Surface treatment method on Micro-arc Oxidation treated Mg alloys

Abstract

Chemically and mechanically protective oxide film was formed on Mg alloys using micro-arc oxidation (MAO) methods. Further modification of the obtained MAO surfaces was made in various aspects and the processes thereof were described. Firstly, the protection is enhanced by forming super-hydrophobic surfaces, with water contact angle higher than 140°, attributed to hierarchical nano-micro structures. Secondly, the electrical property of the MAO surfaces is modified. A film with sheet resistance as low as 0.05 Ω/sq is achieved by electro-less Ni deposition on MAO surfaces. Thirdly, black colors are achieved by the sol-gel process on MAO samples.

What is claimed is: 
     
         1 . A method of treating the surface of micro-arc oxidation treated magnesium alloy, comprising
 a) providing a micro-arc oxidation treated magnesium alloy sample;   b) pre-treating said sample with nickel acetate solution in ethanol solution;   c) activating said pre-treated sample with a solution of reducing agent; and   d) forming electro-less Ni on the surface of said activated sample with a deposition solution,   
       wherein, said treated sample obtained from step (d) is electrically conductive. 
     
     
         2 . The method of  claim 1 , wherein said solution of reducing agent is an ethanol solution of NaBH 4 . 
     
     
         3 . The method of  claim 1 , wherein said deposition solution comprises NiSO 4 .6H 2 O, NaH 2 PO 2 .H 2 O, Na-citrate, H 3 BO 3 , C 3 H 6 O 3  and thiourea. 
     
     
         4 . The method of  claim 1 , wherein said magnesium alloy has a sheet resistance of said treated sample obtained from step (d) is less than 0.05 Ω/sq. 
     
     
         5 . A magnesium alloy comprising a layer of nickel of 10-30 μm thickness on said alloy with a micro-arc oxidation treated layer of 5-40 μm thickness therebetween; said layer of nickel forming a uniform surface on said micro-arc oxidation treated layer to provide improved conductivity such that said alloy has a sheet resistance of less than 0.05 Ω/sq. 
     
     
         6 . The magnesium alloy of  claim 5  wherein said micro-arc oxidation treated layer has pores with an average pore size of 1-3 μm that are filled by nickel. 
     
     
         7 . The magnesium alloy of  claim 5  manufactured by the process of  claim 1 .