On the Corrosion Mechanism of CO2 Transport Pipeline Steel Caused by Condensate: Synergistic Effects of NO2 and SO2

Abstract

To study the effects of condensed acid liquid, hereafter referred to as condensate, on the CO2 transport pipeline steels, gas mixtures containing a varying concentration of H2O, O2, NO2, and SO2, were proposed and resulted in the condensate containing H2SO4 and HNO3 with the pH ranging from 0.5 to 2.5. By exposing the pipeline steel to the synthetic condensate with different concentration of acidic components, the corrosion kinetic is significantly changed. Reaction kinetic was studied using electrochemical methods coupled with water analysis and compared with surface analysis (scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffractometry (XRD)) of corroded coupons. The results showed that, although the condensation of NO2 in the form of HNO3 causes faster general corrosion rate, it is the condensation of SO2 in the form of H2SO4 or the combination of SO2 and NO2 that may cause much more severe problems in the form of localized and pitting corrosions. The resulting corrosion forms were depended on the chemical nature of acids and their concentration at the same investigated pH. The effects of changing CO2 flow rate and renewing condensate on pitting corrosion were further studied.

Early Stage of Corrosion Formation on Pipeline Steel X70 Under Oxyfuel Atmosphere at Low Temperature

“…General information about the properties of the instrumentation and the major setup at the EDDI beamline are listed in [31]. To identify reaction products from the emission line positions, ICSD data [32] and the energy-dispersive Bragg Equations (7) and (8) were applied. The time-resolved measurement at the energy-dispersive X-ray beamline (EDDI) at BESSY II was performed within an energy range of 10-90 keV, setting the data acquisition time to 10min/pattern.…”

“…A total of five signals can be identified, which are located at 20. Based on the energy-dispersive Bragg-equation, Equations (7) and (8) and the use of ICSD data [32] the reflected EDXRD signals can be allocated to specific phases (Table 2). Table 2 lists the corrosion phases detected by in-situ EDXRD, including the energy of the emission line and their onset time.…”

“…Three different starting points (around 150 min, 240 min and 360 min) indicating the presence of various phases or, rather, the formation of preferred crystallographic orientations. Based on the energy-dispersive Bragg-equation, Equations (7) and (8) and the use of ICSD data [32] the reflected EDXRD signals can be allocated to specific phases (Table 2). Table 2 lists the After the in-situ corrosion experiment, the slightly wet specimen surface was tested by a pH indicator (Macherey-Nagel GmbH & Co. KG), suggesting a value around pH 1.5.…”

“…In general, corrosion in pipelines is insignificant if no free water in the system is present. However, in the presence of water, impurities can form acids Equations (1)- (6), which can cause harmful corrosion problems by condensation effects on steel surfaces [5][6][7][8][9][10][11][12][13][14]. SO…”

“…Recent studies have shown that even high-alloyed steels might be susceptible to general and localized corrosion caused by these acidic condensates [6,7]. Crucial points for a sustainable and future proof CCUS procedure are reliability and cost efficiency of the pipeline transport network-in particular, regarding corrosion risks when impurities and moisture are present within the CO 2 stream.…”