Method for the treatment of a metal substrate for the preparation of electrodes

Abstract

A method for surface treatment of a metal substrate, suitable for use as electrode support in electrochemical processes by: (a) immersion of the metal substrate and of at least one counter electrode in an electrolyte selected from hydrochloric acid, nitric acid, boric acid or sulfuric acid at a weight concentration of between 10-40%; (b) application of an anodic current density to the metal substrate of between 0.1 and 30 A/dm2 for a time of between 0.5 and 120 minutes. An electrode for gas evolution in electrochemical processes obtained from a correspondingly treated substrate.

1 . A method for surface treatment of a metal substrate selected from nickel or nickel alloy, suitable for use as electrode support in electrochemical processes, comprising the following steps:
 (a) immersing said metal substrate and at least one counter electrode in an electrolyte selected from hydrochloric acid, nitric acid, boric acid or sulfuric acid at a weight concentration of between 10-40%;   (b) applying an anodic current density to said metal substrate between 0.1 and 30 A/dm 2  for a time between 0.5 and 120 minutes.   
     
     
         2 . The method according  claim 1  wherein said metal substrate is a mesh or a punched or expanded sheet. 
     
     
         3 . The method according to  claim 1  wherein said metal substrate has a thickness below 1.2 mm. 
     
     
         4 . The method according to  claim 3  wherein said metal substrate has a thickness equal to or less than 0.5 mm. 
     
     
         5 . (canceled) 
     
     
         6 . The method according to  claim 1  wherein the applied anodic current density is between 5 and 10 A/dm 2 . 
     
     
         7 . The method according to  claim 6  wherein the application time of the anodic current density is between 2 and 10 minutes. 
     
     
         8 . The method according to  claim 1  wherein the weight concentration of said electrolyte is between 15-30%. 
     
     
         9 . The method according to  claim 1  wherein the metal substrate is nickel or nickel alloy comprising a further step (c) subsequent to step (b) of nickel electrodeposition comprising the addition to said electrolyte of a nickel salt in a concentration by weight between 150 and 300 g/l and subsequent application of a cathodic current density to said metal substrate between 0.1 and 3 A/dm 2  for a time between 0.5 and 120 minutes at a temperature between 15 and 70° C. 
     
     
         10 . A method for manufacturing an electrode for gas evolution in electrochemical processes, comprising the following steps:
 treating a metal substrate with the method of  claim 1 , and   applying a catalytic coating comprising one or more noble or alloy metals or their oxides and/or one or more metals belonging to the rare earth group or their oxides, to said treated metal substrate.   
     
     
         11 . An electrode for gas evolution in electrochemical processes comprising a metal substrate, selected from nickel or nickel alloy, prepared according to the method described in  claim 1 , said metal substrate having a degree of homogeneity of the roughness profile, expressed as the mean square deviation Ra values, of less than 25%, and a catalytic coating comprising one or more noble or alloy metals or their oxides and/or one or more metals belonging to the rare earth group or their oxides. 
     
     
         12 . (canceled) 
     
     
         13 . An electrode for gas evolution in electrochemical processes comprising a metal substrate, selected from nickel or nickel alloy, prepared according to the method described in  claim 9 , comprising a layer of nickel electrodeposited directly on the metal substrate and a catalytic coating comprising one or more metals or alloys or their oxides and/or one or more metals belonging to the group of rare earths or their oxides. 
     
     
         14 . A cell for the electrolysis of water or for the electrolysis of alkali chloride solutions comprising an anodic compartment and a cathodic compartment separated by an ion-exchange membrane or by a diaphragm, wherein the cathodic compartment is equipped with an electrode according to  claim 11 .