Method for passivation of strip black plate

Abstract

A process for passivation of strip steel plate, having the following steps: electrochemical treatment of the black plate by passing the black plate through an electrolyte to form an inert steel surface; rinsing the black plate; and application of an aqueous chromium-free treatment solution to at least one surface of the black plate to form a conversion layer that protects against corrosion and an adhesion layer for paints and organic coating materials. The black plate treated in accordance with this process is characterized by high corrosion resistance and has good bonding capacity for paints and organic coatings and therefore is very suitable as a substitute for tin-free steel (TFS or ECCS) and tinplate for the production of packagings, in particular cans. In contrast to the traditional manufacturing and passivation processes for tin-free steel and tinplate, no chromium VI, which is environmentally hazardous and hazardous to health, is used in this process.

What is claimed is: 
     
         1 . Process for passivation of strip black plate, having the following steps:
 electrochemical treatment of the black plate by passing the black plate through an electrolyte to form an inert steel surface,   rinsing the black plate,   application of an aqueous chromium-free treatment solution to at least one surface of the black plate to form a conversion layer that protects against corrosion and a bonding layer for paints and organic coating materials.   
     
     
         2 . Process as in  claim 1 , in which before the electrochemical treatment, the black plate is first degreased, then rinsed, pickled, and again rinsed. 
     
     
         3 . Process as in  claim 1 , in which the black plate is dried after the application of the treatment solution in order to form a dry application weight of the treatment solution on the black plate surface. 
     
     
         4 . Process as in  claim 1 , in which the electrochemical treatment takes place by guiding the black plate through an alkaline electrolyte while connecting the black plate as anode. 
     
     
         5 . Process as in  claim 1 , in which the conversion layer is deposited by applying the aqueous treatment solution in a no-rinse process. 
     
     
         6 . Process as in  claim 5 , in which the aqueous treatment solution is either applied to the black plate without an excess by means of a rotary sprayer or is applied in an excess amount with a roll coater or spray nozzles and then the excess treatment solution is squeezed off with squeeze rolls. 
     
     
         7 . Process as in  claim 3 , in which the drying takes place at 50-250° C. 
     
     
         8 . Process as in  claim 3 , in which the dry applied amount of the treatment solution is subsequently treated with DOS, ATBC, BSO, or a polyalkylene glycol, in particular polyethylene glycol (PEG). 
     
     
         9 . Process as in  claim 3 , in which the dry weight of the treatment solution is between 1 mg/m 2  and 50 mg/m 2 . 
     
     
         10 . Process as in  claim 1 , in which the black plate is moved at a strip speed of at least 200 m/min. 
     
     
         11 . Process as in  claim 1 , in which the black plate is a cold-rolled, annealed, and rerolled, in particular ferritic or multiphase, steel with a carbon content of 20 to 1000 ppm. 
     
     
         12 . Process as in  claim 1 , in which the temperature of the electrolyte in the electrochemical treatment of the black plate is between 20 and 50° C. 
     
     
         13 . Process as in  claim 1 , in which the current density in the electrochemical treatment of the black plate is between 2 and 10 A/dm 2 . 
     
     
         14 . Process as in  claim 1 , in which the aqueous treatment solution is free of chromium and contains at least one of the following components:
 metal components: selected from Ti, Zr, Mn, Zn, P, and combinations thereof;   organic components: selected from polyacrylate, polycarboxylate, and combinations thereof   
     
     
         15 . Process as in  claim 1 , wherein the treatment solution contains at least one bonding agent for paints or organic coating materials, in which the bonding agent in particular has components of maleic acid, isophthalic acid, and cyclohexanedimethanol (CHDM), or combinations thereof. 
     
     
         16 . A packaging steel for production of packagings, in particular cans, comprising a black plate treated by a process in accordance with  claim 1 , with a chromium-free conversion layer on at least one surface of the black plate.