Abstract
Many corrosion control programmes in oil and gas production rely on chemical treatments. Inhibitor selection is therefore an important technical and economic aspect of the total corrosion engineering system. However, at present there are no widely accepted procedures which both an operator and chemical supplier could use to mutual advantage for the assessment of inhibitors in sweet, mildly sour and high velocity systems.
This paper considers the requirements of various inhibitor evaluation procedures with respect to their ease of laboratory testing and ultimate field applications. Of particular interest is data obtained from relatively simple Bubble Tests which could form the initial stage of inhibitor selection.
A statistical view of the experimental design and analysis demonstrated the importance of well controlled experimental procedures in inhibitor assessments. The deficiency of weight loss measurements compared to electrochemical data, in their ability to discriminate between various inhibitors, is also highlighted by statistical procedures. A lack of control and non-rigorous analysis are reasons for the widely varying responses from various tests conducted in different laboratories.
Controlled hydrodynamic conditions form the basis of the second stage of the selection procedure. Measurements were obtained in both Rotating Cylinder Apparatus and Jet Impingement Rigs. These turbulent fluid flow conditions, with a known wall shear stress, can further discriminate between inhibitors which exhibit good, >80%, efficiencies in a Bubble Test. However, the relatively poor performance of many inhibitors under turbulent flow conditions requires further investigation. The Rotating Cylinder Apparatus is recommended as the basis of a future test for inhibitor evaluations.
