Environment and Development Action Third World

Abstract Pipeline transport of CO2 captured directly from industrial processes to further utilization and storage sites is a fundamental part within CCUS projects. Understanding the effect of the several possible impurities in the CO2 stream on pipeline corrosion is a key factor for establishing safe operational limits for contaminants and for limiting highly expensive purification processes. The effect of Hydrogen Sulfide (H2S) on the formation of Hydrogen Induced Cracking (HIC), which is known to be a serious concern in sour gas pipelines, has not received adequate attention in the context of CCUS projects and has therefore been investigated within this study. HIC tests were performed at lab scale in aqueous test solutions containing mixtures of CO2 and H2S and resistance limits based on pH and H2S concentration could be established for SAWL large-diameter pipe of grade X65 and X70. The results were compared to resistance tests performed in liquid CO2 under operating conditions up to 20 MPa containing H2S and other impurities with a focus on the amount of water present with or without a separate water phase.

Abstract This study explores the transport behavior and corrosion protection performance of volatile corrosion inhibitor (VCI) formulations within a custom-designed enclosed piping system. The experimental setup replicates a 2-inch ID piping network, incorporating field-representative geometries including an inlet, vertical riser, lateral branch, main header, and multiple dead-legs. This design enables evaluation of VCI propagation and distribution across complex internal surfaces. The objective is to assess how effectively different formulations disperse throughout the system and maintain protective efficacy in difficult-to-access voids. Insights gained from this study are intended to inform product selection and deployment strategies for corrosion protection in applications such as pipeline lay-up, long-term preservation, and maintenance. The findings will assist end-users in selecting VCI technologies that provide optimal coverage and performance under real-world conditions.

Abstract Volatile corrosion inhibitors (VCIs) are widely used to mitigate corrosion in enclosed systems such as aboveground storage tank (AST) soil-side bottoms, pipe casing annuli, and complex piping networks by providing a protective airspace environment. Current industry evaluations, such as the VIA “jar test” (NACE TM0208), focus on end-state protectiveness; however, they offer limited understanding of the fundamental transport phenomena that govern VCI performance. This study proposes an integrated experimental and modeling framework aimed at quantifying the kinetics of VCI generation, propagation, and depletion. The approach utilizes metal oxide semiconductor (MOS) chemiresistive sensors, complemented by colorimetric detection, to monitor transient VCI concentrations in controlled bench-scale jar tests and simplified pipeline geometries. Experimental data were used to develop unsteady advection–diffusion–reaction models based on dimensionless numbers, yielding estimates for kinetic generation and effective diffusivity. Results showed good agreement between colorimetric analysis, sensor data, and model predictions.

Abstract The sour-service limits of three precipitation-hardened (PH) martensitic stainless steels, 17-4PH (UNS S17400) at 115 ksi (793 MPa) and 160 ksi (1103 MPa), and 13-8PH (13-8Mo, UNS S13800) at 190 ksi (1310 MPa) specified minimum yield strength (SMYS), were re-evaluated through three pressurized autoclave tests. Despite declining in sour service, these corrosion-resistant alloys (CRAs) have had long-term success in wireline operations, attributed to short service durations, low elastic tensile stresses, and improved inspection protocols. This study evaluates the safe and allowable tensile stresses for these CRAs under 5-week cyclic exposures to hydrogen sulfide (H2S) and carbon dioxide (CO2), with partial pressures up to 1000 psi (68.9 bar), temperatures reaching 450°F (232°C), and brine pH ranging from 2.75 to 3.50, both in the presence and absence of elemental sulfur (S8), to determine their resistance to cracking. Results indicate: (1) extensive pitting, particularly in 17-4PH at low pH with S8; (2) 17-4PH at 115 ksi resists sulfide stress cracking (SSC) up to 40-to-50% SMYS at pH 3.50; (3) 17-4PH at 160 ksi shows cracking resistance only up to 25-to-35% SMYS regardless of S8; and (4) 13-8PH consistently fails beyond ~20% SMYS, even at pH 3.50 without S8. These findings highlight the critical need for a comprehensive understanding of both PH stainless steels and wireline equipment to ensure the reliable use of these CRAs in sour environments, often extending outside the conventional boundaries set by NACE MR0175/ISO 15156.

Abstract Crevices formed in subsea assemblies such as flange interfaces, bolted joints, and tube-to-tube connections, especially those involving bare steel, pose a significant challenge to corrosion control. Depending on geometrical conditions, these confined zones often restrict electrolyte flow and oxygen diffusion, and increase pH towards the deep end, creating conditions where cathodic protection (CP) may not fully penetrate. Predicting the extent of CP penetration into such crevices is essential for ensuring long-term integrity of submerged assets, especially in chloride-rich seawater. This paper describes a deterministic model simulation for CP penetration inside a crevice in a subsea assembly, and presents results obtained in commonly occurring scenarios of crevices occurring in marine offshore environments. The model considers geometrical and physical parameters such as oxygen, and CP potential levels to evaluate their impact on corrosion rates and corrosion risk inside the crevice.

Abstract It is commonly believed that effective corrosion inhibitors (CI) in multiphase systems should strongly partition into the water phase, especially under stratified flow conditions. As a result, pre-partitioning studies are often prioritized. However, their relevance to field conditions is increasingly questioned. When tested under pre-partitioned conditions, water-soluble inhibitors may appear superior to more oil-soluble ones, therefore, the relevance of a pre-partitioned test needed to be investigated, and its results compared to those of a similar test conducted in the presence of an oil phase. This study uses electrochemical impedance spectroscopy (EIS) to evaluate the significance of pre-partitioning tests. Three different oils were tested under six different conditions. EIS measurements were taken at 1, 6, and 24 hours using a fixed CI concentration. A final test compared performance and residuals to better understand their relationship. The results question the field relevance of pre-partitioned conditions for CI selection and highlight the need for a corrosion performance test.

Abstract There has been significant advancement in the development and application of corrosion modeling tools for the aerospace defense industry over the past five years. Easy to use and fast modeling solutions are now available for galvanic design compatibility. These tools use mixed-potential theory and polarization curve crossing principles to determine corrosion rates for bimetallic couples. These same tools support the analytical transformation of polarization curves obtained in bulk electrolytes; creating new data that can be used to model aerospace related thin film environments, more typical of atmospheric exposure. This transformation is achieved using an optimized deconvolution process applied to existing polarization scan data which reduces the experimental testing burden. The industry has also seen significant advancements in the simulation of aircraft component corrosion using physics-based modeling. 3D FEA multiphysics modeling can be used to assess corrosion rates in multi-material assemblies, simulate coating degradation, and model steady-state crevice environments. The advent of this physics-based modeling capability is important when dealing with actual component geometry because the IR drop in the electrolyte film can have significant effects on the spatial distribution and magnitude of corrosion rates. Recent strides have also been made to incorporate corrosion related degradation into model-based simulation engineering tools, making it easier to track damage across the life cycle, and provide critical information to engineers charged with structural integrity decision making. Innovative approaches have been developed to model pitting interaction and perform corrosion fatigue crack propagation simulations using environment representative crack growth kinetics and advanced modeling that supports multi-site damage and short crack growth relationships to better capture near ΔKth behavior. New modeling solutions that simulate different cracking scenarios, found at the boundary of corrosion cavities, are also in the initial stage of development. These new modeling approaches attempt to improve corrosion related damage assessment and advance upon previous ideas in Murakami’s defect √area method and Kondo’s pit-to-crack competition model.

Abstract The extraction and purification of helium from produced natural gas is well defined in conventional oil and gas production. Recent exploration has fostered development of wells in inert gas environments that are liquids deficient in comparison to conventional oil and gas extraction. During initial design and mitigation planning, theoretical corrosion rates predicted through historical models indicated a low risk of internal corrosion within the producing environment. Operating conditions consisting of high pressures in combination with condensed produced water and elevated CO2 concentrations were encountered once production began. Internal monitoring via visual and in-line inspection (ILI) found severe internal corrosion early in the life of the producing infrastructure, which resulted in extensive pipeline repairs that were completed in mid-2024. The increased economic investment fostered changes in both the mechanical and chemical corrosion mitigation practices employed throughout the field to be made. Increased pigging frequency, the application of a water-dispersible oil-soluble batch corrosion inhibitor and co-applying a continuous corrosion inhibitor into the gas stream has maintained the pipeline integrity of the repaired sections. Extensive field monitoring and the sharing of asset integrity best practices has led to the increased expansion of production in this unique environment that is rich in inert gases.

Abstract Severe corrosion has been experienced in pipeline systems in North America due to the effects of fracking of production wells to enhance well performance. The chemical reactions that occur in the reservoir can lead to damaging compounds that when flowed back from the well to the pipeline systems have caused corrosion rates higher than 30 mm/yr. This paper discusses the chemical reactions occurring, the well formation contributions, the nature of the corrosion mechanism, and best practice to prevent damage during the frack flowback and during the years following the frack.

Abstract The integrity of Carbon Capture and Storage (CCS) technologies is challenged by the presence of impurities in supercritical carbon dioxide (sc-CO2), compounded by a lack of field and laboratory data to define safe impurity limits for CO2 transport. Impurities such as SO3, NO2, CO2, H2O, H2S, and O2 are typically encountered in supercritical CO2 streams. Quantum chemical calculations were carried out using Density Function Theory (DFT) with the B3LYP method, implemented through atomistic modeling simulation to determine the thermodynamic properties of the potential reactions under sc-CO2 conditions. The study identifies reaction pathways between CO2 and impurities in both water-solvated and sc-CO2 phases. Gibbs free energies of formation for key reactions are computed to assess their feasibility. Findings indicate that acids formed in sc-CO2 (micro-hydrated states) promote water precipitation, with NOx and SOx significantly promoting acidic phase formation under certain conditions. Several concentrations of sulfuric acid were further tested through electrochemical measurements to assess the corrosion behavior of A106 carbon steel. Based on these insights, we present an integrated framework for predicting corrosion in sc-CO2 environments. The molecular modeling results and experimental approach provide a robust framework for accurately predicting and mitigating corrosion risks, thereby enhancing the safety and efficacy of CCS operations.