CN114703529B - 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 192
- 230000003075 superhydrophobic effect Effects 0.000 title claims abstract description 113
- 239000012528 membrane Substances 0.000 title claims abstract description 80
- 239000002131 composite material Substances 0.000 title claims abstract description 79
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- 238000007745 plasma electrolytic oxidation reaction Methods 0.000 claims abstract description 166
- 239000011159 matrix material Substances 0.000 claims abstract description 70
- 230000004048 modification Effects 0.000 claims abstract description 25
- 238000012986 modification Methods 0.000 claims abstract description 25
- 239000003792 electrolyte Substances 0.000 claims abstract description 21
- 239000012295 chemical reaction liquid Substances 0.000 claims abstract description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 48
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 claims description 44
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 33
- 239000000758 substrate Substances 0.000 claims description 25
- 238000006243 chemical reaction Methods 0.000 claims description 24
- 238000001027 hydrothermal synthesis Methods 0.000 claims description 22
- 235000021355 Stearic acid Nutrition 0.000 claims description 21
- QIQXTHQIDYTFRH-UHFFFAOYSA-N octadecanoic acid Chemical compound CCCCCCCCCCCCCCCCCC(O)=O QIQXTHQIDYTFRH-UHFFFAOYSA-N 0.000 claims description 21
- OQCDKBAXFALNLD-UHFFFAOYSA-N octadecanoic acid Natural products CCCCCCCC(C)CCCCCCCCC(O)=O OQCDKBAXFALNLD-UHFFFAOYSA-N 0.000 claims description 21
- 239000008117 stearic acid Substances 0.000 claims description 21
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 20
- 230000003746 surface roughness Effects 0.000 claims description 18
- 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
- 244000137852 Petrea volubilis Species 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 11
- 239000011777 magnesium Substances 0.000 claims description 10
- 239000008367 deionised water Substances 0.000 claims description 9
- 229910021641 deionized water Inorganic materials 0.000 claims description 9
- 238000004140 cleaning Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 7
- 239000000126 substance Substances 0.000 claims description 7
- 239000003109 Disodium ethylene diamine tetraacetate Substances 0.000 claims description 6
- 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
- 235000019301 disodium ethylene diamine tetraacetate Nutrition 0.000 claims description 6
- 235000019441 ethanol Nutrition 0.000 claims description 6
- 235000019832 sodium triphosphate Nutrition 0.000 claims description 6
- 238000004090 dissolution Methods 0.000 claims description 5
- 238000000227 grinding Methods 0.000 claims description 5
- 238000003801 milling Methods 0.000 claims description 5
- 230000008569 process Effects 0.000 claims description 3
- 235000011121 sodium hydroxide Nutrition 0.000 claims description 3
- 239000010935 stainless steel Substances 0.000 claims description 3
- 229910001220 stainless steel Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 2
- 229910052751 metal Inorganic materials 0.000 claims description 2
- 239000002184 metal Substances 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- 150000001875 compounds Chemical class 0.000 claims 1
- 230000007797 corrosion Effects 0.000 abstract description 40
- 238000005260 corrosion Methods 0.000 abstract description 40
- 230000008021 deposition Effects 0.000 abstract description 5
- 239000010410 layer Substances 0.000 description 212
- 239000000243 solution Substances 0.000 description 28
- 239000011248 coating agent Substances 0.000 description 12
- 238000000576 coating method Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 238000005299 abrasion Methods 0.000 description 9
- 238000009736 wetting Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 7
- 239000002904 solvent Substances 0.000 description 7
- 230000001965 increasing effect Effects 0.000 description 6
- 238000000151 deposition Methods 0.000 description 5
- 238000009826 distribution Methods 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 230000035484 reaction time Effects 0.000 description 5
- 230000009286 beneficial effect Effects 0.000 description 4
- 238000000724 energy-dispersive X-ray spectrum Methods 0.000 description 4
- 125000004185 ester group Chemical group 0.000 description 4
- KYIDJMYDIPHNJS-UHFFFAOYSA-N ethanol;octadecanoic acid Chemical compound CCO.CCCCCCCCCCCCCCCCCC(O)=O KYIDJMYDIPHNJS-UHFFFAOYSA-N 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 230000015556 catabolic process Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000002356 single layer Substances 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
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000000084 colloidal system Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 238000005886 esterification reaction Methods 0.000 description 2
- 230000002209 hydrophobic effect Effects 0.000 description 2
- -1 hydroxyl carboxyl Chemical group 0.000 description 2
- 239000011229 interlayer Substances 0.000 description 2
- 229910000000 metal hydroxide Inorganic materials 0.000 description 2
- 150000004692 metal hydroxides Chemical class 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000005245 sintering 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
- 239000002253 acid Substances 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 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
- 238000013016 damping Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000010438 heat treatment Methods 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
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000007769 metal material Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000011259 mixed solution 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
- 238000012545 processing Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 150000003839 salts Chemical class 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
- 239000002344 surface layer Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
Classifications
-
- 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
-
- 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
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 matrix, 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 matrix is pretreated and then is placed in electrolyte for micro-arc oxidation, then is placed in LDH reaction liquid for LDH deposition, and finally is subjected to super-hydrophobic modification, so that the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer is obtained, the corrosion rate of the magnesium alloy is obviously reduced while the super-hydrophobic effect is realized, and the magnesium alloy can be used in the fields of aerospace, automobiles, medical instruments, 3C numbers 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 21 st century green engineering material with small density (1.8 g/cm) 3 Left and right), high elastic modulus, high strength, good shock absorption, good heat dissipation, larger impact load bearing capacity than aluminum alloy, good corrosion resistance to organic matters and alkalinity, good electric conduction, 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 very high chemical and electrochemical activities and very low standard electrode potentials, so corrosion problems have been the primary and central problem impeding the development of magnesium alloys. At present, a surface treatment method, micro-arc Oxidation (MAO), is developed on the traditional anodic Oxidation technology, and a ceramic film mainly comprising a matrix oxide is formed on the surface of metals such as magnesium and the like in situ through the instant high-temperature sintering action of a Micro-area, so that the corrosion resistance of 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 base material, so that the magnesium alloy has better corrosion resistance. However, the surface of the film prepared by the method is usually provided with tiny holes due to current breakdown, and a small amount of microcracks are formed on the surface of the film. Such micro holes or micro cracks provide a large number of corrosion channels for corrosion ions, thereby causing serious reduction of the corrosion resistance of the magnesium alloy film.
At present, patent number 202110870154.6 discloses a magnesium alloy surface MAO-LDH biological composite membrane layer, a preparation method and application thereof; according to the invention, the LDH layer is deposited on the surface of the MAO layer to cover and seal tiny holes and microcracks on the surface of the MAO layer, which are generated by current breakdown, so that the corrosion resistance of the MAO layer is improved; however, the deposition height of the LDH layer of the MAO-LDH biological composite membrane layer on the MAO layer is low, the surface wetting angle is only 80-85 DEG, and the corrosion current density is high, reaching 1.0x10 -6 ～1.2×10 -6 A·cm -2 Therefore, the magnesium alloy with the MAO-LDH biological composite membrane layer has poor corrosion resistance and cannot achieve ideal application effect when 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 the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer and the 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 overlarge, the bonding 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 matrix, 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 comprises an AZ31 magnesium alloy matrix; the super-hydrophobic modified LDH-SA layer is obtained by modifying a layered double hydroxide LDH layer by stearic acid SA; the chemical structural formula of the layered double hydroxide LDH layer is [ Mg ] 2+ 1-x Ce 3+ x (OH) 2 ][NO 3 - ] x ·mH 2 O,0.17 < x < 0.33; the layered double hydroxide LDH layer is in a hexagonal petal-shaped layered structure, consists of hexagonal lamellar units and is positioned on the micro-arc oxidation film MAO layer, so that the hexagonal petal-shaped layered structure is formed.
A preparation method of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer comprises the following steps:
step (1): sequentially carrying out water milling, cleaning and drying treatment on the magnesium alloy matrix, and reserving after the treatment is finished;
step (2): placing the magnesium alloy substrate treated in the step (1) into electrolyte, taking the magnesium alloy substrate as an anode and a stainless steel groove as a cathode, and performing micro-arc oxidation 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;
step (3): placing the magnesium alloy matrix with the MAO layer into an LDH reaction liquid for hydrothermal reaction, so that the generated layered double hydroxide LDH is deposited on the micro-arc oxidation film MAO layer to form a layered double hydroxide LDH layer, and obtaining the magnesium alloy matrix with the MAO-LDH layer;
step (4): placing the MAO-LDH layer magnesium alloy matrix into a container containing a super-hydrophobic modification solution, and then placing the container into a water bath condition for water bath reaction to enable the layered double hydroxide LDH layer to be modified 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; in the process of water grinding, 240# sand paper, 600# sand paper, 1000# sand paper and 1500# sand paper are sequentially used for water grinding; after finishing the water milling, sequentially using alcohol and deionized water to ultrasonically clean 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 mu m; in the step (3), the surface roughness of the MAO-LDH layer magnesium alloy matrix is 8.8-11.2 mu m. By controlling the surface roughness of the micro-arc oxidation film MAO layer and the MAO-LDH layer, the film layer and the magnesium alloy matrix and the film layer can be ensured to have stronger bonding strength under the film layer thickness when being deposited and combined, and the film layer collapse phenomenon caused by too large roughness can not occur, so that the forming of the magnesium alloy film layer is influenced.
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 ethylenediamine tetraacetate; the mass ratio of the sodium tripolyphosphate to the sodium hydroxide to the disodium ethylenediamine 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 coating generated by different electrolyte systems has very different micro-morphology, for example, if the electrolyte contains aluminum acid salt, the generated micro-arc oxidation coating can show volcanic morphology, and the surface is distributed with nodular particles and merle pits; if silicate is contained in the electrolyte, the generated micro-arc oxidation coating presents a highly porous stent surface formed by micropores and an oxide particle network; if the electrolyte contains phosphate, the formed micro-arc oxidation coating presents a sintering pit structure and has unevenly distributed micropores and microcracks connected to the pores; therefore, the bioelectrolyte used in patent No. 202110870154.6 contains phosphorus, silicon and aluminum simultaneously, so that the three micro-morphologies appear on the surface of the generated micro-arc oxidation coating, thereby leading to different surface morphologies of the coating, being easier to form a corrosion channel for corrosive ions to enter the magnesium alloy tissue, and being unfavorable for improving the corrosion resistance of the coating. The micro-arc oxidation coating generated by the electrolyte has the advantages of single surface morphology, micro-pores and micro-cracks, and is more favorable for the adhesion of a subsequent LDH layer and the plugging of the LDH layer to 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 time of micro-arc oxidation is 12-18 min. The technological parameters during micro-arc oxidation relate to the thickness and roughness of the generated micro-arc oxidation film, and the thickness and roughness of the micro-arc oxidation film directly influence the corrosion resistance of a composite film layer formed on a magnesium alloy substrate; it is found that under the micro-arc oxidation condition, a micro-arc oxidation film with the thickness of 5-10 μm and the surface roughness of 2.2-3.2 μm can be generated on the magnesium alloy substrate, which is more beneficial to depositing an LDH layer to generate a composite film layer with good corrosion resistance.
In the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, in the step (3), the preparation method of the LDH reaction liquid comprises the following steps: adding cerium nitrate into deionized water for full dissolution, and then adjusting the pH value to 10-12 by using a sodium hydroxide solution with the concentration of 2 mol/L; the pH of the LDH reaction solution also has an effect on the performance of the MAO-LDH layer, and if the pH of the LDH reaction solution is lower than 10, the surface layer of the MAO-LDH layer is preparedThe LDH of the shape double metal hydroxide is less in quantity and sparse in distribution, and micropores on the surface of most membrane layers cannot be effectively covered and plugged; if the pH of the LDH reaction solution is higher than 12, ce (NO 3 ) 3 The solution will form too much colloid, ce (NO 3 ) 3 The colloid does not provide free ions for the growth of the layered double hydroxide LDH and thus affects the formation of the layered double hydroxide LDH. In the LDH reaction solution, the concentration of 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 provided 3+ Ions not only lead to thinner layered double hydroxide LDH membrane layers, but also lead to the fact that the layered double hydroxide LDH is difficult to grow into a hexagonal petal-shaped layered structure, and form long strip-shaped thin sheets; if the concentration of cerium nitrate is higher than 0.15mol/L, the generated layered double hydroxide LDH is too thick, so that the binding force is deteriorated.
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 h. The temperature, reaction time and pH of the LDH reaction solution of the hydrothermal reaction jointly determine the morphology and structure of the layered double hydroxide LDH: if the hydrothermal reaction temperature is lower than 120 ℃, the layered double hydroxide LDH is mostly concentrated at the micropores on the micro-arc oxidation MAO layer, and the distribution of other places of the micro-arc oxidation MAO layer is sparse, so that the layered double hydroxide LDH layer is unevenly distributed, but if the hydrothermal reaction temperature is higher than 140 ℃, the thickness of the produced layered double hydroxide LDH is large, the binding force is not strong, for example, when the hydrothermal reaction temperature reaches 180 ℃, the thickness of the produced single layer LDH reaches 1 mu m, and the single layer LDH is easy to fall off and crack, so that the corrosion resistance of a film layer is not improved. Too short hydrothermal reaction time can lead the layered double hydroxide LDH to be distributed sparsely, and micropores and microcracks on the micro-arc oxidation MAO layer can not be effectively plugged; the layered double hydroxide LDH structure and distribution are changed due to overlong hydrothermal reaction time, and the layered double hydroxide LDH structure and distribution are in needle-shaped distribution, so that micropores are exposed, the infiltration of corrosive substances cannot be effectively blocked, and the corrosion resistance of the layered double hydroxide LDH is greatly reduced. The invention forms layered double hydroxide LDH with hexagonal petal-shaped dense growth layered structure by controlling the concentration of cerium nitrate in LDH reaction liquid to be 0.05-0.15 mol/L and regulating the pH value to be 10-12 and preserving heat for 10-12 hours at 120-140 ℃.
In the preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, in the step (4), the preparation method of the super-hydrophobic 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 adopting means such as ultrasonic and heating to assist dissolution during dissolution; the super-hydrophobic modified solution is preferably absolute ethyl alcohol as a solvent, the contact angle of the super-hydrophobic coating prepared in the aqueous solution is 139 DEG, and the contact angle of the super-hydrophobic coating exceeds 150 DEG in the modified solution taking absolute ethyl alcohol as the solvent, because water is taken as a hydroxyl carboxyl dehydration product when the stearic acid SA reacts with the hydroxyl on the layered double hydroxide LDH, and the generation of ester groups is increasingly inhibited according to a chemical reaction equilibrium equation when the water content is higher; if a mixed solution of absolute ethanol and water is selected as a solvent, ethanol can directly react with stearic acid SA under certain conditions, but is difficult to fully react with 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. In the super-hydrophobic modification, the water bath temperature is too low, so that reaction products are fewer, and the effect of the super-hydrophobic modification is not ideal; the water bath temperature is too high, so that the solvent is likely to evaporate much, the solubility of the stearic acid in the ethanol is lower, and the stearic acid content in the solution is reduced when the solvent evaporates too much, so that the effect of superhydrophobic modification is affected. In addition, the shorter the water bath reaction time is during the superhydrophobic modification, the thinner the generated hydrophobic layer is, the longer the reaction time is, the chemical reaction equilibrium equation may deviate to the hydroxyl carboxyl side, so that the ester group generation amount is reduced, and the superhydrophobic effect is affected. The concentration of stearic acid has influence on the water bath reaction during the superhydrophobic modification, and when the concentration of stearic acid is too low, the water bath reaction during the superhydrophobic modification is incomplete, if the concentration of stearic acid is too high, the stearic acid cannot be completely dissolved at first, and then esterification reaction with a solvent can be directly carried out. According to the invention, absolute ethyl alcohol is selected as a reaction solvent, and the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer can be obtained through reaction for 4-8 hours in 0.05-0.15 mol/L stearic acid ethanol solution at the temperature of 60-70 ℃ under the water bath condition.
The preparation method of the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer comprises the steps that the chemical structural formula of the layered double hydroxide LDH layer is [ Mg ] 2+ 1-x Ce 3+ x (OH) 2 ][NO 3 - ] x ·mH 2 O,0.17 < x < 0.33; the layered double hydroxide LDH layer has a hexagonal petal-shaped layered structure.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared by the method can be applied to the fields of aerospace, automobiles, medical appliances, 3C numbers and the like.
The technical scheme of the invention has the following beneficial technical effects:
according to the invention, the micro-arc oxidation MAO layer is prepared on the surface of the magnesium alloy, and the layered double hydroxide LDH layer is deposited on the micro-arc oxidation MAO layer to cover and block micropores and microcracks generated by current breakdown on the micro-arc oxidation MAO layer, and the layered double hydroxide LDH layer also has the effect of capturing corrosion ions, and meanwhile, can store certain corrosion inhibition substances, so that the purpose of improving the corrosion resistance of the magnesium alloy is achieved. In addition, the super-hydrophobic substance is adopted to modify the layered double hydroxide LDH, so that the hydrophobicity of the LDH can be changed, the surface wetting angle of the LDH can reach 139.3-155.7 degrees, and the magnesium alloy has stronger self-cleaning capability and is not easy to contact with corrosive liquid so as to increase corrosion resistance.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared by the invention has the surface roughness of 18.52-23.56 mu m and the impedance value of 2.93 multiplied by 10 9 ～3.99×10 9 Ω·cm 2 The corrosion current density was 3.8X10 -9 ～8.0×10 -9 A·cm -2 The corrosion rate of the magnesium alloy can be reduced while the super-hydrophobic effect is realized, and the magnesium alloy can be used in the fields of aerospace, automobiles, medical appliances, 3C numbers and the like. And has the following componentsCompared with the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer, the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer 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 resistant life of the AZ31 magnesium alloy under the condition that the thickness is not obviously increased.
Drawings
FIG. 1 is a schematic diagram of a process for preparing a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer according to the invention;
FIG. 2a is a microscopic surface topography of a magnesium alloy substrate with MAO layer prepared in example 1 of the present invention;
FIG. 2b is a microscopic surface topography of the MAO-LDH layer magnesium alloy matrix prepared in example 1 of the present invention;
FIG. 3a is a photograph of a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer prepared in example 1 of the invention;
FIG. 3b EDS spectrum (Electron Image) of magnesium alloy with superhydrophobic MAO-LDH composite membrane layer prepared in example 1 of the invention;
FIG. 3c EDS spectrum (O Ka 1) of magnesium alloy with superhydrophobic MAO-LDH composite membrane layer prepared in example 1 of the invention;
FIG. 3d EDS spectrum (MgKa1_2) of magnesium alloy with superhydrophobic MAO-LDH composite membrane layer prepared in example 1 of the invention;
FIG. 3e EDS spectrum (CeKa1_2) of magnesium alloy with superhydrophobic MAO-LDH composite membrane layer prepared in example 1 of the invention;
FIG. 4 is a graph showing polarization curves of magnesium alloy matrix AZ31 (Mg), magnesium alloy matrix with MAO layer (MAO), magnesium alloy matrix with MAO-LDH layer (MAO/LDH) and magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in example 1 of the present invention;
FIG. 5 is a schematic view of FT-IR analysis of magnesium alloy with MAO layer (MAO), MAO-LDH layer (MAO/LDH), magnesium alloy with superhydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) prepared in example 1 of the invention;
FIG. 6 is a Nyquist plot of magnesium alloy matrix AZ31 (Mg), magnesium alloy matrix with MAO layer (MAO), magnesium alloy matrix with MAO-LDH layer (MAO/LDH), and magnesium alloy with superhydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in example 1 of the invention;
FIG. 7 shows Bode diagrams of magnesium alloy matrix AZ31 (AZ 31 Mg), magnesium alloy matrix with MAO layer (MAO), magnesium alloy matrix with MAO-LDH layer (MAO/LDH) and magnesium alloy with superhydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in example 1 of the invention;
FIG. 8a shows the water drop angle of magnesium alloy matrix AZ31 (Mg) in example 1 of the present invention;
FIG. 8b is a drop angle of a 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 the drop angle of magnesium alloy with superhydrophobic MAO-LDH composite membrane layer (MAO/LDH-SA) in example 1 of the invention;
FIG. 9a shows the water drop angle of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer obtained by performing super-hydrophobic modification by using stearic acid aqueous solution in embodiment 1 of the invention;
FIG. 9b is a corner of a water drop of a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer obtained by superhydrophobic modification of example 2 of the invention with an ethanol solution of stearic acid;
FIG. 10a is a graph showing thickness comparisons of magnesium alloy with MAO layer (MAO), MAO-LDH layer (LDH/MAO), and super-hydrophobic MAO-LDH composite membrane layer (SA-LDH/MAO) in example 1 of the present invention;
FIG. 10b is a graph showing the roughness comparison of magnesium alloy matrix with MAO layer (MAO), MAO-LDH layer (LDH/MAO) and magnesium alloy with superhydrophobic MAO-LDH composite membrane layer (SA-LDH/MAO) in example 1 of the invention;
FIG. 10c is a graph showing the comparison of binding force between a magnesium alloy matrix with MAO layer (MAO), a magnesium alloy matrix with MAO-LDH layer (LDH/MAO) and a magnesium alloy with superhydrophobic MAO-LDH composite membrane layer (SA-LDH/MAO) in example 1 of the present invention;
FIG. 10d is a graph showing the abrasion loss of magnesium alloy matrix with MAO layer (MAO), magnesium alloy matrix with MAO-LDH layer (LDH/MAO) and 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 superhydrophobic MAO-LDH composite membrane layer includes the following steps:
step (1): sequentially carrying out water milling, cleaning and drying treatment on the magnesium alloy matrix, and reserving after the treatment is finished; the specific operation is as follows: processing the AZ31 magnesium alloy into a 30mm multiplied by 20mm multiplied by 4mm sample by adopting a wire cutting machine, sequentially carrying out water grinding on the sample surface by using 240# sand paper, 600# sand paper, 1000# sand paper and 1500# sand paper, carrying out ultrasonic cleaning on 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 taking the AZ3 magnesium alloy sample as an anode and a stainless steel groove as a cathode to form a micro-arc oxidation film MAO layer on the surface of the AZ31 magnesium alloy sample so as to obtain a magnesium alloy matrix with the MAO layer; the electrolyte consists of deionized water, sodium tripolyphosphate, sodium hydroxide and disodium ethylenediamine 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 ethylenediamine tetraacetate is 2g/L; the constant pressure 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 time of micro-arc oxidation is 15min; the surface roughness of the magnesium alloy substrate with the MAO layer obtained by 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 oxide film MAO layer has relatively obvious micropores and microcracks, and if not further treated, the corrosive medium easily penetrates to the magnesium alloy substrate through the micropores and microcracks to cause corrosion.
Step (3): placing the magnesium alloy matrix with the MAO layer into an LDH reaction liquid for hydrothermal reaction, so that the generated layered double hydroxide LDH is deposited on the micro-arc oxidation film MAO layer to form a layered double hydroxide LDH layer, and obtaining the magnesium alloy matrix with the MAO-LDH layer; the preparation method of the LDH reaction liquid comprises the following steps: adding 0.01mol of cerium nitrate into 100mL of deionized water for full dissolution, and then adjusting the pH to 11 by using 2mol/L of 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 magnesium alloy matrix with the MAO-LDH layer prepared by 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 hydroxide LDH, which is beneficial to blocking the contact between the corrosion medium and the magnesium alloy substrate, thereby improving the corrosion resistance of the magnesium alloy; as can be seen from fig. 3a to fig. 3e, the surface of the magnesium alloy substrate with the MAO-LDH layer has obvious Ce element enrichment, which indicates that the layered double hydroxide LDH layer is a magnesium-cerium double hydroxide layer.
Step (4): placing the MAO-LDH layer magnesium alloy matrix in a container with super-hydrophobic modification solution, wherein the super-hydrophobic modification solution is stearic acid SA water solution with the concentration of 0.1mol/L, and then placing the container in a water bath at the temperature of 65 ℃ for water bath reaction for 8 hours, so that the layered double metal hydroxide LDH layer is modified 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 superhydrophobic modified LDH-SA layer obtained after superhydrophobic modification is substantially unchanged from the thickness of the layered double hydroxide LDH prepared in step (3). As can be seen from fig. 4, the corrosion performance of the MAO-LDH layer magnesium alloy matrix is significantly 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 corrodes in NaCl solution - Can replace NO 3 - A more stable LDH interlayer is formed, thereby greatly enhancing corrosion resistance. From the infrared spectrum of fig. 5, the absorption peak of-OH and the absorption peak of ester group c=o can be clearly seen, which indicates that the surface of the magnesium alloy forms a hydrophobic ester group after the superhydrophobic modification; as can be seen from fig. 6, the MAO-LDH composite coating of the MAO-LDH layer magnesium alloy substrate has a significant diffusion coefficient, while the micro-arc oxidized MAO layer is absent, compared with the MAO-LDH layer magnesium alloy substrate, the resistance radius is larger, so the corrosion resistance is stronger; as can be seen from FIG. 7, in the low frequency state, the impedance of the MAO-LDH layer magnesium alloy matrix is significantly larger than that of the magnesium alloy matrix with the MAO layer, and the phase angle diagram of the magnesium alloy matrix with the MAO layer can obtain the existence of the magnesium alloy matrix with the MAO layerA passivation zone, but with increasing frequency after 86Hz the phase angle of the MAO-LDH layer magnesium alloy matrix was greater than that of the MAO-layer magnesium alloy matrix, further confirming the corrosion resistance of the MAO-LDH layer magnesium alloy matrix. As can be seen from fig. 8, the water drop angle of the magnesium alloy matrix with the MAO-LDH layer is not obviously increased compared with that of the magnesium alloy matrix with the MAO layer, but the water drop angle of the magnesium alloy with the superhydrophobic MAO-LDH composite film layer obtained after superhydrophobic modification is obviously increased, and the contact angle exceeds 90 degrees, 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 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 matrix, 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 hydroxide LDH layer is [ Mg ] 2+ 0.8 Ce 3+ 0.2 (OH) 2 ][NO 3 - ] 0.2 The method comprises the steps of carrying out a first treatment on the surface of the The layered double hydroxide LDH layer has a hexagonal petal-shaped layered structure.
The magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer prepared in the embodiment has 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 10 9 Ω·cm 2 Corrosion current density of 5.58×10 -9 A·cm -2 The scratch adhesion was 20.47N and the abrasion loss was 3.9mg. Compared with the magnesium alloy matrix of the MAO-LDH layer before the super-hydrophobic modification, the surface roughness of the magnesium alloy matrix is obviously increased after the super-hydrophobic modification, because the stearic acid SA is used as long-chain aromatic hydrocarbon and has a complex structure after participating in acid-base esterification reaction, so that the surface roughness of the super-hydrophobic MAO-LDH composite membrane layer is greatly increased. In this example, as well as in other examples and comparative examples, the abrasion loss of the article was measured by the GB/T12444-2006 abrasion test method for metallic materials.
Example 2
In this example, the preparation method of magnesium alloy with superhydrophobic MAO-LDH composite membrane layer is different from example 1 only in that: in the step (4), the super-hydrophobic modification solution is 0.1mol/L stearic acid ethanol solution, namely: dissolving stearic acid in absolute ethyl alcohol by using absolute ethyl alcohol as a solvent to prepare 0.1mol/L stearic acid ethanol solution; 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 the embodiment has the same structure as that in the embodiment 1, the thickness of the micro-arc oxidation membrane MAO layer is 7.76 mu m, the surface roughness of the magnesium alloy matrix with the MAO layer prepared in the step (1) is 2.93 mu m, and the scratch adhesion is 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 3.99X10 9 Ω·cm 2 Corrosion current density of 5.46×10 -9 A·cm -2 The scratch adhesion was 21.69N and the abrasion loss was 3.8mg.
Fig. 1 is a flow chart of the preparation of magnesium alloys with superhydrophobic MAO-LDH composite membrane layers of example 1 and example 2: firstly, carrying out micro-arc oxidation treatment on magnesium alloy to obtain a magnesium alloy substrate with a MAO layer, wherein the MAO layer on the surface of the magnesium alloy substrate has a certain roughness and micropores, a basal layer is provided for the growth of a subsequent LDH layer, and the interlayer of a magnesium alloy composite membrane layer and the binding force between the membrane layer and the substrate are improved; then carrying out hydrothermal reaction in LDH reaction liquid to generate an LDH layer with a hexagonal petal-shaped structure, and finally carrying out modification treatment by using a super-hydrophobic modification solution to obtain the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer and a larger wetting angle.
Comparing fig. 9a and fig. 9b, it can be found that, after the super-hydrophobic modification treatment of the MAO-LDH composite membrane layer in example 1 and example 2, the contact angle of the super-hydrophobic modified composite membrane layer exceeds 90 °, and the super-hydrophobic performance is better than that of the modified composite membrane layer obtained by modifying the composite membrane layer with stearic acid ethanol solution, which is beneficial to further enhancing the corrosion resistance of the magnesium alloy.
Comparative example 1
The comparative example prepared a magnesium alloy with a MAO-LDH composite membrane layer, the preparation method of which is different from example 1 in that: the magnesium alloy matrix with the MAO-LDH layer prepared by the method from the step (1) to the step (3) in the embodiment 1 is the magnesium alloy with the MAO-LDH composite membrane layer, and the super-hydrophobic modification in the 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 micro-arc oxide film MAO layer prepared in this comparative example had a thickness of 7.3. Mu.m, a layered double hydroxide LDH monolayer had a thickness of 0.85. Mu.m, a height of 6.2 μm deposited on the micro-arc oxide film MAO layer, a surface roughness of 5.84. Mu.m, a surface wetting angle of 15.36℃and a resistance value of 2.69X 10 6 Ω·cm 2 Corrosion current density of 1.51X10 - 7 A·cm 2 Compared with the magnesium alloy matrix with the MAO layer prepared in the step (2), the bonding force of the magnesium alloy matrix with the MAO layer (the bonding force of the scratch is 5.58N) is greatly improved, wherein the bonding force of the scratch is 12.28N; in addition, the abrasion loss of the magnesium alloy with MAO-LDH composite membrane layer prepared in this comparative example was 4.2mg, while the abrasion loss of the magnesium alloy matrix with MAO layer prepared in step (2) was 5.3mg.
Comparative example 2
In this comparative example, the preparation method of the magnesium alloy having the MAO-LDH composite membrane layer is different from comparative example 1 only in that: in step (3), the pH of the LDH reaction solution is adjusted to 11; the temperature of the hydrothermal reaction was 130℃and the time of the hydrothermal reaction was 11 hours.
In this comparative example, the MAO-LDH layer magnesium alloy substrate thus prepared was a magnesium alloy having a MAO-LDH composite film layer with a thickness of 26.4 μm (the thickness of the micro-arc oxidation film MAO layer was 7.68 μm, the height of deposition of the layered double hydroxide LDH on the micro-arc oxidation film MAO layer was 18.82 μm), a surface roughness of 10.48 μm, a surface wetting angle of 23.65℃and a resistance value of 8.73X10% for the film layer 8 Ω·cm 2 Corrosion current density of 5.66×10 -9 A·cm -2 Scratch adhesion was 14.03N, abrasion loss of 3.8mg.
Comparative example 3
In this example, the preparation method of magnesium alloy with superhydrophobic MAO-LDH composite membrane layer is different from example 1 only in that: in 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 hours.
In this comparative example, the MAO-LDH layer magnesium alloy substrate thus prepared was a magnesium alloy having a MAO-LDH composite film layer with a thickness of 32.18 μm (the thickness of the micro-arc oxidation film MAO layer was 8.77 μm, the height of deposition of the layered double hydroxide LDH on the micro-arc oxidation film MAO layer was 23.41 μm), a surface roughness of 9.72 μm, a surface wetting angle of 6.72℃and a resistance value of the film layer of 1.92X 10 6 Ω·cm 2 Corrosion current density of 1.12×10 -5 A·cm -2 The scratch adhesion was 21.17N and the abrasion loss was 7.4mg.
It is apparent that the above examples are given by way of illustration only and are not limiting of the embodiments. Other variations or modifications of the above teachings will be apparent to those of ordinary skill in the art. It is not necessary here nor is it exhaustive of all embodiments. While the obvious variations or modifications which are extended therefrom remain within the scope of the claims of this patent application.
Claims (3)
1. A preparation method of magnesium alloy with super-hydrophobic MAO-LDH composite membrane layer is characterized in that,
the magnesium alloy with the 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 matrix, 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 super-hydrophobic modified LDH-SA layer is obtained by modifying a layered double hydroxide LDH layer by stearic acid SA; the layered double metal oxyhydrogenThe chemical structural formula of the compound LDH layer is [ Mg ] 2+ 1-x Ce 3+ x (OH) 2 ] [NO 3 - ] x ·mH 2 O,0.17 < x < 0.33; the layered double hydroxide LDH layer is in a hexagonal petal-shaped layered structure;
the method comprises the following steps:
step (1): sequentially carrying out water milling, cleaning and drying treatment on the magnesium alloy matrix, and reserving after the treatment is finished;
step (2): placing the magnesium alloy substrate treated in the step (1) into electrolyte, taking the magnesium alloy substrate as an anode and a stainless steel groove as a cathode, and performing micro-arc oxidation 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;
in the step (2), the electrolyte consists of deionized water, sodium tripolyphosphate, sodium hydroxide and disodium ethylenediamine tetraacetate; the mass ratio of the sodium tripolyphosphate to the sodium hydroxide to the disodium ethylenediamine tetraacetate in the electrolyte is 6-10:1:1; in the electrolyte, the concentration of sodium hydroxide is 1.5-2.5 g/L;
step (3): placing the magnesium alloy matrix with the MAO layer into an LDH reaction liquid for hydrothermal reaction, so that the generated layered double hydroxide LDH is deposited on the micro-arc oxidation film MAO layer to form a layered double hydroxide LDH layer, and obtaining the magnesium alloy matrix with the MAO-LDH layer;
in the step (3), the preparation method of the LDH reaction liquid comprises the following steps: adding cerium nitrate into deionized water for full dissolution, and then adjusting the pH value to 10-12 by using a sodium hydroxide solution with the concentration of 2 mol/L; in the LDH reaction solution, the concentration of cerium nitrate is 0.05mol/L to 0.15mol/L;
in the step (3), the temperature of the hydrothermal reaction is 120-140 ℃, and the time of the hydrothermal reaction is 10-12 h;
step (4): placing the MAO-LDH layer magnesium alloy matrix into a container containing a super-hydrophobic modification solution, and then placing the container into a water bath condition for water bath reaction to enable the layered double hydroxide LDH layer to be modified 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; after the water bath reaction is finished, cleaning and naturally drying are carried out, and the magnesium alloy with the super-hydrophobic MAO-LDH composite membrane layer is prepared;
in the step (4), the preparation method of the superhydrophobic modified solution comprises the following steps: 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.
2. The method for producing a magnesium alloy with superhydrophobic MAO-LDH composite membrane layer according to claim 1, wherein in step (1), the magnesium alloy matrix is made of AZ31 magnesium alloy; in the process of water grinding, 240# sand paper, 600# sand paper, 1000# sand paper and 1500# sand paper are sequentially used for water grinding; after finishing the water milling, sequentially using alcohol and deionized water to ultrasonically clean 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 mu m; in the step (3), the surface roughness of the MAO-LDH layer magnesium alloy matrix is 8.8-11.2 mu m.
3. The method for preparing a magnesium alloy with a superhydrophobic MAO-LDH composite membrane layer according to claim 1, wherein in the step (2), a 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 time of micro-arc oxidation is 12-18 min.
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