A rapid and non-destructive identification method for trivalent chromium natural color chemical oxide film of aluminum alloy

Abstract

The present invention discloses a rapid and non-destructive identification method for a trivalent chromium natural color chemical oxide film of an aluminum alloy. The identification solution is composed of 5 to 10 g / L of potassium permanganate, 1 to 3 g / L of sodium silicate nonahydrate, 2.5 to 5 g / L of sodium dodecyl sulfate, and 0.5 to 1 g / L of an organic corrosion inhibitor, and the pH value of the solution is adjusted to 9.5 to 10. The identification method is to drip the identification solution on the surface of the aluminum alloy, and after 40 to 60 seconds, observe the color change of the aluminum alloy surface at the dripping position to identify whether the aluminum alloy has been subjected to trivalent chromium natural color chemical oxidation treatment. The identification method of the present invention can be operated at room temperature, is simple and rapid, has high identification efficiency, and the identification process will not damage the trivalent chromium natural color chemical oxide film of the aluminum alloy.

Description

Technical Field

[0001] The invention relates to a method for rapid non-destructive identification of a trivalent chromium natural color chemical oxide film on an aluminum alloy, and specifically belongs to the technical field of aluminum alloy surface treatment. Background Art

[0002] Aluminum and its alloys have many advantages such as light weight, high strength-to-weight ratio and machinability. They are one of the most versatile engineering materials and are widely used in manufacturing industries such as transportation and electronic communications. Chemical oxidation is one of the commonly used anti-corrosion technologies for aluminum alloy surface treatment. The chemical oxidation film of aluminum alloy not only has a certain corrosion resistance, but also has conductivity. Traditional aviation aluminum alloy chemical oxidation uses hexavalent chromium process. The hexavalent chromium is toxic and a strong carcinogen. Therefore, hexavalent chromium chemical oxidation has been restricted by countries around the world. Trivalent chromium chemical oxidation of aluminum alloy is currently considered the most promising chemical oxidation technology to replace hexavalent chromium. It has similar properties to hexavalent chromium in many aspects, but its toxicity is only 1% of hexavalent chromium. At present, trivalent chromium chemical oxidation of aluminum alloy has been widely used in the electronic communications industry.

[0003] After hexavalent chromium chemical oxidation, aluminum alloy is yellow, so it is easy to distinguish whether the aluminum alloy has been treated with hexavalent chromium chemical oxidation. However, the trivalent chromium natural color chemical oxidation film is the same color as the aluminum alloy, which is difficult to distinguish with the naked eye. In addition, the trivalent chromium natural color chemical oxidation film is conductive like the aluminum alloy, so it is impossible to use the method of detecting the film resistance to distinguish whether the aluminum alloy has been treated with trivalent chromium natural color chemical oxidation. For example, the applicant of the present invention has proposed an environmentally friendly aluminum alloy chemical oxidation liquid and chemical oxidation method (CN113106434A). The color of the aluminum alloy chemical oxidation film treated with the chemical oxidation liquid is consistent with that of the aluminum alloy, and the film layer is conductive. Therefore, it is difficult to judge whether the aluminum alloy product has been treated with trivalent chromium natural color chemical oxidation, which can easily cause production confusion.

[0004] Salt spray test can be used to determine whether aluminum alloy has been treated with trivalent chromium natural color chemical oxidation, but this method is time-consuming and complicated to operate, and during the test, salt spray will have a certain destructive effect on the trivalent chromium natural color chemical oxide film. By dripping sodium hydroxide solution on the surface of aluminum alloy and measuring the time for bubbles to appear on the surface of aluminum alloy, it can also be quickly determined whether the aluminum alloy material has been treated with trivalent chromium natural color chemical oxidation, but this method will also destroy the trivalent chromium chemical oxide film, resulting in unqualified aluminum alloy product quality. Therefore, there is an urgent need for a rapid and non-destructive identification method for the trivalent chromium natural color chemical oxide film of aluminum alloy. Summary of the invention

[0005] Based on this, the purpose of the present invention is to propose a method for rapid and non-destructive identification of the natural color chemical oxidation of trivalent chromium in aluminum alloy, which can solve the technical problem of rapid and non-destructive identification of the natural color chemical oxidation film of trivalent chromium in the production of natural color chemical oxidation of trivalent chromium in aluminum alloy.

[0006] The invention discloses a method for rapidly and non-destructively identifying a trivalent chromium natural color chemical oxidation film of an aluminum alloy. The method uses an identification solution to treat the surface of the aluminum alloy. Under the premise of not damaging the surface of the aluminum alloy, the method rapidly identifies whether the aluminum alloy has been subjected to trivalent chromium natural color chemical oxidation treatment by observing the color change of the surface of the aluminum alloy.

[0007] The identification solution is composed of potassium permanganate, sodium silicate nonahydrate, an organic corrosion inhibitor and a surfactant, and the mass concentrations thereof are 5-10 g / L, 1-3 g / L, 0.5-1 g / L and 2.5-5 g / L, respectively, and the pH of the identification solution is adjusted to 9.5-10 by means of a pH regulator;

[0008] The specific identification method is:

[0009] Step 1: At room temperature, place the aluminum alloy sample to be identified horizontally, and use a dropper to drop 1 to 2 drops of identification solution onto the surface of the aluminum alloy sample;

[0010] Step 2: After 40 to 60 seconds, clean the surface of the aluminum alloy sample with pure water;

[0011] Step 3: Observe the color change on the surface of the aluminum alloy sample to which the identification solution has been added; if there is no color change, it indicates that the aluminum alloy sample has undergone trivalent chromium natural color chemical oxidation treatment; if the color turns yellow, it indicates that the aluminum alloy sample has not undergone trivalent chromium natural color chemical oxidation treatment.

[0012] The organic corrosion inhibitor is one of sodium gluconate and sodium benzoate or a combination of the two.

[0013] The surfactant is sodium lauryl sulfate.

[0014] The pH regulator is sodium hydroxide or potassium hydroxide.

[0015] When the pH of the identification solution of the present invention is 9.5-10, the OH - It can react chemically with the natural oxide film on the surface of aluminum alloy, dissolving the natural oxide film on the surface of aluminum alloy, so that potassium permanganate reacts chemically with the aluminum element in the aluminum alloy to produce MnO2, which adheres to the surface of the aluminum alloy and makes the surface of the aluminum alloy yellow. Sodium dodecyl sulfate is a surfactant with good permeability. It can significantly reduce the surface tension of the identification solution and aluminum alloy, and assist MnO4 - Quickly and evenly contact with aluminum alloy to speed up identification.

[0016] The main component of the trivalent chromium natural color chemical oxidation film of aluminum alloy is Zr-Cr(Ⅲ)-Al mixed oxide, which has stable properties and dense structure. It does not react with OH in a short time in the identification solution with pH of 9.5-10. -Reaction, and will not be oxidized by potassium permanganate. As an inorganic corrosion inhibitor, sodium silicate nonahydrate can inhibit the corrosion reaction of aluminum alloys, and form a compound film layer on the surface of aluminum alloys to play a corrosion inhibition role. Sodium gluconate and sodium benzoate are organic corrosion inhibitors, among which sodium gluconate has excellent chelating properties. It can form a complex protective film with metal ions in the solution to cover the surface of aluminum alloys. The corrosion inhibition effect of sodium benzoate is caused by the adsorption of benzoate on the metal surface. The corrosion inhibitors of sodium silicate nonahydrate, sodium gluconate and sodium benzoate can work together to slow down the damage of the identification solution to the chemical oxidation film of aluminum alloys, but in the identification solution, these corrosion inhibitors have no obvious protective effect on aluminum alloys that have not been chemically oxidized. Therefore, aluminum alloys that have not been chemically oxidized in the identification solution quickly change color.

[0017] Therefore, when the identification liquid is dropped on the surface of the aluminum alloy that has been chemically oxidized, no chemical reaction occurs within 60 seconds, and there is no obvious color change on the surface of the chemically oxidized film. However, when it is dropped on the surface of the aluminum alloy that has not been chemically oxidized, yellow appears at the drop position after 40 to 60 seconds.

[0018] Beneficial effects of the present invention: The identification solution of the present invention can identify whether the aluminum alloy has been subjected to trivalent chromium natural color chemical oxidation treatment under room temperature conditions. The identification method is simple, rapid, and efficient, and will not damage the trivalent chromium natural color chemical oxidation film of the aluminum alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a macroscopic morphology of the surface of a 1016 aluminum alloy sample that has not been subjected to trivalent chromium natural color chemical oxidation treatment when the identification solution of the present invention is dripped onto the surface;

[0020] Figure 2 This is a macroscopic morphology of the surface of a 2024-T3 aluminum alloy sample after the identification solution of the present invention is dropped on the surface of the sample after the trivalent chromium natural color chemical oxidation treatment;

[0021] Figure 3 This is a macroscopic morphology of the surface of a 6061 aluminum alloy sample that has not been subjected to trivalent chromium natural color chemical oxidation treatment when the identification solution of the present invention is dripped onto the surface;

[0022] Figure 4 This is a macroscopic morphology of the surface of a 6063 aluminum alloy sample that has not been subjected to trivalent chromium natural color chemical oxidation treatment when the identification solution of the present invention is dripped onto the surface;

[0023] Figure 5 This is a macroscopic morphology of the surface of a 7075 aluminum alloy sample after trivalent chromium natural color chemical oxidation treatment when the identification solution of the present invention is dripped on the surface;

[0024] Figure 6 The surface macroscopic morphology of a 2024-T3 aluminum alloy sample is treated with trivalent chromium natural color chemical oxidation, immersed in the identification solution of the present invention for 1 minute, and then subjected to a 168-hour neutral salt spray test. DETAILED DESCRIPTION

[0025] The following are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements or modifications may be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

[0026] Example 1

[0027] The composition of the rapid non-destructive identification solution of trivalent chromium natural color chemical oxidation of aluminum alloy is as follows: the concentration of potassium permanganate is 10g / L, the concentration of sodium silicate nonahydrate is 2g / L, the concentration of sodium gluconate is 0.4g / L, the concentration of sodium benzoate is 0.4g / L, the concentration of sodium dodecyl sulfate is 5g / L, and the pH is adjusted to 10 by adding sodium hydroxide.

[0028] Identification process: Identify whether the aluminum alloy model 1060 has been treated with trivalent chromium natural color chemical oxidation.

[0029] At room temperature, use a dropper to absorb the identification solution and drop 1 to 2 drops on the surface of the sample. After 60 seconds, rinse with pure water and observe that the color of the sample surface where the liquid is dripped has changed significantly. The color of the dripping area is yellow, indicating that the sample is bare aluminum.

[0030] Example 2

[0031] The composition of the rapid non-destructive identification solution of trivalent chromium natural color chemical oxidation of aluminum alloy is as follows: the concentration of potassium permanganate is 5g / L, the concentration of sodium silicate nonahydrate is 3g / L, the concentration of sodium gluconate is 0.6g / L, the concentration of sodium benzoate is 0.4g / L, the concentration of sodium dodecyl sulfate is 3g / L, and the pH is adjusted to 9.5 by adding sodium hydroxide.

[0032] Identification process: Identify whether the aluminum alloy model 2024-T3 has been subjected to trivalent chromium natural color chemical oxidation treatment.

[0033] At room temperature, use a dropper to absorb the identification solution and drop 1 to 2 drops on the surface of the sample. After 40 seconds, rinse with pure water and observe that there is no obvious change in the color of the droplets on the surface of the sample, indicating that the sample is 2024-T3 aluminum alloy that has been chemically oxidized with trivalent chromium.

[0034] Example 3

[0035] The composition of the rapid non-destructive identification solution of trivalent chromium natural color chemical oxidation of aluminum alloy is as follows: the concentration of potassium permanganate is 8g / L, the concentration of sodium silicate nonahydrate is 1.5g / L, the concentration of sodium gluconate is 0.4g / L, the concentration of sodium benzoate is 0.4g / L, the concentration of sodium dodecyl sulfate is 2.5g / L, and the pH is adjusted to 9.8 by adding sodium hydroxide.

[0036] Identification process: Identify whether the aluminum alloy model 6061 has been treated with trivalent chromium natural color chemical oxidation.

[0037] At room temperature, use a dropper to absorb the identification solution and drop 1 to 2 drops on the surface of the sample. After 50 seconds, rinse with pure water and observe that the color of the sample surface where the liquid is dripped has changed significantly. The color of the dripping area is yellow, indicating that the sample is bare aluminum.

[0038] Example 4

[0039] The composition of the rapid non-destructive identification solution of trivalent chromium natural color chemical oxidation of aluminum alloy is as follows: the concentration of potassium permanganate is 8g / L, the concentration of sodium silicate nonahydrate is 2g / L, the concentration of sodium gluconate is 0.4g / L, the concentration of sodium benzoate is 0.4g / L, the concentration of sodium dodecyl sulfate is 3g / L, and the pH is adjusted to 9.8 by adding sodium hydroxide.

[0040] Identification process: Identify whether the aluminum alloy model 6063 has been treated with trivalent chromium natural color chemical oxidation.

[0041] At room temperature, use a dropper to absorb the identification solution and drop 1 to 2 drops on the surface of the sample. After 50 seconds, rinse with pure water and observe that the color of the sample surface where the liquid is dripped has changed significantly. The color of the dripping area is yellow, indicating that the sample is bare aluminum.

[0042] Example 5

[0043] The composition of the rapid non-destructive identification solution of trivalent chromium natural color chemical oxidation of aluminum alloy is as follows: the concentration of potassium permanganate is 7.5g / L, the concentration of sodium silicate nonahydrate is 2.5g / L, the concentration of sodium gluconate is 0.5g / L, the concentration of sodium benzoate is 0.3g / L, the concentration of sodium dodecyl sulfate is 4g / L, and the pH is adjusted to 9.5 by adding sodium hydroxide.

[0044] Identification process: Identify whether the aluminum alloy model 7075 has been treated with trivalent chromium natural color chemical oxidation.

[0045] At room temperature, use a dropper to absorb the identification solution and drop 1 to 2 drops on the surface of the sample. After 45 seconds, rinse with pure water and observe that there is no obvious change in the color of the droplets on the surface of the sample, indicating that the sample is 7075 aluminum alloy that has been chemically oxidized with trivalent chromium.

[0046] The effect of the present invention is shown in Figure 1 , 2 , 3, 4, 5 and 6.

[0047] Depend on Figure 1 , 3As shown in Figures 4 and 5, the surface color of the aluminum alloy droplet that has not been chemically oxidized with trivalent chromium has changed significantly when identified by the identification solution.

[0048] Depend on Figure 2 and 5 It can be seen that there is no obvious change in the surface color of the aluminum alloy droplet that has been chemically oxidized with trivalent chromium in its original color and identified using the identification solution.

[0049] Depend on Figure 6 It can be seen that after being immersed in the identification solution for 1 minute and undergoing a neutral salt spray test for 168 hours, no corrosion occurred on the surface of the aluminum alloy trivalent chromium natural color chemical oxidation sample (using the CN113106434A chemical oxidation method), indicating that the aluminum alloy trivalent chromium natural color chemical oxidation rapid non-destructive identification solution and identification method do not cause damage to the aluminum alloy trivalent chromium natural color chemical oxidation film.

Claims

1. A rapid non-destructive identification method for trivalent chromium natural color chemical oxide film of aluminum alloy, characterized by: The identification method uses an identification solution to treat the surface of the aluminum alloy, and without destroying the trivalent chromium natural color chemical oxidation film of the aluminum alloy, quickly identifies whether the aluminum alloy has been subjected to trivalent chromium natural color chemical oxidation treatment by observing the color change on the surface of the aluminum alloy; The identification solution is composed of potassium permanganate, sodium silicate nonahydrate, an organic corrosion inhibitor and a surfactant, and the mass concentrations thereof are 5-10 g / L, 1-3 g / L, 0.5-1 g / L and 2.5-5 g / L, respectively, and the pH of the identification solution is adjusted to 9.5-10 by means of a pH regulator; The specific identification method is: Step 1: At room temperature, place the aluminum alloy sample to be identified horizontally, and use a dropper to drop 1 to 2 drops of identification solution onto the surface of the aluminum alloy sample; Step 2: After 40 to 60 seconds, clean the surface of the aluminum alloy sample with pure water; Step 3: Observe the color change on the surface of the aluminum alloy sample to which the identification solution has been added; if there is no color change, it indicates that the aluminum alloy sample has undergone trivalent chromium natural color chemical oxidation treatment; if the color turns yellow, it indicates that the aluminum alloy sample has not undergone trivalent chromium natural color chemical oxidation treatment.

2. The method for rapid non-destructive identification of trivalent chromium natural color chemical oxide film of aluminum alloy according to claim 1, characterized in that: The organic corrosion inhibitor is one of sodium gluconate and sodium benzoate or a combination of the two.

3. The method for rapid non-destructive identification of trivalent chromium natural color chemical oxide film of aluminum alloy according to claim 1, characterized in that: The surfactant is sodium lauryl sulfate.

4. The method for rapid non-destructive identification of trivalent chromium natural color chemical oxide film of aluminum alloy according to claim 1, characterized in that: The pH regulator is sodium hydroxide or potassium hydroxide.

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