Process to deposit zinc-iron alloy layer material

Abstract

A process for depositing a zinc-iron alloy layer material having a body centred cubic crystal structure of the Γ-phase, a (330) texture and an iron content of 12 to 20 wt.-% including the steps (i) providing a metallic substrate, (ii) contacting the substrate with an alkaline aqueous zinc-iron alloy plating bath containing 4 to 6 g/l zinc ions, 1 to 3 g/l iron ions, 25 to 35 g/l hydroxyl ions, 0.5 to 2.5 g/l of a quaternary ammonium polymer and at least one complexing agent selected from the group consisting of hydroxyl carboxylic acids and salts thereof and simultaneously applying a current to the substrate. The zinc alloy layer material provides a high corrosion protection to metallic substrates, has a high hardness and a bright appearance.

1 . A process for depositing a zinc-iron alloy layer material having a body centred cubic crystal structure of the Γ-phase, a (330) texture and an iron content of 12 to 20 wt.-% comprising the steps
 (i) providing a metallic substrate, 
 (ii) contacting the substrate with an alkaline aqueous zinc-iron alloy plating bath comprising 
 4 to 6 g/l zinc ions 
 1 to 3 g/l iron ions 
 25 to 35 g/l hydroxyl ions, 
 0.5 to 2.5 g/l of a quaternary ammonium polymer and 
 at least one complexing agent selected from the group consisting of hydroxyl carboxylic acids and salts thereof and 
 simultaneously applying a current to the substrate. 
 
     
     
         2 . The process according to  claim 1  wherein the quaternary ammonium polymer is an ureylene quaternary ammonium polymer according to formula (1): 
       
         
           
           
               
               
           
         
         wherein m is 2 or 3, n is at least 2, R1, R2, R3 and R4 are the same and are selected from methyl, ethyl and hydroxyethyl, p ranges from 3 to 12 and X− is selected from Cl−, Br− and I−. 
       
     
     
         3 . The process according to  1  the alkaline aqueous zinc-iron alloy plating bath further comprises an alkanolamine compound. 
     
     
         4 . The process according to  2  the alkaline aqueous zinc-iron alloy plating bath further comprises an alkanolamine compound. 
     
     
         5 . The process according to  claim 3  wherein the alkanolamine compound is selected from monoethanolamine, diethanolamine, triethanolamine, propanolamine, N-methylethanolamine and N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylenediamine. 
     
     
         6 . The process according to  claim 4  wherein the alkanolamine compound is selected from monoethanolamine, diethanolamine, triethanolamine, propanolamine, N-methylethanolamine and N,N,N′,N′-tetrakis-(2-hydroxypropyl)-ethylenediamine. 
     
     
         7 . The process according to  claim 3  wherein the concentration of the alkanolamine compound ranges from 8 to 20 g/l. 
     
     
         8 . The process according to  claim 4  wherein the concentration of the alkanolamine compound ranges from 8 to 20 g/l.