ELECTROCHEMICAL BEHAVIOR STUDY OF X70 STEEL/FUSION BONDED EPOXY COATING(FBEC) WITH LINEARDEFECTS SYSTEM IN 3.5%NaCl

摘要

By means of electrochemical impedance spectroscopy (EIS) technique, the electrochemical behavior offusion bonded epoxy coating (FBEC) with linear defects/X70 steel system in 3.5%NaCl solution wasstudied. The defects were made at right angles to form a 20mm×20mm cross, and the test involvedscribing the sample through the paint down to the bare metal. The experimental results showed thatcorrosion process can be divided into three stages. In the initial stage of eroding,the electrochemicalbehavior of this system is similar to bare steel. In the interim stage, corrosion products accumulate inthe interior of linear defects. It makes pH of solution in the interior of linear defects fall down andcauses the rupture of coating bonded joint. In the final stage of eroding, the EIS data show that alongthe seams,the FBE coating peels off steel substrate. EIS data had been interpreted and discussed interms of the time dependence of the electrical (paint coating) and electrochemical (steel substrate)parameters. The parameters are associated with interfacial processes describing carbon steel/the fusionbonded epoxy coating with linear defects system deterioration.