Direct-contact membrane anode for use in electrolysis cells

Abstract

The present invention relates to an anode system for conventional electrolysis cells, a process for the production thereof and its use for the deposition of electrolytic coatings. The anode system is characterized in that the anode ( 2 ) is in direct contact with a membrane ( 3 ) which completely separates the anode space from the cathode space. This anode system is therefore a direct-contact membrane anode.

1 . Anode system which is configured in such a way that it is suitable for use in electroplating cells for the deposition of electrolytic coatings as a result of simple dipping into the catholyte, wherein, after dipping into the catholyte, the catholyte is separated from the anode by a swollen polymer membrane which is permeable to cations or anions and the polymer membrane is in direct contact with the anode and not with the cathode,
 wherein   the membrane is fixed onto the anode by means of electrolyte-permeable holders and pressing devices by means of a multilayer structure, which ensures good contact of the membrane with the anode.   
     
     
         2 . Anode system according to  claim 1 ,
 wherein.   the anode consists of flat material, sintered material or expanded metal.   
     
     
         3 . Anode system according to  claim 1   wherein   the anode is selected from the group consisting of platinised titanium, graphite, stainless steel, titanium coated with iridium-transition metal mixed oxide, tantalum or niobium sheets coated with mixed oxides and special carbon material (“Diamond Like Carbon” DLC, “glassy carbon” GC) and combinations of these materials.   
     
     
         4 . Anode system according to  claim 1 ,
 wherein   a membrane selected from the group consisting of polypyrrole membranes, olefin polymer membranes, sulphonated polystyrene membranes, fluorinated/perfluorinated sulphonated polymer membranes (PFSA membranes), S-PEEK, S-PSU, PSU-CI, ICVT membranes, aryl polymer membranes, polyether ketone membranes, polybenzimidazole membranes, thermoplastic base polymer membranes, perfluorosulphonic acid polymer membranes, perfluorocarboxylate ionomers, polyamides, polyamines, poly(vinyl alcohol)membranes, perfluorophosphonate membranes is used as the polymer membrane.   
     
     
         5 . Process for producing an anode system according to  claim 1 ,
 wherein   i) the membrane is allowed to preswell in deionized water,   ii) the preswollen polymer membrane is applied directly to the anode,   iii) the membrane is fixed onto the anode by means of electrolyte-permeable holders and pressing devices by means of a multilayer structure, which ensures good contact of the membrane with the anode, and   iv) the anode is enclosed in the polymer membrane so that it cannot be wetted by the catholyte.   
     
     
         6 . A process for the electrochemical deposition of metal coatings on decorative and industrial articles, comprising utilization of the anode of  claim 1  in a catholyte. 
     
     
         7 . The process according to  claim 6 ,
 wherein   an article is dipped into the catholyte and a sufficient flow of current between the article and the anode for deposition of the metal coatings is brought about.   
     
     
         8 . The process according to  claim 6 ,
 wherein   the deposition is carried out in a temperature range of 1-150° C.   
     
     
         9 . The process according to  claim 6 ,
 wherein   a catholyte capable of depositing metals or metal alloys selected from the group consisting of silver, gold, palladium, platinum, rhodium, ruthenium, iridum, rhenium, copper, tin, zinc, iron, nickel, cobalt, chromium, manganese, molybdenum, tungsten, tantalum, thallium, bismuth, antimony, indium, gallium, lead, cerium, selenium, cadmium, samarium, vanadium, tellurium and alloys thereof is selected as the catholyte.   
     
     
         10 . An electrolysis cell comprising a cathode, a catholyte and an anode system according to  claim 1  for the deposition of electrolytic coatings.