Flow-induced corrosion, better known but not accurately termed as erosion, has traditionally been studied from the standpoint of how it is affected by and the protection from it that can be gained by washing out of metal by water or steam-water flow in pipelines of both fossil-fuel and nuclear power plants. Engineers and scientists in different disciplines have worked for many years on methods of complete protection from corrosion or partially reducing corrosion of this type, and they have proposed or applied different countermeasures. The accident at the Surry-2 nuclear power plant (USA) and other similar incidents have once again disturbed the scientific-technical community. This has forced the plant operating personnel and the management to undertake wide-ranging measures in order to discover on time, assess, and monitor such cases. In this paper, we describe briefly three phenomena of washing out of metal. We also discuss the possible methods for observing and assessing the damaged section and the instruments for monitoring the phenomena and countermeasures.