Process for electrolytic derusting of ferrous materials using natural seawater

Abstract

This invention relates to a process for the derusting or removal of corrosion products form ferrous metal substrates by electrochemical treatment.

We claim:  
     
         1 . A process for the derusting or removal of corrosion products from a ferrous material substrate, said process comprising electrochemical treatment of a substrate in natural seawater as electrolyte under an optimum current density in the range of 6 to 8 A/sq. dm using a stainless steel anode.  
     
     
         2 . A process as claimed in  claim 1  wherein the anode is a -304 stainless steel anode.  
     
     
         3 . A process as claimed in  claim 1  wherein the ferrous metal substrate is selected from the group consisting of mild steel, cold rolled steel, carbon steel, stainless steels, reinforcement rods whether plain, twisted or pre-stressed, and intricate metal components such as pins, needles, nails, bolts, hooks, nuts, fasteners and clips.  
     
     
         4 . A process as claimed in  claim 1  wherein the process is carried out at a temperature ranging from 28° C. to 50° C.  
     
     
         5 . A process as claimed in  claim 1  wherein the natural seawater pH of 7.9 to 8.2 is altered by adding few drops of HCl to bring the pH of the bath in the range between 6 to 9.  
     
     
         6 . A process as claimed in  claim 1  wherein there is minimal variation in the pH of the electrolyte during the process.  
     
     
         7 . A process as claimed in  claim 1  wherein the anode comprises a more noble metal than the cathode specimen.  
     
     
         8 . A process as claimed in  claim 1  wherein the electrolyte is recycled on completion of electrolysis after appropriate changes in the solution chemistry.