REVEALING HOW ALKALI CATIONS AFFECT THE ELECTRICAL DOUBLE LAYER STRUCTURE OF STAINLESS STEEL IN ALKALINE AQUEOUS ENVIRONMENTS

摘要

The core components of nuclear power plants arecomposed of stainless steel and other effectively passivatedalloys as primary structural materials. However, theproperties of the passivating oxide films are profoundlyinfluenced by the coolant chemistry, and the breakdown ofthe passive films, e.g., due to pitting or stress corrosioncracking, which renders these alloys susceptible tohyperbolic failure and inconsistent with the leak-beforebreakcriterion. Herein, atomic force microscopy (AFM) isused to examine a negatively charged stainless steelsurface. The interaction between hydrated alkali cations(i.e., K~+, Li~+) and the passivated steel substrate affects thestructure of the electrical double layer (EDL) as revealedby analysis of AFM interaction forces. As a result, a moredisrupted EDL is indicated in the presence of Li~+ relativeto K~+. Hence, the cation species present in the coolant canpotentially have impact on degradation of alloycomponents in nuclear power plants. These findings alsoprovide insights into EDL behaviors in batteries and otherelectrochemical devices.