Siderite micro-modification for enhanced corrosion protection

Production of oil and gas results in the creation of carbon dioxide (CO₂) which when wet is extremely corrosive owing to the speciation of carbonic acid. Severe production losses and safety incidents occur when carbon steel (CS) is used as a pipeline material if corrosion is not properly managed. Currently corrosion inhibitor (CI) chemicals are used to ensure that the material degradation rates are properly controlled; this imposes operational constraints, costs of deployment and environmental issues. In specific conditions, a naturally growing corrosion product known as siderite or iron carbonate (FeCO₃) precipitates onto the internal pipe wall providing protection from electrochemical degradation. Many parameters influence the thermodynamics of FeCO₃ precipitation which is generally favoured at high values of temperatures, pressure and pH. In this paper, a new approach for corrosion management is presented; micro-modifying the corrosion product. This novel mitigation approach relies on enhancing the crystallisation of FeCO₃ and improving its density, protectiveness and mechanical properties. The addition of a silicon-rich nanofiller is shown to augment the growth of FeCO₃ at lower pH and temperature without affecting the bulk pH. The hybrid FeCO₃ exhibits superior general and localised corrosion properties. The findings herein indicate that it is possible to locally alter the environment in the vicinity of the corroding steel in order to grow a dense and therefore protective FeCO₃ film via the incorporation of hybrid organic-inorganic silsesquioxane moieties. The durability and mechanical integrity of the film is also significantly improved

Amorphous dysprosium carbonate: characterization, stability, and crystallization pathways

The crystallization of amorphous dysprosium carbonate (ADC) has been studied in air (21–750 °C) and in solution (21–250 °C). This poorly ordered precursor, Dy2(CO3)3·4H2O, was synthesized in solution at ambient temperature. Its properties and crystallization pathways were studied by powder X-ray diffraction, Fourier transform infrared spectroscopy, scanning and transmission electron microscopy, thermogravimetric analysis, and magnetic techniques. ADC consists of highly hydrated spherical nanoparticles of 10–20 nm diameter that are exceptionally stable under dry treatment at ambient and high temperatures (<550 °C). However, ADC transforms in solution to a variety of Dy-carbonates, depending on the temperature and reaction times. The transformation sequence is (a) poorly crystalline metastable tengerite-type phase, Dy2(CO3)3·2–3H2O; and (b) the orthorhombic kozoite-type phase DyCO3(OH) at 165 °C after prolonged times (15 days) or faster (12 h) at 220 °C. Both the amorphous phase and the kozoite-type phase DyCO3(OH) are paramagnetic in the range of temperatures measured from 1.8 to 300 K