Abstract
Many industrial corrosion control programmes use chemical treatments in process streams, production units, pipelines and cooling water systems as the most appropriate economic solution for solving particular problems. In practice corrosion inhibitors are required to provide adequate protection under the highly turbulent flow encountered in typical operating systems. However, most corrosion inhibitor tests and selection procedures use vessels with stirred or sparged solutions and although this may ensure adequate mixing it does not simulate the service conditions. For example, tests on inhibitors for oil field applications can give efficiencies of 99% in stirred solutions but can be less than 50% under reasonable fluid to wall shear stress levels.
The paper considers the use of relatively simple laboratory apparatus which may be employed in laboratory testing. The emphasis of the work is on the use of known shear stress ranges as a means of characterising the hydrodynamic conditions. Data obtained on both Rotating Cylinder Apparatus and Jet Impingement Rigs is presented. This is used to illustrate some of the fundamental reasoning behind the approach adopted.
At a more practical level the use of such tests as part of an overall inhibitor evaluation methodology is also presented. Some inhibitors are shown to be unaffected in performance over a wide range of flow or fluid to wall shear stress; although the actual corrosion rate can depend on the inhibitor concentration. Other inhibitors are sensitive to fluid flow and are therefore limited in their application range.
