Method for coating metallic interconnect of solid oxide fuel cell

Abstract

Disclosed is a method for coating a metallic interconnect for a solid oxide fuel cell (SOFC), the method including the steps of: carrying out pre-treatment for removing impurities adhered on a surface of the metallic interconnect; and carrying out pulse plating with cobalt as an anode, and the metallic interconnect as a cathode, in which an average current density (I a ) is set in a room-temperature cobalt plating solution, and a maximum current density (I p ), a current-on time (T on ) and a current-off time (T off ) are adjusted based on I a =I p ×T on /(T on +T off ). Through the disclosed method, it is possible to obtain a metallic interconnect having a coating surface which has a high electrical conductivity and a high chrome volatilization inhibiting property and can minimize the occurrence of micro-cracks and micro-pores, thereby improving the performance of the SOFC.

1 . A method for coating a metallic interconnect for a solid oxide fuel cell (SOFC), the method comprising the steps of:
 carrying out pre-treatment for removing impurities adhered on a surface of the metallic interconnect; and   carrying out pulse plating with cobalt as an anode, and the metallic interconnect as a cathode, in which an average current density (I a ) is set in a room-temperature cobalt plating solution, and a maximum current density (I p ), a current-on time (T on ), and a current-off time (T off ) are adjusted based on a Mathematical Formula 1 described below.
     I   a   =I   p   ×T   on /( T   on   +T   off )  [Mathematical Formula 1] 
   
   
   
       2 . The method as claimed in  claim 1 , wherein the pulse plating is carried out under a condition of the current-on time (T on ) of 0.002˜0.005 seconds, the current-off time (T off ) of 0.005˜0.008 seconds, the maximum current density (I p ) of 100˜250 mA/cm 2 , and the average current density (I a ) of 30˜50 mA/cm 2 . 
   
   
       3 . The method as claimed in  claim 1 , wherein the step of carrying out the pre-treatment comprises the steps of polishing the surface of the metallic interconnect by silicon carbide abrasive paper, washing off the impurities on the surface of the metallic interconnect by 10% NaOH aqueous solution and acetone, removing a fine scale on the surface of the metallic interconnect by 10% HCl solution, and carrying out pickling for 30 to 60 seconds. 
   
   
       4 . The method as claimed in  claim 1 , wherein a size of the anode is 1˜1.5 times larger than a size of the cathode, and an interval between the anode and the cathode is 1˜2 times larger than a width of the cathode. 
   
   
       5 . The method as claimed in  claim 1 , wherein the plating solution employs a Watts bath of cobalt sulfate (CoSO 4 .7H 2 O) and cobalt chloride (CoCl 2 .6H 2 O) with pH of 2 to 4, the pH being maintained by a cobalt hydroxide aqueous solution or a diluted hydrochloric acid solution. 
   
   
       6 . The method as claimed in  claim 1 , wherein after the pulse plating, heat-treatment is carried out in a 800° C. reducing atmosphere (10% H 2 +90% N 2 ) for 2˜20 hours to enhance a binding force between the metallic interconnect and a plated coating layer.