Surface treatment agent composition, method for producing surface-treated steel sheet, surface-treated steel-sheet, surface-treated steel sheet with organic coating, can lid, can body, and seamless can

Abstract

A surface treatment agent composition for non-chromium steel sheets for removing iron ions without reducing the amount of aluminum ions when subjecting the steel sheet to surface treatment by means of cathodic electrolysis using a surface treatment agent containing aluminum ions as the main component; and a method for producing a surface-treated steel sheet using the composition. A surface-treated steel sheet exhibiting high corrosion resistance, a surface-treated steel sheet with an organic coating, and a can lid, can body and seamless can produced using the surface-treated steel sheets. A surface treatment agent composition for steel sheets contains aluminum ions, fluorine ions and polycarboxylic acid and is used as the surface treatment bath used for forming a surface treatment coating film on the surface of the steel sheet by cathodic electrolysis.

1 . A surface treatment agent composition for a steel sheet, the composition being used in electrolytic surface treatment of a steel sheet having a surface to which iron is at least partially exposed, and the composition comprising aluminum ions, fluorine ions, and a polycarboxylic acid. 
     
     
         2 . The surface treatment agent composition for a steel sheet according to  claim 1 , wherein the polycarboxylic acid is a homopolymer containing a monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, and itaconic acid as a constitutional unit or a copolymer containing at least one of these monomers as the constitutional unit. 
     
     
         3 . The surface treatment agent composition for a steel sheet according to  claim 1 , wherein a ratio [carboxyl group]/[Al] of a molar concentration [carboxyl group] of carboxyl groups contained in the polycarboxylic acid to a molar concentration [Al] of the aluminum ions is 0.005 to 2.0. 
     
     
         4 . The surface treatment agent composition for a steel sheet according to  claim 1 , wherein the polycarboxylic acid is polyitaconic acid. 
     
     
         5 . The surface treatment agent composition for a steel sheet according to  claim 1 , wherein a ratio [F]/[Al] of a molar concentration [F] of the fluorine ions to a molar concentration [Al] of the aluminum ions is 1 to 4. 
     
     
         6 . The surface treatment agent composition for a steel sheet according to  claim 1 , wherein a mass concentration of the aluminum ions is 100 to 10000 ppm. 
     
     
         7 . The surface treatment agent composition for a steel sheet according to  claim 1 , wherein the surface treatment agent composition has a pH value of 1 to 5 at 25° C. 
     
     
         8 . The surface treatment agent composition for a steel sheet according to  claim 1 , wherein the surface treatment agent composition contains iron ions having a mass concentration of 200 ppm or less. 
     
     
         9 . A method of producing a surface-treated steel sheet, comprising subjecting a steel sheet having a surface to which iron is at least partially exposed to cathodic electrolysis in a surface treatment bath containing aluminum ions, fluorine ions, and a polycarboxylic acid to form a treatment film on the surface of the steel sheet, wherein
 the treatment film contains a metal-oxygen compound and a polycarboxylic acid;   the metal-oxygen compound contains oxygen compounds of aluminum and iron in which the main component is the aluminum-oxygen compound; and   the treatment film has an aluminum amount of 5 to 150 mg/m 2  and a carbon amount of 0.1 to 5.0 mg/m 2 , in terms of metal element.   
     
     
         10 . The method of producing a surface-treated steel sheet according to  claim 9 , wherein the polycarboxylic acid is a homopolymer containing a monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, and itaconic acid as a constitutional unit or a copolymer containing at least one of these monomers as the constitutional unit. 
     
     
         11 . The method of producing a surface-treated steel sheet according to  claim 9 , wherein in the surface treatment bath, a ratio [carboxyl group]/[Al] of a molar concentration [carboxyl group] of carboxyl groups contained in the polycarboxylic acid to a molar concentration [Al] of the aluminum ions is 0.005 to 2.0. 
     
     
         12 . The method of producing a surface-treated steel sheet according to  9 , wherein the polycarboxylic acid is polyitaconic acid. 
     
     
         13 . The method of producing a surface-treated steel sheet according to  claim 9 , wherein in the surface treatment bath, a ratio [F]/[Al] of a molar concentration [F] of the fluorine ions to a molar concentration [Al] of the aluminum ions is 1 to 4. 
     
     
         14 . The method of producing a surface-treated steel sheet according to  claim 9 , wherein in the surface treatment bath, a mass concentration of the aluminum ions is 100 to 10000 ppm. 
     
     
         15 . The method of producing a surface-treated steel sheet according to  claim 9 , wherein the surface treatment bath has a pH value of 1 to 5 at 25° C. 
     
     
         16 . The method of producing a surface-treated steel sheet according to  9 , wherein the surface treatment bath contains iron ions having a mass concentration of 200 ppm or less. 
     
     
         17 . A surface-treated steel sheet comprising a surface treatment film containing a metal-oxygen compound and a polycarboxylic acid formed on a steel sheet having a surface to which iron is at least partially exposed, wherein
 the metal-oxygen compound contains aluminum and iron and mainly includes an aluminum-oxygen compound; and   the surface treatment film has an aluminum amount of 5 to 150 mg/m 2  and a carbon amount of 0.1 to 5.0 mg/m 2 , in terms of metal element.   
     
     
         18 . The surface-treated steel sheet according to  claim 17 , wherein the surface treatment film has an atomic ratio (Fe/Al) of iron to aluminum of 0.5 or less. 
     
     
         19 . The surface-treated steel sheet according to  claim 17 , wherein the polycarboxylic acid is a homopolymer containing a monomer selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, and itaconic acid as a constitutional unit or a copolymer containing at least one of these monomers as the constitutional unit. 
     
     
         20 . A surface-treated steel sheet with an organic coating, comprising a surface-treated steel sheet according to  claim 17  and a thermoplastic resin laminated on at least one surface of the steel sheet. 
     
     
         21 . A surface-treated steel sheet with an organic coating, comprising a surface-treated steel sheet according to  claim 17  and a thermosetting resin laminated on at least one surface of the steel sheet. 
     
     
         22 . A can lid molded from a surface-treated steel sheet with an organic coating according to  claim 20 . 
     
     
         23 . A can body molded from a surface-treated steel sheet with an organic coating according to  claim 20 . 
     
     
         24 . A seamless can molded from a surface-treated steel sheet with an organic coating according to  claim 20  by drawing/bending-stretching and/or ironing.