Pretreatment liquid and pretreatment method before rare earth conversion

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...

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