Method to create functional coatings on magnesium

Abstract

In example implementations, a method for producing a coating is provided. The method includes placing a magnesium substrate into an anodizing bath, applying a voltage for a first amount of time to form a micro-porous anodizing layer having a thickness of between 1 to 50 microns on the magnesium substrate, placing the magnesium substrate with the micro-porous anodizing layer in plating bath, wherein the plating bath comprises a metal and a complexing agent with a pH between 8 and 14, applying a first current to the plating bath for a second amount of time to form an interlock layer on the micro-porous anodizing layer, and applying a second current to the plating bath for a third amount of time to form a coating on the interlock layer.

1 . A method, comprising:
 placing a magnesium substrate into an anodizing bath;   applying a voltage for a first amount of time to form a micro-porous anodizing layer having a thickness of between 1 to 50 microns on the magnesium substrate;   placing the magnesium substrate with the micro-porous anodizing layer in a plating bath, wherein the plating bath comprises a metal and a complexing agent with a pH between 8 and 14;   applying a first current to the plating bath for a second amount of time to form an interlock layer on the micro-porous anodizing layer; and   applying a second current to the plating bath for a third amount of time to form a coating on the interlock layer.   
     
     
         2 . The method of  claim 1 , wherein magnesium substrate comprises a magnesium alloy substrate. 
     
     
         3 . The method of  claim 1 , wherein the anodizing bath comprises at least one of sodium hydroxide or disodium metal silicate. 
     
     
         4 . The method of  claim 1 , wherein the voltage is applied by a pulsed direct current power supply. 
     
     
         5 . The method of  claim 1 , wherein the pulsed direct current power supply applies a constant current between 0.5 to 6 amperes per square decimeter at a temperature of between 18 degrees Celsius to 30 degrees Celsius. 
     
     
         6 . The method of  claim 1 , wherein the voltage has a peak voltage less than 75 volts. 
     
     
         7 . The method of  claim 6 , wherein the anodizing bath comprises an organic agent to control the peak voltage. 
     
     
         8 . The method of  claim 1 , wherein the complexing agent comprises at least one of: cyanide, pyrophosphate, or hydroxide. 
     
     
         9 . The method of  claim 1 , wherein the first current follows a plating current profile to allow the interlock layer to fill micro-pores in the micro-porous anodizing layer. 
     
     
         10 . The method of  claim 1 , wherein the second current is a constant current that is greater than the first current. 
     
     
         11 . The method of  claim 1 , wherein the coating comprises a thickness between 5 to 50 microns. 
     
     
         12 . A method, comprising:
 pre-treating a magnesium substrate;   cleaning the magnesium substrate with de-ionized water;   forming a micro-porous anodizing layer on the magnesium substrate in an anodizing bath, wherein a voltage is applied to the anodizing bath for a first amount of time to form the micro-porous anodizing layer;   rinsing the magnesium substrate with the micro-porous anodizing layer;   forming an interlock layer on the micro-porous anodizing layer in an autocatalytic plating bath for a second amount of time, wherein the plating bath comprises a metal and a complexing agent with a pH between 8 and 14; and   forming a coating on the interlock layer in the autocatalytic plating bath, wherein a current is applied to the plating bath for a third amount of time to form the coating.   
     
     
         13 . The method of  claim 12 , wherein the pre-treating comprises at least one of: treating the magnesium substrate in an acid bath, mechanically roughening the magnesium substrate, or cleaning the magnesium substrate in an alkaline bath. 
     
     
         14 . The method of  claim 12 , wherein the anodizing bath comprises at least one of sodium hydroxide or disodium metal silicate. 
     
     
         15 . The method of  claim 12 , wherein the voltage has a peak voltage less than 75 volts. 
     
     
         16 . The method of  claim 15 , wherein the anodizing bath comprises citric acid to control the peak voltage. 
     
     
         17 . The method of  claim 12 , wherein the second amount of time is sufficient to fill pores of the anodizing layer. 
     
     
         18 . The method of  claim 12 , wherein the autocatalytic plating bath comprises a nickel phosphorous bath or a nickel boron bath. 
     
     
         19 . The method of  claim 18 , wherein the second current is between 0.1 amperes per square decimeter (A/dm 2 ) and 2 A/dm 2 . 
     
     
         20 . A method, comprising:
 placing a magnesium alloy substrate into an anodizing bath;   applying and maintaining a peak voltage below 75 volts for a first timer period of approximately 10 minutes to form a micro-porous anodizing layer having a thickness of between 5 to 15 microns on the magnesium alloy substrate;   placing the magnesium alloy substrate with the micro-porous anodizing layer in plating bath, wherein the plating bath comprises a metal and a complexing agent with a pH between 9 and 12;   applying a first current that is increased over a second time period from 0 amperes per square decimeter (A/dm 2 ) to between 0.01 A/dm 2  to 0.5 A/dm 2  to the plating bath to form an interlock layer on the micro-porous anodizing layer; and   applying a second current that is greater than the first current and between 0.1 A/dm 2  and 2 A/dm 2  to the plating bath for a third time period to form a coating on the interlock layer.