Sealing Composition

Abstract

Disclosed is a method of treating a substrate. The surface is contacted with a sealing composition comprising a lithium cation; and optionally, with conversion composition comprising a cation of a lanthanide, a Group IIIB, and/or a Group IVB metal. The conversion composition is applied to provide a film on the substrate surface resulting in a level of the lanthanide, Group IIIB metal, and/or Group IV metal thereon of at least 100 counts greater than on a surface of a substrate that does not have the film thereon as measured by X-ray fluorescence (measured using X-Met 7500, Oxford Instruments; operating parameters 60 second timed assay, 15 Kv, 45 μA, filter 3, T(p)=1.5 μs for lanthanides, Group IIIB metals, and Group IVB metals except zirconium; operating parameters 60 second timed assay, 40 Kv, 10 μA, filter 4, T(p)=1.5 μs for zirconium). A substrate obtainable by the methods also is disclosed.

We claim: 
     
         1 . A method of treating a substrate comprising:
 contacting at least a portion of the substrate surface with a sealing composition comprising a lithium cation; wherein the sealing composition is applied to provide a layer of the dried sealing composition having a thickness of 5 nm to 550 nm.   
     
     
         2 . The method of  claim 1 , wherein the lithium cation is present in the sealing composition in an amount of 5 ppm to 5500 ppm (as lithium cation) based on total weight of the sealing composition. 
     
     
         3 . The method of  claim 1 , wherein the sealing composition further comprises a carbonate source, a hydroxide source, or combinations thereof. 
     
     
         4 . The method of  claim 1 , wherein the sealing composition further comprises a Group IA metal cation other than lithium, a Group VB metal cation, a Group VIB metal cation, a corrosion inhibitor, an indicator compound, or combinations thereof. 
     
     
         5 . The method of  claim 1 , wherein the pH of the sealing composition is 9.5 to 12.5. 
     
     
         6 . The method of  claim 1 , wherein, following the contacting with the sealing composition, the substrate is not rinsed with water prior to contacting at least a portion of the substrate surface with subsequent treatment compositions. 
     
     
         7 . The method of  claim 1 , wherein the temperature of the sealing composition is 40° F. to 160° F. 
     
     
         8 . The method of  claim 1 , wherein the contacting is for 1 second to 15 minutes. 
     
     
         9 . The method of  claim 1 , further comprising contacting at least a portion of the substrate surface with a conversion composition comprising a lanthanide series metal cation, a Group IIIB metal cation, a Group IVB metal cation, or combinations thereof; wherein the contacting with the conversion composition occurs prior to and/or following the contacting with the sealing composition. 
     
     
         10 . The method of  claim 9 , wherein the conversion composition is applied to provide a film on the substrate resulting in a level of the lanthanide metal, Group IIIB metal cation, and/or Group IV metal cation on the treated substrate surface of at least 100 counts greater than on a surface of a substrate that does not have the film thereon as measured by X-ray fluorescence (measured using X-Met 7500, Oxford Instruments; operating parameters 60 second timed assay, 15 Kv, 45 μA, filter 3, T(p)=1.5 μs for lanthanides, Group IIIB metals, and Group IVB metals except zirconium; operating parameters 60 second timed assay, 40 Kv, 10 μA, filter 4, T(p)=1.5 μs for zirconium). 
     
     
         11 . The method of  claim 1 , wherein the substrate comprises aluminum, aluminum alloys, or combinations thereof. 
     
     
         12 . The method of  claim 9 , further comprising heating the substrate for 15 minutes to 30 minutes at a temperature of 110° C. to 232° C. 
     
     
         13 . A substrate treated with the method of  claim 1 . 
     
     
         14 . A system for treating a substrate comprising:
 a conversion composition for treating at a least a portion of the substrate, the conversion composition comprising a lanthanide series metal cation, a Group IIIB metal cation, a Group IVB metal cation, or a combination thereof; and   a sealing composition for treating at least a portion of the substrate, the sealing composition comprising a lithium cation.   
     
     
         15 . The system of  claim 14 , wherein the lanthanide series metal cation, Group IIIB metal cation and/or Group IVB metal cation comprises cerium, praseodymium, yttrium, zirconium, titanium, or combinations thereof. 
     
     
         16 . The system of  claim 14 , wherein the lanthanide series metal cation, Group IIIB metal cation and/or the Group IVB metal cation is present in an amount of 50 ppm to 500 ppm, based on a total weight of the conversion composition. 
     
     
         17 . The system of  claim 14 , wherein the lithium cation is present in the sealing composition in an amount of 5 ppm to 30,000 ppm (as lithium cation) based on a total weight of the sealing composition. 
     
     
         18 . The system of  claim 14 , wherein the sealing composition has a pH of 9.5 to 12.5. 
     
     
         19 . The system of  claim 14 , further comprising an alkaline cleaning composition comprising an azole. 
     
     
         20 . A substrate treated with the system of  claim 14 . 
     
     
         21 . The substrate of  claim 20 , wherein the substrate has at least a 50% reduction in the number of pits on the substrate surface compared to a substrate not treated with the sealing composition following 3 day exposure in neutral salt spray cabinet operated according to ASTM B117. 
     
     
         22 . The substrate of  claim 20 , wherein the substrate has at least a 50% reduction in the number of pits on the substrate surface compared to a substrate treated with the conversion composition or the sealing composition but not the conversion composition and the sealing composition following 7 day exposure in neutral salt spray cabinet operated according to ASTM B117. 
     
     
         23 . The substrate of  claim 20 , further comprising a primer layer, an electrocoat layer, and/or a topcoat layer.