Coating systems for metal substrates and a method for protecting metal substrates using the coating systems

Abstract

Disclosed are methods of treating a metal to improve the metal's corrosion resistance. In one such method, the method is carried out by applying, to the surface of the metal, a coating which includes magnesium powder and a UV-curable or other radiation-curable binder. In another such method, the method is carried out by applying, to the surface of the metal, a coating which includes magnesium powder and an inorganic binder. In another such method, a coating that includes a magnesium alloy powder and a binder is applied to the surface of the metal. The magnesium alloy powder is selected such that it has a corrosion potential that is from about 0.01 volt to about 1.5 volt more negative than the metal's corrosion potential. Also disclosed are methods of treating a ferrous metals and magnesium alloys to improve the corrosion resistance of these materials.

We claim: 
     
         1 . A method of treating a ferrous metal to improve the ferrous metal's corrosion resistance, said method comprising:
 applying, to the surface of the ferrous metal, a coating which consists essentially of magnesium/aluminum alloy powder and a binder, wherein said magnesium/aluminum alloy powder comprises from about 50% to about 97% by weight of magnesium and from about 3% to about 50% by weight of aluminum.   
     
     
         2 . A method according to  claim 1 , wherein the magnesium/aluminum alloy powder comprises from more than about 6% to about 50% by weight of aluminum. 
     
     
         3 . A method according to  claim 1 , wherein the magnesium/aluminum alloy powder comprises from about 3% to about 30% by weight of aluminum. 
     
     
         4 . A method according to  claim 1 , wherein the magnesium/aluminum alloy powder further comprises one or more additional alloying elements selected from the group consisting of calcium, manganese, lithium, carbon, zinc, potassium, silicon, zirconium, and/or a rare earth metal. 
     
     
         5 . A method according to  claim 1 , wherein the magnesium/aluminum alloy powder has a corrosion potential that is from about 0.01 volt to about 1.5 volt more negative than the ferrous metal's corrosion potential. 
     
     
         6 . A method according to  claim 1 , wherein the binder is a polymeric binder. 
     
     
         7 . A method according to  claim 1 , wherein the binder is a epoxy polyamide polymeric binder. 
     
     
         8 . A method of treating a metal to improve the metal's corrosion resistance, said method comprising: applying, to the surface of the metal, a coating which comprises a magnesium alloy powder and a binder, wherein the magnesium alloy powder has a corrosion potential that is from about 0.01 volt to about 1.5 volt more negative than the metal's corrosion potential. 
     
     
         9 . A method according to  claim 8 , wherein the magnesium alloy powder has a corrosion potential that is from 0.01 volt to 1.5 volt more negative than the metal's corrosion potential. 
     
     
         10 . A method according to  claim 8 , wherein the magnesium alloy powder comprises magnesium and from about 1% to about 50% by weight of one or more alloying elements. 
     
     
         11 . A method according to  claim 8 , wherein the magnesium alloy powder comprises magnesium and at least one alloying element selected from the group consisting of calcium, manganese, lithium, carbon, zinc, potassium, aluminum, silicon, zirconium, and/or a rare earth metal. 
     
     
         12 . A method according to  claim 8 , wherein the binder is a polymeric binder. 
     
     
         13 . A method according to  claim 8 , wherein the binder is a epoxy polyamide polymeric binder. 
     
     
         14 . A method of treating a magnesium alloy to improve the magnesium alloy's corrosion resistance, said method comprising:
 applying/to the surface of the magnesium alloy, a coating which comprises magnesium powder and a binder,   wherein the magnesium powder comprises from about 94% to about 100% by weight of magnesium.   
     
     
         15 . A method according to  claim 14 , wherein the magnesium powder has a corrosion potential that is from about 0.01 volt to about 1.5 volt more negative than the magnesium alloy's corrosion potential. 
     
     
         16 . A method according to  claim 14 , wherein the magnesium powder is substantially free from one or more of calcium, manganese, lithium, carbon, zinc, potassium, silicon, zirconium, and rare earth metals. 
     
     
         17 . A method according to  claim 14 , wherein the magnesium alloy comprises from about 2% to about 15% of aluminum and from about 85% to about 97% of magnesium. 
     
     
         18 . A method according to  claim 14 , wherein the magnesium alloy is selected from AM60, AZ31, AZ61, AZ63, AZ80, AZ91, EZ33, ZM21, HK31, HZ32, QE22, QH21, ZE41, ZE63, ZK40, and ZK60. 
     
     
         19 . A method according to  claim 14 , wherein the binder is a polymeric binder. 
     
     
         20 . A method according to  claim 14 , wherein the binder is a epoxy polyamide polymeric binder.