Metal surface treatment agent

Abstract

The invention discloses a metal surface treatment agent, which belongs to the technical field of metal treatment agents, and is characterized in that the surface treatment agent comprises the following components: 80-100 parts of a nitric acid solution, 15-25 parts of organic acid, 10-30 parts of ethylenediamine phosphate, 20-35 parts of potassium fluoride, 10-20 parts of a corrosion inhibitor, and 8-15 parts of a surfactant. The effects that the oxidation film layer on the magnesium alloy surface can be effectively removed, and meanwhile corrosion of the surface treating agent to a magnesium alloy matrix is reduced are achieved.

Description

Technical Field

[0001] The invention relates to the technical field of metal treatment agents, in particular to a metal surface treatment agent. Background Art

[0002] Magnesium alloy is a metal material with the lowest density currently in use. It has the characteristics of high specific strength, good electrical and thermal conductivity, good machinability, and good biocompatibility. Therefore, it has good application prospects in the fields of automobiles, aerospace, and biomedicine. The development of lightweight in various fields has promoted the increase in demand for magnesium alloys. However, magnesium alloys have poor chemical stability and low electrode potential. They are prone to corrosion and lose their original functions when exposed to the atmosphere. At the same time, excessive humidity will also aggravate the corrosion of magnesium alloys. Therefore, when welding magnesium alloys, it is necessary to first treat the oxide film on the surface of the magnesium alloy to ensure the quality of welding.

[0003] At present, there are many methods for treating the oxide film on the surface of magnesium alloy, such as mechanical grinding, electrolytic cleaning, and chemical dissolution. Although mechanical grinding can effectively remove the oxide layer, it is also easy to damage the substrate itself and has low efficiency. Although electrolytic cleaning can remove the oxide layer more evenly, it is relatively complicated to operate and has high cost. Chemical dissolution is one of the most commonly used methods, but traditional chemical reagents have poor selectivity, which not only has poor effect in removing oxides, but also corrodes the metal matrix. Summary of the invention

[0004] In order to solve the problems in the prior art, the present invention provides a metal surface treatment agent with a simple operation method, which can not only effectively remove the oxide film layer on the surface of the magnesium alloy, but also reduce the corrosion of the surface treatment agent to the magnesium alloy substrate.

[0005] The present invention provides a metal surface treatment agent, which adopts the following technical solution: A metal surface treatment agent comprises the following components: 80-100 parts of nitric acid solution, 15-25 parts of organic acid, 10-30 parts of ethylenediamine phosphate, 20-35 parts of potassium fluoride, 10-20 parts of corrosion inhibitor, and 8-15 parts of surfactant.

[0006] By adopting the above technical scheme, the surface treatment agent of the present application adopts the combination of the above components, which can effectively remove the oxide film on the surface of the magnesium alloy substrate, and at the same time can also reduce the corrosion of the surface treatment agent to the magnesium alloy substrate. The reasons are as follows: after the surfactant wets the magnesium alloy, the combined use of potassium fluoride and ethylenediamine phosphate promotes the close contact between nitric acid and organic acid and the oxide film layer, and potassium fluoride and ethylenediamine phosphate can increase the penetration efficiency of nitric acid and organic acid in the oxide film, thereby improving the dissolution rate of the oxide film layer, effectively removing the oxide film layer on the surface of the magnesium alloy, and the fluoride ions in potassium fluoride can form a magnesium fluoride protective film on the surface of the magnesium alloy substrate. The combination of this film and the corrosion inhibitor reduces the corrosion of the surface treatment agent to the magnesium alloy substrate.

[0007] Preferably, the mass concentration of the nitric acid solution is 90-100 mL / L.

[0008] By adopting the above technical solution, the selection of nitric acid can effectively remove the oxide film layer on the surface of the magnesium alloy, and the removal efficiency of the oxide film layer is relatively fast, and the pitting effect on the magnesium alloy substrate is weak, so that the surface brightness of the treated magnesium alloy substrate is high. When the concentration of nitric acid is reduced, the surface roughness of the magnesium alloy will increase to a certain extent after the oxide film layer is removed. This is because the lower nitric acid concentration will reduce the film removal rate and extend the film removal time. The long-term immersion makes the surface treatment machine selectively contact the magnesium alloy substrate through pore reaction, making the oxide film layer unevenly removed, causing the magnesium alloy substrate to be severely corroded, and the degree of local corrosion and pitting will be aggravated, significantly reducing the film removal effect; when the nitric acid concentration is too high, the high concentration of nitric acid in the surface treatment agent will accelerate the dissolution rate of fluoride ions on the surface of the magnesium alloy substrate to form a magnesium fluoride protective film, and at the same time destroy the corrosion inhibition effect of the corrosion inhibitor, so that the dissolution rate of the magnesium alloy is accelerated. Preferably, the organic acid is one or both of citric acid and phytic acid.

[0009] Preferably, the weight ratio of citric acid to phytic acid is 1:(1.5-2.5).

[0010] By adopting the above technical solution, when the organic acid is selected as citric acid or phytic acid, it coordinates with the metal to form a dense oxide film on the surface of the magnesium alloy matrix, which can further reduce the corrosion effect of nitric acid solution on the magnesium alloy matrix.

[0011] Preferably, the corrosion inhibitor is a mixture of one or both of disodium hydrogen phosphate and sodium tetraborate and calcium petroleum sulfonate.

[0012] Preferably, the weight ratio of disodium hydrogen phosphate / sodium tetraborate to calcium petroleum sulfonate is 1:(1.2-1.6).

[0013] Preferably, the weight ratio of disodium hydrogen phosphate to sodium tetraborate is 1:1.

[0014] Preferably, the surfactant is a mixture of sodium lauryl sulfate and polyethylene glycol in a weight ratio of 1:(1-1.5).

[0015] By adopting the above technical scheme, after the surfactant is composed of sodium dodecyl sulfate and polyethylene glycol, its wetting effect on the oxide film on the surface of the magnesium alloy can make the nitric acid of the surfactant contact with the oxide film and dissolve it, and after the surface of the oxide film is dissolved, the two surfactants can quickly penetrate through the tiny pores in the oxide film under the action of potassium fluoride and ethylenediamine phosphate to achieve wetting of the inside of the oxide film, effectively improving the uniform reaction of nitric acid and the oxide film, so as to quickly remove the oxide film layer on the surface of the magnesium alloy.

[0016] Preferably, the surface treatment agent further comprises 1-4 parts of polydimethylsiloxane.

[0017] By adopting the above technical solution, polydimethylsiloxane as a defoaming agent can effectively improve the contact between the surface treatment agent and the magnesium alloy magnesium oxide layer, improve the contact between the surface treatment agent and the oxide film layer, and improve the removal rate of the oxide film.

[0018] In summary, the present invention has the following beneficial effects: after the surface treatment agent of the present application adopts the combination of the above components, the oxide film on the surface of the magnesium alloy substrate can be effectively removed, and the corrosion of the surface treatment agent to the magnesium alloy substrate can also be reduced. The reasons are as follows: after the surfactant wets the magnesium alloy, the potassium fluoride and ethylenediamine phosphate are used in combination to promote the close contact between nitric acid and organic acid and the oxide film layer, and potassium fluoride and ethylenediamine phosphate can increase the penetration efficiency of nitric acid and organic acid in the oxide film, thereby improving the dissolution rate of the oxide film layer, effectively removing the oxide film layer on the surface of the magnesium alloy, and the fluoride ions in potassium fluoride can form a magnesium fluoride protective film on the surface of the magnesium alloy substrate. The film is combined with the corrosion inhibitor to reduce the corrosion of the surface treatment agent on the magnesium alloy substrate. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below with reference to the embodiments.

[0020] The raw materials used in the examples and comparative examples of the present application are all commercially available.

[0021] A metal surface treatment agent comprises the following components: 80-100 parts of nitric acid solution, 15-25 parts of organic acid, 10-30 parts of ethylenediamine phosphate, 20-35 parts of potassium fluoride, 10-20 parts of corrosion inhibitor, and 8-15 parts of surfactant.

[0022] Preferably, the mass concentration of the nitric acid solution is 90-100 mL / L.

[0023] Preferably, the organic acid is one or both of citric acid and phytic acid.

[0024] Preferably, the weight ratio of citric acid to phytic acid is 1:(1.5-2.5).

[0025] Preferably, the weight ratio of disodium hydrogen phosphate / sodium tetraborate to calcium petroleum sulfonate is 1:(1.2-1.6).

[0026] Preferably, the weight ratio of disodium hydrogen phosphate to sodium tetraborate is 1:1.

[0027] Preferably, the surfactant is a mixture of sodium lauryl sulfate and polyethylene glycol in a weight ratio of 1:(1-1.5).

[0028] Preferably, the surface treatment agent further comprises 1-4 parts of polydimethylsiloxane.

[0029] Example 1 A metal surface treatment agent, comprising the following components: 8 kg nitric acid solution, 1.5 kg organic acid, 1 kg ethylenediamine phosphate, 2 kg potassium fluoride, 1 kg corrosion inhibitor, and 0.8 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is citric acid; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of disodium hydrogen phosphate is 0.45kg and the addition amount of calcium petroleum sulfonate is 0.55kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.4 kg and the added amount of polyethylene glycol is 0.4 kg.

[0030] Example 2 A metal surface treatment agent, comprising the following components: 9 kg nitric acid solution, 2 kg organic acid, 1 kg ethylenediamine phosphate, 2 kg potassium fluoride, 1 kg corrosion inhibitor, and 0.8 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is citric acid; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of disodium hydrogen phosphate is 0.45kg and the addition amount of calcium petroleum sulfonate is 0.55kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.4 kg and the added amount of polyethylene glycol is 0.4 kg.

[0031] Example 3 A metal surface treatment agent, comprising the following components: 10 kg nitric acid solution, 2.5 kg organic acid, 1 kg ethylenediamine phosphate, 2 kg potassium fluoride, 1 kg corrosion inhibitor, and 0.8 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is citric acid; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of disodium hydrogen phosphate is 0.45kg and the addition amount of calcium petroleum sulfonate is 0.55kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.4 kg and the added amount of polyethylene glycol is 0.4 kg.

[0032] Example 4 A metal surface treatment agent, comprising the following components: 9kg nitric acid solution, 2kg organic acid, 2kg ethylenediamine phosphate, 3kg potassium fluoride, 1kg corrosion inhibitor, and 0.8kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is citric acid; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of disodium hydrogen phosphate is 0.45kg and the addition amount of calcium petroleum sulfonate is 0.55kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.4 kg and the added amount of polyethylene glycol is 0.4 kg.

[0033] Example 5 A metal surface treatment agent, comprising the following components: 9 kg nitric acid solution, 2 kg organic acid, 3 kg ethylenediamine phosphate, 3.5 kg potassium fluoride, 1 kg corrosion inhibitor, and 0.8 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is citric acid; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of disodium hydrogen phosphate is 0.45kg and the addition amount of calcium petroleum sulfonate is 0.55kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.4 kg and the added amount of polyethylene glycol is 0.4 kg.

[0034] Example 6 A metal surface treatment agent, comprising the following components: 9 kg nitric acid solution, 2 kg organic acid, 2 kg ethylenediamine phosphate, 3 kg potassium fluoride, 1.5 kg corrosion inhibitor, and 1.2 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is phytic acid; The corrosion inhibitor is composed of sodium tetraborate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of sodium tetraborate is 0.68kg and the addition amount of calcium petroleum sulfonate is 0.82kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.6 kg and the added amount of polyethylene glycol is 0.6 kg.

[0035] Example 7 A metal surface treatment agent, comprising the following components: 9kg nitric acid solution, 2kg organic acid, 2kg ethylenediamine phosphate, 3kg potassium fluoride, 2kg corrosion inhibitor, and 1.5kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is phytic acid; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of disodium hydrogen phosphate is 0.91 kg and the addition amount of calcium petroleum sulfonate is 1.09 kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.75 kg and the added amount of polyethylene glycol is 0.75 kg.

[0036] Example 8 A metal surface treatment agent, comprising the following components: 9 kg nitric acid solution, 2 kg organic acid, 2 kg ethylenediamine phosphate, 3 kg potassium fluoride, 1.5 kg corrosion inhibitor, and 1.2 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is composed of citric acid and phytic acid in a weight ratio of 1:1.5, that is, the added amount of citric acid is 0.8 kg and the added amount of phytic acid is 1.2 kg; The corrosion inhibitor is composed of sodium tetraborate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of sodium tetraborate is 0.68kg and the addition amount of calcium petroleum sulfonate is 0.82kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.6 kg and the added amount of polyethylene glycol is 0.6 kg.

[0037] Example 9 A metal surface treatment agent, comprising the following components: 9 kg nitric acid solution, 2 kg organic acid, 2 kg ethylenediamine phosphate, 3 kg potassium fluoride, 1.5 kg corrosion inhibitor, and 1.2 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is composed of citric acid and phytic acid in a weight ratio of 1:2.5, that is, the added amount of citric acid is 0.57 kg and the added amount of phytic acid is 1.43 kg; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.2, that is, the addition amount of disodium hydrogen phosphate is 0.68kg and the addition amount of calcium petroleum sulfonate is 0.82kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.6 kg and the added amount of polyethylene glycol is 0.6 kg.

[0038] Example 10 A metal surface treatment agent, comprising the following components: 9 kg nitric acid solution, 2 kg organic acid, 2 kg ethylenediamine phosphate, 3 kg potassium fluoride, 1.5 kg corrosion inhibitor, and 1.2 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is composed of citric acid and phytic acid in a weight ratio of 1:1.5, that is, the added amount of citric acid is 0.8 kg and the added amount of phytic acid is 1.2 kg; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.6, that is, the addition amount of disodium hydrogen phosphate is 0.58kg and the addition amount of calcium petroleum sulfonate is 0.92kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1, that is, the added amount of sodium dodecyl sulfate is 0.6 kg and the added amount of polyethylene glycol is 0.6 kg.

[0039] Embodiment 11 A metal surface treatment agent, comprising the following components: 9 kg nitric acid solution, 2 kg organic acid, 2 kg ethylenediamine phosphate, 3 kg potassium fluoride, 1.5 kg corrosion inhibitor, and 1.2 kg surfactant; Wherein, the concentration of nitric acid solution is 90mL / L; The organic acid is composed of citric acid and phytic acid in a weight ratio of 1:1.5, that is, the added amount of citric acid is 0.8 kg and the added amount of phytic acid is 1.2 kg; The corrosion inhibitor is composed of disodium hydrogen phosphate and calcium petroleum sulfonate in a weight ratio of 1:1.6, that is, the addition amount of disodium hydrogen phosphate is 0.58kg and the addition amount of calcium petroleum sulfonate is 0.92kg; The surfactant is composed of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1:1.5, that is, the added amount of sodium dodecyl sulfate is 0.48 kg and the added amount of polyethylene glycol is 0.72 kg.

[0040] Example 12 A metal surface treatment agent, which is different from Example 10 in that the corrosion inhibitor consists of disodium hydrogen phosphate, sodium tetraborate and calcium petroleum sulfonate, wherein the added amount of disodium hydrogen phosphate is 0.29 kg, sodium tetraborate is 0.29 kg, and calcium petroleum sulfonate is 0.92 kg, and the rest are the same as Example 10.

[0041] Embodiment 13 A metal surface treatment agent, which is different from Example 12 in that the concentration of the nitric acid solution is 100 mL / L, and the rest is the same as Example 12.

[0042] Embodiment 14 A metal surface treatment agent, which is different from Example 12 in that the concentration of the nitric acid solution is 110 mL / L, and the rest is the same as Example 12.

[0043] Embodiment 15 A metal surface treatment agent, which is different from Example 12 in that the concentration of the nitric acid solution is 80 mL / L, and the rest is the same as Example 12.

[0044] Example 16 A metal surface treatment agent, which is different from Example 12 in that its raw material components also include 0.1 kg of polydimethylsiloxane, and the rest are the same as Example 12.

[0045] Embodiment 17 A metal surface treatment agent, which is different from Example 12 in that its raw material components also include 0.4 kg of polydimethylsiloxane, and the rest are the same as Example 12.

[0046] Comparative Example 1 A metal surface treatment agent, which is different from Example 2 in that potassium fluoride is not included in the raw material components, and the rest are the same as Example 2.

[0047] Comparative Example 2 A metal surface treatment agent, which is different from Example 2 in that no ethylenediamine phosphate is included in the raw material components, and the rest are the same as Example 2.

[0048] Comparative Example 3 A metal surface treatment agent, which is different from Example 2 in that there is no organic acid in the raw material components, and the rest are the same as Example 2.

[0049] Performance Testing The components in the above-mentioned embodiments and comparative examples are mixed to form a surface treatment agent, which is sprayed on a magnesium alloy with an oxide film at room temperature. When the test time is 10 minutes, the film stripping rate (for the thickness of the oxide film layer) and the amount of oxide film removed are calculated. At the same time, a roughness tester is used to measure the roughness of the magnesium alloy substrate surface treated with the surface treatment agent. The test results are shown in Table 1.

[0050] Table 1 Surface treatment agent stripping performance test results project Stripping rate μm / h <![CDATA[Film stripping quality g / m 2 > Roughness μm Example 1 38.6 52.3 1.21 Example 2 43.3 57.3 1.35 Example 3 45.2 58.4 1.54 Example 4 45.9 59.2 1.29 Example 5 45.1 59.5 1.28 Example 6 47.2 62.8 1.06 Example 7 47.7 63.1 1.01 Example 8 48.1 63.6 0.86 Example 9 47.9 63.5 0.83 Example 10 48.2 63.5 0.45 Embodiment 11 48.6 63.8 0.56 Example 12 48.4 63.5 0.24 Embodiment 13 49.2 64.3 0.21 Embodiment 14 52.2 66.7 0.88 Embodiment 15 45.3 56.2 0.83 Example 16 49.2 63.9 0.19 Embodiment 17 49.4 64.2 0.21 Comparative Example 1 38.6 50.4 1.52 Comparative Example 2 37.9 49.3 1.49 Comparative Example 3 40.2 51.6 1.45 From the table above we can see that: In Examples 1-3 of the present application, when the contents of other components remain unchanged and only the contents of nitric acid and organic acid are changed, the stripping rate and stripping quality of the oxide film of the surface treatment agent of Examples 1-3 increase with the increase of the contents of nitric acid and organic acid, and the roughness of the surface of the magnesium alloy substrate also increases accordingly. It can be seen that the corrosion performance of the magnesium alloy substrate will also increase with the increase of the contents of nitric acid and organic acid, and the rate of increase of the stripping rate and stripping quality of Example 3 is slower than that of Example 2. Therefore, in order to reduce the corrosion effect of the surface treatment agent on the magnesium alloy substrate, when the contents of nitric acid and organic acid are limited to the scope of the present application, the removal effect of the oxide film on the surface of the magnesium alloy can be effectively removed.

[0051] Compared with Example 2, Example 4-5 shows that after further increasing the contents of potassium fluoride and ethylenediamine phosphate on the basis of Example 2, the surface treatment agent obtained in Example 4-5 has higher stripping rate and stripping quality for the oxide film than that in Example 2, while the roughness of the surface of the magnesium alloy substrate is lower than that in Example 2. It can be seen that after increasing the contents of potassium fluoride and ethylenediamine phosphate, the stripping effect of the surface treatment agent on the oxide film can be further improved, and the corrosion effect of the surface treatment agent on the magnesium alloy substrate can also be reduced.

[0052] Compared with Example 4, after further increasing the amount of corrosion inhibitor and surfactant added on the basis of Example 4, the surface treatment agent obtained in Example 6-7 has higher stripping rate and stripping quality for the oxide film than that in Example 4, while the roughness of the magnesium alloy substrate surface is lower than that in Example 4. It can be seen that the increase in the content of corrosion inhibitor and surfactant has a certain effect on the stripping of the oxide film by the surface treatment agent, and can also effectively inhibit the corrosion of the magnesium alloy substrate by the surface treatment agent.

[0053] Compared with Example 6, on the basis of Example 6, after the organic acid is a mixture of citric acid and phytic acid, the surface treatment agent obtained in Example 8-9 has a slight improvement on the stripping rate and quality of the oxide film, but can further reduce the corrosion effect of the surface treatment agent on the magnesium alloy substrate.

[0054] Compared with Example 8, when the ratio of the two components in the corrosion inhibitor and the surfactant is changed, the roughness of the magnesium alloy substrate treated with the surface treatment agent obtained in Examples 10-11 is significantly reduced compared with that in Example 8, which can effectively reduce the corrosion effect of the surface treatment agent on the magnesium alloy substrate.

[0055] Compared with Example 10, when the corrosion inhibitor is composed of disodium hydrogen phosphate, sodium tetraborate and calcium petroleum sulfonate, the roughness of the surface of the magnesium alloy substrate can be further reduced compared with Example 10. It can be seen that when the corrosion inhibitor is composed of disodium hydrogen phosphate, sodium tetraborate and calcium petroleum sulfonate, the corrosion effect of the surface treatment agent on the magnesium alloy substrate can be effectively reduced.

[0056] Compared with Example 12, when the concentration of the nitric acid solution in Examples 13-15 is 90-100 mL / L as specified in the present application, it can effectively ensure the removal effect of the surface treatment agent on the oxide film, and also reduce the corrosion effect of the surface treatment agent on the magnesium alloy substrate.

[0057] Compared with Example 12, when the defoaming agent dimethylsiloxane is added to the raw materials, the surface treatment agent obtained in Examples 16-17 can improve the removal efficiency of the oxide film and also reduce the corrosion effect of the surface treatment agent on the magnesium alloy substrate.

[0058] Compared with Example 2, when potassium fluoride or ethylenediamine phosphate or organic acid is lacking in the raw materials, the surface treatment agents obtained in Examples 1-3 have reduced removal efficiency of the oxide film, and the corrosion effect of the surface treatment agents on the magnesium alloy substrate is increased compared with Example 2. This further illustrates that the combined use of the components in the present application can effectively improve the removal efficiency of the oxide film by the surface treatment agent, and at the same time reduce the corrosion effect of the surface treatment agent on the magnesium alloy substrate.

[0059] The embodiments of this specific implementation method are all preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Therefore, any equivalent changes made based on the structure, shape, and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A metal surface treatment agent, characterized in that: The surface treatment agent comprises the following components: 80-100 parts of nitric acid solution, 15-25 parts of organic acid, 10-30 parts of ethylenediamine phosphate, 20-35 parts of potassium fluoride, 10-20 parts of corrosion inhibitor, and 8-15 parts of surfactant.

2. A metal surface treatment agent according to claim 1, characterized in that: The mass concentration of the nitric acid solution is 90-100 mL / L.

3. A metal surface treatment agent according to claim 1, characterized in that: The organic acid is one or both of citric acid and phytic acid.

4. A metal surface treatment agent according to claim 3, characterized in that: The weight ratio of the citric acid to the phytic acid is 1:(1.5-2.5).

5. A metal surface treatment agent according to claim 1, characterized in that: The corrosion inhibitor is a mixture of one or both of disodium hydrogen phosphate and sodium tetraborate and petroleum calcium sulfonate.

6. A metal surface treatment agent according to claim 5, characterized in that: The weight ratio of the disodium hydrogen phosphate / sodium tetraborate to the calcium petroleum sulfonate is 1:(1.2-1.6).

7. A metal surface treatment agent according to claim 5, characterized in that: The weight ratio of the disodium hydrogen phosphate to the sodium tetraborate is 1:

1.

8. A metal surface treatment agent according to claim 1, characterized in that: The surfactant is a mixture of sodium dodecyl sulfate and polyethylene glycol in a weight ratio of 1: (1-1.5).

9. A metal surface treatment agent according to claim 1, characterized in that: The surface treatment agent also includes 1-4 parts of polydimethylsiloxane.