Surface treatment of a magnesium alloy

Patent metadata

Field	Value
Publication number	US-9506161-B2
Application number	US-201414568210-A
Country	US
Kind code	B2
Filing date	Dec 12, 2014
Priority date	Dec 12, 2014
Publication date	Nov 29, 2016
Grant date	Nov 29, 2016

Abstract

A surface treatment of a magnesium alloy includes preparing a substrate of magnesium alloy, micro-arc oxidizing the substrate of magnesium alloy, forming an oxide layer with a hydroxyl group on the substrate of magnesium alloy, silylizing the oxide layer of the substrate of magnesium alloy with the oxide layer, by soaking the substrate of magnesium alloy in a processing solution with a silyl group-containing compound for 1-300 minutes, and placing the substrate of magnesium alloy with the silylized oxide layer at 70-200° C. for 1-300 minutes, allowing a condensation reaction to occur. The manufactured surface-treated magnesium alloy shows a decreased degradation rate in vivo.

First claim

What is claimed is:

1. A surface treatment of a magnesium alloy for manufacturing a surface-treated magnesium alloy, comprising:
preparing a substrate of magnesium alloy;
preparing an alkaline electrolyte consisting of sodium hydroxide (NaOH), trisodium phosphate (Na 3 PO 4 ), sodium nestasilicate (Na 2 SiO 3 ), chelating agents and calcium salts;
micro-arc oxidizing the substrate of magnesium alloy by immersing the substrate of magnesium alloy in the alkaline electrolyte, forming an oxide layer with a hydroxyl group on a surface of the substrate of magnesium alloy;
silylizing the oxide layer of the substrate of magnesium alloy, by soaking the substrate of magnesium alloy with the oxide layer in a processing solution having a silyl group-containing compound, allowing the silyl group-containing compound adhering on the oxide layer of the substrate of magnesium alloy; and
heating the substrate of magnesium alloy with the silylized oxide layer at 70-200° C., allowing a condensation reaction to occur in which combines the silyl group of the silyl group-containing compound and the hydroxyl group of the oxide layer, together with loss of water.

2. The surface treatment of the magnesium alloy as claimed in claim 1 , with soaking the substrate of magnesium alloy with the oxide layer in the processing solution for 1-300 minutes.

3. The surface treatment of the magnesium alloy as claimed in claim 1 , with heating the substrate of magnesium alloy with the silylized oxide layer for 1-300 minutes.

4. The surface treatment of the magnesium alloy as claimed in claim 1 , with the silyl group-containing compound being selected from (3-aminopropyl)triethoxysilane, (3-mercaptopropyl)trimethoxysilane or bis(trimethysilyl)amine.

5. The surface treatment of the magnesium alloy as claimed in claim 1 , with the processing solution comprising 3-20 wt % of the silyl group-containing compound.

6. The surface treatment of the magnesium alloy as claimed in claim 1 , with soaking the substrate of magnesium alloy with the oxide layer in the processing solution for 10-60 minutes.

7. The surface treatment of the magnesium alloy as claimed in claim 1 , with heating the substrate of magnesium alloy with the silylized oxide layer at 80-150° C. for 20-60 minutes.

8. The surface treatment of the magnesium alloy as claimed in claim 1 , with the oxide layer comprising oxides of magnesium selected from a group consisting of magnesium oxide (MgO), magnesium hydroxide (Mg(OH) 2 ) and magnesium silicate (MgSiO 4 and Mg 2 SiO 3 ).

9. The surface treatment of the magnesium alloy as claimed in claim 1 , with the surface-treated magnesium alloy comparing a condensed oxide layer having a thickness of 5-50 μm.

10. The surface treatment of the magnesium alloy as claimed in claim 1 , with the surface-treated magnesium alloy comprising a condensed oxide layer having a first surface coupling to the substrate of magnesium alloy and a second surface opposite to the first surface, with the condensed oxide layer being a porous layer with a plurality of pores, with the condensed oxide layer being sequentially divided into a first sublayer, a second sublayer and a third sublayer from the second surface to the first surface, with the first sublayer having a thickness of 5 μm and a porosity of 3-5%, with the second sublayer having a thickness of 5 μm and a porosity of 2-3%, with the third sublayer having a thickness of 40 μm and a porosity smaller than 1%.

11. The surface treatment of the magnesium alloy as claimed in claim 1 , with the oxide layer being a porous layer with a plurality of pores, with the surface treatment of the magnesium alloy further comprising:
shrinking the plurality of pores of the oxide layer, by soaking the substrate of magnesium alloy with the oxide layer in water at 70-150° C. before the substrate of magnesium alloy with the oxide layer is soaked in the processing solution.

12. The surface treatment of the magnesium alloy as claimed in claim 11 , with soaking the substrate of magnesium alloy with the oxide layer in water for 1-300 minutes.

13. The surface treatment of the magnesium alloy as claimed in claim 1 , with micro-arc oxidating the substrate of magnesium alloy for 5-30 minutes using a current density of 20-500 mA/cm2, a pulse frequency of 500-5,000 Hz and a duty cycle of 10-60%.

14. A surface-treated magnesium alloy, by manufacturing by the surface treatment of the magnesium alloy as claimed in claim 1 .

15. The surface treatment of the magnesium ahoy as claimed in claim 1 , wherein soaking the substrate of magnesium ahoy is under a vacuum environment.

Assignees

• Metal Ind Res & Dev Ct

Inventors

• Weng Li-Wen
• Tseng Chun-Chieh
• Wang Yue-Jun
• Fu Ho-Chung
• Sue Tzyy-Ker

Classifications

• C25D11/30 Primary

  of magnesium or alloys based thereon · CPC title

• C25D11/024

  Anodisation under pulsed or modulated current or potential · CPC title

• C25D11/026

  Anodisation with spark discharge · CPC title