Erosion-corrosion of carbon and low alloy steels by water at 300°C

Abstract

Examination of ferrules used to control the flow of water at 300°C through individual tubes in an evaporator unit has shown that carbon steels can undergo high rates of erosion–corrosion (up to 3mm/year) under these conditions. It is concluded that such high rates of erosion–corrosion are due to the exceptionally low level of chromium in the steel and a very high mass transfer coefficientfor soluble iron at the surface. For levels of chromium up to 2·3% in carbon and low alloy steels, resistance to erosion–corrosion appears to be directly proportional to the level of chromium in the steel. The absence of any enrichment of molybdenum or copper in the oxide layer indicates that the presence of these elements is unlikely to enhance resistance to erosion–corrosion inflowing water. A simple hydrodynamic model is proposed to account for observed variations in surface condition and rate of erosion–corrosion within the ferrules.