The growth of iron carbonate (FeCO3) on the internal walls of carbon steel pipelines used for oil and gas transportation can reduce internal corrosion significantly. Solution pH can be considered as one of the most influential factors with regards to the kinetics, morphology and protection afforded by FeCO3 films. This paper presents results from a recently developed in situ Synchrotron Radiation-X-ray Diffraction (SR-XRD) flow cell integrated with electrochemistry for corrosion measurements. The cell was used to follow the nucleation and growth kinetics of corrosion products on X65 carbon steel surfaces in a carbon dioxide (CO2)saturated 3.5 wt.% NaCl brine at 80 º C and a flow rate of 0.1 m/s over a range of solution pH values (6.3, 6.8 and 7). In all conditions, FeCO3 was identified as the only crystalline phase to form. Electrochemical results coupled with post-test surface analysis indicate that at higher pH, larger portions of the surface become covered faster with thinner, more protective films consisting of smaller, denser and more compact crystals. The comparison between XRD main peak area intensities and FeCO3 surface coverage, mass and volume indicates a qualitative relationship between these parameters at each pH, providing valuable information on the kinetics of film growth.

The formation of FeCO3 and Fe3O4 on carbon steel and their protective capabilities against CO2 corrosion at elevated temperature and pressure. Corrosion Science, 157. pp. 392-405.

Evaluation of high shear inhibitor performance in CO2-containing flow-induced corrosion and erosion-corrosion environments in the presence and absence of iron carbonate films. Wear, 405. pp. 143-152.

An electrochemically integrated Synchrotron Radiation-Grazing Incidence X-Ray Diffraction (SR-GIXRD) flow cell for studying corrosion product formation on carbon steel in carbon dioxide (CO2)-containing brines typical of oil and gas production has been developed. The system is capable of generating flow velocities of up to 2 m/s at temperatures in excess of 80 °C during SR-GIXRD measurements of the steel surface, enabling flow to be maintained over the course of the experiment while diffraction patterns are being collected. The design of the flow cell is presented, along with electrochemical and diffraction pattern transients collected from an initial experiment which examined the precipitation of FeCO3 onto X65 carbon steel in a CO2-saturated 3.5 wt. % NaCl brine at 80 °C and 0.1 m/s. The flow cell is used to follow the nucleation and growth kinetics of FeCO3 using SR-GIXRD linked to the simultaneous electrochemical response of the steel surface which were collected in the form of linear polarisation resistance measurements to decipher in situ corrosion rates. The results show that FeCO3 nucleation could be detected consistently and well before its inhibitive effect on the general corrosion rate of the system. In situ measurements are compared with ex situ scanning electron microscopy (SEM) observations showing the development of an FeCO3 layer on the corroding steel surface over time confirming the in situ interpretations. The results presented demonstrate that under the specific conditions evaluated, FeCO3 was the only crystalline phase to form in the system, with no crystalline precursors being apparent. The numerous capabilities of the flow cell are highlighted and presented in this paper.

Although corrosion resistance and mechanical properties of sol-gel coatings have been studied independently, there are limited studies that consider both collectively. However, since any form of mechanical damage could impair the protective function of the coating, it is prudent to consider the mechanical durability of coatings as well as their corrosion resistance. The present work considers the impact of silica nanoparticles on the morphology and mechanical properties of a sol-gel derived coating. The relationships between the results obtained from tests such as atomic force microscopy (AFM), nanoindentation or erosion test with previously reported corrosion results obtained via salt spray or electrochemical impedance spectroscopy (EIS) are discussed. Results show that reinforcing a sol-gel coating with silica nanoparticles and, particularly, functionalised silica nanoparticles led to coatings with improved mechanical properties and enhanced erosion impact resistance. The role of nanoparticles on improving mechanical properties and corrosion resistance, which is of importance within the coating industry, is discussed. Highlights:-Effect of SiO2 on morphology and mechanical properties in a sol-gel coating was studied-SiO2 surface treatment improved mechanical durability and corrosion resistance-Importance of studying mechanical and corrosion resistance properties of coatings has been proved

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.

Data of hourly interplanetary plasma (field magnitude, solar wind speed, and ion density), solar (sunspot number, solar radio flux), and geomagnetic indices (Kp, Ap) over the period 1970-2010, have been used to examine the asymmetry between the solar field north and south of the heliospheric current sheet (HCS). A persistent yearly north-south asymmetry of the field magnitude is clear over the considered period, and there is no magnetic solar cycle dependence. There is a weak N-S asymmetry in the averaged solar wind speed, exhibited well at times of maximum solar activities. The solar plasma is more dense north of the current sheet than south of it during the second negative solar polarity epoch (qA < 0). Moreover, the N -S asymmetry in solar activity (Rz) can be statistically highly significant. The sign of the average N -S asymmetry depends upon the solar magnetic polarity. The annual magnitudes of N -S asymmetry depend positively on the solar magnetic cycle. Most of the solar radio flux asymmetries occurred during the period of positive IMF polarity.

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