To address some of the fundamental questions regarding the kinetics of reduction of contaminants by zero-valent iron (Fe 0 ), we have taken advantage of the mass transport control afforded by a polished Fe 0 rotating disk electrode (RDE) in an electrochemical cell. The kinetics of carbon tetrachloride (CCl 4 ) dechlorination at an Fe 0 RDE were studied in pH 8.4 borate buffer at a potential at which an oxide film would not form. In this system, the cathodic current was essentially independent of electrode rotation rate, and the measured first-order heterogeneous rate constant for the chemical reaction (k ct ) 2.3 × 10 -5 cm s -1 ) was less than the estimated rate constant for mass transfer to the surface. Thus, for the conditions of this study, the rate of reduction of CCl 4 by oxide-free Fe 0 appears to be dominated by reaction at the metal-water interface rather than by transport to the metal surface. Activation energies for reduction of CCl 4 and hexachloroethane by oxide-covered granular Fe 0 (measured in batch systems) also indicate that overall rates are limited by reaction kinetics. Since mass transport rates vary little among the chlorinated solvents, it is likely that variation in k ct is primarily responsible for the wide range of dechlorination rates that have been reported for batch and column conditions.

Corrosion has been a great concern in the oil and natural gas industry costing billions of dollars annually in the U.S. The ability to monitor corrosion online before structural integrity is compromised can have a significant impact on preventing catastrophic events resulting from corrosion. This article critically reviews conventional corrosion sensors and emerging sensor technologies in terms of sensing principles, sensor designs, advantages, and limitations. Conventional corrosion sensors encompass corrosion coupons, electrical resistance probes, electrochemical sensors, ultrasonic testing sensors, magnetic flux leakage sensors, electromagnetic sensors, and in-line inspection tools. Emerging sensor technologies highlight optical fiber sensors (point, quasi-distributed, distributed) and passive wireless sensors such as passive radio-frequency identification sensors and surface acoustic wave sensors. Emerging sensors show great potential in continuous real-time in-situ monitoring of oil and natural gas infrastructure. Distributed chemical sensing is emphasized based on recent studies as a promising method to detect early corrosion onset and monitor corrosive environments for corrosion mitigation management. Additionally, challenges are discussed including durability and stability in extreme and harsh conditions such as high temperature high pressure in subsurface wellbores.

Metallic interconnects in solid oxide fuel cells are exposed to a dual environment: fuel on one side (i.e. H 2 gas) and oxidizer on the other side (i.e. air). It has been observed that the oxidation behavior of thin stainless steel sheet in air is changed by the presence of H 2 on the other side of the sheet. The resulting dual environment scales are flaky and more friable than the single environment scales. The H 2 disrupts the scale on the air-side. A model to explain some of the effects of a dual environment is presented where hydrogen diffusing through the stainless steel sheet reacts with oxygen diffusing through the scale to form water vapor, which has sufficient vapor pressure to mechanically disrupt the scale. Experiments on preoxidized 316L stainless steel tubing exposed to air/air, H 2 /air, and H 2 /Ar environments are reported in support of the model.

The stability of yttria‐silica binary aqueous colloidal suspensions is examined as a function of time. It has been observed that initially stable silica particles go through a flocculation period and then restabilize. This phenomenon is attributed to slow dissolution and the specific adsorption of trivalent yttrium cation and its hydroxo complexes on the surface of silica. Furthermore, it is shown that the kinetics of flocculation and restabilization can be controlled by pH adjustment.