Autodeposition metal dip coating process

Abstract

What is disclosed is a no-rinse autodeposition process to dip-apply a metal part in an aqueous resin coating bath with an immersion time and, wherein the removal rate of the dipped part is kept equal or below drainage rate of mobile liquid portion, such that upon removal of the part, drip edge formation is minimized and a DFT is maintained within acceptable tolerance levels.

1 . In an autodeposition coating process for forming a coating on a electrochemically active metal substrate which is dipped in an acidic bath, said coating derived from deposition of a dispersed resin in the bath on interaction of multivalent ions entering the aqueous phase, and wherein said substrate is characterized by no rinsing step, and a substrate withdrawal rate that is less than the drainage rate.  
   
   
       2 . The process according to  claim 1  wherein the electrochemically active metal is selected from zinc, iron, aluminum, cold-rolled steel, polished steel, picked steel, hot-rolled steel and galvanized steel.  
   
   
       3 . The process according to  claim 1  wherein said substrate is immersed in said acidic bath for a time of from 20 to 80 seconds before withdrawal.  
   
   
       4 . The process according to  claim 1  wherein said metal substrate is treated with a primer prior to dipping said substrate.  
   
   
       5 . The process of  claim 1  wherein said dispersed resin is a vinyl-based resin.  
   
   
       6 . The process of  claim 1  wherein said resin is a condensation resin.  
   
   
       7 . The process according to  claim 1  wherein the coating has an average nominal dry film thickness of from 0.5 to 3 mils (0.0127 mm to 0.076 mm).  
   
   
       8 . The process according to  claim 1  wherein said acidic bath has a solids content of from 3% to 10%.  
   
   
       9 . The process according to  claim 1  wherein the withdrawal rate is from 1 to 10 ft./min. (30.48 cm. To 25.4 cm.).  
   
   
       10 . The process according to  claim 1  wherein the dry film thickness of said coating has a standard deviation of within 0.05 to 0.16 mils (0.00127 to 004 mm).  
   
   
       11 . The process according to  claim 1  wherein said dispersed resin is based on a polymerizate from monomer selected from the group consisting of styrene and butadiene, acrylate, alkyl-substituted acrylate, vinyl halide monomer, vinylidene halide monomer, alkylene monomer; halide-substituted alkylene monomer and acrylonitrile monomer.  
   
   
       12 . The process according to  claim 11  wherein said dispersed resin is selected from emulsions or dispersions of (poly)butadiene, neoprene, styrene-butadiene rubber, acrylonitrile-butadiene rubber, halogenated polyolefin, acrylic polymer, urethane polymer, epoxy, polyester, ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, styrene-acrylic copolymer, polyamide, and poly(vinyl acetate).  
   
   
       13 . The process according to  claim 1  wherein said dispersed resin is a butadiene latex polymerized in the presence of a compound selected from the group consisting of styrene sulfonic acid, styrene sulfonate, poly(styrene sulfonic acid), or poly(styrene sulfonate).  
   
   
       14 . The process according to  claim 1  wherein said bath comprises a modified phenolic resin and a flexibilizer.  
   
   
       15 . The process according to  claim 4  wherein said primer comprises a phenolic resole, and the coating on said primer comprises a novolak.  
   
   
       16 . The process of  claim 1  wherein the coating polymer is derived from vinyl monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid esters, methacrylic acid esters, vinyl amides, nitriles, vinyl esters, vinyl ethers, vinyl halides, vinylidene halides, vinyl aromatic compounds, other ethylenically unsaturated compounds and combinations thereof.  
   
   
       17 . The process of  claim 14  wherein said flexibilizer is selected from (poly)butadiene, neoprene, styrene-butadiene rubber, nitrile rubber, halogenated polyolefin, acrylic polymer, urethane polymer, ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, styrene-acrylic copolymer, polyamide and poly(vinyl acetate).