CN102703951B - Room-temperature magnetic field assisted sealing method for aluminum alloy anode oxide film - Google Patents

Abstract

The invention discloses a method for preparation and magnetic field assisted sealing of an aluminum alloy anode oxide film, which is characterized by comprising the following steps of: firstly removing oil stains on surface of an aluminum alloy piece in an alkaline solution (a mixed solution of 80-120g/L NaOH and 70-100g/L Na2CO3); soaking in a neutral cleaning agent for deoiling for 10-15min; pickling in a mixed solution of HCl and H2SO4 at a volume ratio of 1:3 for 5-10s; and carrying out anodization with a mixed organic acid, and finally sealing the anode oxide film in the magnetic field with certain intensity, wherein the sealing conditions are as follows: the pH value of 8.5-10.5, the magnetic field is clearance type and sealing is carried out at room temperature for 10-20s. The prepared anode oxide film is uniform in thickness, energy-saving and environment-friendly, strong in film layer binding force, strong in corrosion resistance, simple in operation and easy to industrialize.

Description

A room temperature magnetic field assisted sealing method for aluminum alloy anodized film

technical field

The invention relates to a sealing technology for anodic oxidation films of aluminum alloy parts, in particular to a magnetic field-induced solution sealing technology for anodic oxidation films of aluminum alloy parts.

Background technique

Due to its high strength/weight ratio, easy forming and processing, and excellent physical and chemical properties, aluminum alloy materials have become the second largest type of metal materials used in industry after steel. However, aluminum alloy materials have low hardness, poor wear resistance and corrosion resistance, and abrasive damage often occurs. Corresponding surface treatment is often required before use to meet its adaptability and safety to the environment, reduce abrasion and prolong its service life. In the industry, anodic oxidation is more and more widely used to form a thick and dense oxide film layer on the surface of aluminum to significantly change the corrosion resistance, wear resistance and decorative properties of aluminum alloys.

However, the aluminum anodized film has high porosity and adsorption capacity, and is easily eroded by pollution and corrosive media. It must be sealed to improve corrosion resistance, anti-pollution ability and fix pigment bodies. The sealing methods of aluminum alloy anodic oxidation film reported in the literature include: hydration sealing, dichromate sealing, hydrolysis salt sealing and rare earth metal salt sealing, etc. The above methods all utilize the hydration reaction of alumina on the surface of the oxide film and the pore wall with water or the hydrolysis reaction of salt to form hydroxides in the micropores, and then fill the micropores to achieve the purpose of sealing. However, the above-mentioned sealing methods are mostly carried out at high temperature. In order to save energy, improve the surface anti-pollution ability of aluminum alloy anodized film and reduce porosity, organic sealing technology and applied voltage sealing method have been developed. Such as Li Baosong, Wu Xuedong, etc., aluminum and aluminum alloy anodized film room temperature sealing agent and sealing method [P], Chinese invention patent, application number: CN200810120737.1, using organic matter and inorganic nickel salt to anodize aluminum alloy at room temperature In 2004, Zhao Jingmao, Zuo Yu, etc. applied for a national invention patent: aluminum alloy anodized film applied voltage sealing method, which promotes the deposition of aluminum hydroxide in the pores of anodized film by applying pulse voltage, and the sealing effect is quite satisfactory.

Contents of the invention

In order to reduce the sealing temperature, save energy, and improve the corrosion resistance and anti-pollution ability of the aluminum alloy anodized film, the present invention uses a certain size of magnetic field to assist in sealing according to the difference in the magnetic permeability of metal ions, so as to improve the metal ion in the anodized film. The adsorption in the pores accelerates the rate of the hydrolysis reaction. The method provided by the invention is simple to operate and easy to industrialize.

The specific technical scheme is as follows:

In the present invention, in order to obtain an aluminum alloy anodized film with excellent corrosion resistance and low porosity, the aluminum alloy is firstly pretreated, then anodized, and then the oxide film is sealed by controlling the magnetic field. The specific steps taken are as follows:

A. Aluminum alloy anodizing pretreatment:

First, degrease the surface of the aluminum alloy parts in an alkaline solution at 45-60°C (a mixed solution of 80g/L-120g/L NaOH and 70-100g/L Na ₂ CO ₃ ); at 20-40°C, 20 Soak in ～50g/L neutral cleaning agent P3- _{GALVACLEAN 20C} solution for 10～15 minutes to remove oil; ~10 seconds. After washing with water, observe the continuous water film on the aluminum alloy surface before proceeding to anodic oxidation.

B. Aluminum alloy anodizing

Sulfuric acid 80-120g/L, oxalic acid 10-20g/L, inorganic additive titanium salt 0.5-0.8g/L; temperature 20-35°C, voltage 30-40V, time 20-40 minutes. Air agitation is used during the anodizing process.

C. Sealing of anodized film

The blocking solution is composed of: nickel sulfate 2~5g/L, cobalt sulfamate 3~10g/L, sodium tungstate 10~20g/L, surfactant S 6~9g/L aqueous solution, pH value is 8.5~10.5 . The magnetic field adopts a gap type, the magnetic field strength is 0.05-0.2T, and the duty ratio is 0.4-0.6. Seal at room temperature for 10-20s.

Owing to adopting above-mentioned technical scheme, the present invention has following advantage:

(1) Due to the pretreatments such as chemical degreasing, pickling, and alkali washing before surface treatment, the anti-pollution ability and compactness of the anodized film surface are enhanced.

(2) The anodized film is sealed with the aid of a magnetic field and has strong corrosion resistance.

(3) Control the porosity of the film by optimizing the size of the magnetic field and the duty ratio in the sealing process, so that the porosity of the anodized film is the lowest.

(4) The technical solution is simple to operate, energy-saving, clean and environmentally friendly, and easy to industrialize.

Detailed ways

The following examples are intended to illustrate the present invention without further limiting the invention.

Example 1: Immerse aluminum alloy parts in alkaline solution (80g/L NaOH and 90g/L Na ₂ CO ₃ mixed solution) at 60°C for 20 minutes; at 25°C, 30g/L neutral cleaning agent P3- Soak in GALVACLEAN 20C solution for 12 minutes. In a mixed solution of HCl and H ₂ SO ₄ with a volume ratio of 1:3, pH=4.0, acid wash at room temperature for 6 seconds. After washing with water, observe the continuous water film on the surface of the aluminum alloy and then carry out anodic oxidation. Put the pretreated aluminum alloy parts in an anodic oxidation solution: sulfuric acid 90g/L, oxalic acid 10g/L, inorganic additive titanium salt 0.8g/L; temperature 25°C, voltage 30V, oxidation time 20 minutes. The cathode is a double electrode, both of which are made of pure aluminum sheets, and air stirring is used during the anodic oxidation process. Wash with water after oxidation, and seal until the water film on the surface is continuous. The composition of blocking solution is: nickel sulfate 3g/L, cobalt sulfamate 8g/L, sodium tungstate 10g/L, surfactant S 6g/L aqueous solution, pH value is 8.5. The magnetic field strength is 0.05T, and the duty ratio is 0.5. Block for 10 s at room temperature.

The thickness of the oxide film obtained in this embodiment is 4.6 μm, the cross-cut test does not find that the oxide layer falls off, the bonding force is good, the anti-pollution ability is high, the admittance is less than 20 μs, and there is no rust on the surface after the neutral salt spray test for 720 hours.

Example 2: Immerse the aluminum alloy parts in an alkaline solution (80g/Lg/L NaOH and 90g/L Na ₂ CO ₃ mixed solution) at 60°C for 20 minutes; at 25°C, 30g/L neutral cleaning agent Soak in P3-GALVACLEAN 20C solution to remove oil for 12 minutes. In a mixed solution of HCl and H ₂ SO ₄ with a volume ratio of 1:3, pH=4.0, acid wash at room temperature for 6 seconds. After washing with water, observe the continuous water film on the surface of the aluminum alloy and then carry out anodic oxidation. Put the pretreated aluminum alloy parts in an anodic oxidation solution: sulfuric acid 100g/L, oxalic acid 15g/L, inorganic additive titanium salt 0.8g/L; temperature 30°C, voltage 30V, oxidation time 20 minutes. The cathode is a double electrode, both of which are made of pure aluminum sheets, and air stirring is used during the anodic oxidation process. Wash with water after oxidation, and seal until the water film on the surface is continuous. The composition of the blocking solution is: an aqueous solution of nickel sulfate 2g/L, cobalt sulfamate 5g/L, sodium tungstate 15g/L, and surfactant S 8g/L, with a pH value of 9.0. The magnetic field strength is 0.08T, and the duty ratio is 0.5. Block for 12 s at room temperature.

The thickness of the oxide film obtained in this example is 5.2 μm, no oxide layer peeling off was found in the cross-cut test, the bonding force is good, the anti-pollution ability is high, the admittance is less than 20 μs, and the surface has no rust after 720 hours of neutral salt spray test.

Example 3: immerse aluminum alloy parts in alkaline solution (80g/Lg/L NaOH and 90g/L Na ₂ CO ₃ mixed solution) at 60°C for 20 minutes; at 25°C, 30g/L neutral cleaning agent Soak in P3-GALVACLEAN 20C solution to remove oil for 12 minutes. In a mixed solution of HCl and H ₂ SO ₄ with a volume ratio of 1:3, pH=4.0, acid wash at room temperature for 6 seconds. After washing with water, observe the continuous water film on the surface of the aluminum alloy and then carry out anodic oxidation. Put the pretreated aluminum alloy parts in an anodic oxidation solution: sulfuric acid 110g/L, oxalic acid 15g/L, inorganic additive titanium salt 0.8g/L; temperature 25°C, voltage 35V, oxidation time 20 minutes. The cathode is a double electrode, both of which are made of pure aluminum sheets, and air stirring is used during the anodic oxidation process. Wash with water after oxidation, and seal until the water film on the surface is continuous. The composition of blocking solution is: nickel sulfate 4g/L, cobalt sulfamate 8g/L, sodium tungstate 18g/L, surfactant S 9g/L aqueous solution, pH value is 9.0. The magnetic field strength is 0.1T, and the duty ratio is 0.5. Block for 10 s at room temperature.

The thickness of the oxide film obtained in this example is 6.2 μm, no oxide layer peeling off was found in the cross-cut test, the bonding force is good, the anti-pollution ability is high, the admittance is less than 20 μs, and the surface has no rust after 720 hours of neutral salt spray test.

Example 4: Immerse aluminum alloy parts in alkaline solution (80g/Lg/L NaOH and 90g/L Na ₂ CO ₃ mixed solution) at 60°C for 20 minutes; at 25°C, 30g/L neutral cleaning agent Soak in P3-GALVACLEAN 20C solution to remove oil for 12 minutes. In a mixed solution of HCl and H ₂ SO ₄ with a volume ratio of 1:3, pH=4.0, acid wash at room temperature for 6 seconds. After washing with water, observe the continuous water film on the surface of the aluminum alloy and then carry out anodic oxidation. Put the pretreated aluminum alloy parts in an anodic oxidation solution: sulfuric acid 120g/L, oxalic acid 20g/L, inorganic additive titanium salt 0.6g/L; temperature 25°C, voltage 35V, oxidation time 30 minutes. The cathode is a double electrode, both of which are made of pure aluminum sheets, and air stirring is used during the anodic oxidation process. Wash with water after oxidation, and seal until the water film on the surface is continuous. The composition of the blocking solution is: an aqueous solution of nickel sulfate 5g/L, cobalt sulfamate 10g/L, sodium tungstate 20g/L, and surfactant S 9g/L, with a pH value of 10.0. The magnetic field strength is 0.2T, and the duty cycle is 0.6. Block for 10 s at room temperature.

The thickness of the oxide film obtained in this example is 5.3 μm, no oxide layer peeling off was found in the cross-cut test, the bonding force is good, the anti-pollution ability is high, the admittance is less than 20 μs, and the surface has no rust after 720 hours of neutral salt spray test.

Using the same cleaning, anodizing formula and process parameters as in Example 4, only changing the magnetic field strength during sealing, the obtained oxide film has good adhesion, high anti-pollution ability, and admittance less than 20μs. The results of the neutral salt spray test are specifically shown in Table 1.

According to the experimental data in Table 1, it is found that the anodized film prepared according to the present invention is sealed under a magnetic field, and the corrosion resistance of the oxide film with a magnetic field strength higher than 0.08T is the best. The corrosion resistance of the oxide film can be controlled by adjusting the size of the auxiliary magnetic field.

Table 1. Neutral salt spray test results of aluminum alloy anodized film (refer to GB/T 10125 artificial atmosphere corrosion test salt spray test)

Claims (3)

1. A room temperature magnetic field assisted sealing method for aluminum alloy anodized film, characterized in that at first the aluminum alloy is pretreated, then organic acid anodic oxidation is carried out; finally the anodized film is used rare earth salt under a certain size of magnetic field The mixed solution with surfactant is sealed, and the specific steps to be taken are as follows: A. Aluminum alloy anodizing pretreatment: First, degrease the surface of aluminum alloy parts in a mixed solution of 80g/L~120g/L NaOH and 70~100g/L Na ₂ CO ₃ in an alkaline solution at 45~60°C. Soak in a solution _of neutral cleaning agent P3-GALVACLEAN 20C/L to remove oil for 10-15 minutes, in a mixed solution of HCl and _H2SO4 with a volume ratio of 1:3, pH = 4.0, pickle at room temperature for 5-10 Seconds, wash with water, observe the continuous water film on the surface of the aluminum alloy before anodizing; B. Aluminum alloy anodizing Sulfuric acid 80-120g/L, oxalic acid 10-20g/L, inorganic additive titanium salt 0.5-0.8g/L, temperature 20-35°C, voltage 30-40V, time 20-40 minutes, air stir; C. Sealing of anodized film The blocking solution is composed of: nickel sulfate 2~5g/L, cobalt sulfamate 3~10g/L, sodium tungstate 10~20g/L, surfactant S 6~9g/L aqueous solution, pH value is 8.5~10.5 , The magnetic field adopts the gap type, the magnetic field strength is 0.05-0.2T, the duty ratio is 0.4-0.6, and it is closed at room temperature for 10-20s. 2. the room temperature magnetic field assisted sealing method of anodized aluminum alloy film as claimed in claim 1, is characterized in that, the content of each component of described sealing solution is respectively: nickel sulfate 3g/L, cobalt sulfamate 10g/L , sodium tungstate 15g/L, surfactant S 6g/L aqueous solution, sealing condition pH value: 8.5~10.5; magnetic field maximum 0.2T, minimum 0.05T, duty cycle 0.5, sealing time 12s. 3. the room temperature magnetic field assisted sealing method of aluminum alloy anodized film as claimed in claim 1, is characterized in that, the content of each component of described sealing liquid is respectively: nickel sulfate 3g/L, cobalt sulfamate 10g/L , sodium tungstate 15g/L, surfactant S 6g/L aqueous solution, sealing condition pH value: 8.5-10.5; magnetic field maximum 0.2T, minimum 0.05T, duty cycle 0.4, sealing time 10s.