Cobaltate conversion liquid and application in surface treatment of magnesium-lithium alloy

Abstract

The invention provides cobaltate conversion liquid and application in surface treatment of a magnesium-lithium alloy. The cobaltate conversion liquid of the magnesium-lithium alloy is prepared by taking cobalt nitrate as main salt, sodium nitrite and hydrogen peroxide as double promoters and sodium acetate, sodium citrate and sodium gluconate as auxiliary additives. A brown cobaltate conversion film can be formed on the surface of the magnesium-lithium alloy by utilizing the cobaltate conversion liquid to treat the magnesium-lithium alloy. The film is compact, even and smooth, does not have obvious pits or peelings, has good binding force with the matrix of the magnesium-lithium alloy and has moderate thickness. The method has low preparation cost, fewer preparation steps, simple operation, moderate reaction conditions, environmental protection, energy saving and fewer conditions required to be controlled and is easy to realized; compared with a chromate conversion film, the corrosionresisting property of the cobaltate conversion film is greatly improved, and thereby, the cobaltate conversion film is very hopeful to be applied to large-scale production.

Description

technical field [0001] The invention relates to a surface treatment solution for alloy materials, in particular to a solution for surface treatment of magnesium-lithium alloys. The invention also relates to a method for forming a chromium-free conversion film on the surface of the magnesium-lithium alloy. It belongs to the field of inorganic metal materials. Background technique [0002] Magnesium-lithium alloy, also known as ultra-light alloy, is by far the lightest alloy among metal structural materials. In addition to the advantages of general magnesium alloys, magnesium-lithium alloys also have the characteristics of low density, high plasticity, excellent electromagnetic shielding and shock resistance, so they have broad application prospects in communication electronics, automobiles, aerospace and other fields. However, for magnesium-lithium alloys, the addition of lithium not only reduces the alloy density and improves plasticity, but also significantly reduces the ...

AI Technical Summary

Problems solved by technology

However, for magnesium-lithium alloys, the addition of lithium not only reduces the alloy density and improves plasticity, but also significantly reduces the corrosion resistance of the alloy, which severely limits the practical application of magnesium-lithium alloys.

At present, among the numerous anti-corrosion treatment methods for magnesium-lithium alloys, the most mature one is chromate conversion coating. Its treatment process is mature and its performance is stable. In consideration of human health and environmental protection, the chromate conversion coating process has been subject to more and more restrictions and will eventually withdraw from the stage of history

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