Corrosion monitoring under iron sulfide deposit: Testing method development

摘要

Different from other types of pipeline solids such as sand and iron carbonates, iron sulfide is semi-conductive and electrochemically reactive. This adds extra complexity to laboratory testing and evaluation compared with inert deposits. Previous laboratory testing has shown that the corrosion rate under iron sulfide deposits can be severely overestimated using electrochemical techniques. In the current work a laboratory iron sulfide synthesis method and an iron sulfide under-deposit corrosion testing methodology were developed to better assess and monitor this type of corrosion in a simulated pipeline environment. Two different types of iron sulfides were used to investigate the corrosion of carbon steel under such deposits. Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD) and laser light extinction particle size analysis were utilized to characterize the surface morphology, composition, crystal structure and particle size of the different iron sulfides. A white light interferometric volume loss method was used to verify the under-deposit corrosion rate continuously monitored by the Linear Polarization Resistance (LPR) technique.