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 . A cathode for an industrial electrolyser comprising a stainless steel electrode comprising less than about 6% by weight nickel and characterized by a surface roughness R q  between about 1.0 and 5.0 micrometers. 
     
     
         2 . The cathode of  claim 1  wherein the stainless steel electrode is characterized by a surface roughness R q  less than about 2.5 micrometers. 
     
     
         3 . The cathode of  claim 1  wherein the stainless steel is a ferritic stainless steel. 
     
     
         4 . The cathode of  claim 3  wherein the stainless steel is selected from the group consisting of 430, 430D, 432, and 436S grades of ferritic stainless steel. 
     
     
         5 . The cathode of  claim 1  wherein the stainless steel comprises a stabilizing dopant selected from the group consisting of Cu, Mo, N, Nb, Sn, Ti, V, and W. 
     
     
         6 . The cathode of  claim 3  wherein the ferritic stainless steel comprises Mo dopant. 
     
     
         7 . The cathode of  claim 3  wherein the ferritic stainless steel comprises Sn dopant. 
     
     
         8 . The cathode of  claim 3  wherein the ferritic stainless steel comprises Ti dopant. 
     
     
         9 . The cathode of  claim 3  wherein the ferritic stainless steel comprises V dopant. 
     
     
         10 . The cathode of  claim 1  wherein the stainless steel is a duplex stainless steel. 
     
     
         11 . The cathode of  claim 10  wherein the stainless steel is selected from the group consisting of S31803, S32101, S32205, S32304, S82441, S82011, and S82122 grades of duplex stainless steel. 
     
     
         12 . The cathode of  claim 1  wherein the stainless steel comprises less than about 0.03% by weight carbon. 
     
     
         13 . The cathode of  claim 12  wherein the stainless steel comprises less than about 0.005% by weight carbon. 
     
     
         14 . The cathode of  claim 1  wherein the stainless steel comprises less than about 0.03% by weight phosphorus and less than about 0.003% by weight sulfur. 
     
     
         15 . The cathode of  claim 1  comprising an electrolysis enhancing coating applied to the low nickel content stainless steel electrode. 
     
     
         16 . An industrial electrolyser comprising the cathode of  claim 1 . 
     
     
         17 . The industrial electrolyser of  claim 16  wherein the industrial electrolyser is a sodium chlorate electrolyser. 
     
     
         18 . The industrial electrolyser of  claim 16  wherein the cathode is welded to a carrier plate made of carbon steel or stainless steel. 
     
     
         19 . The industrial electrolyser of  claim 18  wherein the cathode is welded to a carrier plate made of stainless steel and the electrolyser is absent a cathodic protection unit. 
     
     
         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 roughening the surface of a stainless steel cathode comprising less than about 6% by weight nickel to a surface roughness R q  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.