Application of FFT analysis for the study of directionality of wear scars in exposure to slurry flow of varying velocity

The fast Fourier transform (FFT) has been used extensively in image processing for analyzing periodicity, directionality, and spacing in pattern recognition. This paper describes a procedure for applying FFT technique to images of worn surfaces produced by erosion typical to transport of slurry through tailing pipelines. Rotating cylinder electrode is used for simulating exposure of carbon steel API 5L X65 to flow of different nominal velocities under cathodic protection. Degradation is evaluated by weight loss; whereas the worn surfaces are assessed by scanning electron microscope (SEM). FFT-based analysis of the SEM images reveals that directionality of wear scars evolves with increasing velocity indicating a correlation between erosion wear rate and the condition of the turbulent flow.