Surface preparation and polymeric coating of continuous-strip flat-rolled steel and coated product

Abstract

Engineered composite coated flat-rolled steel strip is produced in continuous line operations, in which flat-rolled steel strip, free of surface iron oxide, having a metallic corrosion-protective coating, is polymer coated in continuous-line operations in which a plurality of adherent thin-film layers of polymeric material are deposited on a strip surface. In a dual-surface polymeric coating embodiment, each surface is separately-pretreated for surface adhesion, solidified, and polymeric overhang is removed. Finish processing re-melts the polymer coating and rapidly cools that coating through glass-transition temperature to establish amorphous characteristics in the polymeric coating materials. An anhydride-modified polypropylene, first contacts the strip, an intermediate layer can include about fifteen to twenty five percent, by weight, polybutylene with the balance polypropylene; an outer surface polymeric layer includes about five to ten percent, by weight, polybutylene with the balance polypropylene.

1 - 11 . (canceled)  
   
   
       12 . Continuous-line apparatus for polymeric coating of continuous-strip flat-rolled steel substrate, comprising: 
 A) means for supplying rigid flat-rolled steel continuous-strip, of predetermined width between longitudinally-extending lateral edges thereof, presenting a pair of substantially-planar opposed metallic substrate surfaces for continuous-line polymeric coating operations,    B) pre-treatment means for activating a single substrate surface at-a-time for polymeric coating, by selecting from the group consisting of: 
 i) solely a single surface of said strip, and  
 ii) said pair of opposed surfaces, which includes means for separate pre-treatment of each said surface for polymeric coating; and in which  
 iii) said pre-treatment means for a single surface at-a-time, are selected from the group consisting of: 
 a) means for producing open-flame impingement of said substrate surface,  
 b) corona-discharge means for ionizing gaseous atmosphere contiguous to said substrate surface, and  
 c) a combination of (a) and (b);  
 
   C) means supplying thermoplastic polymers capable of molding into distinct polymeric coating materials for use in said continuous-line operations;    D) means for heating and pressurizing each said distinct polymeric coating material to enable molten extrusion;    E) means directing continuous-strip travel presenting a single activated substrate surface for polymeric coating free of heating requirements for said strip;    F) means for simultaneously extruding said molten polymeric coating materials, as adherent thin-film layers 
 i) extending across full pre-treated surface width of said strip, and  
 ii) extending further to form a polymeric overhand extending beyond each lateral edge of said pre-treated surface, by  
 iii) selecting from the group consisting of 
 a) association with solely a single pre-treated substrate surface, and  
 b) association separately with each said surface, as separately pre-treated.  
 
   
   
   
       13 - 17 . (canceled)