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Preparation method of magnesium alloy chromeless chemical conversion film and its used film forming solution

A technology of chemical conversion film and magnesium alloy, which is applied in the coating process of metal materials, etc., can solve problems such as poor adhesion, easy peeling off of the paint film, and serious pollution, and achieve low cost, strong paint film adhesion, and improved durability. erosive effect

Inactive Publication Date: 2004-02-18
INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, as a structural metal material, magnesium alloy is the metal with the highest chemical activity, and its corrosion resistance is poor. If it is directly painted without chemical conversion coating treatment, the paint film is easy to fall off and the adhesion is not ideal.
[0003] DOW Company of the United States prepared a chemical conversion coating on the surface of magnesium alloys. The formula mainly contains hexavalent chromium. Although the corrosion resistance and paint film adhesion performance are good, the pollution is particularly serious. This process is restricted and will be gradually banned.

Method used

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  • Preparation method of magnesium alloy chromeless chemical conversion film and its used film forming solution
  • Preparation method of magnesium alloy chromeless chemical conversion film and its used film forming solution

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0030] The composition of the magnesium alloy chromium-free chemical conversion coating solution consists of 20g / l manganese dihydrogen phosphate, 30g / l sodium phosphate and the balance of water;

[0031] The preparation method is as follows: the sample is a die-casting AZ91 D magnesium alloy;

[0032] 1. Mechanical pretreatment: Grinding with sandblasting or sandpaper to remove burrs, firm oxides, lubricants for extrusion, release agents, casting sand, cutting oil and other foreign matter, reduce surface roughness; wash with water;

[0033] 2. Degreasing: wash with a compound solution of 10g / l sodium hydroxide, 15g / l sodium phosphate, and 15g / l sodium carbonate to remove general dirt, lubricants, cutting agents, etc. 5 points; wash with water;

[0034] 3. Pickling: Wash with concentrated hydrofluoric acid and phosphoric acid in a 1:1 compound acid solution to remove scale, corrosion products, sintered lubricants, lubricants, and steel particles that were not removed during d...

Embodiment 2

[0040] The pretreatment method is the same as in Example 1.

[0041] The difference from Example 1 is:

[0042] The sample used is an extruded AZ31D magnesium alloy;

[0043] The degreasing temperature is controlled at 90°C, and the time is 10 minutes; the pickling temperature is 20°C, and the time is 5 minutes; the activation or finishing temperature is 60°C, and the time is 0.5 minutes;

[0044] Film formation: immerse the pretreated magnesium alloy sample in an aqueous solution whose main components are manganese salt, phosphate and fluoride (that is, 20g / l manganese nitrate, 50g / l sodium dihydrogen phosphate and 2g / l potassium fluoride, and the remaining The amount is water), the temperature is controlled at 60°C, the soaking time is 60 minutes, and the pH value of the solution is kept at 5, a dark gray phosphate chemical conversion coating can be obtained;

[0045] The post-treatment immersion time was 50 minutes.

[0046] The obtained magnesium alloy chemical conversi...

Embodiment 3

[0048] The pretreatment method is the same as in Example 1.

[0049] The difference from Example 1 is:

[0050] The sample used is extruded AM60 magnesium alloy;

[0051] The degreasing temperature is controlled at 40°C, and the time is 8 minutes; the pickling temperature is 60°C, and the time is 0.5 minutes; the activation or finishing temperature is 20°C, and the time is 10 minutes;

[0052] Film formation: immerse the pretreated magnesium alloy sample in an aqueous solution of manganese salt and phosphate (ie 30g / l manganese nitrate, 40g / l sodium dihydrogen phosphate, and the balance is water), and control the temperature at 85°C. The immersion time is 40 minutes, and the pH value of the solution is kept at 2.0 to obtain a silver-gray phosphate chemical conversion coating;

[0053] Post-treatment: Immerse in an aqueous solution containing 15g / l cerium nitrate at a temperature of 40°C for 30 minutes to form a golden yellow surface film on the surface of the phosphate chemi...

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Abstract

A chemically transferred non-chromium Mg-alloy film is prepared through grinding said Mg-alloy, removing impurities, washing with alkali solution for defatting, washing with acidic solution for removing surfacial oxide, removing very thin oxidized film and pickling ash from its surface by fluoric acidic solution, immersing the Mg-alloy in filming solution to obtain phosphate film, and immersing in alkaline aqueous solution at 15-100 deg.C for 3-60 min for closing the pores in the film. Said filming solution is prepared from Mn salt, phosphate, fluoride and water.

Description

technical field [0001] The invention relates to a magnesium alloy surface treatment technology, in particular to a preparation method of a chromium-free chemical conversion film of a magnesium alloy and a film-forming solution used. Background technique [0002] In the prior art, based on the requirement of light weight, plastics are widely used to manufacture casings of 3C products (laptop computers, mobile phone casings, household electronic products, etc.). However, plastics have poor electrical conductivity and thermal conductivity, poor electromagnetic shielding, and cannot be recycled, so magnesium alloys are currently used instead. Magnesium alloy has the characteristics of light weight, high specific strength, good electrical conductivity and heat dissipation, electromagnetic shielding, rich storage capacity, and easy recycling. It is known as a green and environmentally friendly product, so it has been widely used, especially in the application of On the car body, ...

Claims

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Application Information

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IPC IPC(8): C23C22/18C23C22/36
Inventor 周婉秋单大勇韩恩厚柯伟
Owner INST OF METAL RESEARCH - CHINESE ACAD OF SCI
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