Abstract
Laboratory studies for an asset confirmed no general or localized corrosion of carbon steel exposed to a sour environment with a corrosion inhibitor (CI) under various concentrations of brine at different temperatures. In an extended program, it was investigated if the same CI can protect the welds and the heat affected zones (HAZ) of the pipeline. It was found that at the upper temperature limit, the HAZ was prone to minor localized corrosion and a higher dosage of the CI could effectively prevent it. In the field, the actual residual CI concentration in the aqueous phase was already high enough and thus protected the welded zones preventing corrosion. In some tests, the current between any two among parent, HAZ and weld was measured, and no evidence of galvanic effect was found. Results at low and high wall shear stress conditions generated in autoclaves and a high shear flow loop respectively, were consistent. Test temperatures ranging from 14-75 °C, total dissolved solids (TDS) from 5.7 to 229 g/L and test fluids with and without monoethylene glycol (MEG) were covered in the study. Both Linear Polarization Resistance (LPR) technique and weight loss measurements were used for calculating the corrosion rate (CR).
