Galvanic Corrosion Behaviors of X65-316L Bimetal Tube in Simulated Production Water

Galvanic corrosion appears in the outer layer of bimetal tube for ocean natural gas transportation after the gavalic corrosion model is built between the outer layer and the inner layer. The corrosive production solution permeates into the space between the outer layer and the inner layer due to perforation of inner layer. In this work, galvanic corrosion was investigated by immersion test and electrochemical measurements. Corrosion morphology of X65-316L bimetal tube was observed by SEM before and after immersion. The open circuit potential (OCP) of X65 and 316L and the gavalic current density (Jcc) were measured during galvanic experiment. Electrochemical parameters were analyzed according to dynamic polarization curves before and after connection of X65 with 316L. The results show that X65 acted as an anodic electrode and 316L was cathodic electrode in the gavalic corrosion couple. The corrosion rate of X65 increased and that of 316L decreased when compared with that before their connection. At the same time, cathodic polarization rate of X65 decreased and anodic polarization rate of 316L increased.