Method of treating magnesium alloy work-piece surface

Abstract

The invention provides a method for treating the surface of a magnesium alloy workpiece. The technological process includes workpiece pretreatment, chemical conversion treatment, drying treatment and water washing treatment between each process. Among them, the chemical conversion treatment is carried out by immersing the magnesium alloy workpiece in the conversion liquid composed of the main film-forming substance and the auxiliary film-forming substance; the main film-forming substance is a transition metal salt such as zirconium salt, manganese salt, molybdate, tungstate, etc. One or more of them, converted into Na2MoO4 2H2O content, the concentration is 5-150g / L; the auxiliary film-forming substance is one or more of the three alkali metal nitrates and sulfates of lithium, sodium and potassium , converted into LiNO3 content, the concentration is 0.5-20g / L; the pH value of the conversion solution is 2-6, the treatment temperature is 10-90°C, and the treatment time is 5-30 minutes. The surface film of the prepared magnesium alloy workpiece has both protective and decorative properties, and its corrosion resistance and bonding force with the paint film are not lower than the film obtained by the conversion solution containing Cr6+. Its color is diverse and the color uniformity and durability It is not inferior to the film layer obtained by electrolytic coloring or chemical dyeing.

Description

technical field [0001] The invention relates to the technical field of magnesium alloy surface treatment, in particular to an environment-friendly preparation method of a protective decorative film on the surface of a magnesium alloy workpiece. Background technique [0002] Magnesium alloys are known as "green engineering materials in the 21st century" due to their advantages such as low density, high specific strength, good processing and welding and damping properties, stable dimensions, low price, and easy recycling. They are used in machinery manufacturing, automobile manufacturing, aerospace, electronics, etc. , military, communications, optical instruments, computers and other fields have a wider range of applications. However, the corrosion resistance of magnesium alloys is very poor, and they are prone to corrosion in humid atmosphere or acidic, neutral, and weakly alkaline solutions, which largely hinders the popularization and application of magnesium alloys. In a...

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Problems solved by technology

However, traditional magnesium alloy chemical conversion treatment solutions usually contain heavy metal ions Cr 6+ , high toxicity, serious environmental pollution

Although the recently published Chinese patent application No. 200510200038.4 "A Surface Treatment Method for Magnesium Alloys" (publication No. CN 1632169A) provides a conversion solution that does not contain harmful Cr 6+ , but there are still problems such as the surface film layer made by it has a single color, the decorative performance is not strong, and it is subject to many restrictions in application.

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