A water-based composition for post-treatment of metal surfaces

Abstract

A water-based composition for post-treatment of metal surfaces, preferably a silver or silver alloy surface, including: an alkanethiol an anionic, cationic, non-ionic, amphoteric or zwitterionic surfactant with a HLB value of 12 to 18, a compound of the general formula I: wherein R 1 is —H, —CH 3 , —C 2 H 5 , —(C 2 H 4 O) p —H, —(C 2 H 4 O) p —CH 3 , —(C 2 H 4 O) p —CH(CH 3 ) 2 , —(C 2 H 4 ) p —C(CH 3 ) 3 , wherein p is 1 to 20, R 2 is H, or CH 3 n is an integer in the range of 0 to 3, m is an integer in the range of 0 to 2.

1 . A water-based composition for post-treatment of metal surfaces, comprising
 an alkanethiol,   an anionic, cationic, non-ionic, amphoteric or zwitterionic surfactant with a HLB value of 12 to 18,   characterized in that the water-based composition further contains   a compound of the general formula I:   
       
         
           
           
               
               
           
         
         wherein 
         R 1  is —H, —CH 3 , —C2H 5 , —(C 2 H 4 O) p —H, —(C 2 H 4 O) p —CH 3 , -(C 2 H 4 O) p —CH(CH 3 ) 2 , —(C 2 H 4 O) p —C(CH 3 ) 3 , wherein p is an integer in the range of 1 to 20, 
         R2 is H or CH 3 , 
         n is an integer in the range of 0 to 3, 
         m is an integer in the range of 0, 1 or 2. 
       
     
     
         2 . The water-based composition according to  claim 1 , wherein in the compound of formula I is m=0, n in the range of 0 to 3 and R1 is independently selected from the group consisting of —H, —CH 3 , —C 2 H 5  and —(C 2 H 4 O) p —H wherein p in the range 2 to 6. 
     
     
         3 . The water-based composition according to  claim 1 , wherein the compound of formula I is selected from the group consisting of 2,3,6,7-tetramethyl-4-octyne-3,6-diol, 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol ethoxylate, 2,4,7,9-tetramethyl-5-decyne-4,7-diol ethoxylate, 2,4,7,9-tetramethyl-5-decyne-4,7-diol-bispolyoxyethyleneether, and 2,4,7,9-tetramethyl-5-decyne-4,7-diol. 
     
     
         4 . The water-based composition according to  claim 1 , wherein the surfactant is an ethoxylated or propoxylated alkyl, ethoxylated or propoxylated amine, ethoxylated or propoxylated amide, ethoxylated or propoxylated alcohol, or a mixture thereof. 
     
     
         5 . The water-based composition according to  claim 1 , wherein the surfactant has the general formula II
   R 3 O(CH 2 CH 2 O) x H   (II)
   wherein   R 3  is a linear or branched alkyl group, having 6-15 carbon atoms,   x is an integer in the range of 3-15.   
     
     
         6 . The water-based composition according to  claim 1 , wherein the alkanethiol is a C 10 - to C 20 -alkanethiol. 
     
     
         7 . The water-based composition according to  claim 1 , wherein the composition comprises a co-emulsifier. 
     
     
         8 . The water-based composition according to  claim 7 , wherein the co-emulsifier has the general formula III
   R 4 O(CH 2 CH 2 O) y H   (III)
   wherein   R4 is a linear or branched alkyl group, having 16-20 carbon atoms,   y is an integer in the range of 2-10.   
     
     
         9 . The water-based composition according to  claim 7 , wherein the co-emulsifier is a polyalkylene glycol ether. 
     
     
         10 . The water-based composition according to  claim 1 , wherein the composition is free of chromate and/or free of organic solvent. 
     
     
         11 . The water-based composition according to  claim 1 , having wherein the composition has a pH in the range of 1 to 10. 
     
     
         12 . (canceled) 
     
     
         13 . A method for post-treatment of a metal surface, in this order, the steps
 a. providing a metal surface,   b. contacting the metal surface, with a water-based composition according to  claim 1 .   
     
     
         14 . The method according to  claim 13 , wherein the contacting in step b. is applied by immersing, by spraying, or by any other suitable method, or combination of any of the foregoing, allowing the contact between the metal and the water-based composition. 
     
     
         15 . The method according to  claim 13 , wherein the contacting in step b. takes place under applying an electrical current between the metal surface, and at least one electrode when the metal is immersed into the claim solution. 
     
     
         16 . The water-based composition according to  claim 1 , wherein the metal surface is a silver or silver alloy surface.