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CN-122013181-A - Preparation method of gradient coating for enhancing corrosion resistance of magnesium-based alloy through carbon embedding

CN122013181ACN 122013181 ACN122013181 ACN 122013181ACN-122013181-A

Abstract

The invention belongs to the technical field of surface modification of metal materials, and discloses a preparation method of a gradient coating for enhancing corrosion resistance of a magnesium-based alloy by carbon embedding. The prepared gradient coating has the advantages of effectively relieving the difference of thermal expansion coefficients and internal stress of the coating and the substrate, avoiding cracking and falling, improving the bonding stability, effectively isolating corrosive media due to the excellent chemical stability and barrier property of the carbon-based coating, having better protection effect than the prior art, solving the core problem of poor corrosion resistance of the magnesium-based alloy, avoiding the influence of high temperature on the substrate performance and the suitability of heat storage phase change related application due to the adoption of 300 ℃ low-temperature treatment, avoiding heavy metal use and harmful substance emission in the whole process, along with easy obtainment of carbon sources, low cost and environmental protection and economy.

Inventors

  • ZHANG RUI
  • YANG XIAOJUN
  • LI HUI
  • ZHANG LINFENG

Assignees

  • 武汉工程大学
  • 武汉萨瓦尼实业有限公司

Dates

Publication Date
20260512
Application Date
20260303

Claims (10)

  1. 1. The preparation method of the gradient coating for enhancing the corrosion resistance of the magnesium-based alloy by carbon embedding is characterized by comprising the following specific steps: Firstly, pretreating a magnesium-based alloy matrix, and sequentially carrying out mechanical polishing, degreasing, pickling and drying treatment to obtain a clean and surface-activated magnesium-based alloy matrix; Preparing carbon-based precursor slurry with high, medium and low carbon contents respectively, wherein the mass fraction of a carbon source in the high-carbon-content precursor is 30% -50%, the mass fraction of the carbon source in the medium-carbon-content precursor is 15% -30%, and the mass fraction of the carbon source in the low-carbon-content precursor is 5% -15%; Step three, gradient embedding and laying, namely placing the magnesium-based alloy matrix treated in the step one into an embedding container, firstly laying low-carbon-content carbon-based precursor slurry with the thickness of 50 mu m on the surface of the matrix, and then sequentially laying medium-carbon-content and high-carbon-content carbon-based precursor slurry with the thickness of 50 mu m on each layer to form a gradient embedding system; step four, low-temperature embedding treatment, namely placing a container with a gradient embedding system in a heating furnace, raising the temperature to 300 ℃ at a temperature raising rate of 5 ℃ per minute under the protection of inert gas, and preserving heat for 2-4 hours to finish the carbon embedding process; step five, post-treatment, namely taking out the magnesium-based alloy matrix after the furnace temperature is reduced to room temperature, removing redundant precursor residues on the surface, and sequentially carrying out cleaning and drying treatment to obtain a magnesium-based alloy workpiece with a gradient carbon embedding coating on the surface; And step six, performance detection, namely performing corrosion resistance, binding force and microhardness detection on the prepared gradient coating, and ensuring that the performance of the coating meets the use requirements.
  2. 2. The method of claim 1, wherein the magnesium-based alloy matrix in the first step comprises one of AZ31, AZ91, WE43 series magnesium alloys.
  3. 3. The preparation method of the gradient coating for enhancing corrosion resistance of the magnesium-based alloy through carbon embedding is characterized by comprising the following steps of sequentially polishing by 400-mesh, 800-mesh and 1200-mesh sand paper in the first step until the surface roughness Ra of a substrate is less than or equal to 0.8 mu m, immersing the substrate in an alkaline degreasing agent at 60-80 ℃ for 10-20 min, wherein the alkaline degreasing agent consists of 50-80 g/L of sodium hydroxide, 30-50 g/L of sodium carbonate, 20-40 g/L of trisodium phosphate and 5-10 g/L of a surfactant, immersing the substrate in a dilute hydrochloric acid solution with mass fraction of 5% -10% for 3-5 min at room temperature in the pickling step, and preserving the substrate in an oven at 80-100 ℃ for 1-2 h in the drying step.
  4. 4. The preparation method of the gradient coating for enhancing corrosion resistance of the magnesium-based alloy by carbon embedding is characterized by further comprising a binder, a dispersing agent and a solvent, wherein the binder is one of phenolic resin and epoxy resin, the dispersing agent is one of polyethylene glycol and sodium dodecyl benzene sulfonate, the mass fraction is 1% -3%, the solvent is a mixed solution of ethanol and deionized water, and the volume ratio of the ethanol to the deionized water is 1:1-3:1.
  5. 5. The preparation method of the gradient coating for enhancing corrosion resistance of the magnesium-based alloy by carbon embedding of claim 1 is characterized in that in the second step, the carbon source is one or more selected from graphite powder, activated carbon, carbon nano tubes and graphene, and the particle size of the carbon source is 50-200 nm.
  6. 6. The method for preparing the gradient coating for enhancing corrosion resistance of the magnesium-based alloy by carbon embedding of claim 1, wherein the paving process in the third step adopts a spraying or blade coating mode to ensure that precursor slurry of each layer is uniformly covered, and no bubble and crack defects exist between layers.
  7. 7. The preparation method of the gradient coating for enhancing corrosion resistance of the magnesium-based alloy by carbon embedding is characterized by comprising the following steps of adopting argon or nitrogen as inert gas in the fourth step, enabling the gas flow to be 0.5-1.5L/min, and stirring the embedded precursor once every 30 minutes in the heat preservation process to ensure uniform distribution of carbon sources.
  8. 8. The preparation method of the gradient coating for enhancing corrosion resistance of the magnesium-based alloy through carbon embedding is characterized by comprising the following steps of cleaning in an ultrasonic mode, wherein a cleaning medium is ethanol, the cleaning time is 10-15 minutes, the drying treatment is carried out in a vacuum oven at 60-80 ℃ for 1-2 hours, and the vacuum degree is 0.05-0.1 MPa.
  9. 9. The method for preparing the gradient coating for enhancing corrosion resistance of the magnesium-based alloy by carbon embedding according to claim 1, wherein the total thickness of the gradient carbon embedding coating in the fifth step is 150 μm, and the interface between the coating and the magnesium-based alloy matrix is in a composite form of metallurgical bonding and mechanical bonding.
  10. 10. The preparation method of the gradient coating for enhancing corrosion resistance of the magnesium-based alloy through carbon embedding, which is disclosed in claim 1, is characterized in that in the sixth step, a neutral salt spray test is adopted for corrosion resistance detection, the test condition is 5% NaCl solution, the temperature is 35 ℃, the atomization pressure is 0.07-0.1 MPa, the test time is not less than 72 hours, the bonding force detection adopts a cross-hatch method, the cross-hatch distance is 1mm, the microhardness detection adopts a Vickers hardness tester, the load is 50g, and the holding time is 10 seconds.

Description

Preparation method of gradient coating for enhancing corrosion resistance of magnesium-based alloy through carbon embedding Technical Field The invention belongs to the technical field of metal material surface modification, and particularly relates to a preparation method of a gradient coating for enhancing corrosion resistance of a magnesium-based alloy by carbon embedding. Background Carbon embedding is an important composite modification process in the field of material science, and refers to a material preparation technology for forming a core-shell, embedded or supported composite structure by taking an active functional material as a core component through physical or chemical means, wrapping, embedding or supporting the active functional material on pores, layers or surfaces of a carbon-based carrier. Magnesium and magnesium alloy have wide application prospects in the fields of aerospace, automobile industry, biomedical treatment, electronic products and the like due to low density, high specific strength, good biocompatibility and degradability, however, the chemical property of magnesium is extremely active, the standard electrode potential is extremely low, the corrosion resistance is poor, the wide application of the magnesium and magnesium alloy is severely limited, in the prior art, the surface treatment technology for improving the corrosion resistance of the magnesium alloy mainly comprises micro-arc oxidation, chemical conversion films, electroplating/chemical plating, vapor deposition, laser surface treatment and the like, but the technologies have certain limitations that micro-arc oxidation coatings have more micropores and cracks, are easy to fail in a long-term corrosion environment, the mechanical strength of the chemical conversion films is low, the protection life is limited, the binding force between the plating layer and a magnesium matrix in the electroplating/chemical plating process is poor, the electroplating process can produce waste water containing heavy metals, the environment pollution is caused, the problems of high equipment cost, the process is complex, large-area treatment is difficult to realize and the like are urgently required to be developed, and the carbon-based modified surface-modified heat storage material suitable for the characteristics of the magnesium alloy, the carbon-based heat storage material is good in environment-friendly and the relevant phase change-enhanced application technology needs. Disclosure of Invention The invention aims to provide a preparation method of a gradient coating for enhancing corrosion resistance of a magnesium-based alloy by carbon embedding, so as to solve the problem of poor corrosion resistance of the magnesium-based alloy and enable the magnesium-based alloy to be better suitable for application scenes of heat storage phase change materials. In order to achieve the aim, the invention provides the following technical scheme that the preparation method of the gradient coating for enhancing the corrosion resistance of the magnesium-based alloy by carbon embedding comprises the following specific steps: Firstly, pretreating a magnesium-based alloy matrix, and sequentially carrying out mechanical polishing, degreasing, pickling and drying treatment to obtain a clean and surface-activated magnesium-based alloy matrix; Preparing carbon-based precursor slurry with high, medium and low carbon contents respectively, wherein the mass fraction of a carbon source in the high-carbon-content precursor is 30% -50%, the mass fraction of the carbon source in the medium-carbon-content precursor is 15% -30%, and the mass fraction of the carbon source in the low-carbon-content precursor is 5% -15%; Step three, gradient embedding and laying, namely placing the magnesium-based alloy matrix treated in the step one into an embedding container, firstly laying low-carbon-content carbon-based precursor slurry with the thickness of 50 mu m on the surface of the matrix, and then sequentially laying medium-carbon-content and high-carbon-content carbon-based precursor slurry with the thickness of 50 mu m on each layer to form a gradient embedding system; step four, low-temperature embedding treatment, namely placing a container with a gradient embedding system in a heating furnace, raising the temperature to 300 ℃ at a temperature raising rate of 5 ℃ per minute under the protection of inert gas, and preserving heat for 2-4 hours to finish the carbon embedding process; step five, post-treatment, namely taking out the magnesium-based alloy matrix after the furnace temperature is reduced to room temperature, removing redundant precursor residues on the surface, and sequentially carrying out cleaning and drying treatment to obtain a magnesium-based alloy workpiece with a gradient carbon embedding coating on the surface; And step six, performance detection, namely performing corrosion resistance, binding force and microhardness detection on the prepared gra