A method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts

Abstract

The invention discloses a method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts, which comprises sequentially performing degreasing, alkali washing, pickling, primary zinc immersion, zinc stripping, secondary zinc immersion, cyanide-free alkali copper, pre-nickel plating, acid copper, activation, semi-bright nickel, full-bright nickel, nickel sealing and trivalent chromium treatment on the aluminum or aluminum alloy parts. The method can form a super corrosion-resistant, high-bonding environmentally friendly chromium plating layer on the surface of the aluminum or aluminum alloy parts, and the method is simple, easy to implement, does not require high technical ability of operators, and the quality of the produced products is very stable.

Description

Technical Field

[0001] The invention belongs to the field of surface treatment of aluminum and aluminum alloys, and in particular relates to a method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts. Background Art

[0002] Aluminum and aluminum alloys have been widely used in the industrial field due to their low density, strong electrical and thermal conductivity, good mechanical properties and good forming processability, especially in high-end building materials, transportation, aerospace and high-end electronic products. At present, it is difficult for products prepared by the existing aluminum and aluminum alloy electroplating process to achieve high corrosion resistance and high bonding strength.

[0003] In the production of bathroom parts, in order to improve the corrosion resistance, decorative performance and environmental protection of aluminum parts, in addition to surface treatment methods such as anodizing and painting, it is also possible to use environmentally friendly chrome plating technology for aluminum parts to treat the surface of such substrate parts. Aluminum is an amphoteric metal that can react with both acid and alkali, so the electroplating of aluminum and aluminum alloys is much more difficult than the electroplating of other metal materials. The most common process flow of aluminum and aluminum alloy electroplating decorative chrome in production is: pre-plating treatment - secondary zinc immersion - pre-nickel plating - copper plating - nickel plating - chrome plating. In actual production, aluminum and aluminum alloy parts treated with decorative chrome plating process have quality problems such as blistering and peeling, poor bonding, and easy corrosion during inspection after electroplating and user use. For example, patent CN102220613A solves the problem of product bonding, but the corrosion resistance needs to be improved.

[0004] This technology aims to solve the problems of poor electroplating bonding and poor corrosion resistance of aluminum and aluminum alloy parts. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for electroplating aluminum and aluminum alloy parts, so as to obtain aluminum and aluminum alloy electroplated products with high corrosion resistance, high bonding strength and environmental protection by optimizing the process flow and adjusting the process parameters.

[0006] One of the technical solutions of the present invention is to provide a method for electroplating environmentally friendly chromium on aluminum and aluminum alloys.

[0007] The specific process steps include:

[0008] Degreasing: Degrease the surface of aluminum or aluminum alloy parts by placing them in a degreasing solution containing 4.5-7.5% sodium hydroxide, 5-10% sodium carbonate, 8-18% sodium metasilicate, <3% trisodium phosphate, <1.2% 4-butynediol and 5-35g / L degreasing agent by weight, at a degreasing temperature of 65-75°C;

[0009] Alkali washing: put the degreased and deoiled aluminum or aluminum alloy parts into a mixed solution containing 12-22g / L sodium hydroxide, 25-35g / L sodium carbonate, and 20-30g / L trisodium phosphate, and perform alkaline washing at 60-70°C for 1-3 minutes to form an oxide film;

[0010] Pickling and polishing: After alkali washing, the aluminum or aluminum alloy parts are treated with pickling at room temperature for 0.5 to 1 minute in a mixed solution containing 70% to 80% nitric acid and 20 to 30% hydrofluoric acid by weight to remove the surface oxide film;

[0011] Zinc immersion: Aluminum is more active. When the surface oxide film and aluminum are dissolved in the solution, an equal amount of zinc is replaced. The reaction is as follows: 2Al+3Zn 2+ →3Zn+2Al 3+ , the reaction stops when the extremely thin zinc layer completely covers. The electroplating decorative chromium process of the present invention adopts the following zinc immersion process: in a mixed solution containing 90-100 g / L zinc oxide, 400-600 g / L sodium hydroxide, 5-15 g / L sodium methyl tartrate, 1-3 g / L ferric chloride and a zinc ion concentration of 8-12 g / L, react at room temperature for 30-120 seconds to form a first zinc layer;

[0012] Zinc stripping: Place the cleaned aluminum or aluminum alloy parts in a nitric acid solution with a concentration of 400-600g / L for surface zinc stripping, and the reaction time is 5-15s;

[0013] Secondary zinc immersion: The first zinc immersion layer is relatively rough and incomplete, and it is easy to corrode the matrix during zinc immersion, resulting in the exposure of aluminum alloy inclusions. The first zinc immersion layer is stripped with diluted nitric acid, and the exposed alloy is also removed to expose the aluminum-rich surface. The second zinc immersion time can be shortened, generally 30 to 60 seconds. The specific steps of secondary zinc immersion are as follows: Put the washed aluminum or aluminum alloy parts into a mixed solution containing 90 to 100 g / L zinc oxide, 400 to 600 g / L sodium hydroxide, 5 to 15 g / L sodium methyl tartrate, 1 to 3 g / L ferric chloride and a zinc ion concentration of 8 to 12 g / L, and zinc immerse for 30 to 60 seconds at room temperature; to ensure the quality of the secondary zinc immersion layer, thoroughly wash in ultrapure cold water after zinc stripping with nitric acid;

[0014] Cyanide-free alkaline copper: put the cleaned aluminum alloy parts into a mixed solution containing 40-80g / L hydroxyethylidene diphosphonic acid, 12-30g / L N,N-diethyl divinyl triamine, 50-100g / L citrate, 30-40g / L copper sulfate, 15-45g / L potassium chloride, 0.4-1.0g / L polyethylene glycol, 0.5-1g / L 1,2-cyclohexanediaminetetraacetic acid, 0.8-1.4g / L 2-mercaptobenzimidazole, and 0.05-0.20g / L (1,2-benzisothiazolin-3-one)-propyne. The pH value of the mixed solution is 8.5-9.0, the reaction temperature is 55-60℃, and the reaction time is 30s-60s.

[0015] Pre-nickel plating: put the cleaned aluminum or aluminum alloy parts into a mixed solution containing 30-35g / L nickel sulfate, 5-10g / L nickel chloride, 4-8ml / L lactic acid, 15-25ml / L ethylene glycol, 20-30g / L boric acid, 0.1g / L-0.4g / L 1,4-butynediol and 0.20-0.30ml / L nickel brightener, the pH value of the mixed solution is 4.0-5.0, the reaction temperature is 45-55℃, the reaction time is 30-60min, and the nickel layer is formed by reaction;

[0016] Acid copper: Place the cleaned aluminum or aluminum alloy parts into a mixed solution containing 160-300g / L copper sulfate, 20-40ml / L sulfuric acid, 80-100ppm chloride ion (provided by hydrochloric acid), 0.02-0.06g / L brightener, 0.02-0.06g / L leveler and 3-6ml / L stabilizer for copper plating. The reaction temperature is 20-30℃, the pH value is 3.8-4.5, and the reaction time is 40-80min.

[0017] Activation: Place the cleaned aluminum or aluminum alloy parts in a solution containing 10-30g / L of activated acid salt and 20-40ml / L of sulfuric acid for activation treatment at room temperature for 40-60s;

[0018] Semi-bright nickel: put the cleaned aluminum or aluminum alloy parts into a mixed solution containing 240-280g / L nickel sulfate, 40-50g / L nickel chloride and 40-50g / L boric acid, with a reaction temperature of 50-60°C and a pH value of 3.8-4.2;

[0019] All-bright nickel: put the cleaned aluminum or aluminum alloy parts into 280-300g / L nickel sulfate, 45-55g / L nickel chloride, and 35-45g / L boric acid solution, the reaction temperature is 50-60℃, and the pH value is 4.3-4.5;

[0020] Nickel sealing: Place the cleaned aluminum or aluminum alloy parts into a mixed solution containing 280-300 g / L nickel sulfate, 45-55 g / L nickel chloride and 35-45 g / L boric acid, with a reaction temperature of 50-60°C and a pH value of 3.8-4.2;

[0021] Trivalent chromium: electroplating trivalent white chromium or trivalent black chromium to obtain a chromium layer;

[0022] The method further comprises the step of washing with water after the above steps are completed. The washing with water is to use ultrapure water to wash the aluminum or aluminum alloy parts for 4 to 8 minutes to make the pH value of the surface of the aluminum alloy-based workpiece 5 to 7.

[0023] After the above steps are completed, water washing is performed. Specifically, the aluminum or aluminum alloy parts are washed with ultrapure water for 4 to 8 minutes to make the pH value of the surface of the aluminum alloy-based workpiece 5 to 7.

[0024] In a preferred embodiment of the present invention, the reaction temperature of the zinc immersion is room temperature, and the reaction time is 1.0 to 2.0 minutes.

[0025] In a preferred embodiment of the present invention, the reaction temperature of the secondary zinc dipping is room temperature, and the reaction time is 30 to 60 seconds.

[0026] In a preferred embodiment of the present invention, the reaction temperature of the cyanide-free alkali copper is 55-60° C., the reaction time is 30s-60s, and the pH value is 8.5-9.0.

[0027] In a preferred embodiment of the present invention, the reaction temperature of the pre-nickel plating is 45-55° C., the reaction time is 30-60 min, and the pH value is 4.0-5.0.

[0028] In a preferred embodiment of the present invention, the reaction temperature of the acid copper is 20-30° C., the reaction time is 40-80 min, and the pH value is 3.8-4.5.

[0029] In a preferred embodiment of the present invention, the reaction temperature of the semi-bright nickel is 50-60° C., the reaction time is 16-48 min, and the pH value is 3.8-4.2.

[0030] In a preferred embodiment of the present invention, the reaction temperature of the all-bright nickel is 50-60° C., the reaction time is 12-36 min, and the pH value is 4.3-4.5.

[0031] In a preferred embodiment of the present invention, the reaction temperature of the nickel seal is 50-60° C., the reaction time is 4-12 min, and the pH value is 3.8-4.2.

[0032] In a preferred embodiment of the present invention, the trivalent white chromium is formed by electroplating a trivalent white chromium plating solution on the surface of aluminum or aluminum alloy, the plating solution temperature is 25-35°C, the plating time is 1-5min, the plating solution pH value is 2.2-3.2, and the trivalent white chromium plating solution contains 200-300g / L ammonium chloride, 50-100g / L potassium chromium oxalate, 10-50g / L potassium dihydrogen phosphate, 20-70g / L ammonium formate, 1-5g / L aminoacetic acid, 5-12g / L hydroxylamine hydrochloride, 0.2-1.2g / L stannous sulfate, 50-100g / L boric acid and 3-12g / L citric acid solution; the trivalent white chromium plating solution is 25-35°C, the plating time is 1-5min, the plating solution pH value is 2.2-3.2, and the trivalent white chromium plating solution contains 200-300g / L ammonium chloride, 50-100g / L potassium chromium oxalate, 10-50g / L potassium dihydrogen phosphate, 20-70g / L ammonium formate, 1-5g / L aminoacetic acid, 5-12g / L hydroxylamine hydrochloride, 0.2-1.2g / L stannous sulfate, 50-100g / L boric acid and 3-12g / L citric acid solution; The black chromium is formed by electroplating a trivalent black chromium plating solution on the surface of aluminum or aluminum alloy, the plating solution temperature is 25-35°C, the plating time is 1-5min, and the plating solution pH value is 2.2-3.2. The trivalent black chromium plating solution contains 200-300g / L of ammonium chloride, 50-100g / L of potassium chromium oxalate, 10-50g / L of potassium dihydrogen phosphate, 20-70g / L of ammonium formate, 1-5g / L of aminoacetic acid, 5-12g / L of hydroxylamine hydrochloride, 0.2-1.2g / L of stannous sulfate, 50-100g / L of boric acid, 1-5g / L of potassium thiocyanate, 2-6g / L of methionine and 3-12g / L of citric acid.

[0033] Compared with the background technology, this technical solution has the following beneficial effects:

[0034] 1. The present invention adopts cyanide-free copper plating, trivalent white chromium electroplating or trivalent black chromium environmentally friendly process, which has relatively little harm to the environment and operators.

[0035] 2. The thickness of the pre-nickel plating layer of the present invention reaches more than 5 μm, the CASS test can reach 96H 10 level, and the ASS test can reach 240H 10 level, thereby achieving high corrosion resistance of the product.

[0036] 3. The product prepared by the method of the present invention passed the bonding strength test, that is: baked at 150°C ± 2°C for 30 minutes, rapidly cooled in room temperature water below 25°C ± 2°C for 2 minutes, and there was no peeling or cracking on the surface.

[0037] 4. The aluminum alloy electroplating process of the present invention is simple and easy to implement, does not require high technical ability of operators, and the quality of the products produced is very stable. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be described in more detail below through embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0039] The test methods and standards used in the embodiments of the present invention are as follows:

[0040] Coating corrosion resistance salt spray test: the test method is in accordance with GB / T 10125;

[0041] Coating adhesion test: bake at 150℃±2℃ for 30min, and cool rapidly in water at room temperature below 25℃±2℃ for 2min.

[0042] Example 1

[0043] Environmentally friendly chromium plating is performed on 6063 and 6463 aluminum alloy parts through the following steps:

[0044] Degreasing: The aluminum alloy parts were placed in a degreasing liquid containing 6.0wt% sodium hydroxide, 7.5wt% sodium carbonate, 13wt% sodium metasilicate, 1.5wt% trisodium phosphate and 0.6wt% 4-butynediol, and 20g / L of a degreasing agent (WIN-58B produced by Guangdong Shanzhifeng Environmental Protection Technology Co., Ltd.), and degreased at 70°C;

[0045] Water washing: rinse the aluminum alloy parts with tap water for 6 minutes to make the pH value of the aluminum alloy substrate surface 6;

[0046] Alkali washing: put the aluminum alloy parts after water washing into a mixed solution containing 17g / L sodium hydroxide, 30g / L sodium carbonate, and 25g / L trisodium phosphate, and perform alkaline washing at 65°C for 2min;

[0047] Water washing: rinse the aluminum alloy parts with tap water for 6 minutes to make the pH value of the aluminum alloy substrate surface 6;

[0048] Pickling and polishing: The aluminum alloy parts are subjected to a surface pickling treatment in a mixed solution containing 75wt% nitric acid and 25wt% hydrofluoric acid at room temperature for 0.8min;

[0049] Water washing: rinse the aluminum alloy parts with tap water for 6 minutes to make the pH value of the aluminum alloy substrate surface 6;

[0050] Primary zinc immersion: react for 30 seconds at room temperature in a zinc immersion bath containing 95g / L zinc oxide, 500g / L sodium hydroxide, 10g / L sodium methyl tartrate, 2g / L ferric chloride and 10g / L zinc ion concentration to form a zinc layer;

[0051] Water washing: rinse the aluminum alloy parts with tap water for 6 minutes to make the surface pH value 6;

[0052] Zinc stripping: Place the cleaned aluminum alloy parts in a nitric acid solution with a concentration of 400-600g / L for surface zinc stripping, and the reaction time is 10s;

[0053] Water washing: rinse the aluminum alloy parts after the above zinc stripping treatment with ultrapure water for 6 minutes to make the surface pH value 6;

[0054] Secondary zinc immersion: put the washed aluminum alloy parts into a zinc immersion bath containing 95g / L zinc oxide, 500 / L sodium hydroxide, 10g / L sodium methyl tartrate, 2g / L ferric chloride and 10g / L zinc ion concentration, and react for 30s at room temperature;

[0055] Water washing: Rinse the aluminum alloy parts treated with secondary zinc immersion with ultrapure cold water for 6 minutes to make the surface pH value 6;

[0056] Cyanide-free alkaline copper: put the cleaned aluminum alloy parts into a mixed solution containing 40-80g / L hydroxyethylidene diphosphonic acid, 12-30g / L N,N-diethyldivinyltriamine, 50-100g / L citrate, 30-40g / L copper sulfate, 15-45g / L potassium chloride, 0.4-1.0g / L polyethylene glycol, 0.5-1g / L 1,2-cyclohexanediaminetetraacetic acid, 0.8-1.4g / L 2-mercaptobenzimidazole, and 0.05-0.20g / L (1,2-benzisothiazolin-3-one)-propyne. The pH value of the mixed solution is 8.8, the reaction temperature is 58°C, and the reaction time is 50s.

[0057] Water washing: rinse aluminum alloy parts with ultrapure water for 6 minutes to make the surface pH value 6;

[0058] Pre-nickel plating: put the cleaned aluminum alloy parts into a mixed solution containing 32g / L nickel sulfate, 8g / L nickel chloride, 6ml / L lactic acid, 20ml / L ethylene glycol, 25g / L boric acid, 0.3g / L 1,4-butynediol and 0.25ml / L Atotech NF nickel brightener (Atotech NF), the pH value of the mixed solution is 4.5, the reaction temperature is 50°C, the reaction time is 45min, and the nickel layer thickness is ensured to be around 10μm;

[0059] Water washing: rinse the aluminum alloy parts with ultrapure water for 6 minutes to make the surface pH value 6;

[0060] Acid copper: Place the cleaned aluminum alloy parts into a mixed solution containing 230g / L copper sulfate, 30ml / L sulfuric acid, 90ppm chloride ions (provided by hydrochloric acid), 0.04g / L brightener (brightener model ULTRA produced by Atotech), 0.04g / L leveler (leveler model ULTRAA produced by Atotech) and 4.5ml / L stabilizer (stabilizer model ULTRAB produced by Atotech) for copper plating. The reaction temperature is 25°C, the pH value is 4.2, and the reaction time is 60min.

[0061] Water washing: rinse the aluminum alloy parts with ultrapure water for 6 minutes to make the surface pH value 6;

[0062] Activation: Place the cleaned aluminum alloy parts in a solution containing 20g / L sodium thiosulfate and 30ml / L sulfuric acid, and activate them at room temperature for 50s;

[0063] Water washing: rinse the aluminum alloy parts with ultrapure water for 6 minutes to make the surface pH value 6;

[0064] Semi-bright nickel: put the cleaned aluminum alloy parts into a mixed solution containing 260g / L nickel sulfate, 45g / L nickel chloride and 45g / L boric acid, with a reaction temperature of 55°C and a pH value of 4.0;

[0065] Water washing: rinse the aluminum alloy parts with ultrapure water for 6 minutes to make the surface pH value 6;

[0066] All-bright nickel: put the cleaned aluminum alloy parts into 290g / L nickel sulfate, 50g / L nickel chloride, and 40g / L boric acid solution, with a reaction temperature of 55°C and a pH value of 4.4;

[0067] Water washing: Rinse the aluminum alloy parts with ultrapure water for 6 minutes to make the surface pH value 6:

[0068] Nickel sealing: Place the cleaned aluminum alloy parts into a mixed solution containing 290g / L nickel sulfate, 50g / L nickel chloride and 40g / L boric acid, with a reaction temperature of 55°C and a pH value of 4.0;

[0069] Water washing: rinse the aluminum alloy parts with ultrapure water for 6 minutes to make the surface pH value 6;

[0070] Trivalent white chromium: Place the cleaned aluminum alloy parts into a solution containing 250g / L ammonium chloride, 70g / L potassium chromium oxalate, 30g / L potassium dihydrogen phosphate, 45g / L ammonium formate, 3g / L aminoacetic acid, 8.5g / L hydroxylamine hydrochloride, 0..7g / L stannous sulfate, 75g / L boric acid and 7.5g / L citric acid.

[0071] Example 2

[0072] Environmentally friendly chromium plating is performed on 6063 and 6463 aluminum alloy parts through the following steps:

[0073] This embodiment adopts the same process steps as that of Embodiment 1, except that Embodiment 1 electroplates trivalent white chromium, while this embodiment electroplates trivalent black chromium; the rest is carried out according to the process steps of Embodiment 1.

[0074] Trivalent black chromium: Place the cleaned aluminum alloy parts into 250g / L ammonium chloride, 75g / L potassium chromium oxalate, 30g / L potassium dihydrogen phosphate, 45g / L ammonium formate, 3g / L aminoacetic acid, 8.5g / L hydroxylamine hydrochloride, 0.7g / L stannous sulfate, 75g / L boric acid, 3g / L potassium thiocyanate, 4g / L methionine and 7.5g / L citric acid solution.

[0075] Embodiment 3:

[0076] Environmentally friendly chromium plating is performed on 6063 and 6463 aluminum alloy parts through the following steps:

[0077] This embodiment adopts the same process steps as Example 1, except that the time of the two zinc immersions is different. In this embodiment, the time of the first zinc immersion is 60 seconds, and the time of the second zinc immersion is 40 seconds; the rest is carried out according to the process steps of Example 1.

[0078] Embodiment 4:

[0079] Environmentally friendly chromium plating is carried out on aluminum alloy parts through the following steps:

[0080] This embodiment adopts the same process steps as Example 1, except that the time of the two zinc immersions is different. In this embodiment, the time of the first zinc immersion is 90 seconds, and the time of the second zinc immersion is 50 seconds; the rest is carried out according to the process steps of Example 1.

[0081] Comparative Example 1

[0082] In this comparative example, the time for the first zinc immersion and the time for the second zinc immersion were both 20 seconds, and the other process steps were the same as those in Example 1.

[0083] Comparative Example 2

[0084] In this comparative example, the first zinc immersion time is 180 s, the second zinc immersion time is 90 s, and the other process steps are the same as those in Example 1.

[0085] Comparative Example 3

[0086] This comparative example did not undergo pre-nickel plating, and the other process steps were the same as those of Example 1. The coating salt spray test (CASS) did not reach 12H 10 level.

[0087] Comparative Example 4:

[0088] In this comparative example, cyanide copper plating is used to replace the cyanide-free alkaline copper in Example 1, and other process steps are the same as in Example 1. The process used in this comparative example is not environmentally friendly.

[0089] Comparative Example 5:

[0090] This comparative example adopts the same process steps as those in Example 1, except that hexavalent chromium electroplating is used to replace the trivalent chromium electroplating in Example 1, and the process is not environmentally friendly.

[0091] The coating adhesion and salt spray test results obtained in Examples 1-4 and Comparative Example 1 are shown in Table 1 below. When the zinc immersion time is within the required range, the coating adhesion is qualified; when the zinc immersion time is insufficient, the coating blisters, and the adhesion between the coating and the substrate is poor; when the zinc immersion time is too long, the coating blisters beyond the required range of the present invention, and the adhesion between the coating and the substrate is also poor.

[0092] Table 1 Test results of coating adhesion at different galvanizing times for Examples 1-3 and Comparative Examples 1-2

[0093] Serial number One zinc immersion time Secondary zinc immersion time Bonding strength test results Comparative Example 1 20S 20S Foaming Example 1 30S 30S qualified Example 2 30S 30S qualified Example 3 60S 40S qualified Example 4 90S 50S qualified Comparative Example 2 180S 90S Foaming

[0094] The salt spray test results of the coatings obtained in Example 1 and Comparative Example 3 are shown in Table 2 below. It can be seen that the pre-nickel plating layer can effectively improve the corrosion resistance of the aluminum alloy substrate.

[0095] Table 2 Salt spray test results of Example 1 and Comparative Example 3

[0096] Serial number Electroplating process Salt spray test results Example 1 Pre-plated nickel layer is about 10μm CASS 96H Level 10 Comparative Example 3 No pre-nickel coating CASS 12H Severe corrosion level 6

[0097] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts, characterized in that: The method comprises the following steps: Degreasing: put the aluminum or aluminum alloy parts into a degreasing liquid containing 4.5-7.5% sodium hydroxide, 5-10% sodium carbonate, 8-18% sodium metasilicate, <3% trisodium phosphate, <1.2% 4-butynediol and 5-35g / L degreasing agent by weight percentage, and the degreasing temperature is 65-75℃; Alkaline washing: put the degreased and deoiled aluminum or aluminum alloy parts into an alkaline washing solution containing 12-22g / L sodium hydroxide, 25-35g / L sodium carbonate and 20-30g / L trisodium phosphate, and perform alkaline washing at 60-70℃ for 1-3min; Pickling and polishing: After alkaline washing, the aluminum or aluminum alloy parts are pickled in a pickling solution containing 70% to 80% nitric acid and 20% to 30% hydrofluoric acid by weight at room temperature for 0.5 to 1 minute; One-time zinc immersion: put the pickled aluminum or aluminum alloy parts into a zinc immersion solution containing 90-100g / L zinc oxide, 400-600g / L sodium hydroxide, 5-15g / L sodium methyl tartrate, 1-3g / L ferric chloride and 8-12g / L zinc ion concentration for one-time zinc immersion; Zinc stripping: put the aluminum or aluminum alloy parts after zinc immersion into a nitric acid solution with a concentration of 400-600g / L for 5-15s. Secondary zinc dipping: the aluminum or aluminum alloy parts after zinc stripping are placed in a mixed solution containing 90-100 g / L zinc oxide, 400-600 g / L sodium hydroxide, 5-15 g / L sodium methyl tartrate, 1-3 g / L ferric chloride and 8-12 g / L zinc ion concentration for secondary zinc dipping; the reaction temperature of the secondary zinc dipping is room temperature, and the reaction time is 40-60 seconds; Cyanide-free alkali copper: put the aluminum or aluminum alloy parts after secondary zinc immersion into a mixed solution containing 40-80g / L hydroxyethylidene diphosphonic acid, 12-30g / L N,N-diethyl divinyl triamine, 50-100g / L citrate, 30-40g / L copper sulfate, 15-45g / L potassium chloride, 0.4-1.0g / L polyethylene glycol, 0.5-1g / L 1,2-cyclohexanediaminetetraacetic acid, 0.8-1.4g / L 2-mercaptobenzimidazole; 0.05-0.20g / L (1,2-benzisothiazolin-3-one)-propyne, and form a copper layer through reaction; the reaction temperature of the cyanide-free alkali copper is 55-60℃, the reaction time is 30s-60s, and the pH value is 8.5-9.0; Pre-nickel plating: put the aluminum or aluminum alloy parts treated with cyanide-free alkali copper into a nickel plating solution containing 30-35g / L nickel sulfate, 5-10g / L nickel chloride, 4-8ml / L lactic acid, 15-25ml / L ethylene glycol, 20-30g / L boric acid, 0.1-0.4g / L 1,4-butynediol and 0.20-0.30ml / L nickel brightener to react and form a nickel layer; Acid copper: Place the pre-nickel-plated aluminum or aluminum alloy parts into a mixed solution containing 160-300g / L copper sulfate, 20-40ml / L sulfuric acid, 80-100ppm chloride ion, 0.02-0.06g / L brightener, 0.02-0.06g / L leveler and 3-6ml / L stabilizer for copper plating; Activation: Place the aluminum or aluminum alloy parts treated with acid copper in a solution containing 10-30g / L of activated acid salt and 20-40ml / L of sulfuric acid for activation treatment at room temperature for 40-60s; Semi-bright nickel: put it into a mixed solution containing 240-280g / L nickel sulfate, 40-50g / L nickel chloride and 40-50g / L boric acid to react and form a nickel layer; Full-bright nickel: put the aluminum or aluminum alloy parts treated with semi-bright nickel into a mixed solution containing 280-300g / L nickel sulfate, 45-55g / L nickel chloride, and 35-45g / L boric acid to react and form full-bright nickel; Nickel seal: put the aluminum or aluminum alloy parts after full nickel treatment into a mixed solution containing 280-300g / L nickel sulfate, 45-55g / L nickel chloride and 35-45g / L boric acid to react and form a nickel seal; Trivalent chromium: electroplating trivalent white chromium or trivalent black chromium to obtain a chromium layer; the trivalent white chromium is formed by electroplating a trivalent white chromium plating solution on the surface of aluminum or aluminum alloy, the plating solution temperature is 25-35°C, the plating time is 1-5min, the plating solution pH value is 2.2-3.2, the trivalent white chromium plating solution contains 200-300g / L ammonium chloride, 50-100g / L potassium chromium oxalate, 10-50g / L potassium dihydrogen phosphate, 20-70g / L ammonium formate, 1-5g / L aminoacetic acid, 5-12g / L hydroxylamine hydrochloride, 0.2-1.2g / L stannous sulfate, 50-100g / L boric acid and 3-12g / L citric acid solution The trivalent black chromium is formed by electroplating a trivalent black chromium plating solution on the surface of aluminum or aluminum alloy, the plating solution temperature is 25-35°C, the plating time is 1-5min, the plating solution pH value is 2.2-3.2, and the trivalent black chromium plating solution contains 200-300g / L of ammonium chloride, 50-100g / L of potassium chromium oxalate, 10-50g / L of potassium dihydrogen phosphate, 20-70g / L of ammonium formate, 1-5g / L of aminoacetic acid, 5-12g / L of hydroxylamine hydrochloride, 0.2-1.2g / L of stannous sulfate, 50-100g / L of boric acid, 1-5g / L of potassium thiocyanate, 2-6g / L of methionine and 3-12g / L of citric acid; The method further comprises the step of washing with water after the above steps are completed. The washing with water is to use ultrapure water to wash the aluminum or aluminum alloy parts for 4 to 8 minutes to make the pH value of the surface of the aluminum alloy-based workpiece 5 to 7.

2. The method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts according to claim 1, characterized in that: The reaction temperature of the zinc immersion is room temperature, and the reaction time is 30 to 120 seconds.

3. The method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts according to claim 1, characterized in that: The reaction temperature of the nickel pre-plating is 45-55° C., the reaction time is 30-60 min, and the pH value is 4.0-5.

0.

4. The method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts according to claim 1, characterized in that: The reaction temperature of the acid copper is 20-30° C., the reaction time is 40-80 min, and the pH value is 3.8-4.

5.

5. The method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts according to claim 1, characterized in that: The reaction temperature of the semi-bright nickel is 50-60° C., the reaction time is 16-48 min, and the pH value is 3.8-4.

2.

6. The method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts according to claim 1, characterized in that: The reaction temperature of the all-bright nickel is 50-60° C., the reaction time is 12-36 minutes, and the pH value is 4.3-4.

5.

7. The method for electroplating environmentally friendly chromium on aluminum and aluminum alloy parts according to claim 1, characterized in that: The reaction temperature of the nickel seal is 50-60° C., the reaction time is 4-12 minutes, and the pH value is 3.8-4.2.