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Pretreatment liquid and pretreatment method before rare earth conversion

A pretreatment liquid and rare earth conversion technology, which is applied in the coating process of metal materials, etc., can solve the problems of large aluminum loss and achieve the effects of reducing aluminum loss, improving corrosion resistance, and improving film formation efficiency

Inactive Publication Date: 2012-12-05
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

General industrial statistics show that the loss of aluminum in the process of alkaline degreasing of aluminum alloys is relatively large. For example, if 1 ton of aluminum is processed, the loss of aluminum after alkaline degreasing treatment can be as high as 40 kg or more.

Method used

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  • Pretreatment liquid and pretreatment method before rare earth conversion
  • Pretreatment liquid and pretreatment method before rare earth conversion
  • Pretreatment liquid and pretreatment method before rare earth conversion

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0053] In order to better understand the technical characteristics of the present invention, the present invention will be further described below in conjunction with the examples. Embodiment 1: The traditional alkali cleaning method of aluminum alloy comprises the following steps:

[0054] (a) Grinding: cut out a sample with a volume of 60cm×6cm×1cm and a mass of 1000g, and use 180#, 400#, 650# and 1000# water-resistant sandpaper to polish step by step to 1000#;

[0055] (b) Degreasing: configure a degreasing solution with a concentration of Na 2 CO 3 : 40g / L, Na 3 PO 4 : 40g / L, Na 2 SiO 3 : 15g / L, immerse the sample in the degreasing solution at 70°C for 5min;

[0056] (c) Alkali corrosion: NaOH (8g / l), N a3 PO 4 12H 2 O (12g / L), Na 2 CO 3 (8g / L) solution, stand at 70°C for 2min;

[0057] (d) light emission: the light emission solution is HNO with a concentration of 20% (volume fraction) 3 , immerse the sample in the light-emitting solution for 60s;

[0058] (e) ...

Embodiment 2

[0066] After film formation, the apparent uniformity and compactness of the film layer are poor, and the corrosion current density is 0.7411μA / cm 2 ,Such as Figure 5 shown. In this embodiment, the corrosion current density of the untreated aluminum alloy was also measured, and the corrosion current density was 5.248 μA / cm 2 ,Such as Figure 6 shown. The corrosion current density of the film layer obtained in Example 1 is reduced to 1 / 7 of that of bare aluminum. That is, the corrosion resistance of the obtained chemical conversion coating is 7 times higher than that of bare aluminum. Example 2: Aluminum alloy mixed pickling + alkali activation pretreatment method.

[0067] Preparation of pretreatment solution:

[0068] The first step is to prepare 1000mL of pretreatment solution before rare earth conversion treatment, including 250mL / L of medium nitric acid, 60g / L of phosphoric acid, 2g / L of octylphenol polyoxyethylene ether, 5g / L of hydrogen fluoride, and 0.5g / L of thio...

Embodiment 3

[0083] Example 3: Aluminum alloy mixed pickling + alkali activation pretreatment method.

[0084] Preparation of pretreatment solution:

[0085] The first step is to prepare 1000mL of pretreatment solution before rare earth conversion treatment, including phosphoric acid 10mL / L, sodium dihydrogen phosphate 20g / L, fatty alcohol polyoxyethylene ether 1g / L, hydrogen fluoride 1g / L, thiourea 0.1g / L, The rest is water. Dissolve phosphoric acid 10mL, sodium dihydrogen phosphate 20g, fatty alcohol polyoxyethylene ether 1g, hydrogen fluoride 1g and thiourea 0.1g in water, stir to dissolve, add water to 1000mL.

[0086] In the second step, prepare 1000 mL of 10 g / L sodium hydroxide.

[0087] The preprocessing method includes the following steps:

[0088] (1) Cut a sample with a volume of 60cm×6cm×1cm and a mass of 1000g, and grind it mechanically to 1000#;

[0089] (2) immerse in the pretreatment solution before the rare earth conversion treatment for 1 minute; wash with water and d...

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Abstract

The invention discloses pretreatment liquid and a pretreatment method before rare earth conversion. The pretreatment liquid consists of acid, a buffering agent, a complexing agent, a surfactant and a surface adsorbent. The pretreatment method comprises the following steps of: immersing an aluminum alloy in the pretreatment liquid, impregnating for 1 to 5 minutes, taking out and washing by using running water; and immersing in alkaline solution for 2 to 60 seconds, taking out and washing by using the running water. Uniform and dense cathode spots can be generated on the surface of the aluminumalloy after the treatment of the method, and good film forming conditions can be provided for the generation of a subsequent rare earth conversion coating. In the pretreatment method, the pretreatment liquid does not need to be heated in the treatment process, and the defects of non-uniform film formation and high aluminum loss in the traditional strong alkali pretreatment can be well overcome. The method is simple, and easy and convenient to operate, and low in cost, and industrialization is easy to realize.

Description

technical field [0001] The invention relates to a metal surface pretreatment method, in particular to a pretreatment liquid and a pretreatment method for rare earth conversion treatment. After applying this method to pre-treat the surface of the aluminum alloy, when the rare earth chemical conversion treatment is performed on the surface of the aluminum alloy, a uniform and dense golden rare earth oxide coating can be obtained on the surface of the aluminum alloy to improve the corrosion resistance of the rare earth conversion film . Background technique [0002] Aluminum alloy is easy to corrode because of its high activity, so it needs anti-corrosion treatment on the surface. The commonly used method is to form a complete, dense and uniform passivation layer on the surface of the aluminum alloy and then spray it. Traditional chromate passivation is one of the most commonly used passivation methods, but due to Cr 6+ Toxic, its application is restricted. It is imminent t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): C23C22/36
Inventor 李文芳张军军杜军
Owner SOUTH CHINA UNIV OF TECH
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