EXPERIMENTAL STUDY OF CO2 CORROSION OF 3Cr PIPE LINE STEEL

Linear polarisation resistance(LPR) was used to trace the corrosion rate of 3Cr pipe line steel during corrosion process.EIS and SEM were used to detect the structure of protective CO_2 corrosion product films.The appearance and evolvement of the loose internal-layer with lower Cr/Fe ration which was observed by SEM,was analyzed by EIS.Amorphous corrosion product film grew from outside to inside with time.The increase of the Cr/Fe ratio and the thickness of the film cause the decrease of momentary corrosion rate.The chromic compound produced by a certainty Cr~(3+) concentration.When the pitting corrosion suppressed,high corrosion rate in the pit resulted in high Cr~(3+) concentration which would produce much chromic compound,and in this way,the development of the pit would be prevented.