zucchini acid 2 g / L, sodium hypophosphite 55 g / L, and ammonia water at a temperature of 78 ° C. Immerse for 40 minutes in an electroless nickel plating solution adjusted to pH 5.0 and rinse three times.

In the eighth process,

After the seventh step, the plated object is washed and dried with distilled water, whereby the plated object becomes a finished product as a plated product.

Reproducible due to the complexity and complexity of the manufacturing process in the anodized and anodized material problem, which is prohibited to use the conventional chromate treatment by performing a double electroless nickel plating of the molding of magnesium and magnesium alloy by the above manufacturing process Its performance yield is low, it is easily damaged by external impact, and the additional productivity of wet process is offset by painting to improve corrosion resistance even after film formation.It is difficult to apply complex shapes in electroplating, and it is difficult to apply to complex shapes in electroplating. Corrosion problems with molded products due to galvanic corrosion and uneven current density. Corrosion problems due to acid dissolution and oxidation. Oxidation of etching formed in pretreatment process due to thin and incomplete coating film formation in substitution plating such as gaskets. It does not compensate for minute irregularities and pinholes on the surface The problem of swelling over time due to lack of adhesion and insufficient adhesion. During the plating in the conventional electroless nickel plating method which forms a protective and anticorrosive film on the surface of magnesium base using acid nickel plating in the range of pH (pH) 4.4-4.8. Instability of the electroless nickel plating bath, excessive pinholes and poor adhesion, extremely low yield of 30-40%, and low strength of the coating film in anodic oxidation and chemical conversion, etc. It is possible to completely solve the problems such as low and extremely low yield and problems commonly encountered in other conventional surface treatment methods.

In addition, the results of testing the durability of the sample coating film prepared for comparing the present invention with the above-described conventional methods, coating unmolding, specific dissolution, pinhole generation, swelling over time and the stability of the treatment solution are shown in Table 1 below. same.

TABLE 1

division Impact Abrasion Resistance Corrosion resistance Over time maintenance Chromate washout 65% pass 100% Anodization washout 72% pass 100% Chemical treatment washout 43% Passed 100% Electroplating No loss 85% pass 75% Jinkate washout 65% pass 70% Acid Electroless Nickel Plating No loss 72% pass 75% The present invention No loss 91% pass 91%

* Abrasion resistance test of Table 1 was confirmed that the wear and tear of the coating after reciprocating 5cm 100 times at 2kg pressure with a daily 10-won coins, and the corrosion resistance test by spraying 5% saline at 35 ℃ according to KSD9502 48 hours later, the rating number was 8 or more. Over time adhesion test was allowed to stand for 6 months in the air, followed by KS-05254's pull-out test tape tape method. It is.

In addition, the comparison of the stability, reproducibility, yield, the need for an additional process, and environmental friendliness of the treatment solution confirmed in the process of preparing the test piece for the test by treatment method is shown in Table 2 below.

TABLE 2

division Repeatability Yield Jig contact trace Treatment solution stability Chromate 100/100 65% none Disposal after 50dm2 Anodization 50/100 43% has exist Disposal after 100dm2 Chemical treatment 73/100 45% none Discard after 30dm2 treatment Electroplating 85/100 78% has exist Maintain after 1000dm2 Jinkate 88/100 81% none Discard after 30dm2 treatment Acid Electroless Nickel Plating 91/100 83% none Disposal after 150dm2 The present invention 92/100 91% none Disposal after 500dm2 treatment

* The criterion for determining reproducibility in Table 2 is the number of specimens showing uniform quality (corresponding to the required characteristics) among the treated specimens, and the yield is a percentage of the result of evaluating the coating properties of the specimen. The jig contact traces indicate that the contact area of the jig used in the anticorrosive treatment remains after the coating film is produced and the stability of the treatment liquid no longer affects the performance of the treatment liquid during the coating film production or during the repeated fabrication of the specimen. It is the sum of the specimen throughputs until discarded, which is not shown.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

Therefore, the present invention is anticorrosive treatment by the double electroless nickel plating method to improve the corrosion resistance of the molded article of magnesium and magnesium alloy, such as conventional chromate, anodization, chemical conversion, electroplating, casting, acidic electroless nickel plating, etc. This method not only solves many problems in impact abrasion resistance, corrosion resistance, adhesion over time, product reproducibility, yield, jig contact traces, and stability of treatment solution. Significantly improved various micro irregularities and pinholes to expand the use of magnesium and its alloying materials, improve the performance of various devices and machines, and improve the recycling of materials. There is.

Claims (1)

A method of electroless nickel plating of magnesium and magnesium alloy which is formed into a mold by die casting or similar molten state; A step of rinsing three times by immersing the coated object of magnesium and magnesium alloy in a 60 ° C. aqueous solution having a concentration of 60-70 g / L for 5-7 minutes using a metal emulsifier at pH 9-10; Immersing for two minutes in an aqueous solution at room temperature mixed with ammonium fluoride 100g / L of hydrate and 200cc / L of hydrofluoric acid through the above steps; Washing with water three times by immersing for 5 minutes in a 40 ° C. aqueous solution of PEHA (pH) 9-10 in which 10 g / L of potassium pyrophosphate hydrate is dissolved through the above steps; Immersing for two minutes in an aqueous solution at room temperature mixed with ammonium fluoride 100g / L of hydrate and 200cc / L of hydrofluoric acid through the above steps; Washing with water three times by immersing for 2 minutes in a 40 ° C. aqueous solution of Peha (pH) 9-10 in which 10 g / L of potassium pyrophosphate hydrate is dissolved through the above steps; Nickel sulfate 10-15g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, zucchini acid 2g / L, sodium hypophosphite 25-45g / L and mixed 75-80 ℃ Immersing for 20 minutes in an electroless nickel plating solution adjusted to pH 7.8-8.2 with ammonia water at a temperature; Nickel sulfate 10-15g / L, ammonia water 5mL / L, ammonium difluoride 0.5g / L, lactic acid 25g / L, zucchini acid 2g / L, sodium hypophosphite 50-60g / L and mixed 75-80 ℃ A double electroless nickel plating method using a pretreatment process of magnesium and magnesium alloy, characterized in that the electroless nickel plating for 40 minutes in an electroless nickel plating solution adjusted to pH 4.8-5.2 with ammonia water at a temperature.