Corrosion-proof aluminum material and method for producing the same

Abstract

Provided is a surface treatment technique for a metal base material, which can be applied also to a metal base material in the form of a thin film, can substantially maintain the function of the surface of the metal base material, and provides excellent corrosion resistance and pitting corrosion resistance. The present invention relates to a corrosion-proof aluminum material, including: a metal base material composed of aluminum or an aluminum alloy; and a coating film layer formed with a silane coupling agent having a sulfur atom and disposed on a surface of the metal base material, wherein the ratio of the concentration of sulfur atom in the surface of the coating film layer to the concentration of aluminum atom is 0.4 or more.

What is claimed is: 
     
         1 . A corrosion-proof aluminum material, comprising:
 a metal base material composed of aluminum or an aluminum alloy; and   a coating film layer formed with a silane coupling agent having a sulfur atom and disposed on a surface of the metal base material, wherein   the ratio of the concentration of sulfur atom in the surface of the coating film layer to the concentration of aluminum atom is 0.4 or more.   
     
     
         2 . The corrosion-proof aluminum material according to  claim 1 , wherein the material has a pitting potential in a 3.5 mass % NaCl aqueous solution of −500 mV or more versus a silver-silver chloride electrode (saturated KCl). 
     
     
         3 . The corrosion-proof aluminum material according to  claim 1 , wherein a primer layer composed of an oxide or a hydroxide of the metal base material having a thickness exceeding the thickness of a native oxide of the metal base material is further provided between the metal base material and the coating film layer. 
     
     
         4 . The corrosion-proof aluminum material according to  claim 1 , wherein a primer layer composed of an oxide or a hydroxide of the metal base material having a thickness of 80 Å or more is further provided between the metal base material and the coating film layer. 
     
     
         5 . A method for producing a corrosion-proof aluminum material which includes a metal base material composed of aluminum or an aluminum alloy, and a coating film layer formed with a silane coupling agent having a sulfur atom and disposed on a surface of the metal base material, comprising:
 a coating film layer forming step in which the metal base material is treated with a coating film forming agent containing a silane coupling agent having a sulfur atom to form a coating film layer on a surface of the metal base material, wherein   the ratio of the concentration of sulfur atom in the surface of the coating film layer formed in the coating film layer forming step to the concentration of aluminum atom is 0.4 or more.   
     
     
         6 . The method for producing a corrosion-proof aluminum material according to  claim 5 , wherein the coating film forming agent further contains an oxidizing agent. 
     
     
         7 . The method for producing a corrosion-proof aluminum material according to  claim 5 , wherein the silane coupling agent having a sulfur atom is selected from the group consisting of at least one type of bifunctional polysulfur silane represented by the formula I: 
       
         
           
           
               
               
           
         
         wherein R 1  to R 6  each independently represent a group selected from the group consisting of alkyl and acetyl; Z represents —S x — or -Q 1 -S x -Q 2 -; Q 1  and Q 2  each independently represent a group selected from the group consisting of a divalent aliphatic group and an aromatic group; x represents an integer of 2 to 9, at least one type of multifunctional mercapto-substituted silane represented by the formula II: 
       
       
         
           
           
               
               
           
         
         wherein R 7  represents alkoxy; R 8  and R 9  each independently represent hydrogen or a group selected from the group consisting of alkyl and alkoxy; and n represents an integer of 0 to 10, and at least one type of thioester compound represented by the formula III: 
       
       
         
           
           
               
               
           
         
         wherein R 10  represents alkoxy; R 11  and R 12  each independently represent hydrogen or a group selected from the group consisting of alkyl and alkoxy; R 13  represents alkyl; and m represents an integer of 0 to 10, and a mixture thereof. 
       
     
     
         8 . The method for producing a corrosion-proof aluminum material according to  claim 7 , wherein the silane coupling agent having a sulfur atom is at least one type of bifunctional polysulfur silane selected from the group consisting of bis(3-triethoxypropyl)tetrasulfide, bis(3-triethoxypropyl)disulfide, bis(2-triethoxyethyl)tetrasulfide, bis(4-triethoxybutyl)disulfide, bis(3-trimethoxypropyl)tetrasulfide, and bis(2-trimethoxyethyl)disulfide, and a mixture thereof. 
     
     
         9 . The method for producing a corrosion-proof aluminum material according to  claim 7 , wherein the silane coupling agent having a sulfur atom is at least one type of multifunctional mercapto-substituted silane selected from the group consisting of 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-mercaptopropylmethyldimethoxysilane, and 2-mercaptoethyltriethoxysilane, and a mixture thereof. 
     
     
         10 . The method for producing a corrosion-proof aluminum material according to  claim 7 , wherein the silane coupling agent having a sulfur atom is a mixture of the bifunctional polysulfur silane and the multifunctional mercapto-substituted silane.