Surface modified stainless steel cathode for electrolyser

Abstract

Sodium chlorate is produced industrially via electrolysis of brine and is thus an energy intensive process. An improved cathode for this and other industrial processes is a low nickel content stainless steel whose surface has been suitably modified. With an appropriate amount of surface roughening, the cathode provides for improved overvoltages during electrolysis while still maintaining corrosion resistance.

1 - 19 . (canceled) 
     
     
         20 . A method of reducing the overvoltage of an industrial electrolyser cathode during electrolysis of brine while maintaining resistance of the cathode to corrosion, the method comprising employing a stainless steel cathode comprising less than about 6% by weight nickel wherein the surface of the stainless steel cathode has been roughened to a surface roughness Rq between about 1.0 and 5.0 micrometers. 
     
     
         21 . The method of  claim 20  wherein the roughening comprises sandblasting the cathode surface with aluminum oxide powder. 
     
     
         22 . The method of  claim 20  wherein the stainless steel electrode is roughened to a surface roughness Rq between about 1.0 and less than about 2.5 micrometers. 
     
     
         23 . The method of  claim 20  wherein the stainless steel is a ferritic stainless steel. 
     
     
         24 . The method of  claim 23  wherein the ferritic stainless steel is selected from the group consisting of 430, 430D, 432, and 436S grades of ferritic stainless steel. 
     
     
         25 . The method of  claim 20  wherein the stainless steel comprises a stabilizing dopant selected from the group consisting of Cu, Mo, N, Nb, Sn, Ti, V, and W. 
     
     
         26 . The method of  claim 23  wherein the ferritic stainless steel comprises Mo dopant. 
     
     
         27 . The method of  claim 23  wherein the ferritic stainless steel comprises Sn dopant. 
     
     
         28 . The method of  claim 23  wherein the ferritic stainless steel comprises Ti dopant. 
     
     
         29 . The method of  claim 23  wherein the ferritic stainless steel comprises V dopant. 
     
     
         30 . The method of  claim 20  wherein the stainless steel is a duplex stainless steel. 
     
     
         31 . The method of  claim 30  wherein the duplex stainless steel is selected from the group consisting of S31803, S32101, S32205, S32304, S82441, S82011, and S82122 grades of duplex stainless steel. 
     
     
         32 . The method of  claim 20  wherein the stainless steel comprises less than about 0.03% by weight carbon. 
     
     
         33 . The method of  claim 32  wherein the stainless steel comprises less than about 0.005% by weight carbon. 
     
     
         34 . The method of  claim 20  wherein the stainless steel comprises less than about 0.03% by weight phosphorus and less than about 0.003% by weight sulfur. 
     
     
         35 . The method of  claim 20  wherein the stainless steel cathode comprises an electrolysis enhancing coating. 
     
     
         36 . The method of  claim 20  wherein the industrial electrolyser is a sodium chlorate electrolyser. 
     
     
         37 . The method of  claim 20  wherein the stainless steel cathode is welded to a carrier plate made of carbon steel or stainless steel. 
     
     
         38 . The method of  claim 37  wherein the cathode is welded to a carrier plate made of stainless steel and the industrial electrolyser does not comprises a cathodic protection unit. 
     
     
         39 . A method for electrolyzing brine with an industrial electrolyser, the method comprising the step of employing a stainless steel cathode comprising less than about 6% by weight nickel, wherein the surface of the stainless steel cathode has been roughened to a surface roughness Rq between about 1.0 and 5.0 micrometers 
     
     
         40 . The method of  claim 39  wherein the brine comprises sodium chloride and the method produces sodium chlorate.