Painted steel sheet provided with a zinc coating

Abstract

A steel sheet is provided with a coating having at least one layer of zinc and a top layer of paint applied by cataphoresis. The zinc layer is deposited by a jet vapor deposition process in a deposition chamber maintained at a pressure between 6·10−2 mbar and 2·10−1 mbar. A fabrication method and an installation are also provided.

What is claimed is: 
     
         1 . A coated steel sheet, the coating comprising:
 at least one layer of zinc, wherein the at least one layer of zinc includes a layer of pure zinc and unavoidable impurities acquired during production and present in trace quantities; and   a top layer of paint applied by cataphoresis;   the at least one layer of zinc being the top layer of the coating before the application of the paint layer,   the at least one layer of zinc being a layer deposited by a jet vapor deposition process in a deposition chamber maintained at a pressure P chamber  between 6·10 −2  mbar and 2·10 −1  mbar.   
     
     
         2 . The coated sheet according to  claim 1 , wherein the jet vapor deposition process further includes maintaining an ejection chamber that is located inside the deposition chamber at a pressure P eject , a ratio of the pressure P chamber  to P eject  being between 2·10 −3  and 5.5·10 −2 . 
     
     
         3 . The coated steel sheet according to  claim 1 , wherein the coated steel is a Very High Strength steel. 
     
     
         4 . A method for the fabrication of a coated and painted sheet comprising the steps of:
 providing a sheet in a deposition chamber;   maintaining a pressure P chamber  inside a deposition chamber between 6·10 −2  mbar and 2·10 −1  mbar; and   coating the sheet with a sonic vapor jet of zinc inside the deposition chamber, said zinc consisting of pure zinc and unavoidable impurities acquired during production and present in trace quantities;   painting the coated sheet.   
     
     
         5 . The method according to  claim 4 , further comprising the step of:
 maintaining an ejection chamber that is located inside the deposition chamber at a pressure P eject , a ratio of the pressure P chamber  to P eject  being between 2·10 −3  and 5.5·10 −2 .   
     
     
         6 . The method according to  claim 4 , wherein a distance between an upper portion of a slot of the ejection chamber and the steel sheet to be coated is between 20 and 60 mm. 
     
     
         7 . The method according to  claim 4 , wherein said painting includes applying a top layer of paint over the zinc coating by cataphoresis. 
     
     
         8 . The method according to  claim 4 , wherein said painting includes applying a cataphoresis layer. 
     
     
         9 . The method according to  claim 8 , wherein said painting includes applying a phosphate layer prior to application of the cataphoresis layer. 
     
     
         10 . The method according to  claim 8 , wherein said applying the cataphoresis layer comprises quenching the sheet in a cataphoresis bath. 
     
     
         11 . The method according to  claim 10 , wherein prior to said quenching, the sheet is subjected to a phosphate treatment. 
     
     
         12 . The method according to  claim 4 , wherein said painting includes applying a layer of primer paint to the sheet. 
     
     
         13 . The method according to  claim 10 , wherein after said quenching, a layer of primer paint is applied to the sheet. 
     
     
         14 . The method according to  claim 11 , wherein the phosphate treatment applies a phosphate layer having a weight between 1.5 and 5 g/m 2 . 
     
     
         15 . The method according to  claim 10 , wherein said cataphoresis bath provides a cataphoresis layer with a thickness of 15 to 25 μm. 
     
     
         16 . The method according to  claim 7 , wherein the top layer of paint is applied directly over the zinc coating by cataphoresis. 
     
     
         17 . An installation for coating a steel sheet comprising:
 a deposition chamber having a pressure P chamber  maintained between 6·10 −2  mbar and 2·10 −1  mbar;   a steel sheet running through the deposition chamber maintained at said pressure P chamber ;   a sonic vapor jet for coating the steel sheet with at least one layer of zinc inside the deposition chamber, said zinc consisting of pure zinc and unavoidable impurities acquired during production and present in trace quantities; and   a cataphoresis bath, a top layer of paint applied to the steel sheet by cataphoresis.   
     
     
         18 . The installation according to  claim 17 , wherein the at least one zinc layer is a top layer of the coating before the application of the paint layer. 
     
     
         19 . The installation according to  claim 17 , further comprising:
 an ejection chamber located inside the deposition chamber, the ejection chamber having a pressure P eject  between 2·10 −3  and 5.5·10 −2 .   
     
     
         20 . The installation according to  claim 17 , wherein a distanced between an upper portion of a slot of the ejection chamber and the steel sheet to be coated is between 20 and 60 mm.