Graduate School of Engineering and Science

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Browsing by Author "Ahmed, Mohammed Salih"

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    Investigation of corrosion in oil pipelines through surface nano-treatment
    (2020-01) Ahmed, Mohammed Salih; Ertunç, Özgür; Ertunç, Özgür; Bundur, Zeynep Başaran; Ünal, Ramazan; Budaklı, M.; Eker, A. A.; Department of Mechanical Engineering; Ahmed, Mohammed Salih
    Corrosion is the unintentional and degradation of a material caused by the reaction of that material with its environment and a natural possible hazard correlated with gas and oil generation and transportation facilities. Steel with low percentage of carbon are utilized in gas and oil industries specially for the pipelines because its excellent mechanical properties and low cost. However, the pipelines are predisposing to failure with one or more types of corrosion when unprotected to acidic or salty environment. The financial issues and the high cost of the equipment maintenances after corrosion, in oil and gas industries and several sectors have increased the need of improvement in corrosion control strategies. Thus, preventing corrosion is often an important part of an overall design philosophy. The main motivation behind a corrosion study always lies in the desire to optimize the life cycle cost and ensure technical integrity of facilities in an industry. The mitigation of corrosion can be achieved by employing various types of surface treatments. This study investigates the chemical mechanical polishing (CMP) as a novel surface treatment technique for corrosion inhibition of carbon steel used in petroleum industry. The behavior of corrosion phenomenon of carbon steel has been investigated in three phases. In the first phase the samples were immersed in DIW having different pH values in order to study static corrosion behavior the steel. Moreover, the dynamic corrosion behavior was investigated, with the flow setup developed for this purpose. Atomic Force Micrography (AFM) was utilized to observe the morphology of surfaces after in steel pipelines. The effect of wall shear stress and time of immersion was evaluated under the dynamic corrosion test. Under the dynamic and static condition, the rate of corrosion of the steel samples was calculated through the weight loss measurements. The scientists reported that rate of corrosion in steel samples under static condition is higher at lower pH values where the minimum and maximum corrosion rates were obtained at pH = 6 and pH = 4. Also the static corrosion tests suggest that the corrosion rate was high throughout the first 48 h and decreases with the increasing time of tests. The results suggest that increased wall shear stress results in increased the corrosion rate specially at pH=4. In the next phase of the current work, CMP applied to the samples by polishing with polymeric pad using the oxidizer in silica based slurry and abrasive paper with only oxidizer. The surfaces obtained are tested under range of flow velocities at changed pH values for their corrosion behavior. The influence of the fluid flow on the surface roughness are evaluated in the developed experimental set up under turbulent conditions. Potentiodynamic analyses are also conducted to understand the electrochemical behavior of the produced surfaces. The outcomes suggest that the corrosion rate of steel samples polished with oxidizer in the silica based slurry is lower as compared to samples polished using abrasive paper in the presence of oxidizer only which can be attributed the formation of oxide film on the surface. This oxide layer formed act as a protective shield against corrosion. Furthermore, the influence of hydrogen peroxide in silica slurry on the wettability, surface roughness and hardness of steel has been investigated using contact angle measurement, profilometry, Scanning Electron Microscopy and Micro Hardness Tester. In the final phase the surfaces prepared with MP and CMP were coated with a set of coating prepared using sol-gel method. These coated samples upon corrosion investigation in an acidic medium offered advanced corrosion resistance characteristic comparing with uncoated samples. The present study conclude the static corrosion rates measured after every 24 hours for seven days show an almost linear decrease with time after 48 hours. The dynamic corrosion rates obtained utilizing the developed setup show that for the same velocity the corrosion rate drops with time. Although the corrosion rates increase with increasing velocity until critical velocity after which the corrosion rate decreases. However, at pH=4 beyond critical velocity an increase in the corrosion rate was observed, which can be liked with more pronounced influence of the acidic environment on steel corrosion as compared to the momentum of the flowing fluid inside the pipe. All the other cases of dynamic corrosion show an inverse relation between corrosion and time. This relationship has also been observed in static corrosion presented above and also proven in other studies.