Method for treating surface of magnesium or magnesium alloy

a magnesium alloy and surface treatment technology, applied in the direction of electrolytic coatings, surface reaction electrolytic coatings, coatings, etc., can solve the problems of poor wear resistance, poor corrosion resistance, and generally unsuitable for mass production of magnesium alloys, and achieve the effect of improving the film forming rate, reducing the film dissolution rate, and stable dimensional precision of the workpi

Inactive Publication Date: 2006-10-26
CHUNG CHENG INST TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0016] In the present invention the Mg or Mg alloy is capable of forming a film mainly constituted of magnesium oxide ceramic ingredient in an alkaline solution by anodic oxidation treatment, and the magnesium oxide ceramic ingredient is slightly soluble in an alkaline solution by chemical dissolution. Since the surface treatment composition according to the present invention contains no fluoride, such a surface treatment composition will not cause severe environmental pollution. Furthermore, the present invention uses a film thickening agent and a film adjustment agent to achieve an increase in the film forming rate, a reduction in film dissolution rate, a uniform and fine film, a stable dimensional precision of the workpiece, and a reduction on the internal stress of the film.

Problems solved by technology

However, Mg alloys are generally not suitable for mass production due to their disadvantages, such as poor corrosion resistance, and poor wear resistance, etc.
However, a surface formed through such a technique is rough due to the formation of a large amount of penetration sparks, and requires an additional coating treatment.
Furthermore, due to the use of fluoride as a main chemical agent, wastewater from such a treatment is difficult to be treated and has a greater pollution impact on the environment.
However, since a Mg alloy dissolves rapidly in an acidic state, the surface of the resulting film is liable to become rough.

Method used

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  • Method for treating surface of magnesium or magnesium alloy
  • Method for treating surface of magnesium or magnesium alloy
  • Method for treating surface of magnesium or magnesium alloy

Examples

Experimental program
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Effect test

example a1

[0029] Surface treatment composition: sodium hydroxide (70 g / L) was used as a hydroxide, sodium metasilicate (64 g / L) was used as a film thickening agent, and trisodium phosphate (19 g / L) and oxalic acid (80 g / L) were used as a film adjustment agent. This example used a d.c. rectifier and adopted the following conditions: temperature 20° C., electric current density 1.6 A / dm2, and reaction time 30 minutes.

example a2

[0030] Surface treatment composition: sodium hydroxide (70 g / L) was used as a hydroxide, sodium vanadate (50 g / L) was used as a film thickening agent, and trisodium phosphate (19 g / L) and oxalic acid (80 g / L) were used as a film adjustment agent. This example used a d.c. rectifier and adopted the following conditions: temperature 20° C., electric current density 1.6 A / dm2, and reaction time 30 minutes.

[0031] Since sodium metasilicate is cheap and readily available, and the resulting anodic film has a fair performance, sodium metasilicate was used as a film thickening agent in the following examples. Meanwhile, various film adjustment agents with different concentrations of agents were used in the examples for investigating the role of each chemical agent in the resulting anodic treated films.

example a3

[0032] Surface treatment composition: sodium hydroxide (70 g / L) was used as a hydroxide, sodium metasilicate (21 g / L) was used as a film thickening agent, and trisodium phosphate (95 g / L) and succinic acid (80 g / L) were used as a film adjustment agent. This example used a d.c. rectifier and adopted the following conditions: temperature 20° C., electric current density 1.6 A / dm2, and reaction time 30 minutes.

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Abstract

A method for surface treatment is disclosed. The method is achieved by forming a MgO film on a metal surface through anode processing of Mg or Mg alloy in an alkaline solution. The alkaline solution includes a hydroxide, a thickening agent, and a film adjusting agent. As the method is performed, the target object is immersed in the alkaline solution, and the target object is connected to an anode with an average electric current density of 1˜5 A/dm, at a temperature of 0˜30° C., and within a time period of 10˜120 minutes to form a film of 5˜25 μm. The forming rate of the film of the method of the present invention is fast, and the formed film is of little stress.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a surface treatment method, particularly a surface treatment method applicable on Mg or Mg Alloy. BACKGROUND OF THE INVENTION [0002] Mg alloys are high in strength and light in weight and are widely used on airplanes, vehicles, and electronic products. Since magnesium is capable of forming alloys of high strength with many types of metal, Mg alloys have a wide variety of applications. However, Mg alloys are generally not suitable for mass production due to their disadvantages, such as poor corrosion resistance, and poor wear resistance, etc. Furthermore, due to an ever increasing expansion on the applications of Mg alloys, the demand on the acid-corrosion-resistance of the alloys is also increasing day by day. [0003] In the past, a Mg alloy is usually protected against acid corrosion by coating a protective paint or forming a protective film on the surface of the alloy. In recent years, due to the improvement in technolo...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C25D11/00
CPCC25D11/30
Inventor GER, MING-DERCHANG, CHIN-LUNGSUNG, YUHWEN, NIANN-TSYRCHEN, WEI-KUN
Owner CHUNG CHENG INST TECH
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