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Inhibition mechanisms of corrosion inhibitors in multiphase flow conditions using electrochemical techniques

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2000, Doctor of Philosophy (PhD), Ohio University, Chemical Engineering (Engineering).

Corrosion and inhibition of imidazoline based inhibitors were studied in a 101.6 mm I.D, 15 m long gas/oil/water three-phase flow loop using electrical impedance spectroscopy (EIS), polarization curves, and electro-chemical noise (ECN)techniques. Inhibitors were initially screened in a rotating cylinder electrode (RCE) cell, and some inhibitors were further studied in the flow loop. Both single phase full pipe flow and oil/water/gas slug flows were generated.

Inhibitors behaved differently in the RCE and flow loop systems. In slug flow, the effectiveness of 25 ppm inhibitors was about 50-84% whilst achieving 95%-98% in the RCE cell. From the EIS Nyquist plots, this is shown to be due to formation of a compact film of the inhibitor on the metal surface in the RCE but could only form a porous film in slug flow. This was due to the turbulence and bubble impacts present in the slug flow.

From the EIS Nyquist plots, equivalent electrical circuits were constructed. At a concentration of 25 ppm of inhibitor, when compared to full pipe flow, results from slug flow indicated that there was a diffusion tail at the low frequencies which was not present in the RCE. This indicated that the inhibitor film was porous which was defined by the Warburg impedance coefficient. Further, when changing from full pipe flow to slug flow, the charge transfer resistance decreased by about 13% and the Warburg impedance decreased by about 36%.

In the presence of oil, it was found that the effectiveness of inhibitors was increased about 10% for all cases.

ECN at a high sampling rate was an effective technique for investigating the instantaneous corrosion in multiphase flow. Results from the ECN showed that the sampling frequency was very important especially for slug flow. Due to the pulses of bubbles and bubble collapse, sampling rates in excess of 60 Hz were needed to identify these phenomena. In slug flow, large, regular peaks were found in the raw data of both current and voltage fluctuations. This indicated a higher corrosion rate in slug flow.

When inhibitor was added, the fluctuation in the current decreased in each case indicating a decrease in the corrosion rate.

In the frequency domain, the roll-off slope of the voltage amplitude was less than-20 dB/decade, which indicated the pitting initiation.

W. Jepson (Advisor)
252 p.

Recommended Citations

Citations

  • Chen, Y. (2000). Inhibition mechanisms of corrosion inhibitors in multiphase flow conditions using electrochemical techniques [Doctoral dissertation, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1179168537

    APA Style (7th edition)

  • Chen, Yue. Inhibition mechanisms of corrosion inhibitors in multiphase flow conditions using electrochemical techniques. 2000. Ohio University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1179168537.

    MLA Style (8th edition)

  • Chen, Yue. "Inhibition mechanisms of corrosion inhibitors in multiphase flow conditions using electrochemical techniques." Doctoral dissertation, Ohio University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1179168537

    Chicago Manual of Style (17th edition)