A pretreatment method for aluminum alloy surface before magnetron sputtering coloring and its application

Abstract

The present invention relates to the technical field of aluminum alloy surface treatment, and discloses a pretreatment method before magnetron sputtering coloring of an aluminum alloy surface, including cleaning the aluminum alloy surface, and sequentially performing zinc dipping, activation, and dark nickel plating on the aluminum alloy for three times, wherein: zinc stripping is performed after the first zinc dipping and the second zinc dipping; the zinc dipping liquid of the zinc-iron binary system is used for the first zinc dipping; the zinc dipping liquid of the zinc-iron-copper ternary system is used for the second zinc dipping; and the zinc dipping liquid of the zinc-iron-copper-nickel quaternary system is used for the third zinc dipping. The pretreatment method of the present invention can form a more dense multi-metal layer of zinc, iron, copper, nickel, etc. on the aluminum alloy surface, and the metal layer has good wear resistance, high hardness, and good adhesion, and cooperates with the nickel plating layer to meet the requirements of the hard film layer of titanium, zirconium, etc. magnetron sputtering on the aluminum alloy surface. Moreover, the magnetron sputtering coloring method provided by the present invention forms a hard film layer with high adhesion on the aluminum alloy surface, and at the same time gives the aluminum alloy surface a richer color.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy surface treatment, and in particular to a pretreatment method and application of an aluminum alloy surface before magnetron sputtering coloring. Background Art

[0002] Aluminum alloys have excellent properties such as excellent corrosion resistance, biocompatibility, low density, and high strength. They are widely used in electronic equipment, biology, chemical industry and other technical fields. However, aluminum alloys have poor wear resistance and high wear, soft texture and low hardness, which limit their application and development. Therefore, in practical applications, it is often necessary to treat the surface of aluminum alloys, such as chemical nickel plating, anodizing, electroplating, ion implantation, etc., to meet their application requirements.

[0003] Unlike chemical nickel plating, anodizing, electroplating and other coatings, ion implantation can form hard metal layers such as zirconium alloy on the surface of aluminum alloy, which significantly improves the wear resistance and hardness of the aluminum alloy surface, making up for the shortcomings of aluminum alloy and becoming a hot topic in current research. Moreover, ion implantation coating can control the relevant parameters in the coating process to make the coating layer form different colors such as gray, golden yellow, bronze, brown, dark purple, silver white, etc., giving the product a more beautiful appearance and meeting the market demand for coloring of aluminum alloy surface. Common ion implantation methods include vacuum evaporation coating, vacuum sputtering coating and vacuum ion plating, among which vacuum sputtering coating has good coating effect, is easy to operate and is widely used.

[0004] However, ion implantation such as vacuum sputtering coating forms a hard coating, while aluminum alloy is relatively soft. Therefore, how to achieve a good match between the hard coating and the aluminum alloy so that the hard coating has a high adhesion on the aluminum alloy surface is a technical problem that must be solved in the surface treatment of aluminum alloy. For example, Chinese patent application CN201610294033.0 discloses a method for plating a TiN or CrN hard film layer on the surface of an aluminum alloy, wherein a Ti transition layer is plated on the surface of the aluminum alloy and then a TiN or CrN film is plated. The maximum adhesion of the hard film layer prepared by this method to the aluminum alloy surface is 34 to 35N (CrN film), and the adhesion needs to be further improved. Summary of the invention

[0005] In view of the problem that the hard film layer on the surface of aluminum alloy is magnetron sputtered and the adhesion of the hard film layer to the aluminum alloy substrate is low due to the different material textures, the purpose of the present invention is to provide a pretreatment method for the surface of aluminum alloy before magnetron sputtering coloring, so as to improve and enhance the density, hardness and wear resistance of the pretreated aluminum alloy surface, thereby improving the adhesion of the sputtered hard film layer on the aluminum alloy surface.

[0006] Another object of the present invention is to provide a method for magnetron sputtering coloring of aluminum alloy surface. The magnetron sputtering Ti and Zr film layers on the aluminum alloy surface treated by the above-mentioned pretreatment method have good adhesion relative to the aluminum alloy surface, and the wear resistance and hardness of the aluminum alloy are further improved. The surface has color, which meets the market demand for colored aluminum alloys.

[0007] The present invention provides the following technical solutions:

[0008] A pretreatment method for the surface of an aluminum alloy before magnetron sputtering coloring comprises cleaning the surface of the aluminum alloy, and sequentially subjecting the aluminum alloy to zinc dipping, activation, and dark nickel plating for three times, wherein:

[0009] Zinc removal is performed after both primary and secondary zinc immersion;

[0010] The primary zinc dipping adopts a zinc-iron binary system zinc dipping solution;

[0011] The secondary zinc dipping adopts the zinc-iron-copper ternary system zinc dipping solution;

[0012] The three-stage zinc immersion adopts a zinc immersion solution of a zinc-iron-copper-nickel quaternary system.

[0013] An important factor affecting the low adhesion between the coloring film and the aluminum alloy substrate is the dense oxide film formed on the surface of the aluminum alloy. The secondary zinc immersion process can remove the oxide film, reduce the surface activity of the aluminum alloy by forming a dense zinc alloy layer, prevent the oxidation of the aluminum alloy, and can serve as a necessary transition metal layer for the new coating. It is currently the most widely used and economical aluminum alloy surface treatment process. However, on the one hand, the magnetron sputtering hard film layer has higher requirements for the aluminum alloy surface, and the film layer formed after the current secondary zinc immersion process is not yet adaptable to the magnetron sputtering hard film layer; on the other hand, the zinc alloy layer formed by the secondary zinc immersion has weak adhesion on the aluminum alloy. In the past, the conventional operation of secondary zinc immersion believed that the purpose of the first zinc immersion was to form a seed crystal, and the second zinc immersion could form a relatively satisfactory dense zinc layer on the aluminum alloy surface. In this way, it is unnecessary to introduce a third zinc immersion because the effect will not be significantly improved compared with the second zinc immersion. The present invention is based on the existing zinc dipping method for the surface of aluminum alloy. Through in-depth research, the conventional concept of only two zinc dippings is broken, and three zinc dippings are adopted. Different from the two zinc dippings, the zinc dipping solution is kept the same or the concentration of the second zinc dipping solution is lower. New metal types are introduced in each zinc dipping process, and the composition of the zinc dipping solution is controlled. Through a hierarchical and superimposed zinc dipping process, a denser zinc alloy layer is formed on the surface of the aluminum alloy, which has good wear resistance and high hardness. The surface hardness is further improved by nickel plating, which can meet the high surface requirements of magnetron sputtering coloring.

[0014] As a preferred embodiment of the method of the present invention, the zinc-iron binary system zinc leaching solution includes: 19-30 g / L zinc oxide, 200-250 g / L sodium hydroxide, 30-50 g / L potassium sodium tartrate, and 2-5 g / L ferric chloride;

[0015] The zinc-iron-copper ternary system zinc leaching solution includes: zinc oxide 19-30 g / L, sodium hydroxide 200-250 g / L, potassium sodium tartrate 30-50 g / L, ferric chloride 2-5 g / L, copper sulfate 1-2 g / L, sodium cyanide 2-3 g / L;

[0016] The zinc immersion solution of the zinc-iron-copper-nickel quaternary system includes: 10-16 g / L zinc oxide, 100-150 g / L sodium hydroxide, 60-80 g / L potassium sodium tartrate, 2-5 g / L ferric chloride, 1-2 g / L copper sulfate, 2-3 g / L sodium cyanide, and 8-10 g / L nickel chloride.

[0017] As the preferred method of the present invention, the mass ratio of sodium hydroxide and zinc oxide in the primary zinc immersion solution and the secondary zinc immersion solution is 7-8:1, and the mass ratio of sodium hydroxide and zinc oxide in the tertiary zinc immersion solution is 10-11:1. In the secondary zinc immersion, the empirical ratio of sodium hydroxide and zinc oxide is 10-12:1, because too low a dosage of sodium hydroxide will cause the zinc alloy layer to be rough and porous, and poor in compactness, and although too much sodium hydroxide can improve the compactness of the zinc layer, it is easy to pit during nickel electroplating. Based on the three zinc immersion operations in the present invention, it is determined by optimization that a slightly low dosage of sodium hydroxide is maintained during the primary and secondary zinc immersions, so that the zinc deposition appears rough to a certain extent, and the ratio of sodium hydroxide to zinc oxide is strictly controlled to be 10-11:1 during the three zinc depositions, which can further enhance the compactness and adhesion of the zinc layer, and the slightly roughened zinc crystals are more conducive to the precipitation crystallization during the three zinc depositions.

[0018] As a preferred embodiment of the method of the present invention, the zinc-iron-copper-nickel quaternary system zinc immersion solution also contains 1-2 g / L of tetraethylene pentamine and 3-5 g / L of benzotriazole. In the prior art, there is research on the use of benzotriazole to replace cyanide to form a cyanide-free zinc immersion solution, which can basically achieve the effect of cyanide zinc immersion. In the case of selecting a cyanide zinc immersion solution in the present invention, the lifting effect of adding benzotriazole alone is not obvious. After the introduction of tetraethylene pentamine, the rich amine groups contained in tetraethylene pentamine can be used to cooperate with benzotriazole to refine the crystals and improve the density of the zinc alloy layer.

[0019] As a preferred embodiment of the method of the present invention,

[0020] The zinc immersion temperature is 15-25°C;

[0021] The zinc immersion time is 1 to 2 minutes.

[0022] Secondary zinc immersion time 1~1.5min;

[0023] The three zinc immersion times are 30 to 60 seconds.

[0024] Galvanizing should be carried out at room temperature or low temperature, and the time should not be too long, especially the three galvanizing times should be shorter.

[0025] As a preferred embodiment of the method of the present invention, a dilute sulfuric acid solution with a concentration of 2 to 5 g / L is used for activation.

[0026] As a preferred embodiment of the method of the present invention, the zinc removal is carried out using a dilute nitric acid solution with a volume concentration of 10 to 20 ml / L.

[0027] As a preferred embodiment of the method of the present invention, the process of cleaning the surface of the aluminum alloy includes degreasing, water washing, alkaline etching, water washing, and polishing.

[0028] Specifically, alkali solution can be used for oil removal, the composition of which is: 100 g / L sodium hydroxide, 50 g / L carbonate, 15 g / L phosphate, 2 g / L sodium alkylbenzene sulfonate, and the oil removal temperature is 60°C;

[0029] Alkali corrosion can be treated with 50g / L sodium hydroxide solution at a temperature of 50°C;

[0030] 100g / L nitric acid can be used to remove the scale.

[0031] In addition, the dark nickel electroplating adopts the following electroplating solution: 280-300 g / L of nickel sulfate, 50-80 g / L of nickel chloride, 50-90 g / L of boric acid, and 100-150 g / L of additives, wherein the additives are benzenesulfonic acid derivatives or salicylic acid derivatives.

[0032] A method for magnetron sputtering coloring of an aluminum alloy surface, using the aluminum alloy treated by the above-mentioned pretreatment method as a substrate for magnetron sputtering coloring, and the target source is at least one of a titanium target, chromium palladium and zirconium palladium.

[0033] As a preferred method of the present invention, the background vacuum of magnetron sputtering is (7-8)×10 -3 Pa, sputtering pressure (1~3)×10 -1 Pa, nitrogen flow rate 10~15mL / min, oxygen flow rate 3~5mL / min.

[0034] The beneficial effects of the present invention are as follows:

[0035] The present invention provides a pretreatment method for the surface of an aluminum alloy. Compared with the existing secondary zinc immersion process, a more compact multi-metal layer of zinc, iron, copper, nickel, etc. can be formed on the surface of the aluminum alloy. The metal layer has good wear resistance, high hardness, and good adhesion. In combination with the nickel plating layer, the obtained pretreated aluminum alloy surface can meet the requirements of magnetron sputtering of titanium, zirconium, etc. hard film layers on the surface of the aluminum alloy. In addition, the magnetron sputtering coloring method provided by the present invention forms a hard film layer with high adhesion on the surface of the aluminum alloy, and at the same time gives the aluminum alloy surface richer colors. DETAILED DESCRIPTION

[0036] The specific implementation modes of the present invention are further described below.

[0037] Unless otherwise specified, the raw materials used in the present invention can be purchased from the market or are commonly used in the art. Unless otherwise specified, the methods in the following embodiments are all conventional methods in the art.

[0038] Example 1

[0039] The method for coloring the aluminum alloy surface by magnetron sputtering is as follows:

[0040] 1) Clean the surface of the 5083 aluminum alloy plate to be treated as follows:

[0041] (1-1) Degreasing and oil removal: The degreasing and oil removal liquid used is 100 g / L sodium hydroxide, 50 g / L sodium carbonate, 15 g / L trisodium phosphate, and 2 g / L sodium alkylbenzene sulfonate. The treatment temperature is 60°C, followed by two water washes;

[0042] (1-2) Alkali etching: The alkaline etching solution used is 50g / L sodium hydroxide, the treatment temperature is 50°C, and then washed twice;

[0043] (1-3) De-ashing, descaling and polishing: Treat with 100g / L nitric acid, then wash twice;

[0044] 2) The 5083 aluminum alloy plate with a bright finish was zinc-dipped once, and the zinc-dipped solution used was: 19 g / L zinc oxide, 210 g / L sodium hydroxide, 30 g / L potassium sodium tartrate, and 2 g / L ferric chloride; the zinc-dipped temperature was 25°C, and the zinc-dipped time was 1.5 min;

[0045] After zinc immersion, wash twice with water, then remove zinc with dilute nitric acid solution with a volume concentration of 20ml / L, and wash twice with water;

[0046] 3) The 5083 aluminum alloy plate is further zinc-dipped for the second time, and the zinc-dipped solution used is: 19 g / L zinc oxide, 210 g / L sodium hydroxide, 30 g / L potassium sodium tartrate, 2 g / L ferric chloride, 1 g / L copper sulfate, and 2 g / L sodium cyanide;

[0047] After zinc immersion, wash twice with water, dezincify with dilute nitric acid solution with a volume concentration of 20ml / L, and wash twice with water again;

[0048] 4) The 5083 aluminum alloy plate was zinc-immersed three times, and the zinc-immersing solution used was: 10 g / L zinc oxide, 120 g / L sodium hydroxide, 60 g / L potassium sodium tartrate, 2 g / L ferric chloride, 1 g / L copper sulfate, 2 g / L sodium cyanide, and 8 / L nickel chloride;

[0049] After zinc immersion, it is activated with 2g / L dilute sulfuric acid and then washed twice;

[0050] 5) The 5083 aluminum alloy plate after three zinc immersions was electroplated with dark nickel, and the composition of the electroplating solution used was as follows:

[0051] Nickel sulfate 280g / L, nickel chloride 50g / L, boric acid 50g / L, additive: 100g / L, the additive is salicylic acid;

[0052] After electroplating, wash twice and then bake at 100℃ for 20min;

[0053] 6) The dried 5083 aluminum alloy plate is placed in a magnetron sputtering device for magnetron sputtering coloring. The magnetron sputtering conditions are as follows:

[0054] With Ti and Zr as target sources, the background vacuum is 7×10 -3 Pa, sputtering pressure 2×10 -1 Pa, nitrogen flow rate 10mL / min, oxygen flow rate 3mL / min.

[0055] Example 2

[0056] The difference from Example 1 is that

[0057] In step 2), the zinc oxide contained in the zinc leaching solution used for zinc leaching once is 26.25 g / L and the sodium hydroxide is 210 g / L;

[0058] In step 3), the zinc oxide contained in the zinc leaching solution used for the secondary zinc leaching is 26.25 g / L and the sodium hydroxide is 210 g / L;

[0059] The zinc immersion solution used for the three zinc immersions in step 4) contains 10.9 g / L zinc oxide and 120 g / L sodium hydroxide.

[0060] The rest remain the same.

[0061] Example 3

[0062] The difference from the embodiment is that

[0063] In step 2), the zinc oxide contained in the zinc leaching solution used for zinc leaching is 30 g / L and the sodium hydroxide is 210 g / L;

[0064] In step 3), the zinc oxide contained in the zinc leaching solution used for the secondary zinc leaching is 30 g / L and the sodium hydroxide is 210 g / L;

[0065] In step 4), the zinc oxide contained in the zinc dipping solution used for the three zinc dippings is 12 g / L and the sodium hydroxide is 120 g / L.

[0066] The rest remain the same.

[0067] Example 4

[0068] The method for coloring the aluminum alloy surface by magnetron sputtering is as follows:

[0069] 1) Clean the surface of the 5083 aluminum alloy plate to be treated as follows:

[0070] (1-1) Degreasing and oil removal: The degreasing and oil removal liquid used is 100 g / L sodium hydroxide, 50 g / L sodium carbonate, 15 g / L trisodium phosphate, and 2 g / L sodium alkylbenzene sulfonate. The treatment temperature is 60°C, followed by two water washes;

[0071] (1-2) Alkali etching: The alkaline etching solution used is 50g / L sodium hydroxide, the treatment temperature is 50°C, and then washed twice;

[0072] (1-3) De-ashing, descaling and polishing: Treat with 100g / L nitric acid, then wash twice;

[0073] 2) The 5083 aluminum alloy plate with a bright finish was zinc-dipped once, and the zinc-dipped solution used was: 30 g / L zinc oxide, 250 g / L sodium hydroxide, 30 g / L potassium sodium tartrate, and 2 g / L ferric chloride; the zinc-dipped temperature was 25°C, and the zinc-dipped time was 1.5 min;

[0074] After zinc immersion, wash twice with water, then remove zinc with dilute nitric acid solution with a volume concentration of 20ml / L, and wash twice with water;

[0075] 3) The 5083 aluminum alloy plate is further zinc-impregnated for the second time, and the zinc-impregnating solution used is: 30 g / L zinc oxide, 250 g / L sodium hydroxide, 30 g / L potassium sodium tartrate, 2 g / L ferric chloride, 1 g / L copper sulfate, and 2 g / L sodium cyanide;

[0076] After zinc immersion, wash twice with water, dezincify with dilute nitric acid solution with a volume concentration of 20ml / L, and wash twice with water again;

[0077] 4) The 5083 aluminum alloy plate was zinc-immersed three times, and the zinc-immersing solution used was: 10 g / L zinc oxide, 150 g / L sodium hydroxide, 60 g / L potassium sodium tartrate, 2 g / L ferric chloride, 1 g / L copper sulfate, 2 g / L sodium cyanide, and 8 / L nickel chloride;

[0078] After zinc immersion, it is activated with 2g / L dilute sulfuric acid and then washed twice;

[0079] 5) The 5083 aluminum alloy plate after three zinc immersions was electroplated with dark nickel, and the composition of the electroplating solution used was as follows:

[0080] Nickel sulfate 280g / L, nickel chloride 50g / L, boric acid 50g / L, additive: 100g / L, the additive is salicylic acid;

[0081] After electroplating, wash twice and then bake at 100℃ for 20min;

[0082] 6) The dried 5083 aluminum alloy plate is placed in a magnetron sputtering device for magnetron sputtering coloring. The magnetron sputtering conditions are as follows:

[0083] With Ti and Zr as target sources, the background vacuum is 8×10 -3 Pa, sputtering pressure 3×10 -1 Pa, nitrogen flow rate 15mL / min, oxygen flow rate 5mL / min.

[0084] Example 5

[0085] The difference from Example 1 is that the zinc dipping solution used for the three zinc dipping steps in step (3) also contains 1 g / L of tetraethylene pentamine and 3 g / L of benzotriazole, wherein the tetraethylene pentamine and benzotriazole are mixed evenly and then added to the zinc dipping solution.

[0086] Example 6

[0087] The difference from Example 1 is that the zinc dipping solution used for the three zinc dipping steps in step (3) also contains 2 g / L of tetraethylene pentamine and 5 g / L of benzotriazole, wherein the tetraethylene pentamine and benzotriazole are mixed evenly and then added to the zinc dipping solution.

[0088] Comparative Example 1

[0089] The difference from Example 1 is that a secondary zinc immersion operation is adopted, and the zinc immersion solutions used are:

[0090] Zinc oxide 10g / L, sodium hydroxide 120g / L, potassium sodium tartrate 60g / L, ferric chloride 2g / L, copper sulfate 1g / L, sodium cyanide 2g / L, nickel chloride 8 / L;

[0091] After one zinc immersion, the zinc is removed and washed with water.

[0092] Comparative Example 2

[0093] The difference from Example 1 is that three zinc immersion operations are adopted, and the zinc immersion solutions used are:

[0094] Zinc oxide 10g / L, sodium hydroxide 120g / L, potassium sodium tartrate 60g / L, ferric chloride 2g / L, copper sulfate 1g / L, sodium cyanide 2g / L, nickel chloride 8 / L;

[0095] After the first and second zinc immersion, the steel is stripped and washed with water.

[0096] Comparative Example 3

[0097] The difference from Example 1 is that the zinc dipping solution used for the three zinc dipping steps in step (3) also contains 4 g / L of benzotriazole.

[0098] Comparative Example 4

[0099] The difference from Example 1 is that the zinc dipping solution used for the three zinc dippings in step (3) also contains 4 g / L of tetraethylenepentamine.

[0100] Comparative Example 5

[0101] The difference from Example 1 is that the secondary zinc dipping operation in step (3) is omitted.

[0102] Comparative Example 6

[0103] The difference from Example 1 is that

[0104] The zinc leaching solution used for the secondary zinc leaching in step (3) is:

[0105] Zinc oxide 19g / L, sodium hydroxide 210g / L, potassium sodium tartrate 60g / L, ferric chloride 2g / L, nickel chloride 8g / L.

[0106] The density and wear resistance of the aluminum alloy plates (zinc alloy layer, nickel plating layer) after the zinc alloy layer was formed in the above embodiments and comparative examples were tested, and the overall adhesion of the multi-layer composite film layer (zinc alloy layer, nickel plating layer, hard film layer) formed after magnetron sputtering of parallel samples was tested. The results are shown in Table 1 below.

[0107] Density is expressed as porosity, and the smaller the porosity, the better the density. The porosity is determined by the immersion method in accordance with "QB / T 3823-1999 Test Method for Porosity of Metal Coatings of Light Industrial Products". The test solution consists of: 3.5g / L aluminum reagent, 150g / L sodium chloride, and 10g / L white gelatin. The porosity is determined based on the number of colored spots on the surface of the aluminum alloy plate.

[0108] Wear resistance is expressed as wear volume. The lower the wear volume, the better the wear resistance. Wear volume is measured using a wear tester under non-lubricated conditions, with a wear time of 30 minutes.

[0109] Adhesion was tested by combining the scratch method with a thermal shock test. Specifically, a hard steel scratcher with a sharp edge of 30° was used to scratch 6 parallel lines 2 mm apart on the surface of the aluminum alloy plate. Then 6 parallel lines perpendicular to them were scratched. The lines were as deep as the aluminum alloy matrix and in the same direction. The aluminum alloy plate was then baked at 220°C for 30 minutes, taken out and immediately put into cold water to observe whether there were bubbling, peeling, etc.

[0110] Table 1 Test results

[0111]

[0112] As can be seen from the above table, the porosity of the aluminum alloy pretreated by the method of the present application is low, the density is high, and the wear resistance is improved. The improved wear resistance also means that the surface hardness is higher. The aluminum alloy magnetron sputtered with colored titanium and zirconium film layers after the pretreatment method forms a multi-layer coating layer with high adhesion. Specifically, as can be seen from the comparison between Example 1 and Example 1, the direct use of the secondary zinc immersion process to treat the aluminum alloy has poor adhesion performance after the color coating under more stringent test conditions, and as shown in Comparative Example 2, adding a zinc immersion process will not further significantly improve the performance of the zinc alloy layer and the color coating layer. For example, it can be seen from the comparison between Comparative Examples 3 and 4 and Examples 1 and 5 that the addition of benzotriazole or tetraethylenepentamine alone, in the presence of cyanide, cannot effectively improve the surface performance of the aluminum alloy. As shown in Comparative Example 5, the performance of quaternary zinc immersion directly used after binary zinc immersion is lower than that of Example 1, which shows the importance of layered and superimposed zinc immersion. As shown in Comparative Example 6, the importance of sequential layering and superposition is reflected, which may be because copper helps to improve the bonding strength, while iron can refine the grains.

Claims

1. A pretreatment method for aluminum alloy surface before magnetron sputtering coloring, It is characterized in that The process includes cleaning the aluminum alloy surface, and subjecting the aluminum alloy to zinc dipping, activation, and dark nickel plating treatments three times in sequence, wherein: Zinc removal is performed after both primary and secondary zinc immersion; The primary zinc dipping adopts a zinc-iron binary system zinc dipping solution; the primary zinc dipping solution includes 19-30 g / L zinc oxide and 200-250 g / L sodium hydroxide, and the mass ratio of sodium hydroxide to zinc oxide is 7-8:1; The secondary zinc dipping adopts a zinc-iron-copper ternary system zinc dipping solution; the secondary zinc dipping solution includes 19-30 g / L zinc oxide and 200-250 g / L sodium hydroxide, and the mass ratio of sodium hydroxide to zinc oxide is 7-8:1; The three-stage zinc dipping adopts a zinc-iron-copper-nickel quaternary system zinc dipping solution, which includes 10-16 g / L zinc oxide, 100-150 g / L sodium hydroxide, 1-2 g / L tetraethylene pentamine and 3-5 g / L benzotriazole, and the mass ratio of sodium hydroxide to zinc oxide is 10-11:

1.

2. The pretreatment method according to claim 1, It is characterized in that The zinc-iron binary system zinc leaching solution includes: 30-50 g / L potassium sodium tartrate and 2-5 g / L ferric chloride; The zinc-iron-copper ternary system zinc leaching solution includes: 30-50 g / L potassium sodium tartrate, 2-5 g / L ferric chloride, 1-2 g / L copper sulfate, and 2-3 g / L sodium cyanide; The zinc leaching solution of the zinc-iron-copper-nickel quaternary system includes: 60-80 g / L potassium sodium tartrate, 2-5 g / L ferric chloride, 1-2 g / L copper sulfate, 2-3 g / L sodium cyanide, and 8-10 g / L nickel chloride.

3. The pretreatment method according to claim 1, It is characterized in that The zinc-iron-copper-nickel quaternary system zinc immersion solution also contains 1g / L tetraethylenepentamine and 3g / L benzotriazole.

4. The pretreatment method according to claim 1, It is characterized in that The zinc-iron-copper-nickel quaternary system zinc immersion solution also contains 2g / L of tetraethylenepentamine and 5g / L of benzotriazole.

5. The pretreatment method according to claim 1, It is characterized in that The zinc immersion temperature is 15-25°C; The zinc immersion time is 1 to 2 minutes. Secondary zinc immersion time 1~1.5min; The three zinc immersion times are 30 to 60 seconds.

6. The pretreatment method according to claim 1, It is characterized in that The activation is carried out using a dilute sulfuric acid solution with a concentration of 2 to 5 g / L.

7. The pretreatment method according to claim 1, It is characterized in that The zinc removal process uses a dilute nitric acid solution with a volume concentration of 10 to 20 mL / L.

8. The pretreatment method according to claim 1, It is characterized in that The process of cleaning the aluminum alloy surface includes degreasing, water washing, alkaline etching, water washing, and polishing.

9. A method for coloring the surface of aluminum alloy by magnetron sputtering, It is characterized in that The aluminum alloy treated by the pretreatment method according to any one of claims 1 to 8 is used as a substrate for magnetron sputtering coloring, and the target source used for magnetron sputtering is at least one of a titanium target, chromium palladium and zirconium palladium.

10. The method for coloring the aluminum alloy surface by magnetron sputtering according to claim 9, It is characterized in that The background vacuum during magnetron sputtering is (7-8)×10 -3 Pa, sputtering gas pressure (1~3)×10 -1 Pa, nitrogen flow rate 10~15mL / min, oxygen flow rate 3~5mL / min.

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