The Corrosion Efficiency Of Midazoline Inhibitor With Different Hydrophilic Group In H₂S/CO₂ Environment At Different Flow Velocity

In our country, along with the west-east natural gas pipeline had officially been launched, and some high sulfur oil and gas fields, deep oil and gas field were exploited. The carbon steel’s corrosion research in H2S/CO2 coexistence environment had become the hot spot. While the deep oil and gas field had some characteristics, such as high pressure, high temperature and high flow rate. So in this paper, had studied the effect of the flow rate on imidazoline’s inhibition effect, in H2S/CO2 coexistence environment.1. In this paper, six imidazoline derivates with different hydrophilic groups were synthesized using oleic acid and ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, polyamine and hydroxyethyl ethylenediamine respectively, named IM, IM-2, IM-3, IM-4, IM-D and IM-O, and characterized by infrared spectroscopy. The main research content is as follows:2. The flow velocity near the specimen surface were obtained for each rotational rate through the MixSim. The relationship between flow rate and 20# carbon steel’s corrosion rate were studied by weight loss experiment, SEM, EDS and XRD. The corrosion condition was non inhibitor,3% NaCl solution, pure CO2, pure H2S and H2S、CO2 coexistence environment and 50℃.3. The results showed that flow rate had a significant effect on the corrosion rate, with the increase of velocity, the corrosion rate increased firstly and then decreased. When the velocity was 2.5m/s, the corrosion rate reached the peak. Compared with the other two system, the corrosion rate in H2S and CO2 coexistence environment was the maximum.4. Through the weight loss experiment, contact angle, AFM force curves, the calculation of quantum chemical and SEM, the effect of the flow rate on the imidazoline which had different number of amino ethylene in hydrophilic group was studied. The results showed that in static condition the corrosion efficiency of imidazoline was the highest when the imidazoline hydrophilic group had two amino ethylene (I.e. IM-3). In dynamic condition the imidazoline hydrophilic group had more amino ethylene, the corrosion efficiency of imidazoline was more better (i.e. IM-D>IM-4>IM-3>IM-2>IM). The corrosion efficiency of the imidazoline inhibitor was not only related with the molecular structure of inhibitors, also had a close relationship with the flow rate. With the increase of velocity of flow, the corrosion efficiency of the imidazoline inhibitor decreased.5. The corrosion efficiency of imidazoline inhibitors were better when amine or hydroxyl was introduced to the hydrophilic group, but the hydrophilic group which had hydroxyl was best (i.e. IM-0>IM-2> IM). The water soluble of the imidazoline inhibitor was better when hydroxyl introduced to hydrophilic group; the hydrophobic of the imidazoline inhibitor was better when amine introduced to hydrophilic group. At the same time, the introduction of hydroxyl and amine groups will make the LUMO reaction activity point of the imidazoline molecule migration from C=C to the ring of imidazoline and the hydrophilic group.