Electrolyte for removing metal-carbide/nitride coatings or metal-carbide-nitride coatings and removing method using same

Abstract

An electrolyte for removing metal-carbide/nitride coatings or metal-carbide-nitride coatings from substrates, the electrolyte includes an acid, an inhibiter and a complexant. The acid is a mixture of a sulfuric acid and a weak acid. The inhibiter is an organic compound containing hydrophilic group, lipophilic group, and at least one polar group selected from nitrogen-containing group, sulfur-containing group, and hydroxyl group. The complexant is capable of complexing with Fe 3+ . A method for removing the metal-carbide/nitride coatings or metal-carbide-nitride coatings using the electrolyte is also provided.

What is claimed is: 
     
         1 . An electrolyte for removing metal-carbide/nitride coatings or metal-carbide-nitride coatings from substrates, the electrolyte comprising:
 an acid, the acid being a mixture of a sulfuric acid and a weak acid;   an inhibiter, the inhibiter being an organic compound containing hydrophilic group, lipophilic group, and at least one polar group selected from nitrogen-containing group, sulfur-containing group, and hydroxyl group; and   a complexant being capable of complexing with Fe 3+ .   
     
     
         2 . The electrolyte as claimed in  claim 1 , wherein the acid is a mixture of sulfuric acid and oxalic acid. 
     
     
         3 . The electrolyte as claimed in  claim 2 , wherein in the electrolyte, the mass percentage of the oxalic acid is about 3% to about 5%. 
     
     
         4 . The electrolyte as claimed in  claim 1 , wherein the acid is a mixture of sulfuric acid and acetic acid. 
     
     
         5 . The electrolyte as claimed in  claim 4 , wherein in the electrolyte, the mass percentage of the acetic acid is about 1%-3%. 
     
     
         6 . The electrolyte as claimed in  claim 1 , wherein the inhibiter is at least one selected from nicotinamide, (N,N-methylenebis N′-1-(hydroxymethyl)-2,5-dioxo-4-imidazolidinyl))-urea, and thiourea. 
     
     
         7 . The electrolyte as claimed in  claim 1 , wherein in the electrolyte, the concentration of the nicotinamide is about 0.1 g/l-0.3 g/l. 
     
     
         8 . The electrolyte as claimed in  claim 6 , wherein in the electrolyte, the concentration of the (N,N-methylenebis N′-1-(hydroxymethyl)-2,5-dioxo-4-imidazolidinyl))-urea is about 0.1 g/l to about 0.3 g/l. 
     
     
         9 . The electrolyte as claimed in  claim 1 , wherein the complexant is edetic acid. 
     
     
         10 . The electrolyte as claimed in  claim 9 , wherein in the electrolyte, the concentration of edetic acid is about 0.1 g/l to about 0.2 g/l. 
     
     
         11 . The electrolyte as claimed in  claim 1 , wherein the electrolyte further comprises accelerant, the accelerant is sodium dodecyl sulphonate. 
     
     
         12 . The electrolyte as claimed in  claim 11 , wherein in the electrolyte, the concentration of sodium dodecyl sulphonate is about 0.1 g/l to about 0.2 g/l. 
     
     
         13 . A method for removing metal-carbide/nitride coatings or metal-carbide-nitride coatings comprising:
 providing a substrate having at least one coating formed thereon, the at least one coating being a metal-carbide coating, a metal-nitride coating, or a metal-carbide-nitride coating;   manufacturing an electrolyte, the electrolyte comprising acid, inhibiter and complexant;   immersing the substrate in the electrolyte to perform an electrolysis to remove the coating, the substrate being an anode;   wherein the acid is a mixture of a sulfuric acid and a weak acid, the inhibiter being an organic compound containing hydrophilic group, lipophilic group, and at least one polar group selected from nitrogen-containing group, sulfur-containing group, and hydroxyl group; and the complexant is capable of complexing with Fe 3+ .   
     
     
         14 . The method as claimed in  claim 13 , wherein the substrate is made of stainless steel or ferric-based alloy. 
     
     
         15 . The method as claimed in  claim 13 , wherein the temperature of the electrolyte during electrolysis is room temperature. 
     
     
         16 . The method as claimed in  claim 13 , wherein during the electrolysis process, the current density is about 0.8 A/dm 2  to about 2 A/dm 2 , the voltage is about 1 V to about 5 V, the electrolysis process takes about 2 min to about 8 min. 
     
     
         17 . The method as claimed in  claim 13 , wherein the acid is a mixture of sulfuric acid and oxalic acid. 
     
     
         18 . The method as claimed in  claim 13 , wherein the acid is a mixture of sulfuric acid and acetic acid. 
     
     
         19 . The method as claimed in  claim 13 , wherein the inhibiter is at least one selected from nicotinamide, (N,N-methylenebis N′-1-(hydroxymethyl)-2,5-dioxo-4-imidazolidinyl))-urea, and thiourea. 
     
     
         20 . The method as claimed in  claim 13 , wherein the complexant is edetic acid.