Hot-dip zn-alloy-plated steel sheet and method for producing same

Abstract

This hot-dip Zn-alloy-plated steel sheet comprises: a steel sheet; and a hot-dip Zn-alloy-plated layer arranged on a surface of the steel sheet. The entire surface of the hot-dip Zn-alloy-plated layer satisfies the following formula (1): S[Zn(OH) 2 ]/(S[Zn(OH) 2 ]+S[Zn])×100≦40. In formula (1): S[Zn] is the area exhibited by a peak having a center at approximately 1022 eV ascribable to metallic Zn in an intensity profile in XPS analysis of the surface of the hot-dip Zn-alloy-plated layer; and S[Zn(OH) 2 ] is the area exhibited by a peak having a center at approximately 1023 eV ascribable to Zn(OH) 2 in an intensity profile in XPS analysis of the surface of the hot-dip Zn-alloy-plated layer.

1 . A hot-dip Zn alloy-plated steel sheet comprising:
 a steel sheet; and   a hot-dip Zn alloy plating layer disposed on a surface of the steel sheet,   wherein the hot-dip Zn alloy plating layer satisfies, at a whole of a surface of the hot-dip Zn alloy plating layer, following Equation 1:   
       
         
           
             
               
                 
                   
                     
                       
                         
                           S 
                            
                           
                             [ 
                             
                               
                                 Zn 
                                  
                                 
                                   ( 
                                   OH 
                                   ) 
                                 
                               
                               2 
                             
                             ] 
                           
                         
                         
                           
                             S 
                              
                             
                               [ 
                               
                                 
                                   Zn 
                                    
                                   
                                     ( 
                                     OH 
                                     ) 
                                   
                                 
                                 2 
                               
                               ] 
                             
                           
                           + 
                           
                             S 
                              
                             
                               [ 
                               Zn 
                               ] 
                             
                           
                         
                       
                       × 
                       100 
                     
                     ≤ 
                     40 
                   
                 
                 
                   
                     ( 
                     
                       Equation 
                        
                       
                           
                       
                        
                       1 
                     
                     ) 
                   
                 
               
             
           
         
         S[Zn] is a peak area derived from metal Zn and centered at approximately 1022 eV in an intensity profile of XPS analysis of the surface of the hot-dip Zn alloy plating layer; and S[Zn(OH) 2 ] is a peak area derived from Zn(OH) 2  and centered at approximately 1023 eV in the intensity profile of XPS analysis of the surface of the hot-dip Zn alloy plating layer. 
       
     
     
         2 . The hot-dip Zn alloy-plated steel sheet according to  claim 1 , wherein:
 the hot-dip Zn alloy plating layer comprises 1.0 to 22.0% by mass of Al, 0.1 to 10.0% by mass of Mg, and the balance of the hot-dip Zn alloy plating layer being Zn and unavoidable impurities.   
     
     
         3 . The hot-dip Zn alloy-plated steel sheet according to  claim 2 , wherein:
 the hot-dip Zn alloy plating layer further comprises at least one selected from the group consisting of 0.001 to 2.0% by mass of Si, 0.001 to 0.1% by mass of Ti, and 0.001 to 0.045% by mass of B.   
     
     
         4 . A method of producing a hot-dip Zn alloy-plated steel sheet comprising:
 dipping a base steel sheet in a hot-dip Zn alloy plating bath to form a hot-dip Zn alloy plating layer on a surface of the base steel sheet; and   contacting an aqueous solution containing a water-soluble corrosion inhibitor with a surface of the hot-dip Zn alloy plating layer to cool the base steel sheet and the hot-dip Zn alloy plating layer having a raised temperature through formation of the hot-dip Zn alloy plating layer,   wherein a temperature of the surface of the hot-dip Zn alloy plating layer when the aqueous solution is to be contacted with the surface of the hot-dip Zn alloy plating layer is equal to or more than 100° C. and equal to or less than a solidifying point of the plating layer; and   wherein the aqueous solution containing the water-soluble corrosion inhibitor satisfies following Equation 2:   
       
         
           
             
               
                 
                   
                     
                       
                         
                           
                             Z 
                             0 
                           
                           - 
                           
                             Z 
                             1 
                           
                         
                         
                           Z 
                           0 
                         
                       
                       × 
                       100 
                     
                     ≥ 
                     20 
                   
                 
                 
                   
                     ( 
                     
                       Equation 
                        
                       
                           
                       
                        
                       2 
                     
                     ) 
                   
                 
               
             
           
         
         Z 0  is a corrosion current density of the hot-dip Zn alloy-plated steel sheet measured in a 0.5 M NaCl aqueous solution not containing the water-soluble corrosion inhibitor, and Z 1  is a corrosion current density of the hot-dip Zn alloy-plated steel sheet measured in the aqueous solution containing the water-soluble corrosion inhibitor, in which NaCl is further dissolved so that a final concentration of NaCl is 0.5 M.