Mechanism of Oxide Scale Removal during Dilute Chemical Decontamination of Carbon Steel Surfaces

Abstract

Possible mechanisms involved in the removal of oxide scale (chiefly Fe₃O₄) over carbon steel during the course of decontamination of mainly the internal surfaces of the primary system of a reactor have been proposed. During the initial stages, the externally added reducing agent was found to aid the reductive dissolution. But once the oxide layer became porous and the decontamination reagent found access to the base metal, electrons available from the base metal oxidation continued the reductive dissolution. Depending on the relative area of the base metal to the oxide layer exposed, base metal may or may not influence the oxide dissolution. The surface area of the specimen exposed and the rate of regeneration of the reagents also have an important role in the oxide scale removal.

KEYWORDS:

• carbon steels
• iron oxides
• oxidation
• decontamination
• removal
• reducing agents
• reduction
• dissolution
• corrosion
• solubility