Electrocoating chrome-plated steel

Abstract

Steel cabinet parts and other steel objects are electrocoated in a cationic resin-containing bath. The steel objects are chromium-coated, free of phosphate and preferably free of chromium oxide. The products are not significantly subject to filiform corrosion, and the process is economically beneficial because throwpower is more easily controlled than in previous processes.

1 - 10 . (canceled)  
   
   
       11 . An appliance cabinet part comprising a piece of steel strip having a chromium undercoat and being substantially free of phosphate, said piece of steel strip being formed into a three-dimensional shape suitable for an appliance cabinet part and having a coating of crosslinked cationic polymer deposited from an aqueous electrolytic bath.  
   
   
       12 . An appliance cabinet Dart of  claim 11  characterized by resistance to filaform corrosion.  
   
   
       13 . An appliance cabinet part of  claim 11  characterized by resistance to detergence.  
   
   
       14 - 20 . (canceled)  
   
   
       21 . An appliance cabinet preform made by the method comprising (a) providing a steel strip, said steel strip having a chromium coating and being substantially free of phosphate, (b) rinsing said steel strip in an alkaline solution, thereby stripping said steel of chromium oxide, (c) forming a portion of said steel strip into a desired three-dimensional shape which is at least part of an incipient appliance cabinet preform, (d) immersing said three-dimensional shape as a cathode into an electrolytic cell containing an aqueous coating bath comprising a cationic polymer (e) holding said three-dimensional shape in said electrolytic cell under coating conditions for a residence time sufficient to form an adherent coating on said three-dimensional shape, (f) removing said three-dimensional shape from said bath, and (g) baking said three-dimensional shape including said adherent coating.  
   
   
       22 . Appliance cabinet preform of  claim 21  wherein said chromium coating comprises from 2 to 20 mg/ft 2  chromium metal per square foot of surface.  
   
   
       23 . Appliance cabinet preform of  claim 21  wherein said three-dimensional shape is cleaned between step (f) and step (g).  
   
   
       24 . Appliance cabinet preform of  claim 21  wherein said steel strip has an open cell potential lower than −500 mV SCE .  
   
   
       25 . Appliance cabinet perform of  claim 21  wherein said electrolytic cell has a carbon anode and is operated with direct current.  
   
   
       26 . Appliance cabinet perform of  claim 21  wherein said bath includes a pigment.  
   
   
       27 . Appliance cabinet perform of  claim 21  wherein said bath includes a crosslinker.  
   
   
       28 . An appliance cabinet perform made by a process comprising (a) providing an incipient steel appliance cabinet perform free of phosphate and having a chromium layer substantially free of chromium oxide, said steel having an open cell potential lower than −500 mV SCE , (b) placing said incipient steel appliance cabinet preform in an electrolytic bath including an organic cationic polymer, and (c) electrolytically coating said incipient steel appliance cabinet preform in said bath with a coating including said cationic polymer.  
   
   
       29 . The appliance cabinet preform of  claim 28  wherein said incipient steel appliance cabinet perform is made of electrolytic chrome/chrome oxide steel which has been treated to remove substantially all the chrome oxide.