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Picture for Impact of O2 Content on Corrosion Behavior of X65 Mild Steel in Gaseous, Liquid and Supercritical CO2 environments
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Impact of O2 Content on Corrosion Behavior of X65 Mild Steel in Gaseous, Liquid and Supercritical CO2 environments

Product Number: 51320-14433-SG
Author: Xiu Jiang, Dingrong Qu , Xiaoliang Song
Publication Date: 2020
$20.00

CO2 stream in CCS system usually contains impurities, such as water, O2, SO2, NO2, H2S, and other trace substances, which could pose a threat to internal corrosion and integrity of CO2 transportation pipelines. The general and localized corrosion behavior of API 5L X65 mild steel were evaluated using an autoclave both in water-saturated CO2 and CO2-saturated water environments in the presence of varying concentrations of O2. Experiments were performed at 25 °C and 35 °C, 8 MPa and 35 °C, 4 MPa to simulate the conditions encountered during dense, supercritical and gaseous CO2 transport. General corrosion rates were obtained by weight-loss method. The surface morphology of the coupons was examined by scanning electron microscopy (SEM). Results indicated that general corrosion rates at each O2 concentration in CO2-saturated water environment were much higher than those in water-saturated CO2 environment. The corrosion rates did not increase with increasing O2 concentration from 0 to 2000 ppm; instead the corrosion rate reached a maximum with 1000 ppm O2 at 25 °C, 8 MPa and 50 ppm O2 at 35 °C, 8 MPa in water-saturated CO2 environment and 50 ppm at 25 °C, 8 MPa and 100 ppm at 35 °C, 8 MPa in CO2-saturated water environment. However, the change trend of general corrosion rate with O2 content at 35 °C, 4 MPa was different from that in 25 °C and 35 °C, 8 MPa both in water-saturated CO2 and CO2-saturated water environments. Localized corrosion or general corrosion rate of over 0.1 mm/y was identified at each test condition both in a water-saturated CO2 and CO2-saturated water environments. When O2 was added, coupon surfaces were covered by a more porous corrosion product scale. A final series of tests conducted with the addition of 100 ppm and 2000 ppm O2 in CO2 environment with 60% relative humidity (RH) and 80% RH revealed that no localized corrosion was observed and the general corrosion rates were lower than 0.1 mm/y at 25 °C and 35 °C, 8