The subsea flow lines of a UK North Sea oilfield were at risk of corrosion and scale. The main corrosion risk was due to the presence of carbon dioxide and also localised areas of high velocity flow. In certain locations the predicted wall shear stress could be as high as 150 Pa. In addition the flow lines were suffering from calcium carbonate scale deposition. Due to the limitations with respect to availability of subsea chemical injection umbilicals and equipment a combined scale / corrosion inhibitor was required to maintain the pipeline integrity and prevent scale deposition. In addition the recommended product was required to be environmentally acceptable. This paper describes in detail the research performed to develop a new environmentally friendly multi-functional scale / corrosion inhibitor. The efficacy of the product in preventing scale and corrosion under the system conditions was confirmed in the laboratory using several standard tests (dynamic scale loop corrosion kettle test and rotating cylinder electrode). Furthermore corrosion inhibition performance in preventing weldment corrosion under high shear conditions was evaluated using a corrosion flow loop.