Role of Asphaltenes in Inhibiting Corrosion and Altering the Wettability of the Steel Surface
Abstract Asphaltenes (heptane insolubles) from a variety of crude oils have been identified previously as contributors to inhibition of internal corrosion of mild steel pipelines. However, the mech...
Evaluation of the Protectiveness of a Paraffin Layer In CO2 Corrosion of Mild Steel
Crude oil composition is highly variable and complex. Its components can be broken down into four different classes by solubility characteristics such as: saturates, aromatics, resins, and asphaltenes. Within each class are myriad of chemical compounds, and many have the potential to interact with the pipeline wall to confer protection from corrosion. In this work the focus is on saturates, with the the n-paraffins chosen as being most relevant for the purposes of the present study. A representative pure model compound for the nparaffins used in the experiments is eicosane (C20H42). A mixture of eicosane and a clear, inert model oil was prepared with a range of paraffin concentrations (0 – 50% eicosane). The chemical properties of the mixture were measured, including the Wax Appearance Temperature (WAT), density, viscosity and interfacial tension. The CO2 corrosion rate for carbon steel was measured both below and above the WAT, using the linear polarization resistance (LPR) technique. The protectiveness of the long-chain paraffin layer was challenged by inducing flow (hydrodynamic shear stress) and by increasing temperature. The eicosane successfully conferred corrosion retardation at temperatures below the WAT; however, this protection did not withstand the effect of shear stress or increased temperature. Further analysis by using sessile drop contact angle measurements using a goniometer revealed that the protectiveness by the eicosane is related to changes in the wettability of the surface. The hydrophobicity of the steel surface increased as the concentration of the paraffins in the synthetic paraffin-oil mixture was increased.
Stability of highly charged particles: bitumen-in-water dispersions
Abstract Electric properties of crude oil/water interface play an important role in many industrial applications such as the enhanced oil recovery and road construction. The understanding of the stability mechanism of bitumen-in-water emulsions is of paramount importance in the cold technology of road construction. The stability (or instability) of the emulsion directly affects the transport, the storage and the application on rocks of bitumen emulsions, whereas it has an indirect influence in the final adhesion bitumen–rock. The high values of electrophoretic mobility found for bitumen particles at high pH as well as the charge inversion at low pH are explained by the presence of ionizable surface groups on the bitumen surface. The elevated surface charge density of the spherical bitumen particles brings about that they can be considered as a model system for verifying the electrophoretic relaxation effect experimentally as well as studying the validity of certain standard electrokinetic theories for spherical colloidal particles. Accordingly, the zeta potential was calculated by using different methods such as the classical models (Booth and Overbeek), the exact computation (O'Brien and White) and recent theories (Ohshima). The Hamaker constant of bitumen in water was computed by means of the Lifshitz theory and the simple spectral method from the dielectric responses of alkanes. The stability results suggest that the bitumen dispersion does conform the DLVO theory. In contrast, Non-DLVO forces (such as the “hydrophobic” force) were not observed in this system.