Preparation method of vertical double-metal hydroxide film on surface of alloy steel and product

Abstract

The invention discloses a preparation method of an upright double-metal hydroxide film on the surface of alloy steel and a product. The preparation method comprises the following steps: 1) firstly removing oily substances on the surface of alloy steel, cleaning and drying for later use; (2) adding the electro-deposition precursor solution into a three-electrode tank, taking an alloy steel substrate as a working electrode, Ag / AgCl as a reference electrode and a platinum sheet as a counter electrode, carrying out deposition by adopting a multi-potential step method, firstly applying anode potential to the surface of the steel substrate to carry out oxidation dissolution to generate corresponding metal ions, and then immediately applying cathode potential to carry out deposition; and (3) cleaning and drying the working electrode after deposition is completed, so as to obtain the lamellar double-metal hydroxide film with vertically grown lamellar layers on the surface of the aluminum-zinc-magnesium plated steel. According to the LDHs prepared by the method, film-forming metal ions do not need to be obtained from the outside, and the obtained film is vertical to the surface of a substrate in a lamellar manner, so that the limitation of film forming is greatly solved, and the production steps and raw materials are greatly simplified.

Description

Technical Field

[0001] The present invention relates to the field of metal protection, and in particular to a method and product for preparing a double metal hydroxide film (LDHs) with upright growth of lamellae on the surface of aluminum-zinc-magnesium-plated steel by a multi-potential step method without adding external metal ions. Background Art

[0002] Layered double hydroxides (LDHs) are anionic layered compounds, usually composed of layers with excess positive core charge formed by trivalent and divalent metal ions and hydroxide ions, and other anions inserted between the layers. It has a rich pore structure, so drugs or corrosion inhibitors can be adsorbed or loaded on the surface and pores of LDHs. This feature has led people to apply it to fields such as drug delivery and metal protection, among which thin films are an important application of LDHs. There are usually three methods for preparing LDH films. The first method is to first synthesize LDHs powder by coprecipitation, hydrothermal synthesis, sol-gel method, ion exchange method and other techniques, and then deposit the powder on the substrate surface by spin coating or hydrothermal film forming method to obtain a thin film. The second method is to directly form a film on the solid surface in a film-forming ion solution by a hydrothermal method. The third method is to deposit the metal ions in the solution on the surface of the substrate metal by applying a cathode potential in one step by an electrodeposition method, but the LDHs film obtained by this technology presents a morphology of sheets flattened on the substrate surface. Summary of the invention

[0003] The purpose of the present invention is to provide a method and product for preparing a vertical double hydroxide film on the surface of alloy steel in view of the problems of the existing LDHs film preparation process being relatively complicated and high in energy consumption, and the limitation that most LDHs films prepared by conventional electrodeposition technology are in the form of flat sheets. The method can prepare an LDHs film with vertical growth of sheets in situ on the surface of aluminum-zinc-magnesium-plated steel without adding any metal ions.

[0004] The objective of the present invention is achieved through the following technical solutions: A method for preparing an upright double metal hydroxide film on the surface of alloy steel comprises the following steps: 1) First remove the oily substances on the surface of the alloy steel, clean it and dry it for later use; 2) Add the electrodeposition precursor solution into the three-electrode tank, use the alloy steel substrate as the working electrode, Ag / AgCl as the reference electrode, and the platinum sheet as the counter electrode, and adopt the multi-potential step method for deposition. First, apply the anodic potential to the surface of the aluminum-zinc-magnesium-plated steel substrate for oxidation and dissolution to generate the corresponding metal ions, and then immediately apply the cathodic potential for deposition; 3) After the deposition is completed, the working electrode is cleaned and dried, and a layered double hydroxide film with upright growth of flakes is obtained on the surface of the aluminum-zinc-magnesium plated steel; one of the metals in the layered double hydroxide is a trivalent aluminum ion, and the other is a divalent zinc or magnesium ion.

[0005] The alloy steel substrate includes low aluminum, medium aluminum and high aluminum aluminum-zinc-magnesium-plated steel, aluminum-zinc alloy steel, magnesium-plated aluminum alloy steel, or the main alloys of these coatings, namely aluminum-zinc alloy and aluminum-zinc-magnesium alloy; the low aluminum: aluminum content is 1% ~ 3.5%, the medium aluminum: aluminum content is 5% ~ 11%, and the high aluminum: aluminum content is 55%.

[0006] The electrodeposition precursor solution is a sodium nitrate solution with a concentration of 0.001-0.1 mol / L.

[0007] The anode potential is 1.0~1.6 V, the oxidation time is 60~200 s, the cathode potential is -1.0~-1.4 V, and the deposition time is 60~300 s.

[0008] An alloy steel having an upright double metal hydroxide film on its surface is prepared according to any one of the above methods.

[0009] Beneficial effects of the present invention: In the present invention, the anode potential applied in the first step dissolves the substrate surface to generate divalent metal ions (Zn 2+ or Mg 2+ ) and trivalent Al 3+ , providing a metal ion source for the formation of LDHs film, and then in the second step, the cathode potential is applied to complete the reaction between the metal ions and the in-situ generated OH- ions to form a film. The prepared LDHs film shows a morphology in which the layers grow perpendicular to the substrate, and is expected to be applied in many fields. Using this method, no metal ions required for film formation need to be added to the solution.

[0010] The present invention proposes to deposit layered double hydroxide (LDHs) thin films directly on the surface of aluminum-zinc-magnesium-plated steel substrates by a multi-potential step method without adding metal ions required for film formation. Compared with conventional hydrothermal methods and electrodeposition methods, the LDHs prepared by this method do not need to obtain film-forming metal ions from the outside, and the obtained LDHs thin films present a morphology in which the sheets are perpendicular to the substrate surface, which greatly solves the limitation of traditional technologies that require the addition of metal ions to form films, and greatly simplifies the production steps and raw materials. The method is simple and controllable, environmentally friendly and safe, and low-cost, and is expected to achieve large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1a This is the SEM photo of high aluminum galvanized aluminum-zinc-magnesium steel before treatment; Figure 1b This is a SEM image of a layered double hydroxide film after electrodeposition by a multi-potential step method.

[0012] Figure 2 This is the in-situ thin film XRD pattern of Al-Zn-Mg-plated steel after layered double hydroxide film deposition by multi-potential step method. DETAILED DESCRIPTION

[0013] The present invention discloses a method for preparing layered double hydroxides (LDHs) on the surface of alloy steel by a multi-potential step method. The preparation steps include: 1) first removing oily substances such as rust-proof oil on the surface of aluminum-zinc-magnesium-plated steel, cleaning and drying for standby use; 2) using the aluminum-zinc-magnesium-plated steel substrate as the working electrode, Ag / AgCl as the reference electrode, and a platinum sheet as the counter electrode, and using a multi-potential step method for deposition, first applying an anodic potential to the surface of the aluminum substrate for oxidation, and then immediately applying a cathode potential for deposition; 3) after the deposition is completed, LDHs can be obtained on the surface of the aluminum-zinc-magnesium-plated steel substrate; compared with other existing technologies of the same kind, the micro-nanoscale LDHs film prepared by the present invention has a morphology of upright growth of sheets, has good bonding with the metal substrate, and has good film uniformity. The same electrodeposition method is also mentioned in ZL201910373258.9 "Method for in-situ preparation of hydrotalcite film on aluminum surface by multi-potential step method" and a vertically grown LDH film is obtained. However, the difference is that the present invention pioneered an electrodeposition method without the need for any external deposition of metal ions and used a different metal matrix. The vertically grown layered double hydroxide can greatly increase the microscopic area of ​​the base metal and is expected to be used in electrocatalysis, corrosion and protection, material separation and other fields. The process is highly operable and greatly solves the problem that traditional technologies require the addition of metal ions to form a film. Example 1

[0014] Preparation of layered double hydroxides on Al-Zn-Mg-coated steel surface by multi-potential step method First, the aluminum-zinc-magnesium-plated steel was ultrasonically cleaned in acetone and ethanol for 10 min, and then dried for later use; 2) Add 0.01 M NaNO3 solution to the three-electrode tank, use the Al-Zn-Mg-coated steel substrate as the working electrode, Ag / AgCl as the reference electrode, and platinum sheet as the counter electrode, and use the multi-potential step method for deposition. First, apply 1.3 V anodic potential to the Al-Zn-Mg-coated steel substrate for oxidation for 100 s, and then immediately apply -1.2 V cathodic potential for deposition for 120 s; 3) After the treatment is completed, the metal substrate is washed with water and ethanol and then dried at 50°C for 2 h, thereby obtaining an Al-Zn-Mg-coated steel sheet covered with a layer of vertically grown LDHs film; The obtained samples were observed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Figure 1a The surface of the aluminum-zinc-magnesium-plated steel under a scanning electron microscope appears black and smooth in a "peak-valley" shape; Figure 1b As shown, the surface of the Al-Zn-Mg-coated steel under the scanning electron microscope after electrodeposition was covered with a uniform gray-white layered double hydroxide film, indicating that LDHs were successfully deposited on the surface of the Al-Zn-Mg-coated steel by this method without adding any film-forming metal ions. Figure 2 In addition to the relevant diffraction peaks of the base metal coating, the XRD spectrum also shows the relevant diffraction peaks of layered double hydroxides (003), which indicates that the LDHs film was successfully prepared on the surface of the aluminum-zinc-magnesium steel by a multi-potential step electrodeposition method without the addition of external film-forming metal ions. Example 2

[0015] The specific implementation steps are similar to those in Example 1, except that the concentration of sodium nitrate in the electrodeposition precursor solution is changed. The obtained sample is dried and observed under a scanning electron microscope. The observation results are shown in Table 1.

[0016] Table 1. Effect of alkali salt concentration in hot alkali solution <![CDATA[NaNO3 concentration in the solution]]> Film coverage Thin film growth 0.001 mol / L 10% Nucleation only 0.01 mol / L 90% Nucleated and fully grown 0.1 mol / L 50% The film dissolves and is covered with hydroxide Example 3

[0017] The specific implementation steps are similar to those of Example 1, except that the applied anode potential is changed. The obtained sample is dried and observed under a scanning electron microscope. The observation results are shown in Table 2.

[0018] Table 2. Effect of applied anodic potential Anode potential Film coverage Thin film growth 1.0 V 0% No growth, large areas of matrix exposed 1.1 V 10% Nucleation only 1.2 V 60% Nucleation and partial growth 1.3 V 98% Complete surface coverage 1.4 V 93% Some depressions have not grown 1.5 V 85% No growth in the depression 1.6 V 60% LDHs begin to dissolve Example 4

[0019] The specific implementation steps are similar to those of Example 1, except that the application time of the anode potential is changed. The obtained sample is dried and observed under a scanning electron microscope. The observation results are shown in Table 3.

[0020] Table 3. Effect of anodic potential application time Anode potential application time Film coverage Thin film growth 60 s 60% Nucleation and partial growth 100 s 95% Complete surface coverage 150 s 95% Complete surface coverage 200 s 90% Complete surface coverage Example

[0021] The specific implementation steps are similar to those of Example 1, except that the applied cathode potential is changed. The obtained sample is dried and observed under a scanning electron microscope. The observation results are shown in Table 4.

[0022] Table 4. Effect of cathode potential application Cathode potential application time Film coverage Thin film growth -1.0 V 5% No growth, bare substrate -1.1 V 70% Nucleation and partial growth -1.2 V 95% Complete surface coverage -1.3 V 90% The surface is completely covered, and some grooves have no growth -1.4 V 65% LDHs begin to dissolve Example 5

[0023] The specific implementation steps are similar to those of Example 1, except that the application time of the cathode potential is changed. The obtained sample is dried and observed under a scanning electron microscope. The observation results are shown in Table 5.

[0024] Table 5. Effect of cathode potential application time Cathode potential application time Film coverage Thin film growth 60 s 60% Nucleation and partial growth 120 s 95% Complete surface coverage 180 s 95% Complete surface coverage 240 s 84% The coverage is higher, but LDHs begin to dissolve 300 s 65% The coverage rate decreased and the amount of LDHs dissolved was large Example 6

[0025] The specific implementation steps are similar to those of Example 1, except that the type of metal substrate is changed. The obtained samples are dried and observed under a scanning electron microscope. The observation results are shown in Table 6.

[0026] Table 6. Effects of different metal substrates on the growth of LDHs Metal substrate type Film coverage Thin film growth Galvalume Steel 95% Complete surface coverage Alu-zinc alloy steel 95% Complete surface coverage Magnesium-plated aluminum alloy steel 95% Complete surface coverage The above embodiments are only used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for preparing an upright double metal hydroxide film on the surface of alloy steel, characterized in that: The steps include: 1) First remove the oily substances on the surface of the alloy steel, clean it and dry it for later use; 2) Add the electrodeposition precursor solution into the three-electrode tank, use the alloy steel substrate as the working electrode, Ag / AgCl as the reference electrode, and the platinum sheet as the counter electrode, and adopt the multi-potential step method for deposition. First, apply the anodic potential to the surface of the aluminum-zinc-magnesium-plated steel substrate for oxidation and dissolution to generate the corresponding metal ions, and then immediately apply the cathodic potential for deposition; 3) After the deposition is completed, the working electrode is cleaned and dried, and a layered double hydroxide film with upright growth of flakes is obtained on the surface of the aluminum-zinc-magnesium plated steel; one of the metals in the layered double hydroxide is a trivalent aluminum ion, and the other is a divalent zinc or magnesium ion.

2. The method according to claim 1, characterized in that The alloy steel substrate includes low aluminum, medium aluminum and high aluminum aluminum-zinc-magnesium-plated steel, aluminum-zinc alloy steel, magnesium-plated aluminum alloy steel, or the main alloys of these coatings, namely aluminum-zinc alloy and aluminum-zinc-magnesium alloy; the low aluminum: aluminum content is 1% ~ 3.5%, the medium aluminum: aluminum content is 5% ~ 11%, and the high aluminum: aluminum content is 55%.

3. The method according to claim 1, characterized in that The electrodeposition precursor solution is a sodium nitrate solution with a concentration of 0.001-0.1 mol / L.

4. The method according to claim 1, characterized in that The anode potential is 1.0~1.6 V, the oxidation time is 60~200 s, the cathode potential is -1.0~-1.4 V, and the deposition time is 60~300 s.

5. An alloy steel, characterized in that: The surface has an upright double metal hydroxide film, which is prepared according to the method described in any one of claims 1 to 4.

Images