CORROSION TESTING OF REINFORCEMENT IN SIMULATED ANNULUS ENVIRONMENTS OF FLEXIBLE PIPELINES

摘要

The multi-layered unbonded structure of a flexible pipe creates an inherent internal volume known as an annulus. This annulus envelops the hoop pressure and tensile reinforcements of the pipe. This presents very specific corrosion conditions if seawater intrudes or water condenses in the annulus and no protection system operates to prevent corrosion. This paper describes an investigation into the effect on general corrosion as a result of this environment utilising small-scale test cells. This was undertaken as an attempt to simulate the corrosion conditions that may occur in differing zones of a flexible pipeline. The cell environment was varied by use of both de-ionised water and seawater. The system was saturated with CO_2 and CH_4 to simulate permeation of this gas through the polymer pressure sheath. Electrochemical and weight loss measurements were undertaken in order to quantify the corrosion rate in these simulated environments. This approach attempts to give useful information regarding the nature of carbon steel tensile reinforcements udes in flexible pipeline under operatinal conditions.