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51318-10997-Effect of Alloying Elements on the Corrosion Behavior of Carbon Steel in CO2 Environments

The objective of the present study was to evaluate the effect of alloying elements (Cr, Mo and Cu) on the corrosion behavior of low carbon steel in CO2 environments. Six samples were prepared with varying Cr content from 0 to 2 wt.% and with added 0.5 wt.% of Mo and Cu.

Product Number: 51318-10997-SG
Author: Yoon-Seok Choi / Srdjan Nesic / Hwan-Gyo Jung
Publication Date: 2018
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The objective of the present study was to evaluate the effect of alloying elements (Cr, Mo and Cu) on the corrosion behavior of low carbon steel in CO2 environments. Six samples were prepared with varying Cr content from 0 to 2 wt.% and with added 0.5 wt.% of Mo and Cu; the specimens had ferritic/pearlitic microstructures. Steel samples were exposed to a CO2-saturated 1 wt.% NaCl solution with different combinations of pH and temperature (pH 4.0 at 25oC, pH 6.6 at 80oC, and pH 5.9 at 70oC). Changes in corrosion rate with time were determined by linear polarization resistance (LPR) measurements. The surface morphology and the composition of the corrosion product layers were analyzed by surface analysis techniques (SEM and EDS). Results showed that the addition of Cr and Cu showed a slight positive effect on the corrosion resistance at pH 4.0 and 25oC. At pH 6.6 and 80oC, regardless of the alloying elements, the trend of corrosion rate with time was similar, i.e., the corrosion rate of all specimens decreased with time due to the formation of protective FeCO3. A beneficial effect of Cr addition was clearly seen at pH 5.9 and 70oC, where steel sample without Cr showed no decrease in corrosion rate with time. The addition of Cr promotes the formation of protective FeCO3 and it decreases the corrosion rate.

Key words: CO2 corrosion, carbon steel, alloying element, FeCO3

The objective of the present study was to evaluate the effect of alloying elements (Cr, Mo and Cu) on the corrosion behavior of low carbon steel in CO2 environments. Six samples were prepared with varying Cr content from 0 to 2 wt.% and with added 0.5 wt.% of Mo and Cu; the specimens had ferritic/pearlitic microstructures. Steel samples were exposed to a CO2-saturated 1 wt.% NaCl solution with different combinations of pH and temperature (pH 4.0 at 25oC, pH 6.6 at 80oC, and pH 5.9 at 70oC). Changes in corrosion rate with time were determined by linear polarization resistance (LPR) measurements. The surface morphology and the composition of the corrosion product layers were analyzed by surface analysis techniques (SEM and EDS). Results showed that the addition of Cr and Cu showed a slight positive effect on the corrosion resistance at pH 4.0 and 25oC. At pH 6.6 and 80oC, regardless of the alloying elements, the trend of corrosion rate with time was similar, i.e., the corrosion rate of all specimens decreased with time due to the formation of protective FeCO3. A beneficial effect of Cr addition was clearly seen at pH 5.9 and 70oC, where steel sample without Cr showed no decrease in corrosion rate with time. The addition of Cr promotes the formation of protective FeCO3 and it decreases the corrosion rate.

Key words: CO2 corrosion, carbon steel, alloying element, FeCO3

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