ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY OF WELDED JOINTS OF COPPER PIPE IN ARTIFICIAL SEAWATER

The corrosion behavior of welded joints of copper pipe in artificial seawater was studied by anodic polarization,electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM).The brass welded joint was dissolved into Zn2+ and CuCl-2,and this process was controlled by the diffusion of Zn2+ and CuCl-2,in the Tafel region.In the anodic region between -0.01 V and +0.31 V(SCE),the anode was covered with Cu2O,CuCl,ZnO and Zn(OH)2ZnCl2 films which hindered electrochemical polarization.Two arcs of capacitive reactance appeared in the EIS.In the region between +0.31 V and +0.57 V(SCE),the dezincification reaction was dominant process which was controlled by the diffusion of Zn2+.