Electrochemical Behavior of Copper Tube with Silica Scale in Synthetic Freshwater

Abstract

Silica scale was formed on copper tubes by immersing in test solutions containing silica and chloride ion for 7 days. The film formed on copper tubes immersed in 20 ppm Cl^－ solution without silica composed mainly cuprous oxide（Cu₂O）. Silica in test water inhibits the formation of Cu₂O on copper tubes. The corrosion potential of the copper tube with silica scale was less-nobler than that of the copper tube without silica scale. The galvanic monitoring was made for a pair consisting of the copper tubes with and without silica scale. The galvanic current flew from the copper tube without silica scale to the copper tube with silica scale. This result indicates that the copper tube with silica scale acted as the anode, whereas the copper tube without silica scale acted as the cathode.