Pretreatment of metal surfaces with a calcium-containing aqueous agent

Abstract

Described herein is a method for treating a metal surface, such as an aluminum alloy surface, which involves contacting the surface coated with a pretreatment coating comprising fluoride ions with an aqueous agent comprising at least 7 ppm calcium ions. The method reduces fluoride ion content in the pretreatment coating, increases calcium ion content in the pretreatment coating, improves corrosion resistance, such as filiform corrosion resistance, of the metal surface, and/or improves adhesion between the surface and a surface coating, such as a paint, lacquer, adhesive or a bonding agent. The aqueous agent can be a calcium-containing rinse, for example, a solution of a calcium salt. Articles of manufacture comprising metal surfaces treated by the above methods as well as the related manufacturing processes are also described.

What is claimed is: 
     
         1 . A method for treating a metal surface, comprising:
 contacting a metal surface one or more times with an aqueous agent comprising at least about 7 ppm calcium ions, wherein the metal surface is coated with a pretreatment coating comprising fluoride ions.   
     
     
         2 . A method for pretreating a metal surface, comprising:
 coating a metal surface with a pretreatment coating; and   contacting the metal surface coated with the pretreatment coating with an aqueous agent comprising at least 7 ppm calcium ions.   
     
     
         3 . A method of improving corrosion resistance of a metal surface, comprising:
 coating a metal surface with a pretreatment coating; and,   contacting the metal surface coated with the pretreatment coating with an aqueous agent comprising at least 7 ppm calcium ions.   
     
     
         4 . The method of  claim 1 , wherein the metal surface comprises an aluminum alloy surface. 
     
     
         5 . The method of  claim 4 , wherein the aluminum alloy surface comprises a surface of a 2xxx, 3xxx, 5xxx, 6xxx or 7xxx aluminum alloy. 
     
     
         6 . The method of  claim 1 , wherein the pretreatment coating comprises a Ti/Zr or Zr/Cr coating. 
     
     
         7 . The method of  claim 1 , wherein the pretreatment coating comprises a hexafluorotitanate, hexafluorozirconate or chromium sulfate coating. 
     
     
         8 . The method of  claim 1 , further comprising, after the contacting step, applying to the metal surface one or more of a paint, a lacquer, an adhesive, a glue or a bonding compound. 
     
     
         9 . The method of  claim 1 , wherein the aqueous agent comprises a solution of a calcium salt. 
     
     
         10 . The method of  claim 9 , wherein the calcium salt comprises a calcium carbonate, a calcium phosphate, a calcium nitrate or a calcium sulfate. 
     
     
         11 . The method of  claim 1 , wherein the aqueous agent comprises a solution of calcium carbonate. 
     
     
         12 . The method of  claim 11 , wherein the aqueous agent comprises a saturated solution of calcium carbonate. 
     
     
         13 . The method of  claim 1 , wherein the aqueous agent comprises calcium ions in an amount of at least about 7.5 ppm. 
     
     
         14 . The method of  claim 1 , wherein the aqueous agent comprises about 7.5 ppm to 9.8 ppm of calcium ions. 
     
     
         15 . The method of  claim 1 , wherein the aqueous agent comprises calcium ions at saturation. 
     
     
         16 . The method of  claim 1 , wherein the step of contacting the metal surface with the aqueous agent comprises one or more of immersing the metal surface in the agent, rinsing the metal surface with the agent, rolling the agent onto the metal surface, or spraying the metal surface with the agent. 
     
     
         17 . The method of  claim 1 , wherein fluoride ion content is reduced in the pretreatment coating after the contacting step or wherein the calcium ion content is increased in the pretreatment coating after the contacting step. 
     
     
         18 . The method of  claim 1 , wherein the metal surface is rinsed with the aqueous agent in the contacting step, and the weight of the pretreatment coating after the contacting step is greater in comparison to a metal surface coated with the pretreatment coating rinsed with deionized water. 
     
     
         19 . An article of manufacture comprising a metal surface treated by the method of  claim 1 . 
     
     
         20 . The article of manufacture of  claim 19 , wherein the article is an aluminum alloy sheet, a motor vehicle panel, an automotive panel, an electronics panel, an architectural panel or a material comprising an aluminum alloy surface.