CN1641075B - Surface activation treatment method and surface plating method for magnesium and magnesium alloy - Google Patents

Abstract

The invention discloses a surface activation treatment method for magnesium and magnesium alloys. The method comprises the steps of removing the oxide film and basic carbonate passivation film on the surface of the workpiece with a strong alkali solution containing fluoride, and then removing the segregated metal with an acid dipping solution. Intermediate compound, and then put it into the activation solution to form an active protective film and put it into the neutralization and consolidation solution to consolidate the protective film. Put the magnesium and magnesium alloy workpiece with the protective film into the zinc-dipping pretreatment solution containing the activator, and then pre-plate copper cyanide; it can also be directly electroless nickel-plated.

Description

Surface activation treatment method and surface plating method of magnesium and magnesium alloy

technical field

The invention relates to a surface activation treatment method for magnesium and magnesium alloys suitable for bright electroplating and electroless nickel plating and a method for performing bright plating or electroless nickel plating on the magnesium and magnesium alloys after surface activation treatment.

Background technique

Due to the high chemical activity of metal magnesium, it is easy to form an oxide film and a basic carbonate passivation film in the air, which leads to weak adhesion between the metal coating and the magnesium and magnesium alloy substrates during electroplating and electroless plating. Can not meet the process requirements of electroplating and electroless plating. Therefore, before electroplating and electroless plating, the passivation film must be eliminated and replaced by an active film, so as to ensure the activation state of the surface of magnesium and magnesium alloys, so as to obtain electroplating layers and electroless plating layers with good adhesion.

At present, there is no completely reliable method for electroplating or direct electroless plating on magnesium materials in the world. American Society for Testing and Testing ASTM B480-68 proposes a method for electroplating on the surface of magnesium and its alloys. Dow Chemicals in the United States, Norsk Hydro in Norway and W.Canning Materials in the UK have each disclosed their unique methods (The Dow Process, The Norsk Hydro Process, Euro Pat 030 305 & The WCM Process). However, the above-mentioned methods all have insufficient activation, or the activation film is not properly consolidated, resulting in poor adhesion and excessive corrosion of the coating, resulting in rough coating surface, failing to achieve the purpose of bright electroplating.

Contents of the invention

The purpose of the present invention is to provide a method for surface activation treatment of magnesium and magnesium alloys that can be used for bright electroplating and electroless nickel plating.

Another object of the present invention is to provide a method for bright electroplating of magnesium and magnesium alloys.

Another object of the present invention is to provide a method for performing electroless nickel plating on magnesium and magnesium alloys.

The surface activation treatment method of magnesium and magnesium alloys in the present invention comprises the following steps: first remove the oxide film and basic carbonate passivation film on the surface of the workpiece with a strong alkali solution containing fluoride; then remove the segregated metal with an acid dipping solution Inter-compound; Put the workpiece into the activation solution to expose the active magnesium and form a living protective film, then put it into the neutralization and consolidation solution to consolidate the protective film.

The method for carrying out bright electroplating of magnesium and magnesium alloys in the present invention comprises the following steps: first remove the oxide film and basic carbonate passivation film on the surface of the workpiece with a strong alkali solution containing fluoride; then remove the segregated metal with an acid dipping solution intermediate compound; then the workpiece is put into the activation solution, and after the active protective film is generated, it is put into the neutralization and consolidation solution to consolidate the protective film, and then the magnesium and magnesium alloy workpieces that have been treated to consolidate the protective film are taken out with a deionized After rinsing with water, carry out zinc dipping pre-treatment, and finally put it into copper cyanide plating solution for pre-plating.

The method for carrying out electroless nickel plating on magnesium and magnesium alloys in the present invention comprises the following steps: first remove the oxide film and basic carbonate passivation film on the surface of the workpiece with a strong alkali solution containing fluoride; then remove the segregation with an acid dipping solution intermetallic compound; then the workpiece is put into the activation solution, and after the active protective film is generated, it is put into the neutralization and consolidation solution to consolidate the protective film, and then the magnesium and magnesium alloy workpieces treated as the consolidated protective film are taken out for use Electroless nickel plating is performed directly after ionized water.

In the surface activation treatment method of magnesium and magnesium alloys of the present invention, due to the thicker oxide film and basic carbonate passivation film on the surface of ordinary magnesium and magnesium alloy metals, the electrochemical reduction method can be used to remove the passivation film. In a strong alkaline solution of sodium chloride, the surface of magnesium and magnesium alloys is passed through a high-density cathodic current, resulting in strong cathodic polarization and a very high cathodic polarization potential. After a certain period of time, due to the electrochemical reduction of the cathode and the cathode The combined effect of the reacted atomic hydrogen eliminates the passivation film on the surface of magnesium and magnesium alloy.

Since segregated intermetallic compounds, such as Mg ₁₇ Al ₁₂ , still exist on the surface of magnesium and magnesium alloys after the passivation film is removed, it is necessary to use a special acid dipping solution to remove these magnesium-aluminum segregated intermetallic compounds. After the passivation film and intermetallic compound are eliminated, the oxide film will still form quickly on the surface of magnesium and magnesium alloy in the air, but compared with the workpiece exposed to the air for a long time, the thickness is thinner, the structure is not dense, and it is easy to dissolve In the acidic activation solution, the active magnesium is exposed. At the same time, the hydrogen ions in the activation solution get electrons to form active atomic hydrogen, which is adsorbed on the surface of magnesium and magnesium alloy, and a part of it forms a gray magnesium hydride film with active magnesium. The magnesium hydride film is consolidated under specific conditions in the neutralizing and consolidating solution, preventing further corrosion of magnesium metal and its alloys. At the same time, this monolayer acts as a barrier layer, keeping the chemical activity of the activated membrane in the air.

In this way, the magnesium and magnesium alloys with activated film can be pre-treated by zinc dipping, and copper cyanide pre-plating can be performed after zinc dipping or electroless nickel plating can be directly performed after the protective film is consolidated.

In addition, the operation of removing the oxide film and the basic carbonate passivation film on the surface of the workpiece in the method of the present invention can be carried out by methods known in the prior art, for example, magnesium or magnesium alloy sample workpiece surface is treated as After brightening the surface, put it into a strong alkali aqueous solution containing 10% fluoride MF and 10% MOH by weight, its pH = 13, so that the surface of magnesium and magnesium alloys passes through a high-density cathode current of 2±1A/dm ² , and the cathode electrode The heating time is 10 minutes to eliminate the oil stains, stains on the surface of the workpiece and the oxide film and basic carbonate passivation film formed on the surface of magnesium and magnesium alloy exposed to the air.

Detailed ways

Example 1:

Magnesium and magnesium alloy surface activation treatment methods for bright electroplating and bright chemical nickel plating in the present invention are processed according to the following steps:

1) Put the surface treatment of die-casting magnesium and magnesium alloy workpieces into a bright surface and then put them into an aqueous solution containing 10% sodium fluoride and 10% sodium hydroxide by weight, and electrolyze them with ^a cathodic current of 2A/dm for 10 minutes. Remove the oxide film and basic carbonate passivation film on the surface of the workpiece;

2) Take out and rinse with deionized water and then immerse in an aqueous solution of 12% by weight of chromic acid, 5% of potassium nitrate, and 10% of nitric acid for immersion treatment to remove segregated intermetallic compounds, such as Mg ₁₇ Al ₁₂ , the immersion The solution is prepared with deionized water, the temperature of immersion is 30°C, and the immersion time is 3 minutes;

3) Take it out and rinse it with deionized water and then immerse it in an aqueous solution of 10% ammonium bifluoride and 5% phosphoric acid by weight for activation treatment to generate an activated protective film. The activation treatment solution is prepared with deionized water, wherein the temperature of activation treatment is at 30°C for 5 minutes;

4) Take it out and rinse it with deionized water, and then immerse it in an aqueous solution of 20% by weight sodium pyrophosphate and 5% sodium fluoride for consolidation, that is, to consolidate and activate the protective film. The consolidation solution is prepared with deionized water, and the temperature for consolidation is 60 °C for 10 minutes.

The workpiece after the surface activation treatment is taken out and rinsed with deionized water and then put into 10% zinc sulfate and 20% sodium pyrophosphate, and 5% (weight) sodium fluoride, and 5% (weight) Sodium carbonate is used for zinc dip pretreatment. The zinc dip pretreatment solution is prepared with deionized water. The temperature of zinc dip pretreatment is 70°C and the time is 10 minutes. Then take out the workpiece and rinse it with deionized water before putting it into cyanide. Pre-plating is carried out in the copper plating solution, the copper cyanide pre-plating solution used is CuCN 20-70g/l, NaCN 30-100g/l, KNaC ₄ H ₄ O ₆ 30-50g/l, the temperature is 50°C, the pH The current density is 10.5-12, the current density is 4A/dm ² in the first minute, then drops to 2A/dm ² , and the plating time is 12 minutes.

In this embodiment, due to the existence of the activated protective film and its proper consolidation, the electroplated metal layer with strong adhesion can be grown to more than 1 micron on the surface, and can be used as an intermediary layer for further electroplated metal layers.

Example 2:

Magnesium and magnesium alloy surface activation treatment methods for bright electroplating and bright chemical nickel plating in the present invention are processed according to the following steps:

1) Treat the surface of the die-casting magnesium and magnesium alloy workpieces to a bright surface, then put them into an aqueous solution containing 10% sodium fluoride and 10% potassium hydroxide by weight, and electrolyze them for 10 minutes with ^a cathodic current of 1A/dm;

2) Take it out and rinse it with deionized water, then immerse it in 2% by weight oxalic acid solution for immersion treatment, the immersion solution is prepared with deionized water, the temperature of immersion is 25°C, and the time of immersion is 2 minutes;

3) After taking it out and rinsing it with deionized water, proceed according to step 3) and subsequent steps in Example 1.

In this embodiment, due to the existence of the activated protective film and its proper consolidation, the electroplated metal layer with strong adhesion can be grown to more than 1 micron on the surface, and can be used as an intermediary layer for further electroplated metal layers.

Example 3:

Magnesium and magnesium alloy surface activation treatment methods for bright electroplating and bright chemical nickel plating in the present invention are processed according to the following steps:

1) Firstly treat the surface of the die-casting magnesium and magnesium alloy workpieces into a bright surface, then put them into an aqueous solution containing 10% sodium fluoride and 10% sodium hydroxide by weight, and electrolyze for 10 minutes through a cathodic current ^{of 2A} /dm;

2) Take it out and rinse it with deionized water and then immerse it in 1.5% by weight oxalic acid and 200ppm ethoxybutynediol (wetting agent) aqueous solution for immersion treatment. The immersion solution is prepared with deionized water and strictly controlled chlorine The ion concentration should not be greater than 2ppm, the temperature is 25°C, and the immersion time is 1 minute;

3) Take it out and rinse it with deionized water, and then process it according to step 3 and subsequent steps in Example 1.

In this embodiment, due to the existence of the activated protective film and its proper consolidation, the electroplated metal layer with strong adhesion can be grown to more than 1 micron on the surface, and can be used as an intermediary layer for further electroplated metal layers.

Example 4:

Magnesium and magnesium alloy surface activation treatment methods for bright electroplating and bright chemical nickel plating in the present invention are processed according to the following steps:

1) Treat the surface of die-casting magnesium and magnesium alloy workpieces to a bright surface first, and then put them into an aqueous solution containing 10% sodium fluoride and 10% sodium hydroxide by weight. The aqueous solution is prepared with deionized water, and the concentration of chloride ions should not exceed 2ppm , through 1A/dm ² cathodic current electrolysis for 10 minutes;

2) Take it out and rinse it with deionized water, and then immerse it in an aqueous solution of 12% by weight chromic acid, 5% potassium nitrate, and 10% nitric acid for immersion treatment. The immersion solution is prepared with deionized water at a temperature of 25° C. and an immersion time of 2 minutes;

3) Take it out and rinse it with deionized water, and then immerse it in an aqueous solution of 10% by weight ammonium bifluoride and 5% phosphoric acid for activation. The activation solution is prepared with deionized water at a temperature of 25° C. and an activation time of 3 minutes;

4) Take it out and rinse it with deionized water, and then immerse it in an aqueous solution of 20% by weight sodium pyrophosphate and 5% sodium fluoride for consolidation treatment. The consolidation solution is prepared with deionized water at a temperature of 80° C. and a consolidation time of 10 minutes.

The workpiece after the surface activation treatment is taken out and rinsed with deionized water and then directly subjected to electroless nickel plating. The electroless nickel plating solution can adopt a formula known to the public in the prior art or other special formulas, for example: 2NiCO ₃ 33Ni(OH) ₂ 4H ₂ O 10g/l, HF (48%) 9ml/l, C ₆ H ₈ O ₇ 5g/l, NH ₄ HF ₂ 10g/l, NH ₄ OH (30%) 31ml/l l, temperature 80°C, pH 4.5, deposition rate 20-25μm/hr.

In this embodiment, due to the presence and proper consolidation of the activated protective film, it is possible to ensure that the electroless metal plating layer with strong adhesion grows on its surface to a thickness of more than 1 micron, and then it can be used as an intermediary layer for further electroplating metal layers.

Example 5:

Magnesium and magnesium alloy surface activation treatment methods for bright electroplating and bright chemical nickel plating in the present invention are processed according to the following steps:

1) Treat the surface of the die-casting magnesium and magnesium alloy workpieces to a bright surface, then put them into an aqueous solution containing 10% sodium fluoride and 10% potassium hydroxide by weight, and electrolyze them for 10 minutes with ^a cathodic current of 1A/dm;

2) Take it out and rinse it with deionized water, and then immerse it in 2% by weight oxalic acid solution for immersion treatment. The immersion solution is prepared with deionized water at a temperature of 25°C and the immersion time is 2 minutes;

3) After taking it out and rinsing it with deionized water, it is processed according to step 3) and subsequent steps in Example 4.

In this embodiment, due to the existence of the activated protective film and its proper consolidation, it can ensure that the electroless metal plating layer with strong adhesion grows on its surface to a thickness of more than 1 micron, and then it can be used as an intermediary layer for further electroplating metal layers.

Embodiment 6:

Magnesium and magnesium alloy surface activation treatment methods for bright electroplating and bright chemical nickel plating in the present invention are processed according to the following steps:

1) Put the die-casting magnesium and magnesium alloy workpieces into a bright surface and then put them into an aqueous solution containing 10% sodium fluoride and 10% sodium hydroxide by weight, and electrolyze them for 10 minutes with a cathodic current ^{of 2A} /dm;

2) Take it out and rinse it with deionized water and then immerse it in 1.5% by weight oxalic acid and 200ppm ethoxybutynediol (wetting agent) aqueous solution for immersion treatment. The immersion solution is prepared with deionized water and strictly controlled chlorine The ion concentration should not be greater than 2ppm, the temperature is 25°C, and the immersion time is 1 minute;

3) After taking it out and rinsing it with deionized water, it is processed according to step 3) and subsequent steps in Example 4.

In this embodiment, due to the existence of the activated film and its proper consolidation, it can ensure that the electroless metal plating layer with strong adhesion grows on its surface to a thickness of more than 1 micron, and then it can be used as an intermediary layer for further electroplating metal layers.

Claims (8)

1. A surface activation treatment method for magnesium and magnesium alloys, comprising the following steps: remove the oxide film and basic carbonate passivation film on the workpiece surface with a strong alkali solution containing fluoride; then remove the segregation with acid dipping solution Intermetallic compounds; then put the workpiece into the activation solution, and after the active protective film is formed, put it into the neutralization and consolidation solution to consolidate the protective film; wherein: The strong lye containing fluoride is: an aqueous solution of 10% sodium fluoride and 10% sodium hydroxide by weight; The composition of described pickling liquid is: the aqueous solution of the chromic acid of 12% by weight, the potassium nitrate of 5% and the nitric acid of 10%, or the oxalic acid of 2% by weight, or the oxalic acid of 1.5% by weight and 200ppm aqueous solution of ethoxylated butynediol; The activation solution is: an aqueous solution of 10% by weight of ammonium bifluoride and 5% of phosphoric acid; The neutralizing and consolidating liquid is: an aqueous solution of 20% by weight sodium pyrophosphate and 5% sodium fluoride; The step of removing the oxide film and the basic carbonate passivation film on the surface of the workpiece with the strong alkali solution containing fluoride is to treat the surface of the magnesium or magnesium alloy workpiece into a bright surface and then put in sodium fluoride containing 10% by weight and 10% sodium hydroxide aqueous solution for cathodic electrolysis. 2. The surface activation treatment method for magnesium and magnesium alloys according to claim 1, characterized in that: the acid dipping solution is prepared with deionized water, wherein the temperature of acid dipping is 20-50°C, and the time is 0.1- 30 minutes. 3. The surface activation treatment method for magnesium and magnesium alloys according to claim 1, characterized in that: the activation solution is prepared with deionized water, wherein the activation treatment temperature is 20-50°C, and the time is 0.1-30 minute. 4. The surface activation treatment method for magnesium and magnesium alloys according to claim 1, characterized in that: the neutralization and consolidation solution is prepared with deionized water, wherein the neutralization and consolidation temperature is 20-90°C, and the time is 0.1-30 minutes. 5. A method for surface plating of magnesium and magnesium alloys, comprising the steps of: removing the oxide film and the basic carbonate passivation film on the workpiece surface with a strong alkali solution containing fluoride; then removing the segregated metal with an acid dipping solution intermediate compound; then the workpiece is put into the activation solution, and after the active protective film is generated, it is put into the neutralization and consolidation solution to consolidate the protective film, and then the magnesium and magnesium alloy workpieces that have been treated to consolidate the protective film are taken out with a deionized After rinsing with water, carry out pre-treatment of zinc immersion, and finally put it into copper cyanide plating solution for pre-plating; where: The strong lye containing fluoride is: an aqueous solution of 10% sodium fluoride and 10% sodium hydroxide by weight; The composition of described pickling liquid is: the aqueous solution of the chromic acid of 12% by weight, the potassium nitrate of 5% and the nitric acid of 10%, or the oxalic acid of 2% by weight, or the oxalic acid of 1.5% by weight and 200ppm aqueous solution of ethoxylated butynediol; The activation solution is: an aqueous solution of 10% by weight of ammonium bifluoride and 5% of phosphoric acid; The neutralizing and consolidating liquid is: an aqueous solution of 20% by weight sodium pyrophosphate and 5% sodium fluoride; The step of removing the oxide film and the basic carbonate passivation film on the surface of the workpiece with the strong alkali solution containing fluoride is to treat the surface of the magnesium or magnesium alloy workpiece into a bright surface and then put in sodium fluoride containing 10% by weight and 10% sodium hydroxide aqueous solution for cathodic electrolysis. 6. according to the surface plating method of magnesium described in claim 5, magnesium alloy, it is characterized in that: described galvanizing treatment liquid is a kind of aqueous solution that is made up of following components: the zinc sulfate of 10% by weight, 20% sodium pyrophosphate, 5% sodium fluoride and 5% sodium carbonate; the copper cyanide pre-plating solution is CuCN20-70g/l, NaCN30-100g/l, KNaC ₄ H ₄ O ₆ 30-50g/l , the pre-plating temperature is 50°C, the pH value is 10.5-12, the current density is 4A/dm ² for the first minute, and then decreased to 2A/dm ² , and the plating time is 12 minutes. 7. A method for surface plating of magnesium and magnesium alloys, comprising the steps of: removing the oxide film and the basic carbonate passivation film on the surface of the workpiece with a strong alkali solution containing fluoride; then removing the segregated metal with an acid dipping solution Then put the workpiece into the activation solution, put it into the neutralization and consolidation solution to consolidate the protective film after the active protective film is generated, and then take out the magnesium and magnesium alloy workpieces that have been treated as the consolidated protective film and use deionization Electroless nickel plating is carried out directly after water washing; where: The strong lye containing fluoride is: an aqueous solution of 10% sodium fluoride and 10% sodium hydroxide by weight; The composition of described pickling liquid is: the aqueous solution of the chromic acid of 12% by weight, the potassium nitrate of 5% and the nitric acid of 10%, or the oxalic acid of 2% by weight, or the oxalic acid of 1.5% by weight and 200ppm aqueous solution of ethoxylated butynediol; The activation solution is: an aqueous solution of 10% by weight of ammonium bifluoride and 5% of phosphoric acid; The neutralizing and consolidating liquid is: an aqueous solution of 20% by weight sodium pyrophosphate and 5% sodium fluoride; The step of removing the oxide film and the basic carbonate passivation film on the surface of the workpiece with the strong alkali solution containing fluoride is to treat the surface of the magnesium or magnesium alloy workpiece into a bright surface and then put in sodium fluoride containing 10% by weight and 10% sodium hydroxide aqueous solution for cathodic electrolysis. 8. according to the surface plating method of magnesium, magnesium alloy described in claim 7, it is characterized in that: the plating solution of described direct electroless nickel plating is 2NiCO ₃ 3Ni(OH) ₂ 4H ₂ O 10g/l, 48 % HF 9ml/l, C ₆ H ₈ O ₇ 5g/l, NH ₄ HF ₂ 10g/l, 30% NH ₄ OH 31ml/l mixture, temperature is 80°C, pH 4.5, deposition rate 20- 25μm/hr.