Method for treatment of iron-based metal surface exposed to superheated steam

Abstract

The present invention provides a surface treatment method for suppressing the formation and growth of superheated steam oxide scale on an iron-based metal surface exposed to superheated steam, comprising treating said iron-based metal surface with a surface-treatment agent which comprises a polyoxy saturated aliphatic mono- or di-carboxylic acid or a salt thereof and an amine compound represented by the following formula (I): Z(CH 2 CH 2 NH) n CH 2 CH 2 NH 2   (I) wherein Z represents H or OH or NH 2 group, and n is an integer of 0-5.

1 . A surface treatment method for suppressing the formation and growth of steam oxide scale on an iron-based metal surface exposed to superheated steam, comprising treating said iron-based metal surface with a surface-treatment agent, wherein said surface-treatment agent comprises a polyoxy saturated aliphatic mono- or di-carboxylic acid or a salt thereof and an aliphatic amine represented by the following formula (I):
   Z(CH 2 CH 2 NH) n CH 2 CH 2 NH 2   (I)
   
       wherein Z represents H, or OH or NH 2  group, and n is an integer of 0-5. 
     
     
         2 . The method of  claim 1 , wherein said amine is an amine represented by the formula (I) wherein n is an integer of 0-3. 
     
     
         3 . The method of  claim 1 , wherein said amine is monoethanolamine or tetraethylenepentamine. 
     
     
         4 . The method of  claim 1 , wherein said amine is tetraethylenepentamine. 
     
     
         5 . The method of  claim 1 , wherein said polyoxy saturated aliphatic mono- or di-carboxylic acid or said salt thereof is selected from the group consisting of gluconic acid, tartaric acid and a salt thereof. 
     
     
         6 . The method of  claim 1 , wherein said surface-treatment agent further comprises an alkali metal hydroxide or an aliphatic cyclic amine. 
     
     
         7 . The method of  claim 1 , wherein said treatment is carried out at a temperature of 120° C. to 380° C. 
     
     
         8 . The method of  claim 1 , wherein said treatment is carried out at a temperature of 120° C. to 250° C. 
     
     
         9 . The method of  claim 1 , wherein said treatment is carried out for a period of from 10 to 100 hours. 
     
     
         10 . The method of  claim 1 , wherein said iron-based metal surface is an inner surface of a main or reheating steam pipe of a power plant. 
     
     
         11 . The method of  claim 1 , wherein said amine is tetraethylenepentamine, said polyoxy saturated aliphatic mono- or di-carboxylic acid or said salt thereof is selected from the group consisting of gluconic acid, tartaric acid and a salt thereof, said treatment is carried out at a temperature of 120° C. to 250° C. for a period of from 10 to 100 hours, and said iron-based metal surface is an inner surface of a main or reheating steam pipe of a power plant. 
     
     
         12 . A surface treatment method for suppressing the formation and growth of steam oxidation scale on an inner surface of a main or reheating steam pipe of a power plant, comprising treating said inner surface with a surface-treatment agent at a temperature of 120° C. to 250° C. for a period of 10 to 100 hours, wherein said surface-treatment agent comprises gluconic acid, tartaric acid or a salt thereof and tetraethylenepentamine and said inner surface is an iron-based metal surface exposed to superheated steam.