Novel assessment of in-operations mapped stainless steel elbow pipe internal wall for detection of corrosion and scale deposition

Corrosion and deposition of scale onto the pipelines pose a great risk in the petroleum industry. If proper detection and monitoring techniques are not employed, scale deposits can lead to a reduction of flow area as well as obstruction of entire sections in pipeline infrastructure. In this work, ultrasonic testing, visual inspection, and spectroscopic techniques have been combined to investigate the influence of simulated seawater on corrosion and scale deposition on 316L stainless steel elbow. Specifically, ultrasonic thickness gauge was used externally to study the changes in wall thickness of the elbow pipe, which was then visually inspected using a borehole camera. To characterize the morphology and composition of the scale deposit, a sample was extracted and characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FT-IR). Scales accumulation on the pipe internal wall prompted a slight increase in the wall thickness before cleaning and a maximum decrease of 14% after cleaning. The extracted scale sample characterization reveals the formation of CaCO3 scale of the Aragonite phase and is traced to the composition of the simulated seawater. Multiple techniques deployments for assessment of corrosion and scale deposition in elbow help stop both processes and ultimately assist in the oil and gas industry.