Aluminum alloy oxidation pretreatment liquid and pretreatment method

Abstract

The invention discloses aluminum alloy oxidation pretreatment liquid and a pretreatment method. The pretreatment liquid is prepared by mixing a fluorine-containing pyridine phosphonic acid corrosion inhibitor, a surfactant, a film-forming agent, sodium hydroxide and deionized water. The fluorine-containing pyridine phosphonic acid corrosion inhibitor has a structure as shown in a formula A. The pretreatment liquid is applied to oxidation pretreatment of the aluminum alloy, grease, metal ions and an oxidation layer on the surface of the aluminum alloy can be effectively removed at the same time, the surface cleanliness of the aluminum alloy is improved, corrosion of alkaline components to the aluminum alloy can be slowed down, the acid pickling process is omitted, the defects of the aluminum alloy are reduced, and the service life of the aluminum alloy is prolonged. The method can be widely applied to the field of aluminum alloy surface treatment. # imgabs0 #

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy surface treatment, and in particular to an aluminum alloy oxidation pretreatment liquid and a pretreatment method. Background Art

[0002] Aluminum is one of the six most widely distributed metals in nature, accounting for about 8.0% of the total mass of the earth's crust. It has a low density, a low melting point, is easy to process, and can be made into various profiles; however, the strength of pure aluminum is very low and it is not suitable for structural materials. After long-term production practice and scientific research, people gradually strengthened aluminum by adding alloy elements and using heat treatment methods to obtain a series of aluminum alloys. Aluminum alloys have high strength while maintaining the advantages of pure aluminum such as lightness, making them ideal structural materials.

[0003] Aluminum alloy is an alloy with aluminum as the base material and a certain amount of other alloying elements added. It is one of the light metal materials. The specific strength of aluminum alloy is close to that of high alloy steel, and the specific stiffness exceeds that of steel. It has good casting performance and plastic processing performance, good electrical and thermal conductivity, good corrosion resistance and weldability. It can be used as a structural material and has a wide range of applications in aerospace, aviation, transportation, construction, electromechanical, light chemicals and daily necessities.

[0004] However, as a structural material, aluminum alloy has the disadvantages of soft texture, poor wear resistance, corrosion resistance under special environment, and high temperature resistance. Although aluminum alloy can spontaneously form Al2O3 film on the surface in the air, the thin layer is very thin and has many defects, which cannot effectively protect the substrate. Therefore, people use various methods to treat the surface of aluminum alloy profiles to improve their performance. In order to further improve the performance of aluminum alloy, a series of surface oxidation treatment technologies for aluminum alloy have been developed, including anodizing, micro-arc oxidation, and thermo-electrochemical oxidation proposed in recent years. After treatment, the surface of aluminum alloy can generate an oxide film of several microns to several hundred microns. Compared with the natural oxide film of aluminum alloy, its corrosion resistance, wear resistance and decorative properties have been significantly improved and enhanced.

[0005] The above-mentioned surface oxidation technologies are all electrochemical oxidations carried out in an electrolyte system. During the treatment, the aluminum alloy parts serve as anodes, and the surface to be treated is completely immersed in the electrolyte. Under the action of an external power source, an electrochemical oxidation reaction occurs to form an oxide film on the surface to be treated. Therefore, the original state of the surface to be treated of the aluminum alloy parts has a direct impact on the treatment effect. For example, the residual oil film of the surface organic processing process, the naturally formed uneven oxide scale, etc., will hinder the contact between the electrolyte and the surface of the aluminum alloy to be treated, thereby resulting in poor treatment effects, peeling, spot ablation, uneven roughness, etc. To solve this problem, it is usually necessary to perform a certain pre-treatment process on the aluminum alloy surface before performing surface oxidation treatment, such as sandpaper polishing, alkali washing, pickling, ultrasonic cleaning, etc. However, the pre-treatment liquid and pre-treatment process of aluminum alloy in the prior art are insufficient in cleaning capacity for impurities, cannot meet the requirements of the cleanliness of the aluminum alloy surface, and have insufficient corrosion inhibition capacity, and are easily corroded during the pre-treatment process, affecting the pre-treatment effect.

[0006] Therefore, there is an urgent need for an aluminum alloy oxidation pretreatment liquid and a pretreatment method that have excellent cleaning ability, can improve the cleanliness of the aluminum alloy surface, and have strong corrosion inhibition ability. Summary of the invention

[0007] Purpose of the invention: In view of the defects of the prior art, the purpose of the present invention is to provide an aluminum alloy oxidation pretreatment liquid and a pretreatment method which have excellent cleaning ability, can improve the cleanliness of the aluminum alloy surface, and have strong corrosion inhibition ability.

[0008] Technical solution:

[0009] An aluminum alloy oxidation pretreatment liquid is prepared by mixing a fluorine-containing pyridine phosphonic acid corrosion inhibitor, a surfactant, a film-forming agent, sodium hydroxide and deionized water;

[0010] The fluorine-containing pyridine phosphonic acid corrosion inhibitor has a structure shown in the following formula A:

[0011]

[0012] The present invention prepares a pretreatment liquid by mixing a fluorine-containing pyridine phosphonic acid corrosion inhibitor, a surfactant, a film-forming agent and sodium hydroxide, which can simultaneously achieve the effects of degreasing and oil removal and alkaline etching, and can not only reduce the aluminum alloy pretreatment process, reduce the process difficulty and cost, but also improve the cleaning effect of grease and oxide layer, thereby improving the cleanliness of the aluminum alloy.

[0013] Furthermore, the fluorine-containing pyridine phosphonic acid corrosion inhibitor is prepared by the following steps: in a reactor, 3,5-difluoro-2,6-diaminopyridine, phosphorous acid and deionized water are added, the temperature is raised to 100-110°C, a catalyst is added, a formaldehyde solution is added after reflux reaction for 2-3 hours, the reflux reaction is continued for 4-6 hours, and then the fluorine-containing pyridine phosphonic acid corrosion inhibitor is obtained after cooling, filtering, washing and drying.

[0014] The present invention uses a fluorine-containing pyridine phosphonic acid corrosion inhibitor as a main component of pretreatment. On the one hand, based on its polyphosphoric acid structure, the corrosion phenomenon of sodium hydroxide on aluminum alloy during the pretreatment process can be significantly slowed down, so that the aluminum alloy can maintain a flat surface in an alkaline environment; on the other hand, its fluorine-containing structure can improve the stability of the corrosion inhibitor in an alkaline environment, so that it can be mixed with sodium hydroxide for a long time and remain stable, and can further improve the corrosion inhibition effect, greatly reduce the occurrence of alkali spots, and thus save the subsequent pickling process.

[0015] Furthermore, the catalyst is selected from concentrated hydrochloric acid or concentrated sulfuric acid; and the mass concentration of the formaldehyde solution is 30-40wt%.

[0016] Furthermore, the mass ratio of the 3,5-difluoro-2,6-diaminopyridine, phosphorous acid and acetaldehyde is (4-6): (6-8): (3-4).

[0017] In the fluorine-containing pyridine phosphonic acid corrosion inhibitor of the present invention, the pyridine structure containing a large π bond can provide electrons to produce a coordination effect, which can not only further improve the corrosion inhibition effect, but also can complex with free metal ions in the bath solution to form precipitation, thereby preventing the metal ions from attaching to the aluminum alloy surface again, thereby improving the cleaning ability of the pretreatment process.

[0018] Furthermore, the surfactant is selected from one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, Tween 60 or Tween 80.

[0019] Furthermore, the film-forming agent is selected from one of hydroxypropyl cellulose, hydroxypropyl methyl cellulose or carboxymethyl cellulose.

[0020] Furthermore, based on the total mass fraction being 100%, the mass percentage of each component is:

[0021]

[0022] The balance was deionized water.

[0023] A pretreatment method comprising any one of the above aluminum alloy oxidation pretreatment solutions, comprising the following steps:

[0024] (1) Use compressed air to blow the aluminum alloy surface to remove dust;

[0025] (2) placing the aluminum alloy prepared in step (1) in an aluminum alloy oxidation pretreatment solution, heating to 40-50° C., and treating under ultrasonic conditions for 5-8 minutes;

[0026] (3) Rinse the aluminum alloy in step (2) with deionized water to complete the aluminum alloy oxidation pretreatment.

[0027] Furthermore, in step (2), the power of ultrasound is 180-220 W and the frequency is 25-35 kHz.

[0028] Furthermore, the deionization temperature in step (3) is 50-60°C.

[0029] Beneficial effects:

[0030] (1) The aluminum alloy oxidation pretreatment liquid and pretreatment method provided by the present invention are prepared by mixing a fluorinated pyridine phosphonic acid corrosion inhibitor, a surfactant, a film-forming agent, sodium hydroxide and deionized water to prepare the pretreatment liquid, and applying the pretreatment liquid to the oxidation pretreatment of the aluminum alloy. The pretreatment liquid can not only effectively remove grease, metal ions and oxide layers on the surface of the aluminum alloy and improve the surface cleanliness of the aluminum alloy, but also slow down the corrosion of the aluminum alloy by alkaline components, thereby eliminating the pickling process and reducing the defects of the aluminum alloy. The pretreatment liquid can be widely used in the field of aluminum alloy surface treatment.

[0031] (2) The aluminum alloy oxidation pretreatment liquid and pretreatment method provided by the present invention are prepared by mixing a fluorinated pyridine phosphonic acid corrosion inhibitor, a surfactant, a film-forming agent and sodium hydroxide to form a pretreatment liquid, which can simultaneously achieve the effects of degreasing and oil removal and alkaline etching. It can not only reduce the aluminum alloy pretreatment process, reduce the process difficulty and cost, but also improve the cleaning effect of grease and oxide layer, thereby improving the cleanliness of the aluminum alloy.

[0032] (3) The aluminum alloy oxidation pretreatment liquid and pretreatment method provided by the present invention use a fluorine-containing pyridine phosphonic acid corrosion inhibitor as the main component of the pretreatment. On the one hand, based on its polyphosphoric acid structure, it can significantly slow down the corrosion of aluminum alloy by sodium hydroxide during the pretreatment process, so that the aluminum alloy can maintain a smooth surface in an alkaline environment; on the other hand, its fluorine-containing structure can improve the stability of the corrosion inhibitor in an alkaline environment, so that it can be mixed with sodium hydroxide for a long time and remain stable, and can further improve the corrosion inhibition effect, greatly reduce the occurrence of alkali spots, and thus save the subsequent pickling process.

[0033] (4) The aluminum alloy oxidation pretreatment liquid and pretreatment method provided by the present invention contain a fluorinated pyridine phosphonic acid corrosion inhibitor, in which the pyridine structure containing a large π bond can provide electrons to produce a coordination effect, which can not only further improve the corrosion inhibition effect, but also can complex with the free metal ions in the bath liquid to form a precipitate, thereby preventing the metal ions from attaching to the aluminum alloy surface again, thereby improving the cleaning ability of the pretreatment process. DETAILED DESCRIPTION

[0034] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following embodiments are examples of the present invention and are only used to illustrate the present invention, but not to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0035] The reagents and equipment in the present invention are conventional reagents and equipment in the technical field.

[0036] Preparation of Fluorine-containing Pyridine Phosphonic Acid Corrosion Inhibitor

[0037] The fluorine-containing pyridine phosphonic acid corrosion inhibitor is prepared by the following steps:

[0038] In a reactor equipped with a reflux condenser and a thermometer, 5 g of 3,5-difluoro-2,6-diaminopyridine, 8 g of phosphorous acid and 100 mL of deionized water were added, the temperature was raised to 110° C., 0.3 g of a 35 wt % concentrated hydrochloric acid solution was added, 10 g of a 30 wt % formaldehyde solution was added after reflux reaction for 3 hours, the reflux reaction was continued for 6 hours, and then the fluorine-containing pyridine phosphonic acid corrosion inhibitor was obtained after cooling, filtering, washing and drying;

[0039] Mass spectral data of the fluorine-containing pyridine phosphonic acid corrosion inhibitor: The product was analyzed by LC-MS, and the m / z of the product was 333.01 (100.0%), 334.13 (10.0%).

[0040] Preparation of Aluminum Alloy Oxidation Pretreatment Solution-1

[0041] The fluorine-containing pyridine phosphonic acid corrosion inhibitor, sodium dodecyl sulfate, hydroxypropyl cellulose, sodium hydroxide and deionized water are mixed to prepare an aluminum alloy oxidation pretreatment liquid-1;

[0042] Taking the total mass fraction as 100%, the mass percentage of each component is:

[0043] Fluorinated pyridine phosphonic acid corrosion inhibitor 15%

[0044] Sodium dodecyl sulfate 3%

[0045] Hydroxypropylcellulose 2%

[0046] Sodium hydroxide 25%

[0047] The balance was deionized water.

[0048] Preparation of Aluminum Alloy Oxidation Pretreatment Solution-2

[0049] The preparation method is basically the same as that of aluminum alloy oxidation pretreatment solution-1, except that the fluorinated pyridine phosphonic acid corrosion inhibitor is replaced by an equal amount of deionized water.

[0050] Preparation of Aluminum Alloy Oxidation Pretreatment Solution-3

[0051] The preparation method is basically the same as that of aluminum alloy oxidation pretreatment liquid-1, except that the fluorine-containing pyridine phosphonic acid corrosion inhibitor is replaced by an equal amount of diethylenetriamine penta (methylene phosphonic acid).

[0052] Example 1

[0053] Take LY12 aluminum alloy profiles and cut them into test pieces of the same size (100mm×100mm×2.0mm). Clean the surface of the test piece with acetone and rinse with water. Dry at 105℃ to constant weight to obtain a clean test piece, and weigh it as m0. Apply a layer of grease evenly on the surface of the clean test piece (the mass ratio of lubricating oil, anti-rust oil and mineral oil is 1:1:1), and dry it at 105℃ to constant weight. Place the test piece with grease at room temperature and in an open air environment for 30 days. The surface grease absorbs dust to form oil stains, and obtains a simulated test piece, which is weighed and recorded as m1;

[0054] The simulated test piece was pre-oxidized by the following steps:

[0055] (1) Use compressed air to blow the aluminum alloy surface to remove dust;

[0056] (2) placing the aluminum alloy prepared in step (1) in aluminum alloy oxidation pretreatment solution-1, heating to 50° C., and treating under ultrasonic conditions of 220 W and 30 kHz for 8 minutes;

[0057] (3) The aluminum alloy in step (2) is rinsed with deionized water at 60° C. to complete the oxidation pretreatment of the aluminum alloy, and the treated test piece is weighed and recorded as m2.

[0058] Example 2

[0059] The process is basically the same as in Example 1, except that in step (2), the temperature is 45° C., the power of the ultrasonic wave is 200 W, and the frequency is 35 kHz.

[0060] Example 3

[0061] The process is basically the same as in Example 1, except that in step (2), the temperature is 40° C., the power of the ultrasonic wave is 180 W, and the frequency is 25 kHz.

[0062] Comparative Example 1

[0063] The method is basically the same as Example 1, except that the aluminum alloy oxidation pretreatment liquid-1 is replaced by an equal amount of aluminum alloy oxidation pretreatment liquid-2.

[0064] Comparative Example 2

[0065] The method is basically the same as Example 1, except that the aluminum alloy oxidation pretreatment liquid-1 is replaced by an equal amount of aluminum alloy oxidation pretreatment liquid-3.

[0066] Performance Testing

[0067] Cleaning ability test: record the values ​​of m0, m1 and m2 in Examples 1-3 and Comparative Examples 1-2 respectively, and calculate the oil removal rate, oil removal rate = (m1-m2) / (m1-m0), the test results are as follows:

[0068] <![CDATA[m0(g)]]> <![CDATA[m1(g)]]> <![CDATA[m2(g)]]> Oil removal rate (%) Example 1 55.927 56.505 55.929 99.65 Example 2 55.897 56.488 55.899 99.66 Example 3 55.905 56.536 55.907 99.68 Comparative Example 1 55.904 56.524 56.052 71.13 Comparative Example 2 55.913 56.493 55.982 88.10

[0069] According to the test results of Examples 1-3, the aluminum alloy oxidation pretreatment liquid and pretreatment method provided by the present invention can effectively remove grease on the surface of the aluminum alloy, improve the surface cleanliness of the aluminum alloy, and can be widely used in the field of aluminum alloy surface treatment.

[0070] According to the comparison of the test results of Examples 1-3 and Comparative Examples 1-2, it can be seen that in the aluminum alloy oxidation pretreatment liquid and pretreatment method provided by the present invention, by adding a fluorine-containing pyridine phosphonic acid corrosion inhibitor during the pretreatment, the cleaning ability can be significantly improved and the surface cleanliness of the aluminum alloy can be improved.

[0071] Corrosion inhibition ability test: The clean test pieces in Examples 1-3 and Comparative Examples 1-2 were not subjected to oil treatment, and the clean test pieces were directly subjected to oxidation pretreatment. The treated test pieces were weighed, recorded as m3, and the corrosion weight loss rate was calculated. The corrosion weight loss rate = (m0-m3) / m0. The test results are shown in the following table:

[0072]

[0073]

[0074] According to the test results of Examples 1-3, the aluminum alloy oxidation pretreatment solution and pretreatment method provided by the present invention can effectively slow down the corrosion of aluminum alloy in an alkaline environment and improve the stability and treatment effect of the pretreatment process.

[0075] According to the comparison of the test results of Examples 1-3 and Comparative Examples 1-2, it can be seen that the aluminum alloy oxidation pretreatment liquid and pretreatment method provided by the present invention have a better corrosion inhibition effect than the corrosion inhibitor in the prior art by adding a fluorine-containing pyridine phosphonic acid corrosion inhibitor in the pretreatment.

[0076] The above implementation modes are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. An aluminum alloy oxidation pretreatment solution, characterized in that: It is prepared by mixing a fluorinated pyridine phosphonic acid corrosion inhibitor, a surfactant, a film former, sodium hydroxide and deionized water; The fluorine-containing pyridine phosphonic acid corrosion inhibitor has a structure shown in the following formula A:

2. The aluminum alloy oxidation pretreatment liquid according to claim 1, characterized in that: The fluorine-containing pyridine phosphonic acid corrosion inhibitor is prepared by the following steps: adding 3,5-difluoro-2,6-diaminopyridine, phosphorous acid and deionized water into a reactor, heating to 100-110° C., adding a catalyst, refluxing for 2-3 hours, adding a formaldehyde solution, continuing the refluxing for 4-6 hours, cooling, filtering, washing and drying to obtain the fluorine-containing pyridine phosphonic acid corrosion inhibitor.

3. The aluminum alloy oxidation pretreatment liquid according to claim 2, characterized in that: The catalyst is selected from concentrated hydrochloric acid or concentrated sulfuric acid; the mass concentration of the formaldehyde solution is 30-40wt%.

4. The aluminum alloy oxidation pretreatment liquid according to claim 2, characterized in that: The mass ratio of the 3,5-difluoro-2,6-diaminopyridine, phosphorous acid and acetaldehyde is (4-6): (6-8): (3-4).

5. The aluminum alloy oxidation pretreatment liquid according to claim 1, characterized in that: The surfactant is selected from one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, Tween 60 or Tween 80.

6. The aluminum alloy oxidation pretreatment liquid according to claim 1, characterized in that: The film-forming agent is selected from one of hydroxypropyl cellulose, hydroxypropyl methyl cellulose or carboxymethyl cellulose.

7. The aluminum alloy oxidation pretreatment liquid according to claim 1, characterized in that: Taking the total mass fraction as 100%, the mass percentage of each component is: The balance was deionized water.

8. A pretreatment method comprising the aluminum alloy oxidation pretreatment solution according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Use compressed air to blow the aluminum alloy surface to remove dust; (2) placing the aluminum alloy prepared in step (1) in an aluminum alloy oxidation pretreatment solution, heating to 40-50° C., and treating under ultrasonic conditions for 5-8 minutes; (3) Rinse the aluminum alloy in step (2) with deionized water to complete the aluminum alloy oxidation pretreatment.

9. The pre-treatment method according to claim 8, characterized in that: In the step (2), the power of ultrasound is 180-220W and the frequency is 25-35kHz.

10. The pre-treatment method according to claim 8, characterized in that: The temperature of deionization in step (3) is 50-60°C.

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