CN114703529A - Magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer and preparation method thereof - Google Patents
Magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer and preparation method thereof Download PDFInfo
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- 229910000861 Mg alloy Inorganic materials 0.000 title claims abstract description 208
- 230000003075 superhydrophobic effect Effects 0.000 title claims abstract description 116
- 239000012528 membrane Substances 0.000 title claims abstract description 98
- 239000002131 composite material Substances 0.000 title claims abstract description 85
- 238000002360 preparation method Methods 0.000 title claims abstract description 24
- 238000007745 plasma electrolytic oxidation reaction Methods 0.000 claims abstract description 173
- 239000011159 matrix material Substances 0.000 claims abstract description 60
- 239000000758 substrate Substances 0.000 claims abstract description 45
- 239000003792 electrolyte Substances 0.000 claims abstract description 23
- 230000004048 modification Effects 0.000 claims abstract description 21
- 238000012986 modification Methods 0.000 claims abstract description 21
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 49
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 33
- 238000006243 chemical reaction Methods 0.000 claims description 27
- 229910000000 metal hydroxide Inorganic materials 0.000 claims description 26
- 235000021355 Stearic acid Nutrition 0.000 claims description 22
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 22
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 claims description 22
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 claims description 22
- 239000008117 stearic acid Substances 0.000 claims description 22
- 230000003746 surface roughness Effects 0.000 claims description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 16
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 claims description 16
- 238000000034 method Methods 0.000 claims description 13
- 239000008367 deionised water Substances 0.000 claims description 9
- 229910021641 deionized water Inorganic materials 0.000 claims description 9
- 150000004692 metal hydroxides Chemical class 0.000 claims description 9
- 239000000126 substance Substances 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 8
- 238000000227 grinding Methods 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 7
- ZGTMUACCHSMWAC-UHFFFAOYSA-L EDTA disodium salt (anhydrous) Chemical compound [Na+].[Na+].OC(=O)CN(CC([O-])=O)CCN(CC(O)=O)CC([O-])=O ZGTMUACCHSMWAC-UHFFFAOYSA-L 0.000 claims description 6
- 229910002651 NO3 Inorganic materials 0.000 claims description 6
- 235000019832 sodium triphosphate Nutrition 0.000 claims description 6
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 claims description 5
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 claims description 5
- 235000019441 ethanol Nutrition 0.000 claims description 5
- 239000010935 stainless steel Substances 0.000 claims description 3
- 229910001220 stainless steel Inorganic materials 0.000 claims description 3
- 244000137852 Petrea volubilis Species 0.000 claims description 2
- 238000003801 milling Methods 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- 238000004506 ultrasonic cleaning Methods 0.000 claims description 2
- 238000005260 corrosion Methods 0.000 abstract description 38
- 230000007797 corrosion Effects 0.000 abstract description 36
- 239000012295 chemical reaction liquid Substances 0.000 abstract description 7
- 230000008021 deposition Effects 0.000 abstract description 5
- 239000010410 layer Substances 0.000 description 210
- 239000000243 solution Substances 0.000 description 28
- 238000000576 coating method Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
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- 238000009736 wetting Methods 0.000 description 9
- 238000005299 abrasion Methods 0.000 description 8
- 239000011777 magnesium Substances 0.000 description 8
- 238000000151 deposition Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 230000001965 increasing effect Effects 0.000 description 6
- 230000009286 beneficial effect Effects 0.000 description 5
- KYIDJMYDIPHNJS-UHFFFAOYSA-N ethanol;octadecanoic acid Chemical compound CCO.CCCCCCCCCCCCCCCCCC(O)=O KYIDJMYDIPHNJS-UHFFFAOYSA-N 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 230000035484 reaction time Effects 0.000 description 5
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- 125000004185 ester group Chemical group 0.000 description 4
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- 230000002209 hydrophobic effect Effects 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 235000011121 sodium hydroxide Nutrition 0.000 description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 238000005886 esterification reaction Methods 0.000 description 2
- -1 hydroxyl carboxyl Chemical group 0.000 description 2
- 239000000463 material Substances 0.000 description 2
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- 238000005245 sintering Methods 0.000 description 2
- 238000000935 solvent evaporation Methods 0.000 description 2
- 238000012876 topography Methods 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- BPQQTUXANYXVAA-UHFFFAOYSA-N Orthosilicate Chemical compound [O-][Si]([O-])([O-])[O-] BPQQTUXANYXVAA-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 150000004645 aluminates Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- RRTQFNGJENAXJJ-UHFFFAOYSA-N cerium magnesium Chemical group [Mg].[Ce] RRTQFNGJENAXJJ-UHFFFAOYSA-N 0.000 description 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 239000007810 chemical reaction solvent Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 150000004679 hydroxides Chemical class 0.000 description 1
- 125000002887 hydroxy group Chemical group [H]O* 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002680 magnesium Chemical class 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000005416 organic matter Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002161 passivation Methods 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- 239000011574 phosphorus Substances 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000002604 ultrasonography Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/30—Anodisation of magnesium or alloys based thereon
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/60—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using alkaline aqueous solutions with pH greater than 8
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C28/00—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D
- C23C28/04—Coating for obtaining at least two superposed coatings either by methods not provided for in a single one of groups C23C2/00 - C23C26/00 or by combinations of methods provided for in subclasses C23C and C25C or C25D only coatings of inorganic non-metallic material
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/026—Anodisation with spark discharge
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Electrochemistry (AREA)
- Mechanical Engineering (AREA)
- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Chemical Treatment Of Metals (AREA)
Abstract
The invention discloses a magnesium alloy with a super-hydrophobic MAO-LDH composite membrane layer and a preparation method thereof, wherein the magnesium alloy consists of a magnesium alloy matrix, a micro-arc oxidation membrane MAO layer and a super-hydrophobic modified LDH-SA layer; the micro-arc oxidation film MAO layer is positioned on the surface of the magnesium alloy substrate, and the super-hydrophobic modified LDH-SA layer is deposited on the micro-arc oxidation film MAO layer; the thickness of the micro-arc oxidation film MAO layer is 5-10 mu m, and the thickness of the super-hydrophobic modified LDH-SA layer is 5-20 mu m; the preparation method comprises the following steps: the magnesium alloy substrate is pretreated and then placed in electrolyte for micro-arc oxidation, then placed in LDH reaction liquid for LDH deposition, and finally super-hydrophobic modification is carried out, so that the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer is obtained, the corrosion rate of the magnesium alloy is remarkably reduced while the super-hydrophobic effect is realized, and the magnesium alloy can be used in the fields of aerospace, automobiles, medical instruments, 3C digital codes and the like.
Description
Technical Field
The invention relates to the technical field of corrosion-resistant magnesium alloy. In particular to a magnesium alloy with a super-hydrophobic MAO-LDH composite membrane layer and a preparation method thereof.
Background
Magnesium and magnesium alloy as green engineering material in 21 st century has low density (1.8 g/cm)3Left and right), large elastic modulus, high strength, good shock absorption, good heat dissipation, larger impact load bearing capacity than aluminum alloy, good organic matter and alkaline corrosion resistance, good electric and thermal conductivity, good damping performance and the like, and is an indispensable important basic material in the fields of aerospace, automobiles, computers and the like. However, magnesium alloys have high chemical and electrochemical activity and extremely low standard electrode potential, so the corrosion problem has been the primary and core problem hindering the development of magnesium alloys. At present, a surface treatment method, Micro-arc Oxidation (MAO), is developed on the basis of the traditional anodic Oxidation technology, and the Micro-arc Oxidation (MAO) is used for treating gold such as magnesium and the like through the instantaneous high-temperature sintering effect of a Micro-areaThe ceramic film mainly containing matrix oxide is formed on the surface in situ, and the corrosion resistance of the magnesium alloy can be effectively improved. The ceramic film layer formed on the surface of the magnesium alloy by adopting the micro-arc oxidation method has good compactness and is tightly combined with the magnesium alloy substrate, so that the magnesium alloy has better corrosion resistance. However, the surface of the film prepared by the method usually has tiny holes due to current breakdown, and a small amount of micro-cracks exist on the surface of the film. Such micro-holes or micro-cracks provide a large number of corrosion channels for corrosion ions, resulting in a severe decrease in the corrosion resistance of the magnesium alloy film.
At present, a patent number '202110870154.6' discloses a magnesium alloy surface MAO-LDH biological composite membrane layer and a preparation method and application thereof; the LDH layer is deposited on the surface of the MAO layer to cover and block micro holes and micro cracks generated on the surface of the MAO layer due to current breakdown, so that the corrosion resistance of the MAO layer is improved; however, the LDH layer of the MAO-LDH biological composite membrane layer has lower deposition height on the MAO layer, the surface wetting angle is only 80-85 degrees, and the corrosion current density is higher and reaches 1.0 multiplied by 10-6～1.2×10-6A·cm-2Therefore, the magnesium alloy with the MAO-LDH biological composite membrane layer has poor corrosion resistance and can not achieve ideal application effect when being used in the fields of aerospace, automobiles, computers and the like.
Disclosure of Invention
Therefore, the technical problem to be solved by the invention is to provide a magnesium alloy with a super-hydrophobic MAO-LDH composite membrane layer and a preparation method thereof, so as to solve the problems that the wetting angle of the MAO-LDH composite membrane layer on the surface of the magnesium alloy is lower than 90 degrees, the corrosion current density is too large, the binding force between the composite membrane layer and a magnesium alloy matrix is weak and the like in the prior art.
In order to solve the technical problems, the invention provides the following technical scheme:
a magnesium alloy with a super-hydrophobic MAO-LDH composite membrane layer consists of a magnesium alloy matrix, a micro-arc oxidation membrane MAO layer and a super-hydrophobic modified LDH-SA layer; the micro-arc oxidation film MAO layer is positioned on the surface of the magnesium alloy substrate, and the super-hydrophobic modified LDH-SA layer is deposited on the micro-arc oxidation film MAO layer; the thickness of the micro-arc oxidation film MAO layer is 5-10 mu m, and the thickness of the super-hydrophobic modified LDH-SA layer is 5-20 mu m.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer has the advantages that the magnesium alloy matrix is AZ31 magnesium alloy; the super-hydrophobic modified LDH-SA layer is obtained by modifying a layered double hydroxide LDH layer with stearic acid SA; the chemical structural formula of the layered double hydroxide LDH layer is [ Mg ]2+ 1-x Ce3+ x(OH)2][NO3 -]x·mH2O, x is more than 0.17 and less than 0.33; the layered double-metal hydroxide LDH layer is in a hexagonal petal-shaped layered structure, and consists of hexagonal sheet units and is positioned on the micro-arc oxidation membrane MAO layer, so that the hexagonal petal-shaped layered structure is formed.
A preparation method of a magnesium alloy with a super-hydrophobic MAO-LDH composite membrane layer comprises the following steps:
step (1): carrying out water grinding, cleaning and drying treatment on the magnesium alloy matrix in sequence, and keeping the magnesium alloy matrix for later use after the treatment is finished;
step (2): placing the magnesium alloy substrate treated in the step (1) in an electrolyte, and performing micro-arc oxidation by using the magnesium alloy substrate as an anode and a stainless steel tank as a cathode to form a micro-arc oxidation film MAO layer on the surface of the magnesium alloy substrate to obtain the magnesium alloy substrate with the MAO layer, wherein the thickness of the micro-arc oxidation film MAO layer is 5-10 mu m;
and (3): placing the magnesium alloy matrix with the MAO layer in LDH reaction liquid for hydrothermal reaction, and depositing the generated layered double-metal hydroxide LDH on the micro-arc oxidation membrane MAO layer to form a layered double-metal hydroxide LDH layer to obtain the MAO-LDH layer magnesium alloy matrix;
and (4): placing the MAO-LDH layer magnesium alloy matrix in a container containing a super-hydrophobic modified solution, and then placing the container in a water bath condition to carry out a water bath reaction so as to modify a layered double-metal hydroxide LDH layer to generate a super-hydrophobic modified LDH-SA layer, wherein the thickness of the super-hydrophobic modified LDH-SA layer is 5-20 mu m; and after the water bath reaction is finished, cleaning and naturally drying to obtain the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer.
In the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, in the step (1), the magnesium alloy matrix is made of AZ31 magnesium alloy; during water grinding, sand paper of 240#, 600#, 1000# and 1500# is used for water grinding in sequence; after the water milling is finished, sequentially using alcohol and deionized water to carry out ultrasonic cleaning on the magnesium alloy matrix;
in the step (2), the surface roughness of the magnesium alloy substrate with the MAO layer is 2.2-3.2 μm; in the step (3), the surface roughness of the MAO-LDH layer magnesium alloy matrix is 8.8-11.2 μm. By controlling the surface roughness of the micro-arc oxidation film MAO layer and the MAO-LDH layer, the strong bonding strength between the film layer and the magnesium alloy matrix and between the film layer and the film layer can be ensured during deposition and bonding, and the film layer collapse phenomenon caused by too large roughness can not occur to influence the molding of the magnesium alloy film layer.
In the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, in the step (2), the electrolyte consists of deionized water, sodium tripolyphosphate, sodium hydroxide and disodium ethylene diamine tetraacetate; the mass ratio of sodium tripolyphosphate, sodium hydroxide and disodium ethylene diamine tetraacetate in the electrolyte is 6-10: 1: 1; in the electrolyte, the concentration of sodium hydroxide is 1.5-2.5 g/L. The electrolyte has simple formula and low cost; the micro-arc oxidation coatings generated by different electrolyte systems have greatly different micro-morphologies, for example, if the electrolyte contains aluminate, the generated micro-arc oxidation coatings can show volcano-like morphology, and nodule particles and meteorite craters are distributed on the surface; if the electrolyte contains silicate, the generated micro-arc oxidation coating presents a highly porous stent surface formed by micropores and an oxide particle network; if phosphate is contained in the electrolyte, the formed micro-arc oxidation coating presents a sintering pit structure and has unevenly distributed micropores and microcracks connected to pores; therefore, the biological electrolyte used in patent No. 202110870154.6 contains phosphorus, silicon and aluminum, so that the three micro-morphologies appear on the surface of the micro-arc oxidation coating generated by the biological electrolyte, which results in different surface morphologies of the coating, and corrosion channels for corrosive ions to enter the magnesium alloy tissue are formed more easily, which is not beneficial to improving the corrosion resistance of the coating. The micro-arc oxidation coating generated by the electrolyte has the advantages of micro-pores and micro-cracks on the surface, single appearance form, and contribution to the adhesion of a subsequent LDH layer and the plugging of the LDH layer on the micro-pores and the micro-cracks.
In the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, in the step (2), a constant pressure mode is adopted during micro-arc oxidation: the voltage is 220-240V, the frequency is 200-400 Hz, the duty ratio is 25-35%, the temperature of the electrolyte is 15-30 ℃, and the micro-arc oxidation time is 12-18 min. The process parameters during micro-arc oxidation are related to the thickness and the roughness of the generated micro-arc oxidation film, and the thickness and the roughness of the micro-arc oxidation film directly influence the corrosion resistance of the composite film layer formed on the magnesium alloy substrate; research shows that under the micro-arc oxidation condition, a micro-arc oxidation film with the thickness of 5-10 mu m and the surface roughness of 2.2-3.2 mu m can be generated on the magnesium alloy substrate, and the composite film with good corrosion resistance can be generated by depositing an LDH layer.
In the above preparation method of the magnesium alloy with the superhydrophobic MAO-LDH composite membrane layer, in the step (3), the preparation method of the LDH reaction solution is as follows: adding cerium nitrate into deionized water, and fully dissolving, and adjusting the pH value to 10-12 by using 2mol/L sodium hydroxide solution; the pH of LDH reaction liquid also has influence on the performance of the MAO-LDH layer, if the pH of the LDH reaction liquid is lower than 10, the prepared LDH of the layered double hydroxides on the surface of the MAO-LDH layer has less quantity and is sparsely distributed, and micropores on the surface of most of the membrane layer can not be effectively covered and blocked; ce (NO) when the pH of the LDH reaction solution is higher than 123)3The solution will form too much colloid, Ce (NO)3)3The colloid does not provide free ions for the growth of the layered double hydroxide LDH, thus affecting the formation of the layered double hydroxide LDH. In the LDH reaction solution, the concentration of the cerium nitrate is 0.05 mol/L-0.15 mol/L. If the cerium nitrate concentration is less than 0.05mol/L, sufficient Ce cannot be supplied3+Ions, not only cause the formed layered double hydroxide LDH membrane layer to be thin, but also cause the layered double hydroxide LDH to be thinThe hexagonal petal-shaped layered structure is difficult to grow, and a long strip-shaped thin slice is generated; if the concentration of the cerium nitrate is higher than 0.15mol/L, the generated layered double hydroxide LDH is too thick, and the binding force is poor.
In the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, in the step (3), the temperature of the hydrothermal reaction is 120-140 ℃, and the time of the hydrothermal reaction is 10-12 hours. The temperature, the reaction time and the pH of the LDH reaction solution of the hydrothermal reaction jointly determine the morphology structure of the layered double hydroxide LDH: if the hydrothermal reaction temperature is lower than 120 ℃, layered double-metal hydroxide LDH is mostly concentrated at micropores on the micro-arc oxidation MAO layer, and the micro-arc oxidation MAO layer is sparsely distributed at other places, so that the layered double-metal hydroxide LDH layer is not uniformly distributed, but if the hydrothermal reaction temperature is higher than 140 ℃, the generated layered double-metal hydroxide LDH is easily large in thickness and not strong in binding force, for example, when the hydrothermal reaction temperature reaches 180 ℃, the generated single-layer LDH is 1 μm in thickness, is easy to fall off and crack, and is not beneficial to improving the corrosion resistance of the membrane layer. If the hydrothermal reaction time is too short, the layered double-metal hydroxide LDH is sparsely distributed, and micropores and microcracks on the micro-arc oxidation MAO layer cannot be effectively blocked; if the hydrothermal reaction time is too long, the structure and distribution of the layered double hydroxide LDH are changed and are distributed in a needle shape, so that micropores are exposed, and the infiltration of corrosive substances cannot be effectively prevented, so that the corrosion resistance of the layered double hydroxide LDH is greatly reduced. According to the invention, the concentration of cerium nitrate in LDH reaction liquid is controlled to be 0.05-0.15 mol/L, the pH value of the LDH reaction liquid is adjusted to 10-12, and the LDH is subjected to heat preservation for 10-12 h at the temperature of 120-140 ℃, so that the layered double-metal hydroxide LDH with a hexagonal petal-shaped dense growth layered structure in a comprehensive appearance is formed.
In the step (4), the preparation method of the superhydrophobic modified solution comprises the following steps: adding stearic acid SA into absolute ethyl alcohol, fully stirring until the stearic acid SA is completely dissolved, and dissolving by means of ultrasound, heating and the like; the super-hydrophobic modified solution preferably adopts absolute ethyl alcohol as a solvent, the contact angle of the prepared super-hydrophobic coating in the aqueous solution is 139 degrees, and the contact angle in the modified solution adopting the absolute ethyl alcohol as the solvent is more than 150 degrees, because when the stearic acid SA and the hydroxyl on the layered double hydroxide LDH react, water is used as the dehydration product of hydroxyl carboxyl, the more the water content is, the generation of ester groups can be more inhibited according to the chemical reaction equilibrium equation; if a mixed solution of absolute ethyl alcohol and water is selected as a solvent, the ethyl alcohol can directly react with stearic acid SA under certain conditions, but cannot sufficiently react with the layered double hydroxide LDH; in the super-hydrophobic modified solution, the concentration of stearic acid SA is 0.05-0.15 mol/L; the temperature of the water bath reaction is 60-70 ℃, and the time of the water bath reaction is 4-8 h. During super-hydrophobic modification, the temperature of the water bath is too low, so that fewer reaction products are generated, and the super-hydrophobic modification effect is not ideal; and too high water bath temperature can cause more solvent evaporation, while the solubility of stearic acid in ethanol is lower, and when the solvent evaporation is too much, the content of stearic acid in the solution is reduced, thereby affecting the effect of super-hydrophobic modification. In addition, the shorter the water bath reaction time is during the super-hydrophobic modification, the thinner the hydrophobic layer is generated, the longer the hydrophobic life is reduced, and the longer the reaction time is, the chemical reaction equilibrium equation may be biased to the hydroxyl carboxyl side, so that the generation amount of ester groups is reduced, and the super-hydrophobic effect is affected. The concentration of stearic acid also has influence on the water bath reaction during the super-hydrophobic modification, when the concentration of stearic acid is too low, the water bath reaction of the super-hydrophobic modification is incomplete, if the concentration of stearic acid is too high, the stearic acid cannot be completely dissolved firstly, and then the stearic acid and a solvent can directly undergo an esterification reaction. According to the invention, anhydrous ethanol is selected as a reaction solvent, and the reaction is carried out for 4-8 hours in 0.05-0.15 mol/L stearic acid ethanol solution in a water bath at the temperature of 60-70 ℃ to obtain the ideal magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer has the chemical structural formula of [ Mg)2+ 1-xCe3+ x(OH)2][NO3 -]x·mH2O, x is more than 0.17 and less than 0.33; the layered double metal hydroxide LDH layer is in a hexagonal petal-shaped layered structureAnd (5) structure.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared by the invention can be applied to the fields of aerospace, automobiles, medical instruments, 3C digital codes and the like.
The technical scheme of the invention achieves the following beneficial technical effects:
according to the invention, the micro-arc oxidation MAO layer is prepared on the surface of the magnesium alloy, the layered double-metal hydroxide LDH layer is deposited on the micro-arc oxidation MAO layer to cover and block micropores and microcracks on the micro-arc oxidation MAO layer, which are generated due to current breakdown, and the layered double-metal hydroxide LDH layer also has the function of capturing corrosive ions and can store certain corrosion inhibition substances, so that the purpose of improving the corrosion resistance of the magnesium alloy is achieved. In addition, the layered double hydroxide LDH is modified by the super-hydrophobic substance, so that the hydrophobicity of the layered double hydroxide LDH can be changed, the wetting angle of the surface of the layered double hydroxide LDH reaches 139.3-155.7 degrees, and the magnesium alloy has strong self-cleaning capability and is not easy to contact with corrosive liquid to increase the corrosion resistance.
The surface roughness of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared by the invention can reach 18.52-23.56 mu m, and the impedance value can reach 2.93 multiplied by 109～3.99×109Ω·cm2The corrosion current density is 3.8 multiplied by 10-9～8.0×10-9A·cm-2The magnesium alloy can reduce the corrosion rate of the magnesium alloy while realizing the super-hydrophobic effect, and can be used in the fields of aerospace, automobiles, medical instruments, 3C digital codes and the like. Compared with the magnesium alloy with the MAO-LDH composite membrane layer which is not subjected to super-hydrophobic treatment, the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, which is prepared by the invention, not only endows the composite coating with super-hydrophobicity, but also increases the roughness of the composite membrane layer, increases the binding force of the composite membrane layer and prolongs the corrosion resistance life of the AZ31 magnesium alloy under the condition that the thickness is not remarkably increased.
Drawings
FIG. 1 is a schematic diagram of the process of the present invention for preparing a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer;
FIG. 2a is a micro-surface topography of the MAO layer magnesium alloy substrate prepared in example 1 of the present invention;
FIG. 2b is a micro surface topography diagram of the MAO-LDH layer magnesium alloy matrix prepared in the example 1 of the present invention;
FIG. 3a is a real shot of a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer prepared in example 1 of the present invention;
FIG. 3b EDS energy spectrum (Electron Image) of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer prepared in inventive example 1;
FIG. 3c EDS energy spectrum (O Ka1) of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer prepared in example 1 of the present invention;
FIG. 3d EDS energy spectrum of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer prepared in example 1 of the present invention (Mg Ka1_ 2);
FIG. 3e EDS energy spectrum of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer prepared in example 1 of the present invention (Ce Ka1_ 2);
FIG. 4 is a graph showing polarization curves of a magnesium alloy substrate AZ31(Mg), a magnesium alloy substrate with an MAO layer (MAO), a magnesium alloy substrate with an MAO-LDH layer (MAO/LDH), and a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in example 1 of the present invention;
FIG. 5 is a schematic diagram of FT-IR analysis of the MAO layer-containing magnesium alloy Matrix (MAO), MAO-LDH layer-containing magnesium alloy matrix (MAO/LDH), and magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) prepared in example 1 of the present invention;
FIG. 6 Nyquist plots for the magnesium alloy substrate AZ31(Mg), the magnesium alloy substrate with MAO layer (MAO), the magnesium alloy substrate with MAO-LDH layer (MAO/LDH), and the magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in inventive example 1;
FIG. 7 Bode plots of a magnesium alloy substrate AZ31(AZ31Mg), a magnesium alloy substrate with MAO layer (MAO), a magnesium alloy substrate with MAO-LDH layer (MAO/LDH), and a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in example 1 of the present invention;
FIG. 8a is a water drop angle of the magnesium alloy substrate AZ31(Mg) in example 1 of the present invention;
FIG. 8b is a water drop angle of the magnesium alloy substrate (MAO) with MAO layer in example 1 of the present invention;
FIG. 8c water drop angle of MAO-LDH layer magnesium alloy matrix (MAO/LDH) in example 1 of the present invention;
FIG. 8d water drop angle of magnesium alloy with super hydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in example 1 of the present invention;
FIG. 9a is a water drop angle of a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer obtained by superhydrophobic modification using an aqueous solution of stearic acid in example 1 of the present invention;
FIG. 9b is the water drop angle of the magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer obtained by super-hydrophobic modification using stearic acid ethanol solution in example 2 of the present invention;
FIG. 10a is a graph comparing the thickness of a magnesium alloy matrix with a MAO layer (MAO), a magnesium alloy matrix with a MAO-LDH layer (LDH/MAO), and a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer (SA-LDH/MAO) in example 1 of the present invention;
FIG. 10b is a graph comparing the roughness of a magnesium alloy with a MAO layer magnesium alloy Matrix (MAO), a MAO-LDH layer magnesium alloy matrix (LDH/MAO), and a super-hydrophobic MAO-LDH composite membrane layer (SA-LDH/MAO) in example 1 of the present invention;
FIG. 10c is a graph comparing the binding force of the magnesium alloy substrate with MAO layer (MAO), the magnesium alloy substrate with MAO-LDH layer (LDH/MAO), and the magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer (SA-LDH/MAO) in example 1 of the present invention;
FIG. 10d is a graph comparing the abrasion loss of the magnesium alloy substrate with MAO layer (MAO), the magnesium alloy substrate with MAO-LDH layer (LDH/MAO), and the magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer (SA-LDH/MAO) in example 1 of the present invention.
Detailed Description
Example 1
In this embodiment, the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer includes the following steps:
step (1): carrying out water grinding, cleaning and drying treatment on the magnesium alloy matrix in sequence, and keeping the magnesium alloy matrix for later use after the treatment is finished; the specific operation is as follows: processing the AZ31 magnesium alloy into a sample of 30mm multiplied by 20mm multiplied by 4mm by a wire cutting machine, grinding the surface of the sample by using 240#, 600#, 1000# and 1500# sandpaper in sequence, ultrasonically cleaning the AZ31 magnesium alloy sample by using alcohol and deionized water, and drying for later use.
Step (2): placing the AZ31 magnesium alloy sample treated in the step (1) into electrolyte, and performing micro-arc oxidation by using the AZ3 magnesium alloy sample as an anode and a stainless steel tank as a cathode to form a micro-arc oxidation film MAO layer on the surface of the AZ31 magnesium alloy sample to obtain a magnesium alloy substrate with the MAO layer; the electrolyte consists of deionized water, sodium tripolyphosphate, sodium hydroxide and disodium ethylene diamine tetraacetate; in the electrolyte, the concentration of sodium tripolyphosphate is 16g/L, the concentration of sodium hydroxide is 2g/L, and the concentration of disodium ethylene diamine tetraacetate is 2 g/L; a constant-voltage mode is adopted during micro-arc oxidation: the voltage is 230V, the frequency is 300Hz, the duty ratio is 30%, the temperature of the electrolyte is 25 ℃, and the micro-arc oxidation time is 15 min; the surface roughness of the magnesium alloy substrate with the MAO layer obtained in the step is 2.89 mu m, and the scratch adhesion is 5.79N; as can be seen from FIG. 2a, the surface of the micro-arc oxidation film MAO layer has relatively obvious micropores and microcracks, and if the surface is not further processed, an etching medium can easily penetrate into the magnesium alloy matrix through the micropores and the microcracks to cause corrosion.
And (3): placing the magnesium alloy matrix with the MAO layer in LDH reaction liquid for hydrothermal reaction, and depositing the generated layered double-metal hydroxide LDH on the micro-arc oxidation membrane MAO layer to form a layered double-metal hydroxide LDH layer to obtain the MAO-LDH layer magnesium alloy matrix; the preparation method of the LDH reaction solution comprises the following steps: adding 0.01mol of cerium nitrate into 100mL of deionized water for full dissolution, and adjusting the pH value to 11 by using 2mol/L sodium hydroxide solution; in the step, the temperature of the hydrothermal reaction is 130 ℃, and the time of the hydrothermal reaction is 11 hours; the surface roughness of the MAO-LDH layer magnesium alloy matrix prepared in the step is 9.57 mu m, and the scratch adhesion is 11.81N; as can be seen from fig. 2b, the micropores and microcracks on the micro-arc oxidation film MAO layer are effectively covered and blocked due to the deposition of the layered double metal hydroxide LDH, which is beneficial to blocking the contact between the corrosive medium and the magnesium alloy matrix, thereby improving the corrosion resistance of the magnesium alloy; as can be seen from fig. 3a to fig. 3e, the surface of the MAO-LDH layer magnesium alloy substrate has a significant Ce element enrichment, indicating that the generated layered double-metal hydroxide LDH layer is a magnesium-cerium double-metal hydroxide layer.
And (4): will be describedPlacing the MAO-LDH layer magnesium alloy matrix in a container containing a super-hydrophobic modified solution, wherein the super-hydrophobic modified solution is 0.1mol/L stearic acid SA water solution, and then placing the container in a water bath condition of 65 ℃ for water bath reaction for 8 hours to modify a layered double-metal hydroxide LDH layer to generate a super-hydrophobic modified LDH-SA layer; and after the water bath reaction is finished, cleaning and naturally drying to obtain the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer. The thickness of the super-hydrophobic modified LDH-SA layer obtained after super-hydrophobic modification is basically unchanged compared with the thickness of the layered double hydroxide LDH prepared in the step (3). As can be seen from FIG. 4, the corrosion performance of the MAO-LDH layer magnesium alloy matrix is obviously better than that of the magnesium alloy matrix with the MAO layer, and is much better than that of the AZ31Mg alloy matrix; this is due to Cl when the layered double hydroxide LDH is corroded in NaCl solution-Will replace NO3 -And more stable LDH interlaminar substances are formed, so that the corrosion resistance is greatly enhanced. An absorption peak of-OH and an absorption peak of an ester group C ═ O can be clearly seen from the infrared spectrum of fig. 5, indicating that a hydrophobic ester group is formed on the surface of the magnesium alloy after the super-hydrophobic modification; as can be seen from FIG. 6, the MAO-LDH composite coating of the magnesium alloy matrix of the MAO-LDH layer has an obvious diffusion coefficient, while the micro-arc oxidized MAO layer does not exist, and compared with the MAO-LDH composite coating, the resistance radius of the magnesium alloy matrix of the MAO-LDH layer is larger, so that the corrosion resistance is stronger; as can be seen from FIG. 7, the MAO-LDH layer magnesium alloy matrix has significantly higher impedance than the MAO layer magnesium alloy matrix at low frequency, and the MAO layer magnesium alloy matrix phase angle plot shows that there is a passivation region, but the MAO-LDH layer magnesium alloy matrix phase angle is larger than the MAO layer magnesium alloy matrix after 86Hz with increasing frequency, which further confirms the corrosion resistance of the MAO-LDH layer magnesium alloy matrix. As can be seen from fig. 8, the water drop angle of the MAO-LDH layer magnesium alloy matrix is not significantly increased compared with the MAO layer magnesium alloy matrix, but the water drop angle of the super-hydrophobic MAO-LDH composite membrane layer magnesium alloy obtained after super-hydrophobic modification is significantly increased, and the contact angle exceeds 90 °, so that the corrosion resistance of the magnesium alloy is further enhanced.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared in the embodiment comprises a magnesium alloy matrix, a micro-arc oxidation membrane MAO layer and a super-hydrophobic MAO layerWater-modified LDH-SA layer composition; the micro-arc oxidation film MAO layer is positioned on the surface of the magnesium alloy substrate, and the super-hydrophobic modified LDH-SA layer is deposited on the micro-arc oxidation film MAO layer; the thickness of the micro-arc oxidation film MAO layer is 7.47 mu m, and the thickness of the super-hydrophobic modified LDH-SA layer is 19.52 mu m; the chemical structural formula of the layered double metal hydroxide LDH layer is [ Mg2+ 0.8Ce3+ 0.2(OH)2][NO3 -]0.2(ii) a The layered double hydroxide LDH layer is in a hexagonal petal-shaped layered structure.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared in the example has a uniform and compact appearance, the surface roughness of the super-hydrophobic MAO-LDH composite membrane layer on the surface of the magnesium alloy is 21.84 mu m, the surface wetting angle is 139.3 degrees, and the impedance value is 2.93 multiplied by 109Ω·cm2The corrosion current density is 5.58 multiplied by 10-9A·cm-2The scratch adhesion was 20.47N and the abrasion loss was 3.9 mg. Compared with the magnesium alloy matrix with the MAO-LDH layer before the super-hydrophobic modification, the surface roughness of the super-hydrophobic modified magnesium alloy matrix is remarkably increased, because the stearic acid SA as long-chain aromatic hydrocarbon has a complex structure after participating in the acid-base esterification reaction, so that the surface roughness of the super-hydrophobic MAO-LDH composite membrane layer is greatly increased. In the embodiment, as well as other embodiments and comparative examples, the abrasion loss of the product is measured by using the GB/T12444-2006 metal material abrasion test method.
Example 2
In this example, the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer is different from that of example 1 only in that: in the step (4), the super-hydrophobic modification solution is a 0.1mol/L stearic acid ethanol solution, namely: dissolving stearic acid in absolute ethyl alcohol by using the absolute ethyl alcohol as a solvent to prepare a 0.1mol/L stearic acid ethanol solution; the other steps and process parameters were the same as in the examples.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared in this example has the same structure as that of example 1, the thickness of the micro-arc oxidation membrane MAO layer is 7.76 mu m, the surface roughness of the magnesium alloy substrate with the MAO layer prepared in step (1) is 2.93 mu m, and the magnesium alloy substrate with the MAO layer is scratchedThe scratch adhesion was 5.73N; the thickness of the super-hydrophobic modified LDH-SA layer is 19.49 mu m, the surface roughness of the MAO-LDH layer magnesium alloy matrix prepared in the step (2) is 9.62 mu m, and the scratch adhesion is 11.85N; the thickness of the super-hydrophobic MAO-LDH composite membrane layer on the surface of the magnesium alloy is 27.25 mu m, the surface roughness is 22.03 mu m, the surface wetting angle is 155.7 degrees, and the impedance value is 3.99 multiplied by 109Ω·cm2The corrosion current density is 5.46 multiplied by 10-9A·cm-2The scratch adhesion was 21.69N, and the abrasion loss was 3.8 mg.
FIG. 1 is a flow chart of preparation of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer in example 1 and example 2: firstly, performing micro-arc oxidation treatment on the magnesium alloy to obtain a magnesium alloy matrix with an MAO layer, wherein the MAO layer on the surface of the magnesium alloy matrix has certain roughness and micropores, so that a substrate layer is provided for the growth of a subsequent LDH layer, and the bonding force between the layers of the magnesium alloy composite membrane layer and between the membrane layer and the matrix is improved; and then carrying out hydrothermal reaction in an LDH reaction solution to generate an LDH layer with a hexagonal petal-shaped structure, and finally carrying out modification treatment on the LDH layer through a super-hydrophobic modification solution to obtain the magnesium alloy with a super-hydrophobic MAO-LDH composite membrane layer with a larger wetting angle.
Comparing fig. 9a and fig. 9b, it can be found that the contact angles of the MAO-LDH composite membrane layers obtained in examples 1 and 2 after the superhydrophobic modification treatment exceed 90 °, and better superhydrophobic performance can be obtained by modifying with a stearic acid ethanol solution than with a stearic acid aqueous solution, which is beneficial to further enhancing the corrosion resistance of the magnesium alloy.
Comparative example 1
This comparative example prepared a magnesium alloy having a MAO-LDH composite membrane layer, which was prepared by a method different from that of example 1: the MAO-LDH layer magnesium alloy matrix prepared by the method of steps (1) to (3) in example 1 is a magnesium alloy with a MAO-LDH composite membrane layer, and the superhydrophobic modification of step (4) is not performed; in addition, in the step (3), the pH of the LDH reaction solution is adjusted to 10, the temperature of the hydrothermal reaction is 120 ℃, and the time of the hydrothermal reaction is 10 hours; the thickness of the micro-arc oxidation film MAO layer prepared by the comparative example is 7.3 mu m, the single-layer thickness of the layered double metal hydroxide LDH is 0.85 mu m, and the micro-arc oxidation film MAO layer is oxidized in the micro-arcThe height of the MAO layer was 6.2 μm, the surface roughness of the prepared magnesium alloy with the MAO-LDH composite membrane layer was 5.84 μm, the surface wetting angle was 15.36 DEG, and the resistance value was 2.69X 106Ω·cm2The corrosion current density is 1.51 multiplied by 10- 7A·cm2The scratch adhesion is 12.28N, so that the bonding force of the magnesium alloy substrate with the MAO layer (scratch adhesion of 5.58N) prepared in the step (2) is greatly improved; in addition, the abrasion amount of the magnesium alloy having the MAO-LDH composite membrane layer prepared in this comparative example was 4.2mg, while that of the magnesium alloy substrate having the MAO layer prepared in the step (2) was 5.3 mg.
Comparative example 2
In this comparative example, the preparation method of the magnesium alloy having the MAO-LDH composite membrane layer was different from that of comparative example 1 only in that: in the step (3), the pH of the LDH reaction solution is adjusted to 11; the temperature of the hydrothermal reaction is 130 ℃, and the time of the hydrothermal reaction is 11 h.
In this comparative example, the prepared MAO-LDH layer magnesium alloy substrate was a magnesium alloy having an MAO-LDH composite membrane layer, on which the MAO-LDH composite membrane layer had a thickness of 26.4 μm (the micro-arc oxidation membrane MAO layer had a thickness of 7.68 μm, the deposition height of the layered double hydroxide LDH on the micro-arc oxidation membrane MAO layer was 18.82 μm), a surface roughness of 10.48 μm, a surface wetting angle of 23.65 °, and a membrane layer resistance value of 8.73X 108Ω·cm2Corrosion current density of 5.66X 10-9A·cm-2The scratch adhesion is 14.03N, and the abrasion loss is 3.8 mg.
Comparative example 3
In this example, the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer is different from that of example 1 only in that: in the step (3), the pH of the LDH reaction solution is adjusted to 12; the temperature of the hydrothermal reaction is 140 ℃, and the time of the hydrothermal reaction is 12 h.
In this comparative example, the prepared MAO-LDH layer magnesium alloy matrix was a magnesium alloy with a MAO-LDH composite membrane layer, the thickness of the MAO-LDH composite membrane layer on the magnesium alloy was 32.18 μm (the thickness of the micro-arc oxidation membrane MAO layer was 8.77 μm, and the layered double metal hydroxide LDH was deposited on the micro-arc oxidation membrane MAO layerProduct height 23.41 μm), surface roughness 9.72 μm, surface wetting angle 6.72 °, and film resistance 1.92 × 106Ω·cm2Corrosion current density of 1.12X 10-5A·cm-2The scratch adhesion is 21.17N, and the abrasion loss is 7.4 mg.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications are possible which remain within the scope of the appended claims.
Claims (10)
1. The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer is characterized by consisting of a magnesium alloy matrix, a micro-arc oxidation membrane MAO layer and a super-hydrophobic modified LDH-SA layer; the micro-arc oxidation film MAO layer is positioned on the surface of the magnesium alloy substrate, and the super-hydrophobic modified LDH-SA layer is deposited on the micro-arc oxidation film MAO layer; the thickness of the micro-arc oxidation film MAO layer is 5-10 mu m, and the thickness of the super-hydrophobic modified LDH-SA layer is 5-20 mu m.
2. The magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer of claim 1, wherein the magnesium alloy substrate is AZ31 magnesium alloy; the super-hydrophobic modified LDH-SA layer is obtained by modifying a layered double hydroxide LDH layer with stearic acid SA; the chemical structural formula of the layered double metal hydroxide LDH layer is [ Mg2+ 1-x Ce3+ x(OH)2][NO3 -]x·mH2O, x is more than 0.17 and less than 0.33; the layered double metal hydroxide LDH layer is in a hexagonal petal-shaped layered structure.
3. A preparation method of a magnesium alloy with a super-hydrophobic MAO-LDH composite membrane layer is characterized by comprising the following steps:
step (1): carrying out water grinding, cleaning and drying treatment on the magnesium alloy matrix in sequence, and keeping the magnesium alloy matrix for later use after the treatment is finished;
step (2): placing the magnesium alloy substrate treated in the step (1) in an electrolyte, and performing micro-arc oxidation by using the magnesium alloy substrate as an anode and a stainless steel tank as a cathode to form a micro-arc oxidation film MAO layer on the surface of the magnesium alloy substrate to obtain the magnesium alloy substrate with the MAO layer, wherein the thickness of the micro-arc oxidation film MAO layer is 5-10 mu m;
and (3): placing the magnesium alloy matrix with the MAO layer in LDH reaction solution for hydrothermal reaction, so that the generated layered double hydroxide LDH is deposited on the micro-arc oxidation membrane MAO layer to form a layered double hydroxide LDH layer, and obtaining the magnesium alloy matrix with the MAO-LDH layer;
and (4): placing the MAO-LDH layer magnesium alloy matrix in a container containing a super-hydrophobic modified solution, and then placing the container in a water bath condition for a water bath reaction to modify a layered double-metal hydroxide LDH layer to generate a super-hydrophobic modified LDH-SA layer, wherein the thickness of the super-hydrophobic modified LDH-SA layer is 5-20 μm; and after the water bath reaction is finished, cleaning and naturally drying to obtain the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer.
4. The method for preparing a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer as claimed in claim 3, wherein, in the step (1), the magnesium alloy substrate is made of AZ31 magnesium alloy; during water grinding, sand paper of 240#, 600#, 1000# and 1500# is used for water grinding in sequence; after the water milling is finished, sequentially using alcohol and deionized water to carry out ultrasonic cleaning on the magnesium alloy matrix;
in the step (2), the surface roughness of the magnesium alloy substrate with the MAO layer is 2.2-3.2 μm; in the step (3), the surface roughness of the MAO-LDH layer magnesium alloy matrix is 8.8-11.2 μm.
5. The method for preparing a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer as claimed in claim 3, wherein in the step (2), the electrolyte is composed of deionized water, sodium tripolyphosphate, sodium hydroxide and disodium ethylenediamine tetraacetic acid; the mass ratio of the sodium tripolyphosphate to the sodium hydroxide to the disodium ethylene diamine tetraacetate in the electrolyte is 6-10: 1: 1; in the electrolyte, the concentration of sodium hydroxide is 1.5-2.5 g/L.
6. The method for preparing the magnesium alloy with the superhydrophobic MAO-LDH composite membrane layer as claimed in claim 3, wherein in the step (2), the constant pressure mode is adopted during the micro-arc oxidation: the voltage is 220-240V, the frequency is 200-400 Hz, the duty ratio is 25-35%, the temperature of the electrolyte is 15-30 ℃, and the micro-arc oxidation time is 12-18 min.
7. The method for preparing the magnesium alloy with the superhydrophobic MAO-LDH composite membrane layer in the step (3), wherein the LDH reaction solution is prepared by the following steps: adding cerium nitrate into deionized water, and fully dissolving, and adjusting the pH value to 10-12 by using 2mol/L sodium hydroxide solution; in the LDH reaction solution, the concentration of the cerium nitrate is 0.05 mol/L-0.15 mol/L.
8. The preparation method of the magnesium alloy with the superhydrophobic MAO-LDH composite membrane layer as claimed in claim 3, wherein in the step (3), the temperature of the hydrothermal reaction is 120-140 ℃ and the time of the hydrothermal reaction is 10-12 h.
9. The method for preparing the magnesium alloy with the superhydrophobic MAO-LDH composite membrane layer as claimed in claim 3, wherein in the step (4), the superhydrophobic modification solution is prepared by: adding stearic acid SA into absolute ethyl alcohol, and fully stirring until the stearic acid SA is completely dissolved; in the super-hydrophobic modified solution, the concentration of stearic acid SA is 0.05-0.15 mol/L; in the step (4), the temperature of the water bath reaction is 60-70 ℃, and the time of the water bath reaction is 4-8 h.
10. The preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer as claimed in any one of claims 3 to 9, wherein the chemical structure of the layered double metal hydroxide LDH layerIs of the formula [ Mg2+ 1-x Ce3+ x(OH)2][NO3 -]x·mH2O, x is more than 0.17 and less than 0.33; the layered double metal hydroxide LDH layer is in a hexagonal petal-shaped layered structure.
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