Two-phase flow in pipelines, particularly slug flow, induces high shear stresses at the walls that can interfere with the performance of corrosion inhibitors. Conventional electrochemical techniques are poorly suited to making corrosion measurements under these conditions in the laboratory. The introduction of electrical resistance or other corrosion probes can disturb the flow pattern. The paper describes the adaptation of an electrical resistance mapping technique to evaluate the performance of corrosion inhibitors in defined two-phase flow regimes in thin-walled (1 mm) tubes in the laboratory over periods of the order of 24 h, providing on-line information in pipeline geometries as a function of circumferential position. Two plastic hernicylindricaljackets were designed and manufactured with 24 pairs of spring loaded pins to contact the outside surface of the tubular test specimen and rneasure metal loss through changes in the voltage between them when a current was passed through the specimen. Tests were carried out in slug flow with
and without corrosion inbibitors in deoxygenated 3 w% NaCl brine under 1 bar CO2 pressure using specimens manufactured from the wall of an X-65 pipeline steel. A sensitivity of 0.1%of wall thickness was demonstrated...
Keywords: corrosion inhibitor, inhibitor efficiency, field signature method, two-phase flow, slug flow, brine, carbondioxide, sensitivity, inhibitor test method