51313-02348-Effect of pH on CO2 Corrosion at Elevated Temperatures

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Product Number: 51313-02348-SG

ISBN: 02348 2013 CP

Author: Tanaporn Tanupabrungsun

Publication Date: 2013

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Electrochemical and surface analysis techniques were used to study the mechanisms of CO2 corrosion of mild steel over the temperature range of 80-200C. Experiments were carried out in a 4-liter autoclave equipped to perform in situ electrochemical measurements with both linear polarization resistance (LPR) and electrochemical impedance spectroscopy (EIS). The electrolyte was 1 wt.% NaCl saturated with CO2 set to correspond to 0.03 M of [CO2]aq. Corrosion tests were conducted at temperatures of 80 120 150 and 200C; pH values of 4.0 and 6.0 were used. After the experiments sample surfaces were characterized via scanning electron microscopy (SEM) energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The results showed that with a constant concentration of CO2 in solution and constant temperature the corrosion rate decreased with time due to formation of corrosion products. For the test series at pH 4.0 the corrosion rate increased with temperature up to 120C where increasingly protective layers formed on the steel surface leading to a decrease in corrosion rate. For the test series at pH 6.0 the corrosion rate decreased with temperature. Analysis of the corrosion products confirmed that FeCO3 layers were observed for all the tests and that there was a mixture of magnetite and iron carbonate at 200C.