Corrosion resistant film prepared by magnesium alloy surface hydrothermal method and preparation technology thereof

A technology of magnesium alloy and surface water, which is applied in the coating process of metal materials, etc., to achieve the effects of easy control of process parameters, rapid film formation and strong affinity

Active Publication Date: 2014-03-05
曾荣昌
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

As far as the current research is concerned, there is no single treatment method that has sufficient ability to prevent the corrosion of magnesium alloys under harsh environmental conditions.

Method used

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  • Corrosion resistant film prepared by magnesium alloy surface hydrothermal method and preparation technology thereof
  • Corrosion resistant film prepared by magnesium alloy surface hydrothermal method and preparation technology thereof
  • Corrosion resistant film prepared by magnesium alloy surface hydrothermal method and preparation technology thereof

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0060] Select the magnesium alloy material: AZ31 magnesium alloy bar, as cast, and then cut it into 25mm×25mm×5mm samples, which are successively polished, tap water cleaning, alkali cleaning, water washing, pickling, water cleaning, hot air drying, and preservation Steps for preprocessing;

[0061] The treatment solution selected in this embodiment is the NaOH of 40g / L, the LiCl of 240g / L, and the filling degree is 50%;

[0062] Put the cleaned magnesium alloy sample into a hydrothermal reaction kettle with a polytetrafluoroethylene liner, then inject the above-mentioned treatment liquid into the reaction kettle, seal the reaction kettle, and place the reaction kettle at a temperature of 120°C. In the drying oven, after keeping warm for 2h, 4h, and 6h, take out the reaction kettle, put it in cold water to cool, open the reaction kettle, take out the sample, wash it with distilled water and dry it, and measure its corrosion potential and corrosion current density respectively....

Embodiment 2

[0066] The difference from Example 1 is:

[0067] The treatment liquid is 40g / L NaOH, 120g / L LiCl, and the filling degree is 70%;

[0068] Put the cleaned magnesium alloy sample into a hydrothermal reaction kettle with a polytetrafluoroethylene inner liner, then inject the above-mentioned treatment liquid into the reaction kettle, seal the reaction kettle, and place the reaction kettle at a temperature of 120°C, In a drying oven at 140°C and 160°C, keep warm for 4 hours; take out the reaction kettle, put it in cold water to cool, open the reaction kettle, take out the sample, wash it with distilled water and dry it, and measure its corrosion potential and corrosion current density respectively. The results are shown in the table 2.

[0069] Table 2

[0070]

[0071] The XRD diagrams before and after corrosion of this embodiment are as follows figure 1 , indicating that the composition of the membrane contains Mg(OH) 2 , Al(OH) 3 and Zn(OH) 2 .

[0072] The SEM topogr...

Embodiment 3

[0074] The difference from Example 1 is:

[0075] The treatment liquid is 40g / L NaOH and 0g / L LiCl, 40g / L NaOH and 60g / L LiCl, 40g / L NaOH and 120g / L LiCl, and the filling degree is 70%;

[0076] Put the cleaned magnesium alloy sample into a hydrothermal reaction kettle with a polytetrafluoroethylene inner liner, then inject the above-mentioned treatment liquid into the reaction kettle, and seal the reaction kettle. Place the reaction kettle in a drying oven at 160°C and keep it warm for 4 hours; take out the reaction kettle, put it in cold water to cool, open the reaction kettle, take out the sample, wash it with distilled water and dry it, and measure its corrosion potential and corrosion current density respectively. as shown in Table 3.

[0077] table 3

[0078]

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Abstract

The invention discloses a corrosion resistant film prepared by a magnesium alloy surface hydrothermal method and a preparation technology thereof, belongs to the technical field of magnesium surface processing, and solves the problem of bad corrosion resistant property of magnesium alloy in the prior art. The technology provided by the invention comprises the following steps: placing a processed magnesium alloy sample into a hydrothermal reactor, then injecting a treating fluid into the reactor according to a certain filling degree, and putting the reactor into a thermotank to maintain the temperature. The treating liquid comprises sodium hydroxide and lithium salt, sodium hydroxide provides a proper alkaline environment for film forming, lithium salt has a large solubility in water, Li+ can hydrolyze in water with a great amount at a certain temperature, so the pH value of the solution is improved so as to promote the film forming reactions on the magnesium alloy surface to move in the positive direction, the obtained film in situ grows on the magnesium alloy surface; the force between the film and the substrate body is excellent, the film is uniform, compact and ultra-thin, and has an excellent corrosion resistant property; the corrosion current density of the conversion film is increased by five magnitude orders compared to that of the substrate body, and reaches 10<-9> A/cm<2> magnitude grade.

Description

technical field [0001] The invention belongs to the technical field of magnesium alloy surface treatment, and in particular relates to a process for preparing a corrosion-resistant film on the surface of a magnesium alloy by using a hydrothermal method. Background technique [0002] Magnesium alloy is the lightest metal structural material in practical application, with high specific strength, specific stiffness, specific elastic modulus, and good machinability, weldability, impact resistance, castability and dimensional stability And other advantages, has been widely used in aviation, aerospace, electronics, communications, automobile manufacturing and other fields. Due to the active chemical properties of magnesium, the standard electrode potential is very low (-2.37V, SHE), resulting in poor corrosion resistance. In corrosive media, especially those containing Cl - In the solution, severe corrosion is easy to occur. Therefore, it is necessary to improve the corrosion r...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C23C22/60
Inventor 曾荣昌杨永欣戚威臣曾美琪
Owner 曾荣昌
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