Method of improving the performance of organic coatings for corrosion resistance

Abstract

This invention pertains to a method of modifying polymeric coating materials by adding organosulfur compounds, so that the metallic substrates coated with the modified polymeric materials become more resistant to corrosion. The organosufur compounds are alkane thiols with a general formula R(CH 2 ) n SH, where R represents H, NH 2 , HOOC, and HO groups and n is in the range of 10 to 21. The reagents are designed to increase the adhesion between the polymeric coating materials and the metallic substrates, which may be conducive to increased corrosion resistance.

1 . A method of improving the performance of organic conversion coatings, whose primary ingredients are polymeric resins, comprising the steps of 
 a. dissolving an organosulfur compound in a solvent,    b. mixing the solution in which said organosulfur compound is dissolved with a solution in which said polymeric resins are dissolved,    c. coating a metallic substrate with the mixture of the solutions containing said organosulfur compound and said polymeric resins,    d. curing the metallic substrate coated with said mixture of the solutions, and thereby increasing the corrosion resistance of said metallic substrate without using chrome.    
     
     
         2 . The method according to  claim 1  wherein said organosulfur compound is selected from the group consisting of alkyl, aryl, and alkyl-aryl thiols, xanthates, sulfides, disulfides, thiocarbamates, dithiocarbamates, thioureas, thiophenols, mercaptopyridines, mercaptoanilines, mercaptoimidazoles, thiophenes, and thiophosphates.  
     
     
         3 . The method according to  claim 1  wherein said organosulfur compound is an alkanethiol with a general formula R(CH 2 ) n SH, where R is a terminal group selected from the group consisting of H—, NH 2 —, HOOC—, and HO—, and n represents the number of hydrocarbons, which can range from 10 to 21.  
     
     
         4 . The method according to  claim 1  wherein said organosulfur compound is 1-octadecanethiol.  
     
     
         5 . The method according to  claim 1  wherein said polymeric resins are selected from the group consisting of acrylic, acrylic-urethane, epoxy, polyester, epoxy-polyester or fluorovinyl polymers, and combinations thereof.  
     
     
         6 . The method according to  claim 1  wherein said metallic substrate includes a substrate selected from the group consisting hot rolled and pickled steel sheet, cold-rolled steel sheet, stainless steel sheet, hot-dipped metallic coated steel sheets, electroplated metallic coated steel sheets, aluminum sheets and aluminum alloy sheets, zinc sheets, zinc alloy sheets, copper sheets, copper alloy sheets, gold, and silver.  
     
     
         7 . The method according to  claim 1  wherein said metallic substrate includes coatings of one or more layers selected from the group consisting of lead, lead alloy, nickel, nickel alloy, zinc, zinc layer, tin, and tin alloy.  
     
     
         8 . The method according to  claim 1  wherein said solvent for said organosulfur compound is selected from the group consisting of alcohols, acetone, turpentine, benzene, ethyl and butyl acetate, toluene, petroleum ester, xylene, alkane, mineral spirit, and water.  
     
     
         9 . The method according to  claim 8  wherein a preferred solvent is selected from the group consisting of ethanol, 1-propanol, 1-butanol, and mixtures thereof.  
     
     
         10 . The method according to  claim 1  wherein the concentration of said organosulfur compound in said polymeric resins is in the range of 0.001-0.5 moles per liter.  
     
     
         11 . The method according to  claim 1  wherein said metallic substrate is coated with said mixture of the solutions containing said organosulfur compound and said polymeric resins by means of a roll or a bar coater, cured at a temperature in the range of 100 to 350° C. to obtain a desired coating thickness.  
     
     
         12 . A method of improving the performance of organic conversion coatings, whose primary ingredients are polymeric resins, comprising the steps of 
 a. mixing an organosulfur compound with a polymeric resin,    b. coating a metallic substrate with said polymeric resin containing said organosulfur compound,    c. curing the metallic substrate coated with said mixture of the solutions, and thereby increasing the corrosion resistance of said metallic substrate without using chrome.    
     
     
         13 . A method according to  claim 12  wherein said metallic substrate is electrogalvanized steel.  
     
     
         14 . A method according to  claim 12  wherein said organosulfur compound is selected from the group consisting of alkyl, aryl, and alkyl-aryl thiols, xanthates, sulfides, disulfides, thiocarbamates, dithiocarbamates, thioureas, thiophenols, mercaptopyridines, mercaptoanilines, mercaptoimidazoles, thiophenes, and thiophosiphates.  
     
     
         15 . The method according to  claim 12  wherein said polymeric resins are selected from the group consisting of acrylic, acrylic-urethane, epoxy, polyester, epoxy-polyester or fluorovinyl polymers, and combinations thereof.