Producing wells in the North Sea Galley Field development require application of scale inhibitor at the sub-sea wellheads to prevent formation of calcium carbonate scale across the sub-sea chokes. The wells tie back to the Northern Producer Floating Process Facility (FPF) through rigid carbon steel flowlines which also require chemical inhibitor application to control corrosion. Historically a combined scale / corrosion inhibitor has been applied to provide the necessary scale and corrosion protection downstream from this point in the production process. Following a series of process upsets which occurred in 1999 due to topsides scale formation, the vaterite polymorph of calcium carbonate was identified as the primary scaling species produced in the process system, with subsequent research showing that vaterite formation was induced by the use of corrosion inhibitor in the process stream. This paper presents information on the stabilisation of the normally metastable vaterite polymorph of calcium carbonate and questions the common perception of direct scale inhibitor / corrosion inhibitor incompatibility as a primary factor in reduced inhibitor performance.