Metal sheet with zinc hydroxysulfate/zinc sulfate-based protection layer

Abstract

A sheet includes a steel substrate; a coating covering at least one face of the steel substrate, the coating comprising zinc, magnesium and aluminum; and a zinc hydroxysulfate/zinc sulfate-based temporary protection layer applied over the coating, the temporary protection layer having a sulfur content greater than or equal to 0.5 mg/m2 and less than or equal to 30 mg/m2.

What is claimed is: 
     
         1 . A sheet comprising:
 a steel substrate;   a coating covering at least one face of the steel substrate, the coating comprising zinc, magnesium and aluminum; and   a zinc hydroxysulfate/zinc sulfate-based temporary protection layer applied over the coating, the temporary protection layer having a sulfur content greater than or equal to 0.5 mg/m 2  and less than or equal to 30 mg/m 2 .   
     
     
         2 . The sheet as recited in  claim 1  wherein the temporary protection layer has a sulfur content greater than or equal to 3.7 mg/m 2  and less than or equal to 27 mg/m 2 . 
     
     
         3 . The sheet as recited in  claim 1  wherein the coating comprises between 0.1 and 10% by weight magnesium and between 0.1 and 20% by weight aluminum. 
     
     
         4 . The sheet as recited in  claim 3  wherein the coating comprises between 2 and 4% by weight magnesium and between 2 and 6% by weight aluminum. 
     
     
         5 . The sheet as recited in  claim 1  wherein the coating consists of zinc, magnesium, aluminum and unavoidable impurities. 
     
     
         6 . The sheet as recited in  claim 1  wherein the coating has a thickness of 10 μm. 
     
     
         7 . The sheet as recited in  claim 1  wherein the coating contains 3% by weight magnesium, 3.7% by weight aluminum and a remainder consisting of zinc and unavoidable impurities.