Method for rack plating of pure aluminum or aluminum-manganese alloy corrosion-resistant plating layer on aluminum alloy connector

Abstract

The invention belongs to the technical field of aluminum alloy coatings, and discloses a method for rack plating of a pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector, which comprises the following steps: step 1, deoiling, step 2, pickling, step 3, anode activation: taking an ionic liquid as an electrolyte, taking the aluminum alloy connector as an anode, taking an aluminum plate as a cathode, dissolving an oxidation film on the surface of a workpiece after electrification, and then, carrying out electroplating on the surface of the workpiece; exposing a fresh metal surface; step 4, electroplating aluminum or aluminum manganese: electroplating aluminum and aluminum manganese alloy in ionic liquid with different molar ratios, wherein the ionic liquid is prepared from EMIC, AlCl3 and anhydrous manganese chloride MnCl2; step 5, shot blasting; step 6, activating; and 7, passivating and sealing. The aluminum electroplating or aluminum-manganese plating of the aluminum alloy connector is an optimal alternative scheme of a cadmium electroplating process, and can meet the corrosion resistance requirements of the aluminum alloy connector for more than 1000h of neutral salt mist and more than 500h of acid salt mist, so that the aluminum alloy connector can keep excellent reliability and longer service life in a harsh corrosion environment.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy plating, and in particular relates to a method for plating a pure aluminum or aluminum-manganese alloy corrosion-resistant plating layer on an aluminum alloy connector. Background Art

[0002] Aluminum alloy connectors are widely used in electronics, communications, automobiles and other fields, and their surface treatment technology has an important impact on their performance and service life. At present, the surface treatment technology of aluminum alloy connectors mainly includes anodizing, electroplating, chemical plating, spraying, chemical conversion, etc. Among them, electroplating and chemical plating can form a metal film on the surface of the connector to increase conductivity, wear resistance, corrosion resistance and aesthetics. Commonly used metal plating layers include nickel, silver, cadmium, etc. The chemical nickel plating layer of aluminum alloy connectors has good wear resistance and conductivity, but the corrosion resistance cannot meet the requirements of use in harsh corrosive environments. In the military field, connectors are required to have high stability and reliability, and high requirements are placed on their service life or corrosion resistance in corrosive environments. Therefore, the military field is still using a large number of cadmium plating processes with good corrosion resistance. However, cadmium electroplating technology is extremely harmful to the environment and has strong carcinogenicity, and other processes are urgently needed to replace it, but there is currently no better alternative to traditional electroplating processes. Summary of the invention

[0003] The object of the present invention is to provide a method for plating a pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector to solve the above-mentioned technical problems.

[0004] In order to solve the above technical problems, the specific technical scheme of the method for mounting pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector of the present invention is as follows: A method for mounting a pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector comprises the following steps: Step 1: Degreasing: Use a degreasing agent or organic solvent that is less corrosive to aluminum alloys for ultrasonic cleaning to achieve the purpose of degreasing; Step 2: Pickling: remove the thick oxide film formed on the surface of the aluminum alloy after long-term oxidation in the air; Step 3: Anodic activation: ionic liquid is used as the electrolyte, the aluminum alloy connector is used as the anode, and the aluminum plate is used as the cathode. After power is applied, the oxide film on the surface of the workpiece is dissolved, exposing a fresh metal surface; Step 4: electroplating aluminum or aluminum manganese: electroplating aluminum and aluminum manganese alloy are electroplated in ionic liquids with different molar ratios configured by EMIC, AlCl3 and anhydrous manganese chloride (MnCl2); Step 5: Shot peening: Shot peening is used to improve the uniformity of the appearance of the aluminum-plated connector and the density of the coating; Step 6: Activation: After the shot peened connector is ultrasonically cleaned in water, it is pickled in a pickling solution of HNO3 and HF to remove the oxide film of the coating before passivation, followed by ultrasonic water washing; Step 7: Passivation and sealing: Use chromate passivator for passivation.

[0005] Furthermore, the step 1 is cleaned more than twice, each cleaning takes 3-30 minutes, and then blow-dried.

[0006] Furthermore, in step 2, the substrate is pickled in a pickling solution of 10-70% HNO3 and 5-50% HF for 5-60 s, then ultrasonically washed three times, and blown dry.

[0007] Furthermore, the anode activation in step 3 is carried out in an electroplating equipment cabin with a water content and an oxygen content of less than 50 ppm, and the anode activation current density is set at 5-50 mA / cm 2 Within the range, activation is repeated 1-5 times, each activation takes 5-120s to dissolve the 0-2 μm oxide film and metal matrix on the surface of the aluminum alloy. The activation solution is composed of aluminum chloride: 1-methyl-3-ethylimidazole chloride (AlCl3: EMIC) with a molar ratio of 1.5-2:1.

[0008] Furthermore, in step 4, the water content and oxygen content in the electroplating chamber are maintained at less than 50 ppm, the ionic liquid aluminum plating solution is composed of AlCl3:EMIC with a molar ratio of 1.5-2:1, and a nitrogen phenanthrene derivative electroplating additive is added, and the ionic liquid aluminum manganese plating solution is composed of AlCl3:EMIC with a molar ratio of 1.5-2:1, 0.06-0.25 mol / L of anhydrous MnCl2 and additives are added, the plating solution temperature during electroplating is controlled at 10-80 °C, and the electroplating current density is controlled at 4-20 A / dm 2 The thickness of the electroplated aluminum and aluminum-manganese alloy coating is 0-100 μm. After electroplating, it is cleaned in an organic solvent and then ultrasonically cleaned in water for more than 2 times.

[0009] Furthermore, the step 5: using spherical sand for shot peening, the shot peening air pressure is controlled in the range of 0.05-0.35MPa, the distance between the spray gun and the workpiece is 5-20 cm, and the shot peening is performed until the appearance of the workpiece is consistent.

[0010] Furthermore, in step 6, the substrate is pickled in a pickling solution of 10-70% HNO3 and 5-50% HF for 3-15 seconds to remove the oxide film of the coating before passivation, followed by ultrasonic water washing 3 times.

[0011] Furthermore, the passivation conditions of the chromate passivator in step 7 are as follows: a passivation temperature of 20-30° C., a pH range of 1.3-1.8, a passivation time of 30-180 s, a drying temperature of 50-120° C., and a drying time of 5-25 min.

[0012] A method for plating pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector of the present invention has the following advantages: the method for plating pure aluminum or aluminum-manganese alloy coating on an aluminum alloy connector using ionic liquid of the present invention has the following advantages: the electrochemical potential of the coating and the substrate is close, the galvanic corrosion current is small, and the bonding force, corrosion resistance, conductivity and wear resistance of the pure aluminum and aluminum-manganese coatings are good. The electroplating process is less harmful to the environment and human body, and can effectively improve the problem of electroplating pollution. The electroplating process is simple, stable and has a high product yield. Therefore, the electroplating of aluminum or aluminum-manganese coating on an aluminum alloy connector is the best alternative to the electroplating cadmium process, which can meet the corrosion resistance requirements of the aluminum alloy connector for more than 1000 hours of neutral salt spray and more than 500 hours of acidic salt spray, so that it can maintain excellent reliability and a long service life in harsh corrosive environments. The hardness range of the pure aluminum-aluminum-manganese coating is 30-500 HV, which can meet the coating mechanical property requirements of different aluminum alloy connectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a flow chart of the method for mounting pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector of the present invention; Figure 2 This is a rendering of Example 1 of the present invention; Figure 3 This is the effect diagram of Example 2 of the present invention. DETAILED DESCRIPTION

[0014] In order to better understand the purpose, structure and function of the present invention, the following is a further detailed description of a method for plating a pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector of the present invention in conjunction with the accompanying drawings.

[0015] like Figure 1 As shown, a method for plating a pure aluminum or aluminum-manganese alloy corrosion-resistant coating on an aluminum alloy connector of the present invention comprises the following steps: Step 1: Degreasing Use a degreasing agent or organic solvent with weak corrosion to aluminum alloy for ultrasonic cleaning to achieve the purpose of degreasing. According to the oil pollution on the surface of the workpiece, determine the specific cleaning times and cleaning time. Generally, clean more than 2 times, each cleaning lasts 3-30 minutes, and then blow dry.

[0016] Step 2: Pickling The aluminum alloy was pickled in a pickling solution of 10-70% HNO3 and 5-50% HF for 5-60 s to remove the thick oxide film formed on the surface of the aluminum alloy due to long-term oxidation in the air, followed by ultrasonic water washing for 3 times and drying.

[0017] Step 3: Anodic Activation Anodic activation is carried out in the electroplating equipment cabin with water content and oxygen content less than 50ppm. Ionic liquid is used as electrolyte, aluminum alloy connector is used as anode, and aluminum plate is used as cathode. After power is applied, the oxide film on the surface of the workpiece is dissolved, exposing the fresh metal surface. The anode activation current density is set at 5-50 mA / cm 2 The activation is repeated 1-5 times within the range of 5-120 s each time, dissolving the 0-2 μm oxide film and metal matrix on the surface of the aluminum alloy. The activation solution is prepared by aluminum chloride: 1-methyl-3-ethylimidazole chloride (AlCl3: EMIC) in a molar ratio of 1.5-2:1.

[0018] Step 4: Electroplating Aluminum or Aluminum Manganese The electroplating of aluminum and aluminum-manganese alloy is carried out in ionic liquids with different molar ratios composed of EMIC, AlCl3 and anhydrous manganese chloride (MnCl2), and the water content and oxygen content in the electroplating chamber are maintained at less than 50ppm. The ionic liquid aluminum plating solution is composed of AlCl3:EMIC with a molar ratio of 1.5-2:1, and a nitrogen phenanthroline derivative electroplating additive of appropriate concentration is added. The ionic liquid aluminum-manganese plating solution is composed of AlCl3:EMIC with a molar ratio of 1.5-2:1, 0.06-0.25mol / L of anhydrous MnCl2, and additives of appropriate concentration. The plating solution temperature during electroplating is controlled at 10-80 ℃, and the electroplating current density is controlled at 4-20 A / dm 2 , the thickness of electroplated aluminum and aluminum-manganese alloy coating is 0-100 μm. After electroplating, it is cleaned in an organic solvent and then ultrasonically cleaned in water for more than 2 times.

[0019] Step 5: Shot Peening Shot peening is used to improve the uniformity of the appearance of aluminum-plated connectors and the density of the coating. Spherical sand such as glass beads and zirconium oxide sand is used for shot peening. The shot peening pressure is controlled in the range of 0.05-0.35MPa, the distance between the spray gun and the workpiece is 5-20 cm, and the shot peening is performed until the appearance of the workpiece is consistent.

[0020] Step 6: Activation After shot peening, the connector was ultrasonically cleaned in water, then pickled in a pickling solution of 10-70% HNO3 and 5-50% HF for 3-15s to remove the oxide film of the coating before passivation, and then ultrasonically washed 3 times.

[0021] Step 7: Passivation and sealing In order to improve the resistance of electroplated aluminum and aluminum manganese and obtain the appearance of golden yellow, green and other products, chromate passivation agent is required for passivation. The passivation conditions of chromate passivation agent are passivation temperature 20-30℃, PH range 1.3-1.8, passivation time 30-180 s, drying temperature 50-120℃, and drying time 5-25 min.

[0022] Technology Examples Example 1: (1) Degreasing: The 6061 aluminum alloy was ultrasonically cleaned with acetone for 15 min and then ultrasonically cleaned with anhydrous ethanol for 15 min to remove the oil.

[0023] (2) Pickling: Pickle in a 20% HNO3 and 10% HF pickling solution for 10 seconds, then ultrasonically rinse three times and blow dry.

[0024] (3) Anodic activation: Anodic activation was performed in an AlCl3:EMIC ionic liquid with a molar ratio of 2:1 at a current density of 30 mA / cm 2 , repeated activation 3 times, each activation takes 10-20s.

[0025] (4) Aluminum electroplating: Add 1g / L of electroplating additive to the plating solution of AlCl3: EMIC ionic liquid with a molar ratio of 1.8:1 at 10 mA / cm 2 The current density was 2.500, the electroplating time was 90 min, and the plating temperature was 40°C. After electroplating, the samples were ultrasonically cleaned with anhydrous ethanol and water.

[0026] (5) Shot peening: Use 120 mesh glass beads for shot peening at 0.15 MPa. The distance between the spray gun and the workpiece is 5-20 cm. Shot peening is performed until the workpiece has a consistent appearance.

[0027] (6) Activation: After ultrasonic cleaning three times, pickling in a 25% HNO3 and 5% HF pickling solution for 5 s, followed by ultrasonic water washing three times.

[0028] (7) Passivation: Passivate in chromate passivation solution for 2 min, passivation temperature 25 ℃, and dry in a drying oven at 80 ℃ for 10 min.

[0029] Example 1 Technical Effect: like Figure 2 As shown in the figure, after electroplating, a 18-20 μm uniform and dense pure aluminum coating is formed on the connector surface. The coating has good interface bonding with the 6061 substrate, and good bonding strength is shown after shot peening and 1×1mm 100-grid test. The hardness of the pure aluminum coating is 32-35HV. The green aluminum-plated connector after passivation has no corrosion after 1000h of neutral salt spray test and no corrosion after 500h of acid salt spray test, showing strong corrosion resistance, meeting the corrosion resistance requirements of replacing electroplated cadmium.

[0030] Example 2: (1) Degreasing: The 6061 aluminum alloy was ultrasonically cleaned with acetone for 15 min and then ultrasonically cleaned with anhydrous ethanol for 15 min to remove the oil.

[0031] (2) Pickling: Pickle in a 40% HNO3 and 20% HF pickling solution for 10 s, then ultrasonically rinse three times and blow dry.

[0032] (3) Anodic activation: Anodic activation was performed in an AlCl3:EMIC ionic liquid with a molar ratio of 1.5:1 at a current density of 20 mA / cm 2 , and the activation was repeated 3 times, each activation taking 40 s.

[0033] (4) Electroplating aluminum manganese: Add 0.25 mol / L MnCl2 to the AlCl3: EMIC ionic liquid with a molar ratio of 2:1 as the aluminum manganese alloy plating solution at 8 mA / cm 2 The current density was 200, the electroplating time was 100 min, and the bath temperature was 25°C. After electroplating, the samples were ultrasonically cleaned with anhydrous ethanol and water.

[0034] (5) Shot peening: Use B170 zirconium oxide sand for shot peening at 0.2 MPa. The distance between the spray gun and the workpiece is 5-20 cm. Shot peening is performed until the workpiece has a consistent appearance.

[0035] (6) Activation: After ultrasonic cleaning three times, pickle in a 20% HNO3 and 30% HF pickling solution for 5 seconds, and then ultrasonically wash with water three times.

[0036] (7) Passivation: Passivate in chromate passivation solution for 60 s, passivation temperature 25 ℃, and dry in a drying oven at 70 ℃ for 10 min.

[0037] Example 2 Technical Effect: like Figure 3 As shown in the figure, after electroplating, a 15-16 μm uniform and dense aluminum-manganese coating is formed on the connector surface. The coating has good interface bonding with the 6061 substrate, and has shown good bonding strength after shot peening and 1×1mm 100-grid test. The hardness of the aluminum-manganese coating is 350-400HV. The dark green connector after passivation has no corrosion after 1000 h of neutral salt spray test and no corrosion after 1000 h of acid salt spray test, showing extremely strong corrosion resistance.

[0038] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating, characterized in that: The steps include: Step 1: Degreasing: Use a degreasing agent or organic solvent that is less corrosive to aluminum alloys for ultrasonic cleaning to achieve the purpose of degreasing; Step 2: Pickling: Use pickling solution to remove the thick oxide film formed on the surface of aluminum alloy after long-term oxidation in the air; Step 3: Anodic activation: Ionic liquid is used as electrolyte, the aluminum alloy connector is used as anode, and the aluminum plate is used as cathode. After power is applied, the oxide film on the surface of the workpiece is dissolved, exposing a fresh metal surface. Step 4: electroplating aluminum or aluminum manganese: electroplating aluminum and aluminum manganese alloy are electroplated in ionic liquids with different molar ratios configured by EMIC, AlCl3 and anhydrous manganese chloride (MnCl2); Step 5: Shot peening: Shot peening is used to improve the uniformity of the appearance of the aluminum-plated connector and the density of the coating; Step 6: Activation: After the shot peened connector is ultrasonically cleaned in water, it is pickled in a pickling solution of HNO3 and HF to remove the oxide film of the coating before passivation, followed by ultrasonic water washing; Step 7: Passivation and sealing: Use chromate passivator for passivation.

2. The method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating according to claim 1, characterized in that: The step 1 is to clean for more than 2 times, each cleaning takes 3-30 minutes, and then blow dry.

3. The method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating according to claim 1, characterized in that: In step 2, the substrate is pickled in a pickling solution of 10-70% HNO3 and 5-50% HF for 5-60 s, then ultrasonically washed three times, and blown dry.

4. The method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating according to claim 1, characterized in that: The anode activation in step 3 is carried out in an electroplating equipment cabin with a water content and an oxygen content of less than 50 ppm, and the anode activation current density is set at 5-50 mA / cm 2 Within the range, activation is repeated 1-5 times, each activation takes 5-120 s to dissolve the 0-2 μm oxide film and metal matrix on the surface of the aluminum alloy. The activation solution is composed of aluminum chloride: 1-methyl-3-ethylimidazole chloride (AlCl3: EMIC) with a molar ratio of 1.5-2:

1.

5. The method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating according to claim 1, characterized in that: In step 4, the water content and oxygen content in the electroplating chamber are maintained at less than 50 ppm, the ionic liquid aluminum plating solution is composed of AlCl3:EMIC with a molar ratio of 1.5-2:1, and a nitrogen phenanthrene derivative electroplating additive is added, and the ionic liquid aluminum manganese plating solution is composed of AlCl3:EMIC with a molar ratio of 1.5-2:1, 0.06-0.25 mol / L of anhydrous MnCl2 and additives are added, the plating solution temperature during electroplating is controlled at 10-80 °C, and the electroplating current density is controlled at 4-20 A / dm 2 The thickness of the electroplated aluminum and aluminum-manganese alloy coating is 0-100 μm. After electroplating, it is cleaned in an organic solvent and then ultrasonically cleaned in water for more than 2 times.

6. The method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating according to claim 1, characterized in that: Step 5: Shot peening is performed using spherical sand, the shot peening air pressure is controlled in the range of 0.05-0.35 MPa, the distance between the spray gun and the workpiece is 5-20 cm, and the shot peening is performed until the workpiece has a consistent appearance.

7. The method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating according to claim 1, characterized in that: Step 6: Pickle in a pickling solution of 10-70% HNO3 and 5-50% HF for 3-15s to remove the oxide film of the coating before passivation, and then ultrasonically rinse with water for 3 times.

8. The method for coating an aluminum alloy connector with a pure aluminum or aluminum-manganese alloy corrosion-resistant coating according to claim 1, characterized in that: The passivation conditions of the chromate passivator in step 7 are as follows: a passivation temperature of 20-30° C., a pH range of 1.3-1.8, a passivation time of 30-180 s, a drying temperature of 50-120° C., and a drying time of 5-25 min.

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