Ultrasonic thickness gauges are used to accurately determine the thickness of a variety of materials when only one side is accessible - ideal for monitoring corrosion and erosion. Converting the time of flight of pulse of sound energy, sent into and reflecting back from a defect or opposite surface, ultrasonic thickness gauges are ideal for measuring a material's thickness and detecting pits and flaws in a material without damage. A coated surface may disguise defects in the substrate beneath; the wall thickness of a pipeline, for example, may have been eroded by the flow of the material inside.