CRUD deposition in accelerated high-temperature water: Investigation on the effect of substrate material and water chemistry

Abstract

Deposition of corrosion products (CRUD) on micro-orifice specimens under accelerated flow conditions was investigated in high-temperature water on several substrate materials (SS 304L, Titanium, Alloy 690, Zirlo and magnesia stabilised Zirconia) and water chemistries (0–2 ppm of Li, 0–2.5 ppm of H2). Regardless of the substrate material, no significant differences in radial CRUD build-up were observed in high purity water (0 ppm of Li and either 0 or 2.5 ppm of H2). Conversely, in lithiated water (2 ppm of lithium and 2.5 ppm of H2), the CRUD surface build-up was dependent on the oxide electrical conductivity, which in turn depends on the substrate material. In fact, no build-up occurred on Zirconia and only a minor deposition on Zirlo. The deposition mechanism was ascribed to be dominated by particulate deposition at neutral pH where magnetite solubility is the highest. Conversely, crystalline build-up induced by electrokinetic activity played an important role at alkaline pH where oxide solubility was the lowest.