Impact of Prolonged Exposure to Sour Service on the Mechanical Properties and Corrosion Mechanism of NACE Carbon Steel Material Used in Wet Sour Gas Multiphase Pipeline

Abstract

The oil and gas industry is involved with severe corrosive/sour environmental conditions due to H2S, CO2, and moisture content. The National Association of Corrosion Engineers (NACE) has developed standards to enable users to select suitable materials for given sour conditions which utilize laboratory testing. A failed piping sample (API-5L-X65) was removed from a pipeline after 15 years of service. Optical microscopy was used to compare the microstructure of the corroded sample near the exposed surface to both the service environment, and further away from it. Moreover, pitted samples were analyzed using a scanning electron microscope coupled with energy dispersive X-ray (SEM/EDS) to understand the deposits’ morphology. Furthermore, XPS analysis proves the presence of a significant content of sulfur compound. Additionally, the mechanical properties of both corroded and non-corroded samples were evaluated and compared. Micro-hardness was carried out on the cross-section of the removed sample to understand any evident hardness variation from the inner diameter (ID) to the outer diameter (OD) of the piping. All the results suggest that prolonged service exposure has resulted in the development of micro defects, resulting in the reduction of strength and impact toughness, and the reduction in the hardness at the exposed surface of the corroded piping. Understanding the corrosion mechanism of pipelines exposed to sour media in the long-term helps in repair/replacement planning and extending the usable design life of the material, and paving the way for the oil and gas industry to develop additional ways to monitor the changes in the critical materials’ properties when exposed to sour service.

An Eco-Friendly Quaternary Ammonium Salt as a Corrosion Inhibitor for Carbon Steel in 5 M HCl Solution: Theoretical and Experimental Investigation

“…The diameter of the semicircles of the Nyquist plots increases at higher concentrations of Q-22 inhibitor. This indicates a stimulated inhibition process upon the addition of more inhibitor molecules [ 47 ]. The results at high concentrations of Q-22 demonstrate that the inhibition process becomes effective at such concentrations, possibly due to the formation of a denser protective layer thanks to the Q-22 molecules on the C-steel electrode surface.…”

“…The results at high concentrations of Q-22 demonstrate that the inhibition process becomes effective at such concentrations, possibly due to the formation of a denser protective layer thanks to the Q-22 molecules on the C-steel electrode surface. The Nyquist fitted curves show a figure for a defective heterogeneous surface in aqueous media with a corrosion product and a metal surface response [ 47 ]. The semicircles become depressed at higher temperatures [ 48 ] and deviate from perfect circular shapes, especially at higher temperatures [ 49 ].…”

Polymeric Membranes for H2S and CO2 Removal from Natural Gas for Hydrogen Production: A Review

“…However, for sour natural gases illustrated in Figure 5b, the application of membranes is limited to a very narrow range of concentrations. When H2S concentrations exceed 1-2%, gas treatment becomes prohibitively expensive at small scales due to the requirement of expensive, corrosion-resistant materials [78][79][80]. It should be noted that the figures are based on rough estimates and are not meant to be binding [5,6].…”