Electrochemical studies of the galvanic coupling zinc/pipeline steel in the presence of an applied alternating current

Abstract

The effects of alternating current on the galvanic coupling zinc/pipeline steel were investigated in 4 g/L Na 2 SO 4 simulated backfill solution by weight-loss measurements for 96 hr, electrochemical measurements, and surface examinations. Alternating current accelerates the dissolution of zinc significantly but reduces the corrosion rate of pipeline steel. Under an applied alternating current, zinc DC potential shifts negatively while the DC potential shift direction of pipeline steel is closely related to the value of alternating current density. When the alternating current density is low the DC potential shifts negatively. It, however, shifts positively under higher alternating current density. Besides, the coupling current increases with alternating current density.