Tin-plated steel sheet and method for manufacturing the same

Abstract

A tin-plated steel sheet includes a steel sheet; an Sn-containing plating layer in which the mass per unit area of Sn is 0.05 to 20 g/m 2 disposed on at least one surface of the steel sheet; a first chemical conversion coating which contains P and Sn, in which the mass per unit area of P is 0.3 to 10 mg/m 2 , disposed on the Sn-containing plating layer; and a second chemical conversion coating which contains P and Al, in which the mass per unit area of P is 1.2 to 10 mg/m 2 and the mass per unit area of Al is 0.24 to 8.7 mg/m 2 , disposed on the first chemical conversion coating.

1 . A tin-plated steel sheet comprising:
 a steel sheet;   an Sn-containing plating layer in which the mass per unit area of Sn is 0.05 to 20 g/m 2  disposed on at least one surface of the steel sheet;   a first chemical conversion coating which contains P and Sn, in which the mass per unit area of P is 0.3 to 10 mg/m 2 , disposed on the Sn-containing plating layer; and   a second chemical conversion coating which contains P and Al, in which the mass per unit area of P is 1.2 to 10 mg/m 2  and the mass per unit area of Al is 0.24 to 8.7 mg/m 2 , disposed on the first chemical conversion coating.   
     
     
         2 . A method for manufacturing a tin-plated steel sheet comprising:
 forming an Sn-containing plating layer on at least one surface of a steel sheet so that the mass per unit area of Sn is 0.05 to 20 g/m 2 ;   immersing the steel sheet in a chemical conversion solution containing tetravalent tin ions and phosphate ions or cathodically electrolyzing the steel sheet in the chemical conversion solution;   immersing the steel sheet in a chemical conversion solution containing 5 to 200 g/L of aluminum phosphate monobasic and having a pH of 1.5 to 2.4 or cathodically electrolyzing the steel sheet in the chemical conversion solution; and   drying the steel sheet.   
     
     
         3 . The method according to  claim 2 , wherein the drying is performed at a temperature lower than 60° C.