One-step pretreatment method of metallic substrates for metal cold forming

Abstract

Disclosed herein is a method for pretreatment of a metallic substrate for a subsequent metal cold forming process, said method including (1) providing at least one substrate, (2) contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A). and optionally (3) drying the coating film obtained after having performed step (2). Further disclosed herein are a pretreated metallic substrate obtainable by the aforementioned method, a method of cold forming of a metallic substrate including a step of subjecting the inventive pretreated metallic substrate to a cold forming process, an aqueous lubricant composition (A) as defined above, and a master batch for preparing the aqueous composition (A).

1 . A method for pretreatment of a metallic substrate for a subsequent metal cold forming process, said method comprising at least steps (1) and (2) and optionally step (3),
 (1) providing at least one substrate having at least one surface at least partially made of at least one metal,   (2) contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A) having a pH value below 2.0, wherein the aqueous lubricant composition (A) comprises, in addition to water:
 (a1) oxalate anions, 
 (a2) thiosulfate anions, 
 (a3) chloride anions, 
 (a4) at least one film-forming polymer, which is a homopolymer and/or copolymer being prepared by polymerization of at least one ethylenically unsaturated monomer, 
 (a5) at least one wax, which is different from constituent (a4), and 
 (a6) fluoride anions and/or bifluoride anions, 
   and   (3) optionally drying the coating film obtained after having performed step (2).   
     
     
         2 . The method according to  claim 1 , characterized in that composition (A) has a pH value below 1.9. 
     
     
         3 . The method according to  claim 1 , characterized in that the at least one film-forming polymer (a4) is a homopolymer and/or copolymer, said homopolymer and/or copolymer prepared from at least one monomer selected from the group consisting of vinyl amine, vinyl alcohol, vinyl formamide, vinyl pyrrolidone, vinyl caprolactam, vinyl acetate and vinyl imidazole. 
     
     
         4 . The method according to  claim 1 , characterized in that the at least one film-forming polymer (a4) is present in the composition (A) in an amount in the range of from 0.05 to 20 wt.-% based on the total weight of the composition (A). 
     
     
         5 . The method according to  claim 1 , characterized in that the at least one wax (a5) is selected from the group consisting of polyolefin waxes, paraffin waxes and natural waxes, and mixtures thereof. 
     
     
         6 . The method according to  claim 1 , characterized in that the at least one wax (a5) is present in the composition (A) in an amount in the range of from 0.1 to 20 wt.-%, based on the total weight of the composition (A). 
     
     
         7 . The method according to  claim 1 , characterized in that
 oxalate anions (a1) are present in the composition (A) in an amount in the range of from 2 to 500 g/l calculated as oxalic acid dihydrate, and/or   thiosulfate anions (a2) are present in the composition (A) in an amount in the range of from 0.01 to 25 g/l, calculated as sodium thiosulfate, and/or   chloride anions (a3) are present in the composition (A) in an amount in the range of from 0.1 to 25 g/l, calculated as sodium chloride.   
     
     
         8 . The method according to  claim 1 , characterized in that composition (A) comprises at least one of fluoride anions and bifluoride anions as constituent (a6) in each case independently of one another in an amount in the range of from 0.01 to 25 g/l, calculated as sodium fluoride in case of fluoride anions and as sodium bifluoride in case of bifluoride anions. 
     
     
         9 . The method according to  claim 1 , characterized in that contacting step (2) is performed by at least partially dipping the substrate into a bath containing the aqueous lubricant composition (A) having a bath temperature in the range of from 20 to 95° C. 
     
     
         10 . The method according to  claim 1 , characterized in that the at least one surface of the substrate is at least partially made of stainless steel. 
     
     
         11 . A pretreated metallic substrate obtained by the method according to  claim 1 . 
     
     
         12 . The pretreated metallic substrate according to  claim 11 , characterized in that the coating film present on the surface of the substrate after having performed step (2) and optionally step (3) has a coating weight in a range of from 1.0 to 40.0 g/m 2 . 
     
     
         13 . A method of cold forming a metallic substrates comprising a step of subjecting the pretreated metallic substrate according to  claim 11  to a cold forming process. 
     
     
         14 . An aqueous lubricant composition (A) as defined in  claim 1 . 
     
     
         15 . A master batch to produce the aqueous composition (A) according to  claim 14  by diluting the master batch with water and if applicable by adjusting the pH value. 
     
     
         16 . The method according to  claim 1 , characterized in that the at least one film-forming polymer (a4) is a homopolymer and/or copolymer, said homopolymer and/or copolymer being prepared from at least one monomer selected from the group consisting of vinyl pyrrolidone and vinyl acetate. 
     
     
         17 . The method according to  claim 1 , characterized in that the at least one film-forming polymer (a4) is a homopolymer and/or copolymer, said homopolymer and/or copolymer being prepared from vinyl pyrrolidone. 
     
     
         18 . The method according to  claim 1 , characterized in that the at least one film-forming polymer (a4) is present in the composition (A) in an amount in the range of from 0.10 to 15 wt.-% based on the total weight of the composition (A). 
     
     
         19 . The method according to  claim 1 , characterized in that the at least one wax (a5) is selected from the group consisting of polyethylene waxes, polypropylene waxes, montan waxes, bee waxes, carnauba waxes, and mixtures thereof. 
     
     
         20 . The method according to  claim 1 , characterized in that the at least one wax (a5) is present in the composition (A) in an amount in the range of from 0.5 to 15 wt.-% based on the total weight of the composition (A).