CN101285185A - Preparation method of corrosion-resistant hydrotalcite-like film on the surface of aluminum and its alloy parts - Google Patents

Abstract

The invention relates to a method for preparing a corrosion-resistant hydrotalcite-like film on the surface of aluminum and its alloy parts. Metal aluminum and aluminum alloy parts are ultrasonically treated in deionized water and acetone respectively to remove impurities and oil stains on the surface, and then placed In the reaction solution of soluble divalent metal salt containing ammonium salt, the aluminum on the surface of the component is used as the aluminum source to interact with the soluble divalent metal salt in the reaction solution to synthesize a hydrotalcite-like film on the surface of the component. The general chemical formula of the film layer Yes: [M ²⁺ _1－x Al ³⁺ _x (OH) ₂ ] ^x+ ·(Y ^n－ ) _x/n ·mH ₂ O. The process used in the method is simple, the raw materials are easy to obtain, the cost is low, and the repeatability is good. The prepared film has excellent corrosion resistance. Corrosion coatings are used.

Description

Preparation method of corrosion-resistant hydrotalcite-like film on the surface of aluminum and its alloy parts

Technical field:

The technology belongs to the technical field of anticorrosion of aluminum and its alloy parts, and specifically relates to a method for preparing a hydrotalcite-like film by using a surface crystallization method and using aluminum and aluminum alloy parts as a substrate.

technical background:

Aluminum is the metal material with the largest amount of use and the widest application range among non-ferrous metals, and the scope of application is still expanding. Aluminum materials have a series of excellent physical, chemical, mechanical and processing properties, such as low density, high plasticity, easy strengthening, good electrical conductivity, easy recycling, and easy surface treatment. Aluminum and aluminum alloys are widely used in the fields of defense industry, aerospace industry, automobile manufacturing, electronics, instrumentation and daily products due to their excellent performance. However, the activity of aluminum is relatively high. In the dry atmosphere, although an oxide film can be formed on the surface, which has a certain protective effect on the substrate, but the oxide film is loose and porous, and its corrosion resistance is poor, so it presents a high corrosion resistance. The chemical activity and electrochemical activity, especially in humid air, sulfur-containing atmosphere and marine atmosphere, will suffer severe electrochemical corrosion. The corrosion resistance of chromate is very good, and the process is relatively stable. It is often used for the anticorrosion of aluminum and its alloys and the bottom layer of organic coatings. Although chromate surface treatment can effectively improve the corrosion resistance of aluminum and its alloys, especially when combined with coatings, it can be used in a higher temperature environment, but the chromate treatment process contains hexavalent chromium ions , is toxic, pollutes the environment, and the cost of waste liquid treatment is high, which brings serious harm and unnecessary trouble to the control, treatment and management of toxic materials related to the coating process. Since 1982, the World Environmental Protection Organization has proposed Limit the use of chromates and other chromate-containing compounds. The development of chromium-free, effective, low-price, environment-friendly substitutes for chromate and corrosion inhibitors and environment-friendly conversion layer treatment process is an urgent problem to be solved in the aviation coating industry, and it is also a new topic faced by scientific and technological workers. Therefore, the use of hydrotalcite compounds in the field of corrosion resistance of aluminum and its alloys has a broad application prospect due to its simple process, non-toxicity, low energy consumption, economy and excellent corrosion resistance.

Hydrotalcite compounds include Hydrotalcite and Hydrotalcite-like compound, the main body of which is generally composed of two metal hydroxides, so it is also called Layered Double Hydroxide Metal Oxide (Layered Double Hydroxide, Abbreviated as LDH). The intercalation compound of LDH is called intercalation hydrotalcite. Hydrotalcites, hydrotalcite-like materials, and intercalated hydrotalcites are collectively referred to as hydrotalcite-like intercalation materials (LDHs). This kind of material is a kind of inorganic material with unique structural characteristics, such as the type of intercalation anion can be adjusted in a wide range, which lays the foundation for this kind of material to become a corrosion-resistant material with potential application prospects. .

Literature 1.RGBuchheit et al. mixed V ₁₀ O ₂₈ ^6- intercalated zinc-aluminum hydrotalcite compounds and quinone compounds on the surface of the substrate in Progress in Organic Coating 47 (2003) 174-182, thinking that inhibition The VO ₃ ^- and Zn ²⁺ released during the corrosion process have a certain protective effect on the substrate.

Literature 2. Geraint Williams et al. published two papers in Electrochemical and Solid-State Letters in which different anion-intercalated hydrotalcite compounds were incorporated into PVB to study their protective effect on aluminum alloys. They both proposed that the ability of intercalation anions to exchange with Cl ^- determines the corrosion resistance of hydrotalcite-like compounds.

Document 3. In the patent application 200610088993.8, our experimental group provided a method for preparing zinc-aluminum hydrotalcite films on anodized aluminum. complex.

In the above literature, the application of hydrotalcite-like materials as corrosion-resistant materials has better corrosion resistance. However, most of them use powder materials, which are mixed with organic adhesives to increase their viscosity and then coated on the surface of the metal substrate to form a film for research. This will limit the durability of the film to a certain extent. After adding organic compounds, Its thermal stability is also affected. The hydrotalcite-like film prepared by our surface crystallization method is directly synthesized on the surface of aluminum and its alloy parts as a corrosion-resistant material for aluminum and its alloy parts. It does not need to add organic adhesives and has no toxic effects on the human body. The environment is pollution-free.

Invention content:

The object of the present invention is to provide a method for preparing a hydrotalcite-like film by surface crystallization of aluminum and aluminum alloy parts. Under the condition of not adding an organic adhesive, this type of hydrotalcite film can improve the corrosion resistance of aluminum and aluminum alloy parts, and realize that the preparation process has no poisonous effect on the human body and no pollution to the environment.

The hydrotalcite-like film provided in the present invention is prepared by a surface crystallization method. Using aluminum and its alloy parts as the matrix, using the aluminum on the surface of the parts as the aluminum source, and then synthesizing the hydrotalcite-like film in a solution containing divalent ions. The general chemical formula of the film layer is;

[M ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(Y ^n- ) _x/n ·mH ₂ O,

Where M ²⁺ represents any one of divalent metal ions Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ , Zn ²⁺ , preferably Zn ²⁺ , Mg ²⁺ , Co ²⁺ , Ni ²⁺ ; Y ^n- represents any one of intercalated anions CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- species, preferably CO ₃ ^2- , SO ₄ ^2- , NO ₃ ^- or Cl ^- ; 0.2≤x≤0.4, 0≤m≤2.

The present invention uses the surface crystallization method to prepare hydrotalcite-like thin films on the surface of aluminum and its alloy parts, without anodic oxidation, in an inert atmosphere, deionized water does not need to remove CO ₂ , and does not need to add organic The adhesive can be directly applied to the corrosion resistance research of aluminum and its alloy parts.

The specific preparation method is as follows:

A. Ultrasonic cleaning of aluminum or aluminum alloy parts with deionized water and acetone for 10 minutes to remove surface impurities and oil stains, and then soak in sodium hydroxide solution with a mass fraction of 0.1-5% to remove the oxide layer on the surface;

_B. Dissolve soluble ammonium salt ⁽ NH ₄ ^{+ )} _n A ^n- and soluble divalent metal inorganic salt M ²⁺ B ^n- in deionized In water, prepare a solution with an M2 ⁺ metal ion concentration of 0.01-1mol/L, and then use 0.1-3% dilute ammonia water to adjust the pH of the solution to 4-10;

C. Suspend the pretreated aluminum or aluminum alloy parts in the reaction solution, react at 75-180°C for 6-120 hours, take out the substrate, rinse with ethanol solution, and dry at room temperature to obtain water-like Talc film, the general chemical formula of the film layer is: [M ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(Y ^n- ) _x/n ·mH ₂ O, where 0.2≤x≤0.4, 0 ≤m≤2.

In step B, A ^n- is any one of CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- , preferably CO ₃ ^2- , SO ₄ ^2- , NO ₃ ^- or Cl ^- ; M ²⁺ is a divalent metal cation, which can be Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ or Zn ²⁺ , etc. , preferably Mg ²⁺ , Co ²⁺ , Zn ²⁺ or Ni ²⁺ ; B ^{n- is} any one of NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- , preferably SO ₄ ^2- , NO ₃ ^- or Cl ^- . The molar ratio of (NH ₄ ⁺ )/M ²⁺ B ^n- is 3-10. The preferred pH range of the reaction solution is 6.0-8.0.

The preferred reaction temperature in step C is 90-180° C., and the preferred reaction time range is 12-120 hours.

The samples were qualitatively analyzed by XRD-6000 X-ray diffractometer from Shimadzu and Vector22 Fourier transform infrared spectrometer from Bruker, Germany. The results are shown in Figure 1. FIG. 1 is the X-ray diffraction (XRD) spectrum of the hydrotalcite-like thin film obtained at different times in Example 1. Except that the diffraction peaks near 45° and 65° are the diffraction peaks of Al ₂ O ₃ , other diffraction peaks can be attributed to (003), (006), (012) diffraction peaks of nitrate-type hydrotalcite-like films. With the increase of time, the diffraction intensity of the film increases, indicating that the thickness of the film increases with the prolongation of the reaction time. 2 is an XRD spectrum of the zinc-aluminum hydrotalcite film obtained in Example 1 and the powder obtained by scraping the zinc-aluminum hydrotalcite film from the surface of an aluminum part. Curve a in Fig. 2 is the XRD spectrum of the scraped zinc-aluminum hydrotalcite powder, and its (003) diffraction peak is the strongest. Curve b in Figure 2 is the XRD pattern of the zinc-aluminum hydrotalcite film, and its (012) diffraction peak is the strongest, indicating that the orientation of the zinc-aluminum hydrotalcite film prepared by the surface crystallization method is relatively good.

The Japanese HITACHI S-3500N scanning electron microscope (SEM) was used to observe the morphology of the film surface and its cross-section (all SEM samples were sprayed with gold for clearer photos). FIG. 3 is an SEM picture of the zinc-aluminum hydrotalcite film prepared in Example 1. It can be seen from the picture that the hydrotalcite-like film obtained by the crystallization method on the surface of the aluminum part is relatively uniform and dense. FIG. 4 is an SEM picture of the cross-section of the zinc-aluminum hydrotalcite film prepared in Example 1. It can be seen from this figure that the flat hydrotalcites are closely arranged and grow along the direction perpendicular to the substrate.

The German VECTOR22 Fourier transform infrared spectrometer was used to detect the intercalation anion type of the hydrotalcite-like film. Fig. 5 is the FT-IR spectrum of the powder scraped from the zinc-aluminum hydrotalcite film prepared in Example 1. 3450cm ^-1 is the characteristic vibration absorption peak of OH, the absorption peak at 1628cm ^-1 is the bending vibration absorption peak of H ₂ O molecule, and the absorption peak at 1384cm ^-1 is the vibration absorption peak of NO ₃ ^- . The intercalation anion of the hydrotalcite-like film prepared by the surface crystallization method in Example 1 is NO ₃ ^- .

The domestic CS300 corrosion electrochemical measurement system was used to measure the polarization curves of aluminum parts and hydrotalcite-like film samples. Fig. 6 is the polarization curve figure of the aluminum part of embodiment 1 and the aluminum part after the surface crystallization method synthesizes the hydrotalcite-like thin film, and curve a is the polarization curve of the aluminum part template, and curve b is the surface crystallization method to synthesize the hydrotalcite-like film Polarization curve plot of aluminum part after talc film. It can be seen from the figure that the corrosion current of the aluminum alloy parts after the hydrotalcite-like film synthesized by the surface crystallization method is significantly reduced, indicating that its corrosion resistance performance is significantly improved. Figure 7 is a comparison of the polarization curves of the hydrotalcite-like film obtained by the surface crystallization method in Example 1 and the hydrotalcite-like film prepared in Document 3 (patent application 200610088993.8), and curve a is the curve of the hydrotalcite-like film synthesized in Example 1 , Curve b is the polarization curve of the hydrotalcite-like film synthesized in Document 3. By comparison, it can be seen that the polarization current of the hydrotalcite-like film in the example is smaller, indicating that its corrosion resistance is better.

The beneficial effects of the present invention are: without anodic oxidation, omitting this cumbersome operation, and without using deionized water to remove _CO2 in an inert atmosphere, the surface crystallization method is used to successfully prepare hydrotalcite-like film, and the hydrotalcite-like film prepared by the present invention is denser and has better corrosion resistance. The hydrotalcite-like film prepared by the surface crystallization method has a good bonding force with the surface of the component. It does not need to add organic adhesives when used as a corrosion-resistant material, and the film does not contain toxic ions. It has no poisonous effect on the human body and no pollution to the environment. . The process used in this method is simple, the raw materials are readily available, the cost is low, and the repeatability is good. The prepared film has excellent corrosion resistance. This type of hydrotalcite film is expected to be used as a corrosion-resistant coating for aluminum and its alloy parts in engineering materials.

Description of drawings:

Fig. 1 is the XRD of the hydrotalcite-like film of different time that embodiment 1 obtains;

Fig. 2 is the XRD of the hydrotalcite-like film that embodiment 1 obtains and the powder scraped off from the surface of the aluminum part;

Fig. 3 is the SEM of the hydrotalcite-like film that embodiment 1 obtains;

Fig. 4 is the SEM of the hydrotalcite-like film section that embodiment 1 obtains;

Fig. 5 is the FT-IR of the powder that the hydrotalcite-like film that embodiment 1 obtains scrapes off;

Fig. 6 is the aluminum part that embodiment 1 obtains and the polarization curve of the aluminum part after the surface crystallization method prepares hydrotalcite-like film;

FIG. 7 is the polarization curves of the hydrotalcite-like film obtained in Example 1 and the hydrotalcite-like film prepared by the method of Document 3.

Specific implementation plan:

The present invention is further described below in conjunction with specific examples:

Example 1:

A. Pretreatment of aluminum parts: ultrasonically clean the aluminum parts with deionized water and acetone for 10 minutes to remove impurities and oil stains on the surface, and then soak them in 0.5% sodium hydroxide solution to remove the oxide layer on the surface;

B. Weigh 0.595g of zinc nitrate and 0.96g of ammonium nitrate, dissolve them in 200ml of deionized water, and prepare 200ml of a reaction solution whose molar ratio of NH ₄ ⁺ : Zn ²⁺ is 6, wherein the molar concentration of Zn ²⁺ is 0.01mol/L , adjust the pH to 6.5 with 1% ammonia water;

C. Suspend the pretreated aluminum parts in the reaction solution and place at 120°C for 24h. After that, take out the substrate, wash it with ethanol, and dry it naturally to obtain an aluminum part covered with a zinc-aluminum hydrotalcite film whose interlayer anion is NO ₃ ^- , the molecular formula of this hydrotalcite film is [Zn ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(NO ₃ ⁻ ) _x/n · mH ₂ O.

Example 2:

A. Pretreatment of aluminum parts: ultrasonically clean the aluminum parts with deionized water and acetone for 10 minutes to remove impurities and oil stains on the surface, and then soak them in 0.5% sodium hydroxide solution to remove the oxide layer on the surface;

B. Weigh 1.745g of nickel nitrate and 2.881g of ammonium nitrate, dissolve them in 200ml of deionized water, and prepare 200ml of a reaction solution whose molar ratio of NH ₄ ⁺ : Ni ²⁺ is 6, wherein the molar concentration of Ni ²⁺ is 0.03mol/L , adjust the pH to 7.5 with 0.5% ammonia water;

C. Suspend the pretreated aluminum parts in the reaction solution and place at 150°C for 24h. After that, take it out, wash it with ethanol, and dry it naturally to obtain an aluminum part covered with a nickel-aluminum hydrotalcite film whose interlayer anion is NO ₃ ^- . The molecular formula of this hydrotalcite film is [Ni ²⁺ _1-x Al ^{3 +} _x (OH) ₂ ] ^x+ ·(NO ₃ ⁻ ) _x/n · mH ₂ O.

Example 3:

A. Pretreatment of aluminum parts: ultrasonically clean the aluminum parts with deionized water and acetone for 10 minutes to remove impurities and oil stains on the surface, and then soak them in a sodium hydroxide solution with a mass fraction of 1.0% to remove the oxide layer on the surface;

B. Weigh 27.232g of zinc chloride and 32.094g of ammonium chloride, dissolve them in 200ml of deionized water, and prepare 200ml of a reaction solution whose molar ratio of NH ₄ ⁺ : Zn ²⁺ is 4, wherein the molar concentration of Zn ²⁺ is 1.0mol /L, adjust the pH to 7.0 with 0.1% dilute ammonia solution;

C. Suspend the pretreated aluminum parts in the reaction solution and place at 90°C for 36h. After that, take it out, wash it with ethanol, and dry it naturally to obtain an aluminum part covered with a zinc-aluminum hydrotalcite film whose interlayer anion is Cl ^- . The molecular formula of this hydrotalcite film is [Zn ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(Cl ⁻ ) _x/n · mH ₂ O.

Example 4:

A. Pretreatment of aluminum parts: ultrasonically clean the aluminum parts with deionized water and acetone for 10 minutes to remove impurities and oil on the surface, and then soak them in 1.0% sodium hydroxide solution to remove the oxide layer on the surface ;

B. Weigh 0.323g of zinc sulfate and 2.642g of ammonium sulfate, dissolve them in 200ml of deionized water, and prepare 200ml of a reaction solution whose molar ratio of NH ₄ ⁺ : Zn ²⁺ is 10, wherein the molar concentration of Zn ²⁺ is 0.01mol/L , with a concentration of 2% ammonia solution to adjust the pH to 6.0;

C. Suspend the pretreated aluminum parts in the reaction solution and place at 180°C for 12h. After that, take it out, wash it with ethanol, and dry it naturally to obtain an aluminum part covered with a zinc-aluminum hydrotalcite film whose intercalation anion is SO ₄ ^2- . The molecular formula of this hydrotalcite film is [Zn ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(SO ₄ ^2- ) _x/n ·mH ₂ O.

Example 5:

A. Pretreatment of aluminum alloy parts: ultrasonically clean the aluminum alloy parts with deionized water and acetone for 10 minutes to remove surface impurities and oil stains, and then soak them in a sodium hydroxide solution with a mass fraction of 3.0% to remove surface oxidation layer;

B. Weigh 0.595g of zinc nitrate and 2.40g of ammonium nitrate, dissolve them in 200ml of deionized water, and prepare 200ml of a reaction solution whose molar ratio of NH ₄ ⁺ : Zn ²⁺ is 15, wherein the molar concentration of Zn ²⁺ is 0.01mol/L , with a concentration of 3% ammonia solution to adjust the pH to 5.5;

C. Suspend the pretreated aluminum alloy part in the reaction solution, place it at 150°C for 24 hours, take it out, wash it with ethanol, and dry it naturally to obtain a zinc-aluminum hydrotalcite film whose surface is covered with an intercalation anion of NO ₃ ^- For aluminum alloy parts, the molecular formula of the hydrotalcite film is [Zn ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(NO ₃ ^- ) _x/n ·mH ₂ O.

Embodiment 6:

A. Pretreatment of aluminum alloy parts: ultrasonically clean the aluminum alloy parts with deionized water and acetone for 10 minutes to remove surface impurities and oil stains, and then soak them in a sodium hydroxide solution with a mass fraction of 3.0% to remove surface impurities. oxide layer;

B. Weigh 5.816g of nickel nitrate and 12.806g of ammonium nitrate, dissolve them in 200ml of deionized water, and prepare 200ml of a reaction solution whose molar ratio of NH ₄ ⁺ : Ni ²⁺ is 8, wherein the molar concentration of Ni ²⁺ is 0.1mol/L , with a concentration of 1.5% ammonia water to adjust the pH to 7.5;

C. Suspend the pretreated aluminum alloy parts in the reaction solution, place them at 120°C for 36 hours, take them out, wash them with ethanol, and dry them naturally to obtain a nickel-aluminum hydrotalcite film whose surface is covered with an intercalation anion of NO ₃ ^- For aluminum alloy parts, the molecular formula of the hydrotalcite film is [Ni ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(NO ₃ ^- ) _x/n ·mH ₂ O.

Claims (4)

1. A method for preparing a corrosion-resistant hydrotalcite-like film on the surface of aluminum and its alloy parts, the specific steps are: A. Ultrasonic cleaning of aluminum or aluminum alloy parts with deionized water and acetone for 10 minutes to remove surface impurities and oil stains, and then soak in sodium hydroxide solution with a mass fraction of 0.1-5% to remove the oxide layer on the surface; B. Dissolve soluble ammonium salt (NH ₄ ⁺ ) _n A ^n- and soluble divalent metal inorganic salt M ²⁺ B ^n- in the ratio of (NH ₄ ⁺ )/M ²⁺ molar ratio of 2 to 20 In ionized water, prepare a reaction solution with an M2 ⁺ metal ion concentration of 0.01-1mol/L, and then use 0.1-3% dilute ammonia water to adjust the pH of the solution to 4-10; C. Suspend the pretreated aluminum or aluminum alloy parts in the reaction solution, react at 75-180°C for 6-120 hours, take out the substrate, rinse with ethanol solution, and dry at room temperature to obtain water-like Talc film, the general chemical formula of the film layer is: [M ²⁺ _1-x Al ³⁺ _x (OH) ₂ ] ^x+ ·(Y ^n- ) _x/n ·mH ₂ O, where 0.2≤x≤0.4, 0 ≤m≤2; In step B, A ^n- is any one of CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- ; B ^n- is NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- in any one; M ²⁺ described in steps B and C represents any one of divalent metal ions Mg ²⁺ , Co ²⁺ , Ni ²⁺ , Ca ²⁺ , Cu ²⁺ , Fe ²⁺ , Mn ²⁺ , Zn ²⁺ species; Y ^n- in Step C represents any one of the intercalated anions CO ₃ ^2- , NO ₃ ^- , SO ₄ ^2- , Cl ^- , F ^- or Br ^- . 2. The preparation method of the corrosion-resistant hydrotalcite-like film on the surface of aluminum and its alloy parts according to claim 1, wherein the molar ratio of (NH ₄ ⁺ )/M ²⁺ in step B is 3 to 10, The pH value of the reaction solution is adjusted to 6.0-8.0 with diluted ammonia water; the reaction temperature of the components in the reaction solution in step C is 90-180° C., and the reaction time is 12-120 hours. 3. The preparation method of the corrosion-resistant hydrotalcite-like film on the surface of aluminum and its alloy parts according to claim 1, characterized in that, in step B, A ^n- is CO ₃ ^2- , SO ₄ ^2- , NO ₃ ^- or Cl ^- ; Bn ^- is SO ₄ ^2- , NO ₃ ^- or Cl ^- . 4. The preparation method of the corrosion-resistant hydrotalcite-like film on the surface of aluminum and its alloy parts according to claim 1, wherein the M2 ⁺ described in step C is Zn2 ⁺ , Mg2 ⁺ , ^{Co2 +} or Ni ²⁺ , Y ^n- is CO ₃ ^2- , SO ₄ ^2- , NO ₃ ^- or Cl ^- .

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