Nonchromate metallic surface-treating agent, nonchromate metallic surface-treating method, and aluminum or aluminum alloy

Abstract

An object of the present invention is to provide a nonchromate metallic surface-treating agent capable of achieving the corrosion resistance and adhesion with a coating film equal to a chromium phosphate surface-treating agent. A nonchromate metallic surface-treating agent comprising a water-soluble zirconium compound and/or a water-soluble titanium compound (1), an organic phosphonic acid compound (2) and a tannin (3), wherein a content of zirconium and/or titanium of said water-soluble zirconium compound and/or the water-soluble titanium compound (1) is 40 to 1000 ppm on a mass basis, a content of said organic phosphonic acid compound (2) is 20 to 500 ppm on a mass basis, a content of said tannin (3) is 200 to 5000 ppm on a mass basis, and a nonchromate metallic surface-treating agent has a pH of 1.6 to 4.0.

1 . A nonchromate metallic surface-treating agent comprising 
 a water-soluble zirconium compound and/or a water-soluble titanium compound (1), an organic phosphonic acid compound (2) and a tannin (3),    wherein a content of zirconium and/or titanium of said water-soluble zirconium compound and/or the water-soluble titanium compound (1) is 40 to 1000 ppm on a mass basis,    a content of said organic phosphonic acid compound (2) is 20 to 500 ppm on a mass basis,    a content of said tannin (3) is 200 to 5000 ppm on a mass basis, and    a nonchromate metallic surface treating-agent has a pH of 1.6 to 4.0.    
     
     
         2 . The nonchromate metallic surface-treating agent according to  claim 1 , wherein 
 said organic phosphonic acid compound is a compound in which phosphorus atom forming a phosphonic group combines with carbon atom.    
     
     
         3 . A nonchromate metallic surface-treating method comprising 
 a step (A) of treating a substrate to be treated with the nonchromate metallic surface-treating agent according to  claim 1  or  2 .    
     
     
         4 . The nonchromate metallic surface-treating method according to  claim 3  comprising 
 an acid cleaning step followed by said step (A).  
 
     
     
         5 . The nonchromate metallic surface-treating method according to  claim 3 , wherein 
 an alkaline cleaning step is performed and then an acid cleaning step is performed before said step (A) is performed.    
     
     
         6 . Aluminum or an aluminum alloy having a coat obtained by the nonchromate metallic surface-treating method according to any of  claims 3  to  5 .  
     
     
         7 . The aluminum or aluminum alloy according to  claim 6 , 
 wherein said coat, after drying, contains said water-soluble zirconium compound and/or the water-soluble titanium compound (1) with zirconium and/or titanium atom of 4.0 to 30 mg/m 2 , by mass per one surface, and said organic phosphonic acid compound (2) with phosphorus atom of 0.05 to 0.3 and said tannin (3) with carbon atom of 0.5 to 3 relative to zirconium and/or titanium atom of said water-soluble zirconium compound and/or said water-soluble titanium compound (1), on a mass basis.