CN104087801A - Corrosion-resistant magnesium alloy and method for improving corrosion resistance of corrosion-resistant magnesium alloy - Google Patents

Abstract

The invention discloses a corrosion-resistant magnesium alloy which comprises the following components in percentage by mass: y: 0.8-2.8%, Sn: 0.2-1.6%, the total amount of inevitable impurities is less than or equal to 0.03%, wherein Fe is less than or equal to 0.002%, Cu is less than or equal to 0.002%, Si is less than or equal to 0.001%, and the balance is magnesium. The invention also discloses a method for improving the corrosion resistance of the magnesium alloy, which comprises the steps of heating the magnesium alloy material to 450-520 ℃, preserving heat and oxidizing for 6-8 h, and then cooling the oxidized magnesium alloy with water at 70-80 ℃. The magnesium alloy contains Y, Sn, the alloy material is heated to 450-520 ℃, is subjected to heat preservation and oxidation for 6-8 h, and is cooled by warm water, so that an oxide layer with excellent corrosion resistance can be obtained on the surface of the magnesium alloy.

Description

A kind of anti-corrosion magnesium alloy and the method for improving its anti-corrosion performance

technical field

The invention belongs to the technical field of magnesium alloys, relates to a magnesium alloy with excellent corrosion resistance, and also relates to a method for improving the corrosion resistance of the magnesium alloy.

Background technique

Magnesium alloys have excellent comprehensive properties and are widely used. However, due to the active chemical properties of magnesium alloys, their corrosion resistance is poor in humid environments, and the oxide film of ordinary magnesium alloys is generally loose and porous, which cannot provide effective protection.

In order to overcome the defects of poor corrosion resistance of magnesium alloys, anodic oxidation treatment, surface coating treatment and chemical conversion film treatment technology are usually used to coat a protective film on the surface of magnesium alloys to avoid oxidation of the magnesium alloy matrix: the anodic oxidation method can significantly Improving the corrosion resistance of magnesium alloys, and the obtained oxide film has a strong bonding ability with the magnesium alloy matrix, so it is widely used, but due to the large amount of electrolyte used in the treatment process, there is a potential threat to human health and the environment; surface coating treatment It can also improve the corrosion resistance of magnesium alloys, but the coating obtained by ordinary chemical conversion coating treatment technology has weak bonding ability with the body and is easy to fall off. However, the more mature chromate treatment technology, although the treated chromium-containing conversion coating has an anti-corrosion effect Better, but the chromate treatment process contains hexavalent chromium ions, which is highly toxic and its use is strictly limited.

Therefore, it becomes an urgent need to provide a magnesium alloy with excellent corrosion resistance and a method for improving the corrosion resistance of the magnesium alloy.

Contents of the invention

In view of this, the object of the present invention is to provide a corrosion-resistant magnesium alloy.

To achieve the above object, the present invention provides the following technical solutions:

The corrosion-resistant magnesium alloy is composed of the following components in terms of mass percentage: Y: 0.8-2.8%, Sn: 0.2-1.6%, and the rest are magnesium and unavoidable impurities.

As a preferred embodiment of the corrosion-resistant magnesium alloy of the present invention, the mass percentage of Y is 1.4-2.2%, and the mass percentage of Sn is 0.2-0.5%.

As a further preference of the corrosion-resistant magnesium alloy of the present invention, the total amount of inevitable impurities is ≤0.03%, wherein Fe≤0.002%, Cu≤0.002%, and Si≤0.001%.

The present invention also provides a method for improving the corrosion resistance of the magnesium alloy:

Firstly, the magnesium alloy material is heated to 450°C-520°C and oxidized for 6-8 hours, and then the oxidized magnesium alloy is cooled with 70-80°C water.

The anti-corrosion magnesium alloy of the present invention can adopt following method to make:

1), materials: take pure Mg, pure Sn and Mg-Y master alloy, wherein the mass percentage of Y in the Mg-Y master alloy is 25-30%;

2) Melting: under the protection of CO ₂ and SF ₆ atmosphere, first heat pure magnesium to 690-705°C, then add pure Sn and Mg-Y master alloy, fully stir and smelt to obtain magnesium alloy melt;

3), pouring: heat the magnesium alloy melt in step 2) at 715-730°C for 15-25 minutes, remove impurities, and cast into shape;

4), air cooling the ingot obtained in step 3).

The beneficial effects of the present invention are: the present invention adds Y and Sn with larger PBR value to the magnesium alloy, and the _Y2O3 and _SnO2 obtained during oxidation can significantly enhance the compactness of the oxide film, overcome the loose _and porous defects of the MgO film, Moreover, SnO ₂ , Y ₂ O ₃ and MgO have good compatibility, and the effect of enhancing the corrosion resistance of magnesium alloys is very obvious. In the present invention, the magnesium alloy material is further heated to 450°C-520°C and oxidized for 6-8 hours. Under this condition, the surface of the magnesium alloy can quickly form an oxide film with uniform thickness, high density and excellent corrosion resistance. The present invention strictly limits the content of impurities in the alloy, especially Cu, Fe, and Si, which can avoid the influence of impurities on the corrosion resistance of the alloy. Uniform, less macro and micro defects, further enhance the corrosion resistance of the alloy.

Description of drawings

In order to make the purpose, technical scheme and beneficial effect of the present invention clearer, the present invention provides the following drawings for illustration:

Fig. 1 is the corrosion hydrogen evolution curve of the sample obtained in Example 1-3 in 3.5wt% NaCl solution;

Fig. 2 is the polarization curve of the samples obtained in Examples 1-3.

Detailed ways

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

The following examples will disclose a new type of magnesium alloy, the chemical composition and ratio of which are as follows: Y: 0.8-2.8%, Sn: 0.2-1.6%, and the rest is magnesium and unavoidable impurities.

Further, the mass percentage of Y in the alloy is 1.4-2.2%, and the mass percentage of Sn is 0.2-0.5%.

Further, the total amount of unavoidable impurities in the alloy is ≤0.03%, wherein Fe≤0.002%, Cu≤0.002%, and Si≤0.001%.

The following examples will also disclose a method for improving the corrosion resistance of the magnesium alloy. First, the magnesium alloy material is heated to 450°C-520°C and oxidized for 6-8 hours, and then cooled with water at 70-80°C. magnesium alloy.

Example 1:

The method for preparing the novel anti-corrosion magnesium alloy in this embodiment includes:

1), drawing materials: take a certain amount of pure Mg, pure Sn and Mg-Y master alloy, wherein the mass percentage of Y in the Mg-Y master alloy is 30%;

2) Melting: under the protection of CO ₂ and SF ₆ atmosphere, the pure magnesium is first heated to 700°C, then pure Sn and Mg-Y master alloy are added, fully stirred and smelted to obtain a magnesium alloy melt;

3), pouring: heat the magnesium alloy melt in step 2) at 720° C. for 10 minutes, remove impurities, pour it into a steel mold with a diameter of 80 mm, and cast it to obtain an ingot;

4), air cooling the ingot obtained in step 3).

After testing, the chemical composition and ratio of the magnesium alloy obtained in this example are as follows: Y: 1.5%, Sn: 0.25%, total amount of impurities: 0.03%, of which Fe: 0.002%, Cu: 0.001%, Si: 0.001%, The rest is magnesium.

Example 2:

The method for preparing the novel anti-corrosion magnesium alloy in this embodiment includes:

1), drawing materials: take a certain amount of pure Mg, pure Sn and Mg-Y master alloy, wherein the mass percentage of Y in the Mg-Y master alloy is 30%;

2) Melting: under the protection of CO ₂ and SF ₆ atmosphere, the pure magnesium is first heated to 700°C, then pure Sn and Mg-Y master alloy are added, fully stirred and smelted to obtain a magnesium alloy melt;

3), pouring: heat the magnesium alloy melt in step 2) at 720° C. for 10 minutes, remove impurities, pour it into a steel mold with a diameter of 80 mm, and cast it to obtain an ingot;

4), the ingot obtained in air cooling step 3); (after testing, the chemical composition and proportion of the ingot are as follows: Y: 1.4%, Sn: 0.9%, total amount of impurities: 0.03%, wherein Fe: 0.001%, Cu: 0.00:1%, Si: 0.001%, the rest is magnesium)

5) The magnesium alloy material obtained in 4) is heated to 500° C. and oxidized for 6 hours to fully form an oxide film, and then cooled with 75° C. water.

Example 3:

The method for preparing the novel anti-corrosion magnesium alloy in this embodiment includes:

1), drawing materials: take a certain amount of pure Mg, pure Sn and Mg-Y master alloy, wherein the mass percentage of Y in the Mg-Y master alloy is 30%;

2) Melting: under the protection of CO ₂ and SF ₆ atmosphere, the pure magnesium is first heated to 700°C, then pure Sn and Mg-Y master alloy are added, fully stirred and smelted to obtain a magnesium alloy melt;

3), pouring: heat the magnesium alloy melt in step 2) at 720° C. for 10 minutes, remove impurities, pour it into a steel mold with a diameter of 80 mm, and cast it to obtain an ingot;

4), the ingot obtained in air cooling step 3); (after testing, the chemical composition and proportion of the ingot are as follows: Y: 1.6%, Sn: 0.7%, total amount of impurities: 0.02%, wherein Fe: 0.001%, Cu: 0.001%, Si: 0.001%, the rest is magnesium)

5), heating the magnesium alloy material obtained in 4) to 500 ° C for 6 hours, and then cooling it with 75 ° C water;

6) Remove the oxide film on the surface of the ingot.

Performance Testing:

1. Hydrogen evolution test:

The magnesium alloy product obtained in Examples 1-3 was subjected to a hydrogen evolution test in a 3.5% NaCl solution, and the results are shown in FIG. 1 .

It can be seen from Figure 1 that firstly, the corrosion resistance of the magnesium alloy removed from the surface oxide film after heat preservation treatment at 500°C for 6 hours is greater than that of the as-cast magnesium alloy, which is mainly because the heat preservation process eliminates the corrosion resistance of the as-cast magnesium alloy. The composition and structure segregation; secondly, the corrosion resistance of the coated magnesium alloy after 7h heat preservation treatment at 500°C is greatly improved compared with that of the film-free magnesium alloy, which shows that the oxide film obtained by the 7h heat preservation treatment at 500°C in the present invention has excellent corrosion resistance. (Conventional magnesium alloy oxide film has poor corrosion resistance), and the oxide film has played a very good role in protecting the substrate.

2. Potentiodynamic polarization curve test:

Get the magnesium alloy product obtained in Examples 1-3 and carry out the potentiodynamic polarization curve test (Shanghai Chenhua CHI660D electrochemical workstation) in 3.5% NaCl solution, and obtain Fig. 2 and table 1 by CHI660D software analysis of Shanghai Chenhua electrochemical workstation Column data; As can be seen from Figure 2 and Table 1, after the high temperature oxidation of Example 2, the corrosion current density of the magnesium alloy decreased by an order of magnitude, further illustrating that the oxide film has good corrosion resistance.

Table 1 Corrosion current densities of magnesium alloys obtained in various examples

Mg-Y-Sn Example 1 Example 3 Example 2 I _corr (μA/cm ² ) 55.18 33.25 4.81

Table 2 compares the method for improving the corrosion resistance of magnesium alloys of the present invention with other schemes for improving the corrosion resistance of magnesium alloys:

Table 2 Comparison of various methods to improve the corrosion resistance of magnesium alloys

Detailed description of cathodic electrolytic deposition related content in the table References: [1] M.-J.Wang, C.-F.Li, S.-K.Yen, Electrolytic MgO/ZrO2duplex-layer coating on AZ91D magnesium alloy for corrosion resistance , Corrosion Science, 76(2013) 142-153.

Anodic electrolytic deposition related content detailed description References: [2] T.Lei, C.Ouyang, W.Tang, L.-F.Li, L.-S.Zhou, Preparation of MgO coatings on magnesium alloys for corrosion protection, Surface and Coatings Technology, 204(2010) 3798-3803.

Detailed description of microarc oxidation related content References: [3] J.Liang, L.Hu, J.Hao, Characterization of microarc oxidation coatings formed on AM60B magnesium alloy in silicate and phosphate electrolytes, Applied Surface Science, 253(2007) 4490-4496 .

As can be drawn from Table 2, the method for improving the corrosion resistance of magnesium alloys by high temperature oxidation of the present invention is compared with other methods; The method has the advantages of simple operation and no environmental pollution, and has high promotion value.

It should be noted that the composition of the magnesium alloy of the present invention is not limited to the scope disclosed in the above examples, as long as the composition of the alloy satisfies Y: 0.8-2.8%, Sn: 0.2-1.6% (preferably the mass percentage of Y is 1.4-2.2%) , the mass percentage of Sn is 0.2-0.5%), the total amount of unavoidable impurities ≤ 0.03%, of which Fe ≤ 0.002%, Cu ≤ 0.003%, Si ≤ 0.002%, and the rest are magnesium. Corrosion effect; while in high temperature oxidation, as long as the magnesium alloy material is heated to 450 ° C ~ 520 ° C for 6 ~ 8 hours, and then cooled, an oxide layer with excellent performance can be obtained.

Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that it can be described in terms of form and Various changes may be made in the details without departing from the scope of the invention defined by the claims.

Claims (5)

1. a Corrosion-resistant magnesia alloy, is characterized in that, described magnesium alloy is composed of the following components by mass percentage: Y:0.8～2.8%, and Sn:0.2～1.6%, all the other are magnesium and inevitable impurity.

2. Corrosion-resistant magnesia alloy according to claim 1, is characterized in that: the quality percentage composition of described Y is 1.4-2.2%, the quality percentage composition of described Sn is 0.2-0.5%.

3. according to resistance to high temperature oxidation magnesium alloy described in claim 1 or 2, it is characterized in that: described inevitable total impurities≤0.03%, wherein Fe≤0.002%, Cu≤0.002%, Si≤0.001%.

4. the method that improves Magnesium Anti-Corrosion as described in claim 1-3 any one, is characterized in that: first described magnesium alloy materials is heated to 450 DEG C～520 DEG C insulation oxidation 6～8h, then with the magnesium alloy after the water cooling oxidation of 70～80 DEG C.

5. the method for preparation Corrosion-resistant magnesia alloy as described in claim 1-3 any one, is characterized in that, comprises the following steps:

1), draw materials: get pure Mg, pure Sn and Mg-Y master alloy, wherein in Mg-Y master alloy, the mass percent of Y is 25-30%;

2), melting: at CO ₂and SF ₆under atmosphere protection, first pure magnesium is heated to 690-705 DEG C, then adds pure Sn and Mg-Y master alloy, fully stir-melting obtains magnesium alloy liquation;

3), cast: by step 2) magnesium alloy liquation in 715-730 DEG C of insulation 15-25 minute, casting after removal of impurities;

4), air cooling step 3) gained ingot casting.