Rotating Cylinder Vs. Loop testing of inhibitors for CO2 Corrosion.
S.Nesic, G. T. Solvi and S. Skjerve.

A study was carried out to investigate the effect of various hydrodynamic parameters on the corrosion rate of low carbon steel in CO2 environments in the presence of inhibitors. Two different flow geometries: rotating cylinder and pipe flow were studied simultaneously in the same electrolyte within a glas loop. The comparisons were carried out at room temperature, pH 4-6, pCO2=1 bar, V=0-13 m/s.the hydrodynamic conditions studied cover the range from static to highly turbulent flow.The corrosion process was monitored with the following electrochemical measuring impedance. The comparison of the two flow geaometries was carried out in terms of hydrodynamics, mass transfer and CO2 corrosion.
The measured mass transfer rates were found to agre wll with previously publishd correlations for the rotating cylinder and straight pipe case of CO2 corrosion without it was possible to achieve good agreement between corrosion rates in the two flow geometries by having the same water chemistry and mass transfer conditions.This conclusion is valid for the case whn no protective corrosion product or scale are present.With the inhibitors present th perormance of both the amine and imidazoline based inhibitor measured using the rotating cylinder was identical to the one in the straight pipe flow geometry. The performance of the inhibitors was not significantly affected by the flow, in the range from 2 m/s to 10 m/s (corresponding to a shear stress to 13 Pa and 222 Pa respectively).

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