Effects of dissolved oxygen on the corrosion-related unidentified deposit formed of 304 SS in the flow accelerated zone under the simulated secondary water chemistry

Abstract

Effects of dissolved oxygen (DO) on the deposition characteristics of corrosion-related unidentified deposit (CRUD) were investigated by using 304 stainless steel micro-orifices. The main results indicate that the change of DO concentration resulted in a change of the composition of the outermost deposition layer. The DO concentration amplifies/diminishes the porosity in CRUD effect by changing the rate of ion transport. Meanwhile, the electrokinetic effect is weakened by the decrease of the thickness of the electric double layer, which is caused by the dissolution of Cr ions increased by increasing the DO concentration. Meanwhile, the chromium ion concentration increases with the dissolved oxygen concentration, which leads to a decrease in the thickness of the electric double layer, weakening the electrodynamic effect. The above results in the thickness and width of CRUD in the flow acceleration zone vary in varying degrees. This suggests that the deposition process of CRUD occurs under the mechanism of mass transfer and electrokinetic mechanism.