Electrolyte for the galvanic deposition of aluminium from aprotic solvents in a plating barrel

Abstract

The invention relates to an electrolyte for the electrodeposition of aluminium from aprotic solvents containing a compound of the formula: N(R 1 ) 4 X.(m-n-o)Al(C 2 H 5 ) 3 .nAlR 2 3 oAlR 3 3 , wherein R 1 is a C 1 to C 4 alkyl group, X is F, Cl or Br, m is equal to 1 to 3, preferably 1.7 to 2.3, n is equal to 0.0 to 1.5, preferably 0.0 to 0.6, o is equal to 0.0 to 1.5, preferably 0.0 to 0.6, R 2 , R 3 is a C 1 or C 3 to C 6 alkyl group, wherein R 2 is unequal to R 3 , in an organic solvent. A further object of the invention is a method for producing the electrolyte, a method for coating and the coated material parts.

1 . An electrolyte for the electrodeposition of aluminium from aprotic solvents containing a compound of the formula:
   N(R 1 ) 4 X.( m - n - o )Al(C 2 H 5 ) 3   .n AlR 2   3   .o AlR 3   3 ,  (I)   
     wherein
 R 1  is a C 1  to C 4  alkyl group, 
 X is equal to F, Cl or Br, 
 m is equal to 1.7 to 3, preferably 1.7 to 2.3, 
 n is equal to 0.0 to 0.6, 
 o is equal to 0.0 to 1.5, preferably 0.0 to 0.6, 
 R 2 , R 3  is a C 1  or C 3  to C 6  alkyl group, wherein R 2  is unequal to R 3  in an organic solvent. 
 
   
   
       2 . The electrolyte according to  claim 1 , wherein the electric conductivity of the electrolyte is greater than 25 mS/cm at 95° C. 
   
   
       3 . The electrolyte according to  claim 1  wherein the organic solvent is selected from the group consisting of toluene, xylene or benzene and mixtures thereof. 
   
   
       4 . The electrolyte according to  claim 1 , wherein the solvent is at a concentration of 1 to 4 mol per mol of compound. 
   
   
       5 . The electrolyte as claimed in  claim 1 , wherein the compound has the composition N(C 2 H 5 ) 4 Cl.2Al(C 2 H 5 ) 3 .2 toluene. 
   
   
       6 . The electrolyte as claimed in  claim 1 , wherein the compound has the composition N(C 2 H 5 ) 4 Cl.1.5Al(C 2 H 5 ) 3 .0.5Al(CH 3 ) 3 .2 toluene or N(C 2 H 5 ) 4 Cl.1.5Al(C 2 H 5 ) 3 .0.5Al(C 4 H 9 ) 3 .2 toluene. 
   
   
       7 . A method to produce the electrolyte as claimed in  claim 1 , comprising the following process steps:
 i) drying of the compound N(R 1 ) 4 X in order to remove humidity,   ii) preparing a suspension from the dried compound N(R 1 ) 4 X in an organic aprotic solvent, and   iii) adding the aluminium alkyls or the mixtures of aluminium alkyls by dropwise addition during cooling until a clear solution is obtained,   wherein   R 1  is a C 1  to C 4  alkyl group, and   X is equal to F, Cl or Br.   
   
   
       8 . A method for the electrodeposition of aluminium on material parts comprising placing the material parts in the electrolyte according to  claim 1 , wherein aluminum is electrodeposited on said material parts. 
   
   
       9 . The method claimed in  claim 8 , wherein the material parts are selected from the group of materials consisting of metals, alloys, ceramics, plastics, and composite materials made of one or more of said materials. 
   
   
       10 . The method as claimed in  claim 8 , wherein the material parts to be coated are placed inside a coating barrel and are coated with aluminium therein. 
   
   
       11 . A method for coating material parts with aluminium, comprising the following process steps:
 i) placing the parts to be coated into a coating barrel,   ii) dipping the coating barrel into an electrolyte according to  claim 1 ,   iii) applying a cathodic current to the coating barrel and an anodic current at the Al-electrodes that are located according to  claim 1 , wherein aluminium de-posits itself on the parts present in the coating barrel,   iv) coating the parts with aluminium,   v) removing the parts from the coating barrel and drying the parts.   
   
   
       12 . Aluminium-coated parts produced by the method according to  claim 11 .