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Methods of predicting mineral scale formation have evolved over the years from simple empirical fittings to sophisticated computational programs. Though best practices can now solve complex multi-phase, multi-component systems, they are largely restricted to temperatures below 300 °C. This review examines critical gaps in existing mineral scale modeling approaches as well as strategies to overcome them. Above 300 °C, the most widely used model of standard thermodynamic functions for aqueous species fails when fluid densities are below 0.7 g cm−3. This failure occurs due to the model’s reliance on an empirical form of the Born equation which is unable to capture the trends observed in these high temperature, low density regimes. However, new models based on molecular solvent-solute interactions offer a pathway to overcome some of the deficiencies currently limiting high-temperature and high-pressure mineral scale predictions. Examples of the most common scale prediction methods are presented, and their advantages and disadvantages are discussed.

In this study, we explored the extent to which hydrotropes can be used to increase the aqueous solubilities of redox-active compounds previously used in flow batteries. We measured how five hydrotropes influenced the solubilities of five redox-active compounds already soluble in aqueous electrolytes (≥0.5 M). The solubilities of the compounds varied as a function of hydrotrope type and concentration, with larger solubility changes observed at higher hydrotrope concentrations. 4-OH-TEMPO underwent the largest solubility increase (1.18 ± 0.04 to 1.99 ± 0.12 M) in 20 weight percent sodium xylene sulfonate. The presence of a hydrotrope in solution decreased the diffusion coefficients of 4-OH-TEMPO and 4,5-dihydroxy-1,3-benzenedisulfonate, which was likely due to the increased solution viscosity as opposed to a specific hydrotrope-solute interaction because the hydrotropes did not alter their molecules' hydraulic radii. The standard rate constants and formal potentials of both 4-OH-TEMPO and 4,5-dihydroxy-1,3-benzenedisulfonate remained largely unchanged in the presence of a hydrotrope. The results suggest that using hydrotropes may be a feasible strategy for increasing the solubilities of redox-active compounds in aqueous flow batteries without substantially altering their electrochemical properties.

SummaryInnovative approaches are needed to improve the efficiency of oil recovery technologies to meet the growing demands of fossil-fuel based energy consumption. Enhanced oil recovery (EOR) methods such as low-salinity waterflooding and chemically tuned waterflooding aim to optimize the reservoir’s wetting properties, detaching oil globules from rock surfaces and allowing easier oil flow through pore throats. This wetting behavior is commonly quantified by contact angle measurements of the rock-oil-brine interface, which have been thoroughly investigated and theorized for many systems at ambient temperatures and pressures. However, few studies exist for extending contact angle theories away from ambient conditions. In this paper, we model the contact angles of a quartz-water-decane system at elevated temperatures using the surface tension component (STC) approach. Temperature-dependent van der Waals [Lifshitz-van der Waals (LW)] interactions and hydrogen-bonding (acid-base) interactions were calculated and are incorporated into the model for the quartz-water-decane interface. The Hough and White procedure was used to create temperature-dependent dielectric functions of quartz, water, and normal decane for calculations of Hamaker coefficients. Hamaker coefficients calculated this way are highly linear with temperature and agree well with Israelachvili’s approximation. The acid-base interactions likely contribute the most to system wettability changes. Resulting contact angles of the quartz-water-decane system shift from water-wet (16°) to slightly water-wet (57.4°) as temperature increases. The model was also successfully verified for the quartz-air-water system. Our results can be used in future studies to determine optimal injected water compositions for specific rock-oil-brine and other systems with consideration of reservoir temperature.

This paper will report on a new membrane-based electrochemical sensor that may provide an important utility in monitoring and characterizing internal corrosion of natural gas pipelines. Using this sensor, the corrosion rate of X65 steel exposed to H2S in humidified environments up to 60°C has been measured. Consistent with the authors’ earlier CO2 study, the membrane’s conductivity did not change when exposed to H2S-containing acidic gas. Introducing H2S consistently increased the measured corrosion rate between testing conditions, though corrosion rates were typically less than 2 μm/y. At 30°C, the corrosion rate doubled from 7.3 nm/y to 14 nm/y below a relative humidity of 30%, and it increased by an order of magnitude (0.19 μm/y to 1.9 μm/y) at 55% relative humidity, showing that the influence of H2S on corrosion increases dramatically with greater humidity. Trends with relative humidity match industry expectations: the corrosion rate is low (

Models predicting wettability alteration of mineral-brine-oil interfaces during low-salinity-waterflooding (LSW) should account for the elevated temperatures typically found in oil reservoirs. For the first time, high temperature ζ-potential (zeta potential) data for silica are collected and used to interpret surface chemistries and interactions at reservoir-like conditions to predict temperature’s effect on wettability alteration. Mobility data for amorphous silica in varying NaCl(aq) concentrations at 25, 100, and 150 °C and neutral pH were obtained through microelectrophoresis experiments. Calculated ζ-potentials were fit with surface complexation model (SCM) parameters to predict electrical double layer (EDL) parameters based upon the Gouy-Chapman-Stern-Grahame (GCSG) model. ζ-potentials increased with increasing temperature (around 50% increase from 25 to 150 °C) and decreasing NaCl concentrations (10−1–10−4 mol kg−1). These trends, along with Derjaguin-Verwey-Landau-Overbeek (DLVO) theory, suggests that overall repulsive forces extend farther from the surface at low salinity and higher temperatures, implying greater wetting thickness/surface wettability in these environments. The resulting surface concentration calculations suggest that LSW is most impactful up to 10−2 mol kg−1 of salt, and that additional dilution below 10−3 mol kg−1 will negligibly impact oil recovery, particularly at reservoir temperatures above 100 °C. The analysis provides a framework for treating more complex reservoir systems, such as carbonates in multivalent brines.

Reference electrodes (RE) are essential to many electrochemical measurements and monitoring technologies. True reference electrodes allow measurement of pH, oxidation-reduction potentials, corrosion potentials, and more. The primary role of these REs is to maintain a stable and predictable potential while withstanding an application environment. When these goals cannot be maintained for a suitable amount of time due to complications like contamination or degradation, a pseudo-reference electrode is often used (e.g., a platinum wire) but diminishes the value of the collected electrochemical data (i.e., potential measurements are no longer traceable to the standard hydrogen scale.) To limit the use of pseudo-reference electrodes, new RE designs are being produced to be more compatible with specific environments, to be more cost-effective, or to exhibit better potential stability for a longer time. Additionally, the operational lifetime/stability of the RE should reflect its application: a small, disposable reference electrode may only need to be stable for a few hours; a reference electrode for daily lab use may need maintenance once every other week; a reference electrode used in a remote location may need to be stable for months or many years without servicing. RE lifetimes are typically determined a posteriori (from observation) and not predicted at the design phase, which can make the process of designing a new RE very inefficient. In this paper, we will discuss key design considerations that impact the stability and lifetime for true reference electrodes.

A significant amount of the potential energy that is generated during energy harvesting worldwide is discarded as waste heat because of inefficient power generation cycles. Much of this wasted power source goes unused because it is trapped as low-grade thermal energy (< 100 °C), which traditional power cycles cannot viably harness. With the advent of electrochemical power systems such as redox flow batteries and fuel cells, researchers are investigating new methods of providing usable electric power from these unused low-grade thermal energy sources. The thermally regenerative ammonia battery (TRAB) is one promising technology in this space, as it operates with the same principles as a flow battery except that TRABs can be recharged using low-grade waste heat instead of electric power. Of the TRAB chemistries proposed, the all-aqueous copper TRAB chemistry is capable of both large power densities and energy densities, and high coulombic efficiencies. In this presentation, we discuss how key performance metrics relevant to power generation from low grade thermal energy sources are strongly influenced by electrolyte composition and battery operating parameters. Manipulating the ammonia to copper ratio demonstrated clear tradeoffs between achievable energy and power capacities. Increasing ligand concentration had a large impact on electroactive species solubility and cell potential differences, which increased the theoretical energy density limit of the battery. Increasing the amount of ammonia relative to dissolved copper raised peak power density, but adversely affected energy density. Moderate increases in discharge current density did not decrease the energy density due to reduced impact of ammonia crossover which appears to be a dominant source of energy loss in TRABs.

A new analytical expression was derived for the chemical potential of a hard sphere dipole in hard sphere dipole fluid at infinite dilution of the solute using the mean spherical approximation (MSA). A set of Monte Carlo (MC) simulations has been carried out to investigate the scope of applicability of the derived equation. The mean reaction field (MRF) approach was used in our MC computations. Two different MC methods (Widom particle insertion and thermodynamic integration) were applied for obtaining the chemical potential change associated with the dipole creation at the solute particle to provide adequate accuracy of the MC simulations. Also, corresponding changes in the mean potential energy were calculated by direct method and by thermodynamic integration. The solvation energies have been obtained for the systems of dipolar hard spheres with reduced dipole moment 1.0 at the reduced densities 0.2, 0.5, and 0.8. Computations have been made for solute particles with the reduced dipole moment varied from 0.0 to 1.5 and the hard sphere diameter varied from 0.5 to 2.0. The variation of those quantities with the molecular parameters was analyzed and compared with the MSA equation and Kirkwood classical expressions. It was found that the MSA calculations agree relatively well with MC simulations at densities less than 0.5 and solute dipole moment less than 1.0.

An increasing number of industrial applications rely on controlling solutes in water above and below its critical point. Processes such as hydrothermal synthesis, steam power generation and ultra-high enthalpy geothermal power are all influenced by factors such as mineral precipitation, pH and solute speciation. The supercritical point of water is remarkable in that slight changes in temperature and pressure can cause dramatic changes in some solute properties. Here, it was found that our approach reliant on molecular statistical thermodynamic expressions for hard sphere (HS), ion-dipole and dipole-dipole interactions via mean spherical approximation (MSA) provided excellent agreement to available experimental data. In addition to model parameters having some physical meaning, this approach used less adjustable parameters than the well-known Helgeson-Kirkham-Flowers (HKF) model. Furthermore, the model was used to obtain standard thermodynamic values for HCl0(aq), KCl0(aq) and NaOH0(aq) ion pairs. In total, modeling parameters for 10 different aqueous species were obtained to demonstrate the capabilities of the approach.

Monitoring simultaneously water-content and corrosion rates in low conductivity natural gas pipeline systems) is carried out using membrane-based electrochemical sensors. An ion conducting membrane improves conductivity in humid natural gas in which electrochemical measurements can be performed. In this study, we monitor corrosion rate and humidity of a gas pipeline through the use of commercial Nafion™ membranes, whose conductivity depends on the partial pressure of water vapor in the gas stream. To improve the accuracy, consistency, and reproducibility of data collection, sensor designs vary between electrode preparation using platinum wires versus nanofabricating flat electrode surfaces and configuration. Data for humidity and corrosion rates within various environments is collected using electrochemical impedance spectroscopy and linear polarization resistance tests. Data for 2-, 3-, and 4-electrode cell tests are presented to compare experimental artefacts among sensor designs.

The silver-based thermally regenerative ammonia battery is a new technology for converting low-grade waste heat (

Corrosion studies were conducted for martensitic carbon steels in 5 wt% NaCl brine solutions at 4°C and 10 MPa (1,450 psi). These studies simulated different subsurface environments relevant to Arctic drilling. Here, two high-strength martensitic carbon steels, S-135 and UD-165, were studied in three different environments: (1) a CO2-NaCl-H2O solution with a CO2:H2O molar ratio of 0.312 in the whole system, (2) an H2S-NaCl-H2O solution with an H2S:H2O molar ratio of 3.12 × 10−4, and (3) a CO2-H2S-NaCl-H2O solution with the same acid gas to water ratios as environments 1 and 2. Results from the CO2+H2S mixed environment indicated that sour corrosion mechanism was dominant when the CO2:H2S molar ratio was 1,000. This impact of a small amount of H2S on the corrosion mechanism could be attributed to the specific adsorption of H2S on the steel surface. Electrochemical and mass loss measurements showed a distinct drop in the corrosion rate (CR) by more than one order of magnitude when transitioning from sweet to sour corrosion. This inhibiting effect on CR was attributed to the formation of a protective sulfide thin film. Tafel analyses of the anodic reaction showed that the Bockris mechanism was unlikely in the conditions tested. When comparisons were made between modeled and experimental CRs, good agreement was found in the CO2-only and H2S-only environments, but not in the CO2+H2S environment.

High-temperature corrosion of ultra-high strength low-alloy carbon steel, grade UD-165, was investigated using in situ electrochemical techniques in H 2 S-containing alkaline brines (5 wt% NaCl; pH 8.1, 9.8, and 10.8) at 200 °C. After 60 hours of electrochemical testing, the corrosion rate (CR) at pH 9.8 was the highest, almost twice of the lowest CR found at pH 8.1. The highest CR correlated with the highest HS − (aq) ratio to the total reactive anions. The CR was accelerated at 200 °C by at least one order of magnitude compared with that at 85 °C. A modified method was used to obtain Tafel slopes from linear sweep voltammetry (LSV) plots with the limiting current effect, and the anodic and cathodic reactions were discussed based on the solution speciation, the Tafel slopes, and the corrosion products. Scanning electron microscopy (SEM) showed two layers of corrosion products at pH 8.1 and 9.8. The sulfur distribution moved outwards from the inner layer as pH increased from 8.1 to 10.8. With the pH increase at 200 °C, the major corrosion products changed from pyrrhotite and siderite to magnetite, which was in accordance with the reactive species and the Pourbaix diagram.

This paper presents recent advances by an international team of five countries – Canada, U.S., China, Slovenia and Romania – on the development and scale-up of the copper–chlorine (Cu Cl) cycle for thermochemical hydrogen production using nuclear or solar energy. Electrochemical cell analysis and membrane characterization for the CuCl/HCl electrolysis process are presented. Constituent solubility in the ternary CuCl/HCl/H 2 O system and XRD measurements are reported in regards to the CuCl 2 crystallization process. Materials corrosion in high temperature copper chloride salts and performance of coatings of reactor surface alloys are examined. Finally, system integration is examined, with respect to scale-up of unit operations, cascaded heat pumps for heat upgrading, and linkage of heat exchangers with solar and nuclear plants.

LHD’s are expensive vehicles; therefore, it is important to accurately define the financial consequences associated with the investment of purchasing the mining equipment. This study concentrates on long-term incremental and sensitivity analysis to determine whether it is feasible to incorporate current battery technology into these machines. When revenue was taken into account, decreasing the amount of haulage in battery operated equipment by 5% or 200 kg per h amounts to a $4.0 × 104 loss of profit per year. On average it was found that using battery operated equipment generated $9.5 × 104 more in income annually, reducing the payback period from seven to two years to pay back the additional $1.0 × 105 investment of buying battery powered equipment over cheaper diesel equipment. Due to the estimated 5% increase in capital, it was observed that electric vehicles must possess a lifetime that is a minimum of one year longer than that of diesel equipment. Keywords: Sensitivity analysis, Underground mining vehicles, Battery power, Battery mining equipment, Economic evaluation

A copper-copper sulfate electrode (CSE) was constructed and tested at elevated temperatures. Experimental cell potentials versus a silver-silver chloride electrode were compared against results from Gibbs energy minimization (GEM) calculations. After accounting for irreversible thermodynamic processes, experimental and calculated CSE potentials , were generally within 3% of the observed potential from 25 to 150 °C at 3 MPa. The CSE potentials changed by less than 20 mV with increasing temperature, compared to 120 mV for the silver-silver chloride electrode. With its repeatability and small temperature dependence, the CSE electrode appears to be a viable reference electrode for measuring in-situ real time cell potentials in aqueous phase-containing media at elevated temperature and pressure.

As the need for a sharp reduction in carbon emissions continues to grow, many researchers are looking to electrochemical technologies to provide sustainable power to the grid. One promising technology is the silver thermally regenerative ammonia battery (Ag-TRAB), which is a new approach for converting low-grade waste heat ( A 2D numerical model was created using COMSOL Multiphysics to study the relationship between fluid flow, electrode structure, and electrodeposition in the porous electrodes using cylinders in cross-flow to represent the internal structure of a porous carbon fiber electrode. Lower void fractions resulted in 2.5% higher power density, but less uniform deposition and the pores clogging 3-5 times faster due to nonuniform deposition normal to the membrane boundary. It was found that the electric field resultant from the void fraction and fiber arrangement was critical to the performance of the electrode. The electrode microstructure can be modified to better distribute the deposition rate relative to the pore size to allow for higher power output for a longer discharge time before the pores begin to clog. An electrode with variable void fraction increased the peak power by 7.5% but the pores clogged 23% faster compared to homogenous void fraction.

We present a new, capillary-based contact angle system capable of operation at elevated temperatures up to 200 °C and pressures of 69 bar. New data collected at the quartz/distilled water/n-decane interface from 25 °C to 200 °C indicate a strong temperature linear dependence (1.1° increase for every 5 °C) on the contact angle. This increase cannot be solely attributed to viscous forces influencing the dynamic contact angle, nor can it be sufficiently described by changes in the n-decane/distilled water interfacial tension. Changes to the liquid/solid adhesions also seem likely to be responsible for this temperature dependency. The experimental system will prove useful in fundamental wettability studies through porous media as a function of temperature and add depth to our understanding of enhanced oil recovery processes and interfacial phenomena as a whole. The data highlights the importance of temperature on the wetting behavior of relatively simple, homogeneous, and immiscible materials.

Fouling in boilers has been a problem for decades. In addition to iron oxide deposits on tube walls impeding heat transfer, some forced circulation boilers experience magnetite deposition in lower orifices. These deposits impede flow, cause inefficiencies and lead to boiler tube failures from overheating and corrosion. Particle deposition in some boiler/reactor type environments has been attributed to particle transport and the probability of particle attachment. The attachment is governed by both the inter-particle and particle-substrate interactions, which depend on the aqueous environment. In this study, a novel experimental system is presented, which focusses on the particle attachment aspect of the deposition issues observed in boiler type environments. To identify the effect of boiler water chemistry on the deposition of suspended magnetite on stainless steel, a high temperature high pressure electrophoretic deposition cell with provisions to test metal substrates and different chemistries was developed. Tests were conducted at pH 25 °C of 9.3 in simulated boiler conditions in terms of temperature, pressure and water chemistry. In addition to visual observations, the deposition was investigated using in-situ Electrochemical Impedance Spectroscopy (EIS) and post-test surface analyses including Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS). As predicted by Derjaguin-Landau-Verwey- Overbeek (DLVO) theory, deposition was confirmed possible in the above-mentioned aqueous environment at 300 °C. The experimental system presented here was successful in simulating boiler type environments with accelerated deposition. The capability to understand particulate fouling and also to study interfacial phenomena in high temperature, high pressure aqueous environments has been demonstrated.

Electrochemical corrosion of ultra-high strength carbon steel UD-165 was investigated using in-situ electrochemical techniques in H2S-containing alkaline brines (5 wt% NaCl; pH 7.9, 10.7, and 12.4) with four H2S partial pressures (pH2S) from 0 to 69 kPa at 85 °C. The effects of pH and pH2S were studied in terms of corrosion rate (CR), reaction mechanism, and corrosion products considering the Fe dissolution reactions with HCO3−(aq), OH−(aq), and HS−(aq). While CR generally decreased at higher pH and increased at higher pH2S, both accelerating and inhibiting effects of H2S on CR were observed. High CR at pH 10.7 correlated with a high ratio of HS−(aq) to the total concentration of reactive anions. The corrosion products changed from iron carbonate and sulfides to iron oxides as the pH increased. Sulfur was detected mostly in the inner layer of corrosion products at pH 7.9.

Low-temperature corrosion relevant to oil and gas wells was investigated. Casing cement was exposed to brine in contact with CO2 at 4 °C and 10 MPa. Pore water was extracted from wet cement using a die press, and a cement simulated pore solution (CSPS) was developed to be used for corrosion studies. High levels of chloride similar to the original brine solution were found. The sodium content was well below that of the original brine, with the change in charge mostly balanced by an increase in dissolved calcium. The calcium content was above predictions for brine-CO2-Ca(OH)2 equilibrium, suggesting that sodium was displaced in favor of calcium. Corrosion measurements were performed on casing steel using linear polarization resistance, electrochemical impedance spectroscopy, and mass loss samples with H2S:CO2 ratios from 0 to 0.001. The corrosion rate was found to decrease slightly with increasing sulfide content from 0.02 to 0.01 mm y-1.

We modified the binary interaction parameter in Wong-Sandler mixing rule for cubic EOS as a two-parameter linear function of composition. We then incorporated the Non-Random-Two-Liquid excess Gibbs energy model into the modified Wong-Sandler mixing rule to correlate the phase boundaries of the CO 2 –H 2 O system through the ϕ − ϕ approach by using Peng–Robinson-Stryjek-Vera equation of state. The proposed EOS/ G ex model has four adjustable temperature-dependent parameters for polar molecules; and it can be reduced smoothly to the van der Waal one-fluid mixing rule with only one binary interaction parameter for hydrocarbon systems. An excellent result was obtained when compared the modeling results with a large amount of the vapor–liquid equilibria experimental data (more than 1300 experimental data points located in a P-T region of 273–623 K and 0.1–200 MPa) for the CO 2 –H 2 O system. The average absolute deviations (AAD%) of modeling results from experimental data (mutual solubilities of CO 2 and H 2 O) are less than 7.5% for both phases. In addition, the proposed model can be easily extended to a multi-component system on condition that the binary interaction parameters of each binary pair in the multi-component system are known. We provided a calculation example for the ternary CO 2 –CH 4 –H 2 O system and found that the modeling result agrees very well with experimental data for this ternary system.

Research efforts on the CuCl(aq)/HCl(aq) electrolyzer would greatly benefit from the ability to quantify the dissipative processes that undesirably increase the cell’s applied potential, E cell , which decreases its efficiency. To date, little is known about what impact further improvements to active surface area, extent of CuCl(aq) conversion and ohmic resistance would exactly have on the electrolyzer performance. To better understand how this electrolyzer can be improved, a model was developed to quantify and separate the effects of electrochemical kinetics, membrane transport and open circuit potential, E OCP, on E cell for a given current density. By employing data obtained from previous studies with electrochemical cells into the developed model, it was possible to calculate E cell values that agreed with data collected from a lab scale electrolyzer using just one adjustable parameter, the Nernst diffusion layer at limiting current. The model was then used to identify the predicted E cell contributions as a function of CuCl(aq) conversion, active electrode area and ohmic resistance. It was found that the extent of CuCl(aq) conversion can dramatically impact the electrolyzer electrode kinetics and E OCP . More importantly, as CuCl(aq) conversion increased, the E cell values needed consistently increased to keep the same current density. Overall, E cell could be most readily reduced by improving R ohm , whereas improvements to electrode kinetics have limited impacts.

Deep cuts to global carbon emissions are only possible with a dramatic increase in energy storage capacity. However, the cost of the storage options available hinders the timely deployment of the necessary energy storage. Promising supplements to conventional storage are thermally regenerative ammonia batteries (TRABs), which have an additional advantage of being able to capture low-grade waste heat into dispatchable electricity for the grid. This new battery technology can potentially provide power on demand using low-cost chemistries and waste energy sources relative to their purely electric battery counterparts. Most of the research to date for TRABs has been proof-of-concept in nature. As such, little is known about how the electrolytes used in these devices impact their theoretical energy storage capacity. Here we present the general principles of TRABs from an electrochemical and aqueous chemistry perspective. Energy storage density values and Eh-pH diagrams are presented to highlight key factors that govern these complex but versatile energy storage devices. Ag-based and Cu-based TRABs are discussed, and some experimental data confirming the conclusions of the Eh-pH diagrams are presented.

Internal corrosion monitoring programs are essential for the safe management of natural gas transmission pipelines. Electrochemical technologies can provide reliable, real-time monitoring of key risk factors, such as solution conductivity, corrosion rates, and localized corrosion risk. A novel, membrane-based sensor is being developed to perform electrochemical tests in both aqueous and gaseous environments, allowing for continuous operation and data collection within a pipeline environment. This sensor can be used to determine water content in the presence of a number of gases (CH4, H2S, CO2), to monitor the pipeline’s corrosion rate with and without a condensed phase, and to provide localized corrosion data in the presence of a pitting agent. Here, we explore the sensor’s design, validation through finite-element analysis, and performance data for general and localized forms of corrosion.

As the need for a sharp reduction in carbon emissions continues to grow, many researchers are looking to electrochemical technologies to provide sustainable power to the grid. One promising technology is the silver thermally regenerative ammonia battery (Ag-TRAB), which takes advantage of low-grade waste heat (

One aspect of effective steam/water cycle chemical treatment programs is their ability minimize corrosion and corrosion related failures. In this study, we examine how corrosion product layers on the surface of tubing samples impact corrosion rate for a series of test specimens prepared from boiler/steam piping provided from operating power plants. Corrosion rates were estimated using the following electrochemical techniques: linear sweep voltammetry (LSV), linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). Two sources of Tafel slopes were the standard assumptions used if the corrosion mechanism is not known and those obtained from LSV curves. In total, five variations of corrosion rate measurements were compared. For these corrosion tests, water chemistries representative of conditions that induced online hydrogen damage and offline pitting were used. Field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDS/EDX) were the electron microscopy techniques applied to examine the corrosion product layers. Using these techniques, the microstructure and elemental composition of the tubing sample corrosion product layers were examined. These techniques could be utilized to evaluate the effectiveness or reduction in corrosion rates with the application of film forming products.

For meeting ambitious carbon-free electricity goals, low-cost electrical energy storage solutions are needed. Although redox flow batteries are a promising option to satisfy this need, the cost of these devices must decrease before widespread adoption can take place. As the electrolytes are the most significant expense for MW-scale flow batteries, new chemistries derived from inexpensive metals is one approach that may alleviate this bottleneck towards a carbon-free power grid. Here we use an electrochemical approach by applying a rotating disc electrode (RDE) to quantify how ligand chemistries can favorably manipulate the electrochemical parameters of the Cu(I/II) redox reaction, progressing these chemistries forward as potential low-cost electrolytes for redox flow batteries. In this research, multiple ligands were used to analyze such impacts on aqueous copper metal complexes by using both a platinum and carbon tipped electrode installed into the RDE. Electrochemical Impedance Spectroscopy (EIS), Linear Sweep Voltammetry (LSV) and Open Circuit Potential (OCP) were the three techniques utilized to analyze the effects of these metal complexes. The experimental data was analyzed using the Butler-Volmer and Nernst equations. As step reactions are mostly unknown for these reactions, LSV and EIS data gave insights into what may be occurring at the electrode interfaces. OCP data quantified how different ligands modified the standard electrode potentials of the Cu(I/II) redox reaction.

The electrochemical corrosion behavior of high strength low alloy carbon steel API S-135 was investigated using in-situ electrochemical measurements, ex situ surface analyses, and software modeling in the alkaline brines at pH of 7.9, 10.7, and 12.4 and at four different P H2S equal to 0 kPa, 0.83 kPa, 8.3 kPa, and 69 kPa at 85 oC. Linear polarization resistance (R pol) at steady state increased as pH increased from 7.9 to 12.4 at lower P H2S whereas R pol decreased and then increased at higher P H2S. The fastest corrosion rate (CR) was 0.26 mm yr-1 at pH 10.7 with P H2S 69 kPa, and the slowest CR was 0.0053 mm yr-1 at pH 12.4 with P H2S 0.83 kPa. The correlation between the primary species, corrosion products, localized corrosion and R pol were discussed. The experimental CR and corrosion products were compared with the modeling CR and Pourbaix diagram.

A phenomenological model describing the transport processes across a cation exchange membrane was developed. Using data obtained from conductivity, permeability and transport number experiments, the model quantified the direct and indirect influences of CuCl(aq) chemical potential and electric potential gradients on the fluxes of H+(aq), CuCl(aq) and charged species across a pressed Nafion 117 membrane in contact with 7 mol L-1 HCl(aq). This system is of particular interest for the CuCl(aq)/HCl(aq) electrolytic cell, a key component in the Cu-Cl hybrid thermochemical cycle. It was found that in highly reduced CuCl(aq) solutions, the flux of protons and charged species were influenced by the presence of copper species.

A test procedure was designed and employed for exposure and degradation testing of well cements in a simulated downhole environment of offshore deep drilling. A Class H cement sample was crushed to coarse grains and was exposed to 5 % mass NaCl(aq) solution in contact with CO2(g) at 100 ˚C. The partial pressure of CO2 was 10 MPa. After the 200-hour exposure, the liquid phase from the testing, or the ‘original pore solution’, was diluted and extracted for qualitative and quantitative analyses of the key ionic species. Significant variation was observed between samples drawn in situ and ex situ from the original pore solution. Ca2+(aq), Na+(aq), and some K+(aq) were determined to be the primary cationic species. Cl-(aq) and SO4 2-(aq) were found to be major anionic species, though the concentration of Cl-(aq) was lower than that originally in the NaCl(aq) solution. The compounds used to achieve the equilibrium speciation corresponding to the “original pore solution” were modeled using commercial software OLI Analyzer Studio 9.0, and were used to develop the cement synthetic pore solution (CSPS) recipe. The CSPS was then used for corrosion characterization of high chromium well casing steel, type 13Cr, grade L-80. The steel samples were exposed to CSPS at 100 ˚C and 10 MPa pressure in contact with CO2(g) with a Pt mesh counter electrode and a custom made Ag/AgCl electrode. The corrosion behavior of the steel was investigated using a set of electrochemical methods consisting of the open circuit potential, linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS) at 3-hour intervals to detect steady state conditions. The CO2-rich CSPS was stirred during these experiments, which lasted 60 hours. At the end of 60-hour exposure, the stirring was stopped and the same set of electrochemical tests was performed without stirring to detect any effect of convection or diffusion. The corrosion potential in the measurements was similar, between -0.4 and -0.5 V vs. standard hydrogen electrode. The average corrosion rate of the steel samples was on the order of 0.1 mm/year. This was considered high for an environment in which steels expected to be passivated. Polarization resistance obtained from EIS data was similar to that determined through LPR. No significant change in the corrosion behavior was observed between stirred and unstirred conditions, and the EIS data did not suggest that corrosion process was controlled by diffusion. The high corrosion rate was believed to be due to neutralization of the calcium hydroxide by the dissolved CO2, which then moved the corrosion potential of the steel from the passive region to the active region. This would provide a highly corrosive environment when combined with the high chloride content and high temperature of the CSPS. While it was noted that the condition studied here represented a worst-case scenario for degradation of the cement material, the magnitude of the corrosion rate shows that care must be taken to prevent damage to the cement coating, as the resulting environment could result in severe corrosion and premature failure of critical steel components like a well casing.