Particulate metal alloy coating for providing corrosion protection

Abstract

Coatings containing particulate metal alloy are disclosed. The coatings provide corrosion protection to a substrate, such as a metal substrate. The coatings contain zinc-metal-containing alloy in flake form, most particularly an alloy flake of zinc and aluminum. The coating can be from compositions that are water-based or solvent-based. The compositions for providing the coating may also contain a substituent such as a water-reducible organofunctional silane, or a hexavalent-chromium-providing substance, or a titanate polymer, or a silica substance constituent. the coating may desirably be topcoated.

I claim:  
     
         1 . In a coating composition adapted for application to, and curing on, a substrate, which composition contains particulate metal in a liquid medium and provides corrosion resistance as a cured coating on said substrate, the improvement in the particulate metal constituency of said composition comprising: 
 zinc alloy in flake form comprising from about 87 to about 90 percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake.    
     
     
         2 . The coating composition of  claim 1  wherein said zinc alloy in flake form is zinc alloyed with one or more of aluminum, tin, magnesium, nickel, cobalt and manganese.  
     
     
         3 . The coating composition of  claim 1  wherein said zinc is alloyed with one or more of tin and aluminum.  
     
     
         4 . The coating composition of  claim 1  wherein said zinc alloy in flake form is a zinc-aluminum-magnesium alloy flake.  
     
     
         5 . The coating composition of  claim 5  wherein said zinc alloy in flake form comprises from about 87 to about 89 percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid in said alloy flake.  
     
     
         6 . The coating composition of  claim 1  wherein said zinc alloy in flake form is an alloy having at least about 90 percent of the flake particles with a longest dimension of less than about 15 microns and has at least about 50 percent of the flake particle with a longest dimension of less than about 13 microns, and said composition further contains non-alloyed particulate metal.  
     
     
         7 . The method of preparing a corrosion-resistant coated substrate protected with a corrosion-resistant coating, which method comprises: 
 (1) applying to said substrate a coating composition comprising: 
 (A) liquid medium; and  
 (B) zinc alloy in flake form comprising from about 87 to about 90 percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake.  
   (2) curing applied coating composition on said substrate.    
     
     
         8 . The method of  claim 7  wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid.  
     
     
         9 . A coated substrate protected with a chrome-free, corrosion-resistant coating form a composition comprising: 
 (A) liquid medium;    (B) zinc alloy in flake form comprising from about 87 to about 90 percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake;    (C) silane binding agent.    
     
     
         10 . The coated substrate of  claim 9  wherein said liquid medium is one or more of water and organic liquid and said water, when present, is present in an amount above about 25 weight percent of said coating composition.  
     
     
         11 . The coated substrate of  claim 9  wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid.  
     
     
         12 . The coated substrate of  claim 9  wherein said zinc alloy in flake form is zinc alloyed with one or more of aluminum, magnesium, tin, nickel, cobalt and manganese.  
     
     
         13 . The coated substrate of  claim 9  wherein said zinc alloy in flake form is a zinc-aluminum-magnesium alloy flake.  
     
     
         14 . The coated substrate of  claim 9  wherein said silane binding agent is a water-reducible, organofunctional binding agent containing alkoxy groups, which silane binding agent contributes from about 3 to about 20 weight percent of said coating composition.  
     
     
         15 . The coated substrate of  claim 9  wherein said coating composition has a pH within the range of from greater than 6 to about 7.5, contains water in an amount above about 30 weight percent, and has a molar ratio of water to silane alkoxy groups above about 4.5:1.  
     
     
         16 . The coated substrate of  claim 9  wherein said coating additionally contains one or more of thickener and wetting agent, said coating is topcoated with a composition containing silica substance and said topcoating provides silica substance from one or more of colloidal silica, organic silicate and inorganic silicate.  
     
     
         17 . The method of preparing a corrosion-resistant coated substrate protected with a chrome-free, corrosion-resistant coating, which method comprises: 
 (1) applying to said substrate a coating composition comprising: 
 (A) liquid medium;  
 (B) zinc alloy in flake form comprising from about 87 to about 90 percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake;  
 (C) silane binding agent; with said coating composition being applied in an amount sufficient to provide, upon curing, above about 500 but not substantially above about 9,000 mg/ft 2  of coating on said metal substrate; and  
   (2) heat curing applied coating composition on said substrate at a temperature up to about 700° F. for a time of at least about 10 minutes.    
     
     
         18 . The method of  claim 17  wherein said applied coating composition is cured at an elevated temperature within the range from about 330° C. (626° F.) to about 360° C. (680° F.).  
     
     
         19 . A coated substrate protected with a corrosion-resistant coating from a coating composition comprising: 
 (A) liquid medium;    (B) zinc alloy in flake form comprising from about 87 to about 90 percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake;    (C) a hexavalent-chromium-providing substance.    
     
     
         20 . The coated substrate of  claim 19  wherein said liquid medium is one or more of water and organic liquid.  
     
     
         21 . The coated substrate of  claim 19  wherein said zinc alloy in flake form is zinc alloyed with one or more of aluminum, tin, magnesium, nickel, cobalt and manganese.  
     
     
         22 . The coated substrate of  claim 19  wherein said alloy flake is a zinc-aluminum-magnesium alloy flake.  
     
     
         23 . The coated substrate of  claim 19  wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid.  
     
     
         24 . The coated substrate of  claim 19  wherein said coating additionally contains one or more of thickener and wetting agent, said coating is topcoated with a composition containing silica substance, and said topcoating provides silica substance from one or more of colloidal silica, organic silicate and inorganic silicate.  
     
     
         25 . The method of preparing a corrosion-resistant coated substrate protected with a chrome-free, corrosion-resistant coating, which method comprises: 
 (1) applying a coating composition comprising 
 (A) liquid medium;  
 (B) wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid;  
 (C) a hexavalent-chromium-providing substance; with said coating composition being applied in an amount sufficient to provide, upon curing, above about 500 but not substantially above about 9,000 mg/ft 2  of coating on said coated substrate; and  
   (2) heat curing applied coating composition on said substrate at a temperature up to about 700° F. for a time of at least about 10 minutes.    
     
     
         26 . The method of  claim 25  wherein said applied coating composition is cured at an elevated temperature within the range from about 300° C. (626° F.) to about 360° C. (680° F.).  
     
     
         27 . A coated substrate protected with a chrome-free, corrosion-resistant coating from a coating composition comprising: 
 (A) wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid;    (B) a titanate polymer; and    (C) a liquid vehicle comprising organic liquid for said titanate polymer.    
     
     
         28 . The coated substrate of  claim 27  wherein said coating composition additionally contains manganese dioxide, and said manganese dioxide is present in an amount equal to about 30 weight percent to about 100 weight percent of said zinc alloy in flake form.  
     
     
         29 . The coated substrate of  claim 27  wherein said liquid vehicle is a blend of water with organic liquid.  
     
     
         30 . The coated substrate of  claim 27  wherein said zinc alloy in flake form is zinc alloyed with one or more of aluminum, tin, magnesium, nickel, cobalt and manganese.  
     
     
         31 . The coated substrate of  claim 27  wherein said zinc alloy in flake form is a zinc-aluminum-magnesium alloy flake.  
     
     
         32 . The coated substrate of  claim 27  wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid.  
     
     
         33 . The coated substrate of  claim 27  wherein said titanate polymer is selected from the group consisting of tetraisobutyl titanate, tetra-isopropyl titanate, tetra N-butyl titanate and mixtures thereof, and said titanate is present in an amount equal to about 9 weight percent to about 47 weight percent of said metal alloy in flake form.  
     
     
         34 . The coated substrate of  claim 27  wherein said coating is topcoated.  
     
     
         35 . The method of preparing a corrosion-resistant coated substrate protected with a chrome-free, corrosion-resistant coating, which method comprises: 
 (1) applying a coating composition comprising: 
 (A) wherein said zinc alloy in flake form comprises from about 87 to about 90 weight percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake;  
 (B) a titante polymer; and  
 (C) a liquid vehicle comprising organic liquid for said titanate polymer; and  
   (2) heat curing applied coating composition on said substrate at a temperature up to about 600° F. for a time of at least about 10 minutes.    
     
     
         36 . The method of preparing the coated substrate of  claim 35  wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid.  
     
     
         37 . A coated substrate protected with a corrosion-resistant coating from a coating composition comprising: 
 (A) liquid medium;    (B) zinc alloy in flake form comprising from about 87 to about 90 percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake;    (C) one or more of a water-soluble and water dispersible silica substance.    
     
     
         38 . The coated substrate of  claim 37  wherein said silica substance is selected from the group consisting of alkali metal silicate, organic silicate ester, colloidal silica sol, organic ammonium silicate and mixtures of the foregoing.  
     
     
         39 . The coated substrate of  claim 37  wherein said composition has a water-based-liquid medium and additionally contains one or more of a thickening agent and metallic oxide pigment.  
     
     
         40 . The coated substrate of  claim 39  wherein said thickening agent is one or more of cellulose ether and xanthan gum and said metallic oxide pigment is one or more of zinc oxide, iron oxide and titanium oxide.  
     
     
         41 . The coated substrate of  claim 37  wherein said zinc alloy in flake form is zinc alloyed with one or more of aluminum, tin, magnesium, nickel, cobalt and manganese.  
     
     
         42 . The coated substrate of  claim 37  wherein said zinc alloy in flake form is a zinc-aluminum-magnesium alloy flake.  
     
     
         43 . The coated substrate of  claim 37  wherein said coating is topcoated.  
     
     
         44 . The method of preparing a coated substrate protected with a corrosion-resistant coating, which method comprises: 
 (1) applying a coating composition comprising: 
 (A) liquid medium;  
 (B) zinc alloy in flake form comprising from about 87 to about 90 percent zinc and from about 1 to about 4 weight percent aluminum in said alloy flake;  
 (C) one or more of a water-soluble and water dispersible silica substance; and  
   (2) heat curing applied coating composition on said substrate at a temperature up to about 700° F. for a time of at least about 10 minutes.    
     
     
         45 . The method of preparing the coated substrate of  claim 44  wherein said zinc alloy in flake form comprises from about 87 to about 89 weight percent zinc, from about 2 to about 4 weight percent aluminum, and from about 7 to about 10 weight percent paste liquid.